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ObjectiveSrc family kinase (SFK) activation circumvents epidermal growth factor receptor (EGFR) targeting in head and neck squamous cell carcinoma (HNSCC); dual SFK-EGFR targeting could overcome cetuximab resistance.Patients and methodsWe conducted a Simon two-stage, phase II trial of the SFK inhibitor, dasatinib, and cetuximab in biomarker-unselected patients with cetuximab-resistant, recurrent/metastatic HNSCC. Pre- and post-treatment serum levels of interleukin-6 (IL6) were measured by ELISA. HNSCC cell lines were assessed for viability and effects of IL6 modulation following dasatinib-cetuximab treatment.ResultsIn the first stage, 13 patients were evaluable for response: 7 had progressive and 6 had stable disease (SD). Enrollment was halted for futility, and biomarker analysis initiated. Low serum IL6 levels were associated with SD (raw p=0.028, adjusted p=0.14) and improved overall survival (p=0.010). The IL6 classifier was validated in a separate trial of the same combination, but was unable to segregate survival risk in a clinical trial of cetuximab and bevacizumab suggesting serum IL6 may be specific for the dasatinib-cetuximab combination. Enhanced in vitro HNSCC cell death was observed with dasatinib-cetuximab versus single agent treatment; addition of IL6-containing media abrogated this effect.ConclusionClinical benefit and overall survival from the dasatinib-cetuximab combination were improved among patients with low serum IL6. Preclinical studies support IL6 as a modifier of dasatinib-cetuximab response. In the setting of clinical cetuximab resistance, serum IL6 is a candidate predictive marker specific for combined dasatinib-cetuximab. The trial was modified and redesigned as a biomarker-enriched Phase II study enrolling patients with undetectable IL6.

BackgroundWe previously reported the safety of concurrent cetuximab, an antibody against epidermal growth factor receptor (EGFR), pemetrexed, and radiation therapy (RT) in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN). In this non-comparative phase II randomized trial, we evaluated this non-platinum combination with or without bevacizumab, an inhibitor of vascular endothelial growth factor (VEGF).Patients and methodsPatients with previously untreated stage III-IVB SCCHN were randomized to receive: conventionally fractionated radiation (70 Gy), concurrent cetuximab, and concurrent pemetrexed (arm A); or the identical regimen plus concurrent bevacizumab followed by bevacizumab maintenance for 24 weeks (arm B). The primary end point was 2-year progression-free survival (PFS), with each arm compared with historical control. Exploratory analyses included the relationship of established prognostic factors to PFS and quality of life (QoL).ResultsSeventy-eight patients were randomized: 66 oropharynx (42 HPV-positive, 15 HPV-negative, 9 unknown) and 12 larynx; 38 (49%) had heavy tobacco exposure. Two-year PFS was 79% [90% confidence interval (CI) 0.69-0.92; P < 0.0001] for arm A and 75% (90% CI 0.64-0.88; P < 0.0001) for arm B, both higher than historical control. No differences in PFS were observed for stage, tobacco history, HPV status, or type of center (community versus academic). A significantly increased rate of hemorrhage occurred in arm B. SCCHN-specific QoL declined acutely, with marked improvement but residual symptom burden 1 year post-treatment.ConclusionsRT with a concurrent non-platinum regimen of cetuximab and pemetrexed is feasible in academic and community settings, demonstrating expected toxicities and promising efficacy. Adding bevacizumab increased toxicity without apparent improvement in efficacy, countering the hypothesis that dual EGFR-VEGF targeting would overcome radiation resistance, and enhance clinical benefit. Further development of cetuximab, pemetrexed, and RT will require additional prospective study in defined, high-risk populations where treatment intensification is justified.

Objective: Src family kinase (SFK) activation circumvents epidermal growth factor receptor (EGFR) targeting in head and neck squamous cell carcinoma (HNSCC); dual SFK-EGFR targeting could overcome cetuximab resistance., Patients and Methods: We conducted a Simon two-stage, phase II trial of the SFK inhibitor, dasatinib, and cetuximab in biomarker-unselected patients with cetuximab-resistant, recurrent/metastatic HNSCC. Pre- and post-treatment serum levels of interleukin-6 (IL6) were measured by ELISA. HNSCC cell lines were assessed for viability and effects of IL6 modulation following dasatinib-cetuximab treatment., Results: In the first stage, 13 patients were evaluable for response: 7 had progressive and 6 had stable disease (SD). Enrollment was halted for futility, and biomarker analysis initiated. Low serum IL6 levels were associated with SD (raw p=0.028, adjusted p=0.14) and improved overall survival (p=0.010). The IL6 classifier was validated in a separate trial of the same combination, but was unable to segregate survival risk in a clinical trial of cetuximab and bevacizumab suggesting serum IL6 may be specific for the dasatinib-cetuximab combination. Enhanced in vitro HNSCC cell death was observed with dasatinib-cetuximab versus single agent treatment; addition of IL6-containing media abrogated this effect., Conclusion: Clinical benefit and overall survival from the dasatinib-cetuximab combination were improved among patients with low serum IL6. Preclinical studies support IL6 as a modifier of dasatinib-cetuximab response. In the setting of clinical cetuximab resistance, serum IL6 is a candidate predictive marker specific for combined dasatinib-cetuximab. The trial was modified and redesigned as a biomarker-enriched Phase II study enrolling patients with undetectable IL6., (Copyright © 2017. Published by Elsevier Ltd.)

BACKGROUND. EGFR and Src family kinases are upregulated in head and neck squamous cell carcinoma (HNSCC). EGFR interacts with Src to activate STAT3 signaling, and dual EGFR-Src targeting is synergistic in HNSCC preclinical models. pSrc overexpression predicted resistance to the EGFR inhibitor, erlotinib, in a prior window trial. We conducted a 4-arm window trial to identify biomarkers associated with response to EGFR and/or Src inhibition. METHODS. Patients with operable stage II-IVa HNSCC were randomized to 7-21 days of neoadjuvant erlotinib, the Src inhibitor dasatinib, the combination of both, or placebo. Paired tumor specimens were collected before and after treatment. Pharmacodynamic expression of EGFR and Src pathway components was evaluated by IHC of tissue microarrays and reverse-phase protein array of tissue lysates. Candidate biomarkers were assessed for correlation with change in tumor size. RESULTS. From April 2009 to December 2012, 58 patients were randomized and 55 were treated. There was a significant decrease in tumor size in both erlotinib arms ( P = 0.0014); however, no effect was seen with dasatinib alone ( P = 0.24). High baseline pMAPK expression was associated with response to erlotinib ( P = 0.03). High baseline pSTAT3 was associated with resistance to dasatinib ( P = 0.099). CONCLUSIONS. Brief exposure to erlotinib significantly decreased tumor size in operable HNSCC, with no additive effect from dasatinib. Baseline pMAPK expression warrants further study as a response biomarker for anti-EGFR therapy. Basal expression of pSTAT3 may be independent of Src, explain therapeutic resistance, and preclude development of dasatinib in biomarker-unselected cohorts. TRIAL REGISTRATION. NCT00779389. FUNDING. National Cancer Institute, American Cancer Society, Pennsylvania Department of Health, V Foundation for Cancer Research, Bristol-Myers Squibb, and Astellas Pharma., Competing Interests: Conflict of interest: The authors have declared that no conflict of interest exists.

Background: Fabry disease is an X-linked disorder of glycosphingolipid catabolism that is the result of an intracellular deficiency in the lysosomal enzyme alpha-galactosidase A (alpha-Gal A). This enzymatic defect results in the accumulation of globotriaosylceramide (Gb(3)) within cells and causes progressive neurological, cardiovascular and renal dysfunction. Our objective is to describe the safety and renal effects of long-term enzyme replacement therapy., Methods: This was a single centre, prospective open-label treatment trial in 25 adult male Fabry patients who had completed a 6-month randomized placebo-controlled study and subsequently enrolled in an open-label extension study. Patients were treated every other week with agalsidase alfa (0.2 mg/kg) infused intravenously over 40 min. The main outcome measures were safety, antibody response and renal glomerular filtration rate (GFR)., Results: During the 4-4.5 years of enzyme replacement therapy, all eligible subjects were able to transition to home therapy. Eight patients developed persistent IgG antibodies to agalsidase alfa, but IgE antibodies were not detected in any patient. The development of IgG antibodies appeared not to affect any clinical end points. Estimated GFR remained stable in subgroups of patients with Stage I (GFR >90 ml/min) or Stage II (GFR 60-89 ml/min) chronic kidney disease at baseline. In contrast, in the subgroup of patients with Stage III chronic kidney disease (GFR 30-59 ml/min), the slope of the decline in GFR was reduced compared with comparable historical controls, suggesting that enzyme replacement therapy was slowing the decline of renal function in this susceptible population., Conclusions: Long-term enzyme replacement therapy with agalsidase alfa is safe and may slow the progressive decline in renal function that was commonly observed in adult males with Fabry disease.

Infarct expansion starts within hours to days after transmural myocardial injury. Previous echocardiographic and left ventriculographic studies demonstrated that angiotensin-converting enzyme (ACE) inhibitor therapy limits left ventricular dilatation, particularly in patients with anterior wall acute myocardial infarction (AMI) or impaired left ventricular function. Forty-three patients with an acute Q-wave AMI were randomized within 24 hours of symptom onset to intravenous enalaprilat (1 mg) or placebo. Patients were then given corresponding oral therapy and followed for 1 month. Predrug and 1-month gated blood pool scans were obtained in 32 patients to evaluate changes in cardiac volumes and ejection fraction. Twenty-three patients underwent magnetic resonance imaging at 1 month to evaluate left ventricular infarct expansion. Blood pressure decreased at 6 hours but returned to baseline in both groups after 1 month of therapy. The change in cardiac volumes from baseline to 1 month differed between the placebo (end-diastolic volume +16 +/- 5 ml, end-systolic volume +8 +/- 6 ml), and enalapril (end-diastolic volume -8 +/- 9 ml and end-systolic volume -14 +/- 7 ml) groups (p < 0.05 vs placebo). Global and infarct zone ejection fractions improved significantly at 1 month in the enalapril group (+6 +/- 3% and 19 +/- 5%, respectively) but did not change over 1 month in the placebo group. Infarct segment length and infarct expansion index by magnetic resonance imaging were significantly less in those treated with enalapril, suggesting less infarct expansion in this group. Thus, early administration of enalaprilat to patients presenting with a first Q-wave AMI prevents cardiac dilatation and infarct expansion.

Background: Animal studies have demonstrated a burst of oxygen free radical generation after reperfusion of ischemic myocardium that could be blocked by administration of the free radical scavenger recombinant human superoxide dismutase (h-SOD). A multicenter, randomized, placebo-controlled clinical trial was designed to test the hypothesis that free radical-mediated reperfusion injury could be reduced by intravenous administration of h-SOD begun before percutaneous transluminal coronary angioplasty (PTCA) in patients with acute transmural myocardial infarction., Methods and Results: One hundred twenty patients were randomized to receive placebo (n = 59) or h-SOD (n = 61) given as a 10-mg/kg intravenous bolus followed by a 60-minute infusion of 0.2 mg.kg-1.min-1. Left ventricular function was analyzed via paired contrast left ventriculograms performed before PTCA and after 6 to 10 days and paired radionuclide ventriculograms performed within 24 hours of PTCA and after 4 to 6 weeks. Both h-SOD- and placebo-treated patients showed improvement in global and regional left ventricular function after successful reperfusion. Compared with the placebo group, no additional improvement was observed in the patients treated with h-SOD., Conclusions: The results of this clinical trial failed to demonstrate a beneficial effect of h-SOD on global or regional left ventricular function in patients who underwent successful PTCA for treatment of acute myocardial infarction.

The detection of coronary artery disease is difficult if a patient has electrocardiographic evidence of left bundle branch block (BBB). Septal blood flow may be reduced in patients with left BBB, despite no angiographic evidence of left anterior descending (LAD) coronary artery disease. We have developed a new method of quantification of Thallium-201 single-photon emission computed tomographic (SPECT) images with the aim of better separating patients with left BBB and LAD disease from those with left BBB alone. The study cohort comprised 8 normal subjects (group I) and 20 patients with left BBB and chest pain who underwent thallium-201 SPECT imaging and coronary angiography. Eight patients (group II) had < or = 50% LAD stenosis, and 12 (group III) had > or = 70% LAD stenosis. Septal abnormality scores on the second short-axis slice from the base were computed, based on comparison of each subject's short-axis circumferential profile with a normal reference curve. This followed a procedure in which each profile was scaled to minimize differences in its absolute level in relation to the reference curve. Septal abnormality scores on stress images were 0.8 +/- 22 for group I, 27 +/- 43 for group II, and 165 +/- 67 for group III (p = 0.15 for group I vs II, and p < 0.0001 between groups I and III, and II and III).(ABSTRACT TRUNCATED AT 250 WORDS)

Hydroxyl radical formation, secondary to superoxide radical generation, has been advocated as the actual mechanism of oxygen radical-mediated damage in biological systems. The present study was designed to compare the efficacy of administration of the hydroxyl radical scavenger mannitol vs. that of the superoxide radical scavenger superoxide dismutase (SOD) in reducing myocardial reperfusion injury, and to test whether combined treatment with both agents would confer better tissue protection compared with either intervention alone. Rabbit hearts perfused within a 31P nuclear magnetic resonance (31P-NMR) spectrometer were subjected to 30 minutes of total global ischemia at 37 degrees C. At reflow, 12 hearts in each group received either (a) a bolus of standard perfusion buffer, followed by 45 minutes of reperfusion (controls); (b) the superoxide radical scavenger recombinant human SOD (h-SOD, as a 60,000 U bolus followed by a 100 U/ml infusion for 15 minutes); (c) the hydroxyl radical scavenger mannitol (50 mM bolus followed by 15 minutes of 50 mM infusion; or (d) a combination of both agents. All treated hearts were switched to standard buffer for the remaining 30 minutes of reperfusion. Treatment with h-SOD alone was associated with a significant improvement in the recovery of cardiac contractility and coronary flow, as well as of ATP content, compared to control hearts. In contrast, mannitol treatment resulted in a small, nonsignificant improvement in these parameters. The addition of mannitol to h-SOD did not result in further significant improvement of contractility and ATP recovery compared to h-SOD alone. These data demonstrate that under our experimental conditions significant protection against reperfusion injury can be achieved by the administration of h-SOD alone, without the need for additional hydroxyl radical scavenger therapy with mannitol. These results do not exclude that significant tissue protection may be achieved by different doses of mannitol or by other agents. However, they suggest that under definite experimental conditions prevention of hydroxyl radical formation, rather than attempts to minimize hydroxyl radical toxicity, might be a more efficient method to prevent oxygen radical-mediated reperfusion injury in isolated hearts.

Objectives: The purpose of this study was to determine whether postischemic reperfusion of the heart in living rabbits induces a burst of oxygen free radical generation that can be attenuated by recombinant human superoxide dismutase administered at the moment of reflow., Background: This phenomenon was previously demonstrated in crystalloid perfused, globally ischemic rabbit hearts., Methods: Thirty-two open chest rabbits were assigned to one of four groups of eight animals each: Group I (control animals), no coronary artery occlusion; Group II, 30 min of circumflex marginal coronary artery occlusion without reperfusion; Group III, 30 min of coronary occlusion followed by 60 s of reperfusion, and Group IV, 30 min of coronary occlusion followed by treatment with recombinant human superoxide dismutase (a 20-mg/kg body weight bolus 90 s before reperfusion and a 0.17-mg/kg infusion during 60 s of reperfusion). Full thickness biopsy specimens taken from the ischemic region were then rapidly freeze clamped and electron paramagnetic resonance spectroscopy was performed at 77 degrees K., Results: Three radical signals similar to those previously identified in the isolated, crystalloid perfused rabbit heart were observed: an isotropic signal with g = 2.004 suggestive of a semiquinone, an anisotropic signal with g parallel = 2.033 and g perpendicular = 2.005 suggestive of an oxygen-centered alkyl peroxy radical, and a triplet with g = 2.000 and aN = 24 G suggestive of a nitrogen-centered radical. In addition, a fourth signal consistent with an iron-sulfur center was seen. The oxygen-centered free radical concentration during normal perfusion (Group I) was 1.8 +/- 0.8 mumol compared with 4.4 +/- 0.9 mumol after 30 min of regional ischemia without reperfusion (Group II) and 13.0 +/- 2.5 mumol after 60 s of reperfusion (Group III) (p < 0.05 among all three groups). In contrast, superoxide dismutase treated-rabbits (Group IV) demonstrated a peak oxygen radical concentration of only 5.9 +/- 1.2 mumol (p < 0.05 vs. Group III)., Conclusions: This study demonstrates that reperfusion after regional myocardial ischemia in the intact rabbit is associated with a burst of oxygen-centered free radicals. The magnitude of this burst is greater than that seen after a comparable duration of global ischemia in the isolated, buffer-perfused rabbit heart preparation and is significantly reduced by superoxide dismutase administration begun just before reflow.

In patients with acute myocardial infarction, intravenous nitroglycerin lowers left ventricular filling pressure and systemic vascular resistance. At lower infusion rates (less than 50 micrograms/min) nitroglycerin is principally a venodilator, whereas at higher infusion rates more balanced venous and arterial dilating effects are seen. Patients with left ventricular failure demonstrate increased or maintained stroke volumes, whereas patients without failure show a decrease in stroke volume. All hemodynamic subgroups show a decrease in left ventricular filling pressures and a reduction in electrocardiographic evidence of regional myocardial ischemia. Longer-term infusions (24-48 hours) have been shown to result in myocardial preservation, as assessed by global and regional left ventricular function and laboratory indices of infarct size. Comparison of intravenous nitroglycerin and sodium nitroprusside reveals increased intercoronary collateral flow with nitroglycerin, in contrast to a decrease with nitroprusside, compatible with a "coronary steal." Short-term administration of intravenous nitroglycerin with or without chronic administration of long-acting nitrates have been found both to reduce short-term mortality and to have long-term beneficial effects on left ventricular remodeling in patients with anterior transmural infarctions. Current clinical practice would utilize intravenous nitroglycerin as initial therapy for patients receiving intravenous thrombolytic therapy and/or acute percutaneous transluminal coronary angioplasty within 4-6 hours of the onset of symptoms of acute myocardial infarction, in order to optimize intercoronary collateral flow until reperfusion can be accomplished. Patients reaching the hospital greater than 6 hours but less than 14 hours after symptom onset can still benefit from intravenous nitroglycerin for 24-48 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Timely reperfusion with intravenous thrombolytic agents has been shown to reduce mortality in patients with acute myocardial infarction. However, the magnitude of improvement in left ventricular function has always been less than expected. Reperfusion in fact causes a specific form of tissue injury, termed reperfusion injury, which would subtract from the benefit obtained by terminating ischemia. Oxygen free radical generation has been proposed to be a major mechanism in the pathogenesis of reperfusion injury. Using an isolated perfused rabbit heart model we have demonstrated that administration of oxygen free radical scavengers, such as recombinant human superoxide dismutase (h-SOD) and iron chelators, such as deferoxamine, beginning at the time of reperfusion, reduce the severity of reperfusion injury, as judged by recovery of ventricular function and high energy phosphate metabolism, assessed quantitatively using 31-phosphorus nuclear magnetic resonance spectroscopy. Using electron paramagnetic resonance spectroscopy we have documented a burst of oxygen free radical generation during the early minutes of reperfusion and that this burst can be eliminated by superoxide radical scavengers, such as h-SOD, hydroxyl radical scavengers, such as mannitol, as well as agents that inhibit generation of oxygen free radicals, such as the iron chelator, deferoxamine. Taken together these results strongly support the role of oxygen free radicals in the pathogenesis of reperfusion injury. We have recently completed the first randomized placebo controlled clinical trial of a free radical scavenger (h-SOD) in patients with acute myocardial infarction, undergoing urgent angioplasty of their occluded coronary artery with preservation of left ventricular function as the major study endpoint.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of simultaneous infusions of low-dose recombinant tissue-type plasminogen activator (t-PA) and single-chain urokinase-type plasminogen activator (scu-PA, pro-urokinase) on coronary arterial thrombolysis was investigated in 23 patients treated within 6 hours (mean 2.6 +/- 1.1, range 1.2 to 5.9) of symptoms of an acute myocardial infarction. Infarct artery patency at 90 minutes was achieved in 16 (70%, 95% confidence limits of 0.47 to 0.87) of 23 patients after a 1-hour intravenous infusion of 20 and 16.3 mg of t-PA and scu-PA, respectively. At 90 minutes, the fibrinogen concentration decreased from 369 +/- 207 to 316 +/- 192 mg/dl (p = not significant), while plasminogen decreased to 69 +/- 24% (p = 0.001) and alpha-2-antiplasmin to 77 +/- 24% (p = 0.001) of pretreatment values. Although no bleeding requiring termination of drug infusion or transfusion occurred, 1 patient with cerebrovascular amyloidosis had a fatal intracerebral hemorrhage. These findings suggest that combination therapy may allow substantial reductions in total thrombolytic doses while still achieving effective fibrin-specific coronary thrombolysis.

Oxygen radical toxicity has been implicated in the pathogenesis of myocardial reperfusion injury. In the present study we sought to document the existence of a precise temporal relationship between the time course of free radical generation and the time course of alterations of myocardial energy metabolism during early reperfusion. Rabbit hearts perfused within the bore of a 31-Phosphorous NMR spectrometer were subjected to 30 min of total global ischemia at 37 degrees C. At reflow, 12 control hearts received a bolus of normal perfusate and 12 hearts recombinant human superoxide dismutase (h-SOD) as a 60,000 IU bolus followed by a 100 IU/ml infusion for 15 min. Ischemia resulted in similar depletion of tissue ATP and phosphocreatine (PCr) in the two groups. During the first minute of reflow, recovery of PCr was similar in both groups. However, PCr recovery arrested in control hearts after 2 min, at 63% of baseline, and averaged 64 +/- 4% after 45 min of reperfusion. In contrast, h-SOD treated hearts recovered 86.7% of baseline PCr content after 2 min, 102% after 10 min of reperfusion (P less than 0.001), and 93 +/- 6.4% at the end of the 45 min of reflow (P less than 0.01). The time course of free radical formation during reperfusion was assessed by EPR spectroscopy using both the frozen tissue and the spin trapping methodologies. In control hearts, peak generation of oxygen radicals was reached after 20 s of reflow. h-SOD treatment decreased concentrations of the oxygen-centered radicals in myocardial tissue and of the radical-adducts in the coronary effluent by approximately 80%. Thus, in reperfused hearts peak oxygen radical generation is followed by the occurrence of alterations in the recovery of high energy phosphate metabolism. Both events were largely prevented by administration of h-SOD at reflow. These results provide strong support for a link between oxygen free radical generation and post-ischemic reperfusion injury.

Increasing evidence suggests that oxygen free radicals play a major role in the pathogenesis of reperfusion injury. Initial indirect evidence was based on beneficial effects of free radical scavengers administered exogenously at the time of postischemic reperfusion. Recent electron paramagnetic resonance (EPR) spectroscopy studies show a burst of oxygen-centered free radical generation during the first 60 seconds of reflow and administration of either a free radical scavenger, such as superoxide dismutase (SOD), or an iron chelator, such as deferoxamine, prevents this burst. The in vitro data obtained in a perfused rabbit heart model and the impressive reduction in infarct size, shown in an intact canine model, suggest that well-designed, randomized, placebo-controlled clinical trials of free radical scavengers and/or antioxidants should be performed to determine if postischemic reperfusion injury can be shown and/or prevented in humans.

To test whether generation of oxygen radicals during postischemic reperfusion might promote peroxidation of cardiac membrane lipids, four groups of Langendorff-perfused rabbit hearts were processed at the end of (a) control perfusion, (b) 30 min of total global ischemia at 37 degrees C without reperfusion, (c) 30 min of ischemia followed by reperfusion with standard perfusate, (d) 30 min of ischemia followed by reperfusion with the oxygen radical scavenger human recombinant superoxide dismutase (h-SOD). The left ventricle was homogenized and tissue content of malonyldialdehyde (MDA), an end product of lipid peroxidation, was measured on the whole homogenate as well as on various subcellular fractions. Reperfusion was accompanied by a significant increase in MDA content of the whole homogenate and of the fraction enriched in mitochondria and lysosomes. This phenomenon was not observed in hearts subjected to ischemia but not reperfused, and was similarly absent in those hearts which received h-SOD at reflow. Reperfused hearts also had significantly greater levels of conjugated dienes (another marker of lipid peroxidation) in the mitochondrial-lysosomal fraction. Again, this phenomenon did not occur in ischemic hearts or in reperfused hearts treated with h-SOD. Unlike the effect on tissue MDA and conjugated dienes, reperfusion did not significantly stimulate release of MDA in the cardiac effluent. Treatment with h-SOD was also associated with significant improvement in the recovery of cardiac function. In conclusion, these data directly demonstrate that postischemic reperfusion results in enhanced lipid peroxidation of cardiac membranes, which can be blocked by h-SOD, and therefore is most likely secondary to oxygen radical generation at reflow.

Background: Iron may play a central role in oxygen radical generation during myocardial ischemia and after reperfusion. Because conditions during ischemia may also liberate iron, we hypothesized that administration of the iron chelator deferoxamine during ischemia would result in improved functional and metabolic recovery after postischemic reperfusion., Methods and Results: Isolated, perfused rabbit hearts were studied by phosphorus-31 nuclear magnetic resonance spectroscopy. The hearts received one of three treatments: deferoxamine at the onset of 30 minutes of global ischemia (n = 9), deferoxamine as a bolus followed by a continuous 15-minute infusion begun at reflow (n = 9), or standard perfusate (n = 7). Hearts treated with deferoxamine during ischemia showed better recovery of developed pressure than did control hearts (63.2 +/- 7.5% versus 41.2 +/- 2.9% of baseline) (p = 0.02) and better recovery of myocardial phosphocreatine content (92.4 +/- 10.3% versus 68.2 +/- 4.5% of baseline, p less than 0.05). These functional and metabolic benefits were comparable to those obtained with deferoxamine treatment during early reperfusion. In 15 additional hearts, intraischemic treatment with deferoxamine resulted in no reduction in oxygen radical concentrations as measured on frozen tissue by electron paramagnetic resonance spectroscopy at end ischemia, but the treatment eliminated the reperfusion-induced increase of free radical generation observed in control hearts (2.9 +/- 0.01 versus 7.0 +/- 0.07 microM, p less than 0.001). The magnitude of reduction was similar to that when deferoxamine was given at the onset of reflow (2.4 +/- 0.02 microM, p less than 0.001 versus control)., Conclusions: These results demonstrate improved functional and metabolic recovery of myocardium treated with deferoxamine during ischemia, accompanied by a reduction in reperfusion-induced oxygen free-radical generation to the same degree as reflow treatment, confirming the importance of iron in the pathogenesis of myocardial reperfusion injury.

The pathophysiologic mechanisms responsible for the clinical syndrome known as unstable angina pectoris are complex but provide a framework for a rational medical approach to this ischemic condition. The combined use of nitrates, beta-blockers, calcium antagonists, antiplatelet agents, and anticoagulants has been shown to reduce recurrent ischemia, and the latter therapies have reduced the incidence of progression to myocardial infarction and death. A rational risk stratification scheme, which utilizes the presenting symptoms, electrocardiographic, and anatomic information to identify patients for whom additional revascularization procedures are warranted, is presented.

Conventional coronary arteriography is able to demonstrate the presence of coronary collateral vessels but cannot delineate the specific region of myocardium to which they supply blood. To test the hypothesis that contrast echocardiography can specifically identify collateralized myocardium, contrast echocardiographic perfusion "maps" were compared in patients with (n = 12) and without (n = 12) angiographic evidence of coronary collateral flow, both before and after coronary angioplasty. Contrast echocardiographic images of the mid-left ventricle in the short-axis view at end-diastole were obtained after separate injections of a sonicated contrast agent into both the right and the left coronary arteries. A computer-based contouring system was used to determine the individual areas of myocardium perfused by each of the two coronary arteries and then to superimpose the images of the two perfusion beds. The resulting area of overlapping perfusion represented myocardium receiving blood flow from both coronary systems and was defined as collateralized myocardium. To normalize for heart size, overlap area was expressed as a percent of total myocardial area, which was the area between endocardium and epicardium in the short-axis view. To adjust for differences in vascular distribution, overlap area was expressed as a percent of the perfusion area of the recipient vessel. In patients with angiographic collateral flow, the recipient vessel was that vessel receiving the collateral flow. In patients without angiographic collateral flow, the right coronary artery was considered the recipient vessel. Overlap area was 1.3 +/- 0.4% of total myocardial area and 6.6 +/- 1.7% of recipient vessel area in patients without angiographic evidence of collateral flow compared with 30.6 +/- 2.5% and 89.2 +/- 6.4%, respectively, in patients with angiographic collateral flow (p less than 0.001 for both). In four patients in whom angiographic collateral flow was abolished by angioplasty, overlap area decreased from 30.3 +/- 5.3% to 6.8 +/- 2.7% of total myocardial area and from 100% to 18.5 +/- 5.4% of recipient vessel area (p less than 0.05 for both). Thus, contrast echocardiography is able to map the specific myocardial territory perfused by coronary collateral flow and document an immediate reduction in perfusion in this territory when collateral flow is abolished by angioplasty.

Initial studies from our institution demonstrated beneficial anti-ischemic effects of short-term infusion of intravenous nitroglycerin in patients with acute myocardial infarction. At lower doses, nitroglycerin was shown to be principally a venodilator; at higher doses, a mixed venous and arterial dilating effect was demonstrated. The acute hemodynamic effects of nitroglycerin varied in the presence or absence of left ventricular failure; patients with the most severe degree of left ventricular dysfunction had the most beneficial hemodynamic effect. Similar differential effects have been demonstrated for nitroprusside in other studies. A comparison of the arterial vasodilating potency of nitroglycerin and nitroprusside in patients in whom acute hypertension develops following coronary artery bypass surgery revealed that equal lowering of arterial pressure and systemic vascular resistance could be demonstrated in 85 percent of the patients with comparable infusion rates. Review of previous clinical and laboratory studies in animals, in which the effects of nitroglycerin and nitroprusside were compared, in most cases revealed opposite effects on intercoronary collateral flow and, thereby, opposite effects on the severity of regional ischemia. Our recently completed randomized placebo-controlled clinical trial employing a 48-hour infusion of nitroglycerin demonstrated a higher incidence of significant improvement in abnormalities noted on scintigraphy when nitroglycerin treatment was initiated within 10 hours of the onset of symptoms. Beneficial effects of early nitroglycerin treatment have also been demonstrated in previous clinical trials. In similar studies, which utilized nitroprusside infusions in patients with acute myocardial infarction, some investigators found an increase in short-term mortality with early nitroprusside treatment whereas others found benefit. The uniformly favorable results of the clinical trials that utilized intravenous nitroglycerin, although not necessarily supporting its routine use in all patients, would support a preference for nitroglycerin over nitroprusside for the treatment of congestive heart failure and/or acute hypertension complicating acute myocardial infarction.

The development of and recovery from a severe yet nonlethal myocardial injury following hyperkalemic cardioplegia and prolonged hypothermic global ischemia was examined over 14 days in a rat model of heterotopic intraabdominal cardiac isograft transplantation. Mitochondrial enzymatic markers of myocardial ischemic injury and light microscopic signs of damage were examined. Eighteen hearts were arrested in situ using hyperkalemic cardioplegia and subjected to a mean of 38 min of ischemia at 20 degrees C as transplantation was achieved. No changes in mitochondrial creatine kinase (CKm) activity, mitochondrial malate dehydrogenase (MDHm) activity, their ratio, or morphologic evidence of injury were found during 8 days of reperfusion. In a second group of 66 hearts, the duration of hypothermic cardioplegic ischemia was extended by 120 min before transplantation. Neither unreperfused hearts nor hearts reperfused for only 1 hr demonstrated significant depression of enzyme activities or microscopic evidence of injury. However, after 1 day of reperfusion, CKm and MDHm activities were depressed to 36 and 44% of control levels (P less than 0.05). These activities had returned to control levels by 2 days of reperfusion and remained stable for 12 days thereafter. Light microscopic analysis revealed cellular injury to be maximal at 1 to 2 days of reperfusion with gradual improvement noted over the following 12 days. These observations suggest the existence of a mitochondrial injury following prolonged cardioplegic arrest and hypothermic global ischemia that is maximal after 24 hr of reperfusion but shows evidence of improvement thereafter. These findings justify aggressive support of the poorly functioning heart for the first few days after prolonged global ischemia.

Previous studies from our laboratory utilized an isolated isovolumic Langendorff heart preparation to study myocardial metabolism and preservation of left ventricular function following global ischemia and reperfusion. The present study employed a similar preparation to assess the utilization of various glycolytic substrates by monitoring the level of left ventricular developed pressure. Twenty-one rabbit hearts were perfused with an oxygenated but substrate-free Krebs-Ringer-bicarbonate solution in order to deplete the hearts of endogeneous substrate stores. Following a brief period of anoxic, substrate-free perfusion, hearts were perfused with one of seven test substrates under anaerobic, then aerobic conditions. Under anaerobic conditions only perfusion of glucose resulted in a measurable increase in ventricular function which was still less than 20% of control. Under aerobic conditions, provision of glucose, pyruvate, or the combination of alpha-glycerol phosphate and pyruvate resulted in significant increases in contractile function which were 40-70% of control. These results obtained in normal hearts will provide a base line for future studies of the metabolism of postischemic hearts which may have altered cell membrane permeability and/or enzymatic activity.

The use of propranolol with multidose potassium cardioplegia was studied in 32 in situ canine hearts subjected to 90 minutes of global ischemia at 15 degrees C and 60 minutes of reperfusion at 37 degrees C. All hearts received potassium (37 mEq/l) every 30 minutes during ischemia. There were four groups of equal size: group 1 received no propranolol, group 2 received low-dose propranolol and group 3 received high-dose propranolol. Group 4 received high-dose propranolol only with the initial potassium infusion. Myocardial CO2 (PmCO2) was monitored by mass spectrometry as an indicator of metabolic activity. An intraventricular balloon was used to measure isovolumic developed pressure, maximal dP/dt and end-diastolic pressure (EDP) before and after ischemia. During ischemia, peak PmCO2 was significantly higher in group 1 (45.6 +/- 2.8 mm Hg) than in groups 2, 3 and 4 (35.2 +/- 2.8 mm Hg, 33.4 +/- 2.8 mm Hg and 30.4 +/0 2.8 mm Hg, respectively) (p less than 0.05). There were no differences between the four groups in systolic ventricular function assessed by developed pressure and dP/dt. Hearts that received high-dose propranolol had significantly lower EDP after 60 minutes of reperfusion (group 3 13.3 +/- 1.5 mm Hg, group 4 10.4 +/0 1.5 mm Hg) compared with group 1 hearts (25.3 +/- 3.8 mm Hg, p less than 0.05). Hearts in groups 3 and 4 exhibited less ischemic injury as assessed by electron microscopy than hearts in groups 1 and 2. These data show that propranolol added to multidose potassium cardioplegia reduced metabolic activity during ischemia and improved ventricular compliance during reperfusion without depressing systolic function. Because left ventricular compliance and morphologic preservation were similar in groups 3 and 4, it appears that a single high dose of propranolol is sufficient and that subsequent doses do not further enhance the beneficial effects.

The exact mechanism or mechanisms by which nitroglycerin exerts its beneficial effect on pacing-induced regional myocardial ischemia has not been ellucidated previously. In an open-chest, anesthetized canine preparation a fixed, flow limiting stenosis was applied to the left anterior descending (LAD) coronary artery and heart rate was increased by atrial pacing. Mass spectrometry was used to measure myocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions. Myocardial blood flow was measured by the radioactive microsphere technique. Application of the stenosis resulted in regional decreases in PmO2 and increases in PmCO2 of greater magnitude in the subendocardial than in the subepicardial layer. Atrial pacing resulted in a further decrease in PmO2 and increase in PmCO2 as well as a reduction in subendocardial blood flow. Nitroglycerin (TNG) infusion reduced mean arterial pressure 20 mm Hg, resulting in a 14 mm Hg reduction in PmCO2 in the more ischemic subendocardial layer (P less than 0.05). Myocardial blood flow decreased in all regions; however, the magnitude of this decrease was less in the ischemic region. Addition of aortic constriction abolished both the afterload and preload lowering effects of nitroglycerin but improved ischemic zone blood flow. These data demonstrate that nitroglycerin reduces the severity of pacing-induced regional myocardial ischemia primarily by reducing the determinants of myocardial oxygen demand. We found that when these effects are counteracted, improvement in myocardial oxygen supply becomes the dominant mechanism.

Organic nitrates are well established in the treatment of a wide variety of cardiovascular disorders, most notably angina pectoris and congestive heart failure. However, attenuation of, or tolerance to, haemodynamic and anti-ischaemic effects may occur with all long-acting nitrate formulations. In the majority of patients continuous administration of long acting nitrates tends to promote the development of attenuation, while intermittent administration avoids it. Likewise, higher-doses appear to induce attenuation to a greater degree than lower doses. Attenuation of haemodynamic effects and exercise tolerance in heart failure patients, and of clinical end-points in angina patients, appears to be less than attenuation of exercise testing end-points in angina patients. While the use of intermittent therapy avoids the development of attenuation, it may expose the patient to an as yet undefined risk of silent and/or symptomatic anginal episodes occurring during the nitrate-free interval. Likewise, the role of concomitant therapy in avoiding this potential risk remains to be defined. Means of avoiding attenuation may include the coadministration of sulfhydryl donors such as N-acetylcysteine. Alternatively, angiotension-converting enzyme (ACE) inhibitors such as captopril may block renin-angiotensin system-induced reflex sympathetic stimulation. Attenuation may occur to a greater or lesser degree in individual patients. The proportion of attenuators vs non-attenuators remains to be defined, as does a means of identifying such patients prospectively by clinical and/or laboratory parameters. Conflicting results among smaller studies may reflect variable proportions of attenuators vs non-attenuators. However, conflicting results among larger studies may reflect differences in patient selection criteria, such as selecting patients with positive and reproducible stress tests and little in the way of spontaneously occurring angina versus selecting patients with positive but variable stress tests and frequent episodes of spontaneously induced angina. The former group may reflect pure fixed coronary artery disease with little in the way of vasospasm, or change in vasomotor tone, while the latter group may reflect greater variability in vasomotor tone and/or more in the way of plaque instability. The clinical efficacy of long acting nitrates might therefore be expected to be greatest in those patients with larger numbers of spontaneously occurring angina episodes. Recent data suggest that nitrates may have important direct effects on coronary vessels including dilating eccentric coronary stenoses, dilating intercoronary collateral channels and having greater dilating effects on more diseased segments as opposed to less diseased coronary segments.(ABSTRACT TRUNCATED AT 400 WORDS)

To assess the effects of left ventricular distention during the early reperfusion period following ischemic arrest, 16 canine heart preparations were subjected to 45 minutes of hypothermic (27 degree C) cardioplegic arrest and normothermic reperfusion. Isovolumic left ventricular developed pressure and rate of rise of left ventricular pressure (dp/dt) were measured with an intraventricular balloon; endocardial/epicardial flow ratios were determined with microspheres; and myocardial gas tensions were monitored with mass spectrometry. During early reperfusion, Group 1 hearts (n = 8) were not distended (end-diastolic pressure = 0). Group 2 hearts (n = 8) were subjected to an enddiastolic pressure of 20 mm Hg for the initial 15 minutes of reperfusion. Group 2 hearts demonstrated impaired subendocardial blood flow after 5 minutes of reflow (0.75 +/- 0.06 vs 0.96 +/- 0.04, endocardial/epicardial flow rates, Group 2 vs Group 1) and persistent elevation of intramyocardial carbon dioxide (CO2) tension (68 +/- 4 vs 51 +/- 4 mm Hg, Group 2 vs Group 1). In addition, postischemic ventricular function was significantly worse in Group 2 hearts (60 +/- 7 vs 79 +/- 3% of control dP/dt, Group 2 vs Group 1, and 53 +/- 6 vs 81 +/- 5% of control left ventricular developed pressure, Group 2 vs Group 1). These data demonstrate that even mild distention during early reperfusion can result in reduced subendocardial perfusion and delayed washout of tissue CO2. Although myocardial blood flow and CO2 tension subsequently returned to normal in the distended hearts, left ventricular performance remained significantly depressed. This injury can occur clinically in nonvented hearts prior to the resumption of effective ventricular contraction.

Patients presenting within four hours of the onset of acute myocardial infarction were randomly assigned to receive 80 to 100 mg of recombinant human-tissue plasminogen activator (t-PA) intravenously over a period of three hours (n = 72) or placebo (n = 66). Administration of the study drug was followed by coronary arteriography, and candidates for percutaneous transluminal coronary angioplasty were randomly assigned either to undergo angioplasty on the third hospital day (n = 42) or not to undergo angioplasty during the 10-day study period (n = 43). The patency rates of the infarct-related arteries were 66 percent in the t-PA group and 24 percent in the placebo group. No fatal or intracerebral hemorrhages occurred, and episodes of bleeding requiring transfusion were observed in 7.6 percent of the placebo group and 9.8 percent of the t-PA group. As compared with the use of placebo, administration of t-PA was associated with a higher mean (+/- SEM) ejection fraction on the 10th hospital day (53.2 +/- 2.0 vs. 46.4 +/- 2.0 percent, P less than 0.02), an improved ejection fraction during the study period (+3.6 +/- 1.3 vs. -4.7 +/- 1.3 percentage points, P less than 0.0001), and a reduction in the prevalence of congestive heart failure from 33 to 14 percent (P less than 0.01). Angioplasty improved the response of the ejection fraction to exercise (+8.1 +/- 1.4 vs. +1.2 +/- 2.2 percentage points, P less than 0.02) and reduced the incidence of postinfarction angina from 19 to 5 percent (P less than 0.05), but did not influence the ejection fraction at rest. These data support an approach to the treatment of acute myocardial infarction that includes early intravenous administration of t-PA and deferred cardiac catheterization and coronary angioplasty.

The present study was designed to test the hypothesis that i.v. nitroglycerin is as effective as sodium nitroprusside for managing acute hypertension early after coronary artery bypass surgery. Seventeen patients received both nitroglycerin and nitroprusside in a randomized crossover protocol. Infusion rates were increased stepwise to lower mean arterial pressures comparably with each drug. In 14 of 17 patients, similar infusion rates of the two vasodilators resulted in equal lowering of both blood pressure and systemic vascular resistance. In the remaining three patients, very high infusion rates of nitroglycerin were required and achieved only 20-50% of nitroprusside's response in two of three. Hemodynamic responses to the two vasodilators were similar, except that nitroglycerin increased cardiac output more than nitroprusside did. In contrast, pulmonary gas exchange responses differed in that nitroglycerin improved intrapulmonary shunting, while nitroprusside worsened it. Similarly, nitroglycerin resulted in a significantly smaller increase in the alveolar arterial oxygen gradient than did nitroprusside. These results suggest that in the majority of patients, i.v. nitroglycerin was as effective as nitroprusside in controlling acute hypertension after coronary artery bypass surgery. In addition, nitroglycerin appeared to have more favorable effects on pulmonary gas exchange. Because nitroglycerin has more beneficial effects on intercoronary collateral blood flow in the setting of regional ischemia, it may be preferable to nitroprusside in patients with ischemic heart disease.

To identify the source of noncoronary collateral myocardial blood flow and to establish methods to control it during induced ischemia, 29 dogs were placed on cardiopulmonary bypass. The right and left ventricles were vented, vent flows were measured volumetrically, and intracavitary left ventricular (LV) pressures were monitored. After induction of ischemia by aortic cross-clamping and infusion of cardioplegic solution, six different microspheres 7 to 10 microns in diameter were injected into the aorta at six different times to measure myocardial blood flow during the following interventions:vent drainage of the right or left ventricle or both, proximal ligation of both coronary arteries, severance of the proximal pulmonary artery or the ascending aorta or both, and ligation of the bronchial arteries. Without effective LV venting, LV intracavitary pressure rose to 7.0 +/- 0.1 mm Hg (mean +/- standard error of the mean) and myocardial blood flow in the anterior left ventricle was 2.3 +/- 1.3 ml/100 gm/min. When the LV vent was opened, vent flow was 35.9 +/- 3.5 ml/min and myocardial blood flow fell to 0.3 +/- 0.2 ml/100 gm/min. Right ventricular (RV) vent flow was absent except when the LV vent was occluded, and this RV vent flow was abolished by ligating the coronary arteries. With bronchial artery ligation, LV vent flow ceased and myocardial blood flow was virtually absent. These studies demonstrate that myocardial blood flow does occur during induced ischemia, but that the source of this blood flow is primarily through systemic-pulmonary channels. True noncoronary collateral myocardial blood flow was virtually nonexistent.

The extent of myocardial protection afforded by a procaine cardioplegic solution during cardiac ischemia has been evaluated and compared with the protection seen using a potassium cardioplegic solution. An isolated cat heart model was employed, and ventricular function parameters, intramyocardial gas tensions, and postischemic myocardial edema were measured and compared following 60 minutes of induced ischemia at 37 degrees C. and 27 degrees C. There was no significant improvement in recovery of postarrest ventricular function when procaine cardioplegia was used during normothermic ischemia. When used at 27 degrees C., however, both cardioplegic solutions were associated with significantly better recovery of postarrest ventricular function, although there was less myocardial edema formation in the potassium-treated hearts. Results of this study indicate that procaine-induced cardioplegia provides myocardial protection during anoxic cardiac arrest which is additive to that afforded by hypothermia alone. In addition, procaine cardioplegia results in postarrest functional recovery which is similar to that seen with potassium cardioplegia.

An oxygenated perfluorocarbon solution containing 25 mEq/L potassium has been investigated as a potentially useful cardioplegic solution to be administered to patients undergoing prolonged induced global myocardial ischemia during open-heart surgical procedures. Experimental studies have demonstrated that, compared to simply crystalloid and cold-blood cardioplegic solutions, an oxygenated perfluorocarbon cardioplegic solution administered at low temperatures can deliver oxygen to the ischemic heart and that this available oxygen is utilized by the heart. In an experimental study in which a Fluosol-43 solution was compared to both crystalloid and oxygenated-blood cardioplegia, Fluosol-43-treated hearts demonstrated better recovery of left ventricular function following postischemic reperfusion.

To ascertain the immediate effects of coronary artery bypass grafting on regional myocardial function, intraoperative transesophageal two-dimensional echocardiograms were obtained in 20 patients using a 3.5 MHz phased array transducer at the tip of a flexible gastroscope. Cross-sectional images of the left ventricle were obtained at multiple levels before skin incision and were repeated serially before and immediately after cardiopulmonary bypass. Using a computer-aided contouring system, percent systolic wall thickening was determined for eight anatomic segments in each patient at similar loading conditions (four each at mitral and papillary muscle levels). Of the 152 segments analyzed, systolic wall thickening improved from a prerevascularization mean value (+/- SEM) of 42.7 +/- 2.9% to a postrevascularization mean value of 51.6 +/- 2.6% (p less than 0.001). Thickening improved most in those segments with the worst preoperative function (p less than 0.001). Chest wall echocardiograms obtained 8.4 +/- 2.3 days after operation showed no deterioration or further improvement in segmental motion compared with transesophageal echocardiograms obtained after revascularization. Thus: regional myocardial function frequently improves immediately after bypass grafting, with increases in regional thickening being most marked in those segments demonstrating the most severe preoperative dysfunction, and this improvement appears to be sustained; and in some patients, chronic subclinical ischemic dysfunction is present which can be improved by revascularization.

To assess the potential benefit of pulsatile perfusion inthe hypertrophied heart during fibrillation, 10 dogs with left ventricular hypertrophy, produced by previous supravalvular aortic banding, were used to compare linear and pulsatile perfusion in the fibrillating heart during total cardiopulmonary bypass. The mass spectrometer was used to measure subendocardial PCO2 and PO2 (PmCO2 and PmO2), and radioactive microspheres were utilized to measure myocardial blood flow in the same layers. Pulsatile perfusion was established using the recently develop "bubble tubing," which produces a pulse pressure of at least 20 mm Hg and can be used in a standard roller-pump apparatus. Both linear and pulsatile flows were compared at mean aortic root pressures of 80 and 50 mm Hg, and these four combinations of aortic root pressure and type of flow were employed for periods of 30 minutes each. Myocardial ischemia developed during linear coronary perfusion at 50 mm Hg, as evidenced by an elevation of PmCO2. Ischemia was not evident during pulsatile perfusion at the same mean pressure. Reversal ischemia was a result of increased myocardial blood flow and pulsatile perfusion, and this increase was shown to occur maximally in the deeper subendocardial layer. Ischemia was not eviden during linear or pulsatile perfusion at an mean perfusion pressure 80 mm Hg. Thus, if lower perfusion pressures are to be tolerated in patients with left ventricular hypertrophy, pulsatile perfusion with the bubble tubing technique may prevent the development of subendocardial ischemia or infarction.

Myocardial carbon dioxide tension and intramyocardial S-T segment voltage have previously been shown to provide useful quantitative indexes of the severity of regional myocardial ischemia. This study was designed to determine if (1) changes in intramyocardial S-T segment voltage and myocardial gas tensions, with the addition of atrial pacing, could be used to assess the functional significance of a coronary stenosis, and (2) if changes in S-T voltage recorded in intramyocardial electrodes proved a more sensitive indicator of ischemia than changes recorded in epicardial electrodes. In 12 open chest dogs, a variable constrictor and an electromagnetic flow probe were placed on the proximal left circumflex coronary artery. Myocardial carbon dioxide and oxygen tensions were recorded with mass spectrometry and unipolar intramyocardial S-T segment voltage with multicontact plunge electrodes. Intramyocardial S-T voltage and myocardial carbon dioxide tension showed parallel increases with atrial pacing in the presence of subcritical, critical and supercritical coronary stenoses. In the presence of a critical stenosis, S-T segment changes recorded in deepr myocardial layers were of greater magnitude than those recorded near the epicardial surface. These findings suggest that the severity of myocardial ischemia can be assessed by measuring intramyocardial S-T voltage or myocardial gas tensions at resting and paced heart rates. They also suggest that intramyocardial S-T voltage is a more sensitive indicator of the severity of pacing-induced myocardial ischemia than epicardial S-T changes. Application of this technique to patients undergoing coronary revascularization could allow intraoperative determination of the functional significance of questionable angiographic lesions and a more rational approach to the assignment of priorities to individual arteries when multiple bypasses are being considered.

Fifteen patients receiving propranolol preoperatively and undergoing coronary artery bypass grafting had serum propranolol levels determined preoperatively and at several times early postoperatively. In addition, the patients' hemodynamic parameters and postoperative sodium nitroprusside dose requirements were monitored. All patients had significant multivessel disease and normal left ventricular function. Preoperative serum propranolol levels ranged from 16 to 243 ng/ml, with a mean level of 92 +/- 17 ng/ml; propranolol measured at the end of bypass ranged from 0 to 92 ng/ml, with a mean level of 23 +/- 7 ng/ml. Fourteen patients (93%) had hypertension postoperatively and required intravenous sodium nitroprusside to maintain mean blood pressure at or below 90 mm Hg. According to linear regression analysis, the severity of the postoperative hypertension or, specifically, the nitroprusside dose requirements, correlated significantly with the patients' serum propranolol levels postoperatively (correlation coefficient, R = 0.76, with p less than 0.001). The one normotensive patient had no detectable serum propranolol at any time postoperatively. No correlation was noted between the patient's preoperative serum propranolol levels and the need for nitroprusside therapy postoperatively. These results demonstrate that there is a significant relationship between residual propranolol and the development of hypertension postoperatively.

We used phosphorus-31 nuclear magnetic resonance to test the ability of a perfluorocarbon blood substitute that has been shown in previous studies to improve oxygen delivery to hypothermic myocardium to maintain aerobic high-energy phosphate metabolism during total global ischemia. Twenty-three isolated perfused rabbit hearts were subjected to 180 min of hypothermic (23 degrees C) global ischemia followed by 45 min of normothermic reperfusion. Hearts received multiple doses of a cardioplegic solution that contained either oxygenated perfluorocarbon (Fluosol O2), nonoxygenated perfluorocarbon (Fluosol N2), or standard crystalloid hyperkalemic cardioplegic solution (STD-KCl) at 30 min intervals. Recovery of isovolumic left ventricular developed pressure (LVDP) was used to assess preservation of contractile function. Recovery of LVDP was 84 +/- 19% of preischemic control values with Fluosol O2, 68 +/- 16% with Fluosol N2, and 67 +/- 17% with STD-KCl (p = .058 vs Fluosol N2 and p = .056 vs STD-KCl). During 3 hr of ischemia intracellular pH (pHi) fell to 6.68 +/- 0.20 with STD-KCl and to 6.71 +/- 0.14 with Fluosol N2 but remained above 7.00 throughout the ischemic period with Fluosol O2 (p less than .0001 vs Fluosol N2 or STD-KCl). Myocardial ATP content was better preserved at 107 +/- 14% of control values with Fluosol O2 compared to 60 +/- 18% of control with Fluosol N2 and 75 +/- 21% of control with STD-KCl (p less than .001 vs Fluosol N2, p = .002 vs STD-KCl). Phosphocreatine (PCr) was also better preserved with Fluosol O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorus-31 nuclear magnetic resonance (31P NMR) can estimate tissue intracellular pH as well as the content of high-energy phosphate metabolites in isolated perfused hearts. We used 31P NMR to examine mechanisms associated with the recovery of ventricular function in hearts subjected to global ischemia and reperfusion, with special emphasis on intracellular pH, a previously unreported variable. Single-dose and multiple-dose administration of a hyperkalemic cardioplegic solution were compared with hypothermia alone in 18 isolated perfused rabbit hearts. Hearts in group 1 were subjected to 24 degrees C hypothermia during 60 minutes of global ischemia; group 2 hearts received a single injection of 37-mM KCL cardioplegic solution at 10 degrees C at the onset of ischemia; and group 3 hearts received a similar initial cardioplegic injection followed by two subsequent 24 degrees C injections at 20-minute intervals during the ischemic period. Using an intraventricular balloon, maximal dP/dt provided a quantitative index of left ventricular performance before and after ischemia. Return of ventricular function expressed as a percentage of control was 54 +/- 11% for group 1, 84 +/- 6% for group 2, and 101 +/- 18% for group 3. Differences in the rate of development of intracellular acidosis were noted during the 60-minute ischemic period. Intracellular pH fell to 6.09 +/- 0.12 in group 1, 6.31 +/- 0.09 in group 2, an 6.79 +/- 0.03 in group 3. In all three groups intracellular pH returned to control (pH 7.20) within 10 minutes of reflow. The metabolic correlates of functional recovery appeared to be the tissue content of ATP at the end of ischemia and after reflow. ATP content at the end of ischemia was 22 +/- 2% of control in group 1 hearts, 31 +/- 4% in group 2 and 64 +/- 2% in group 3. After 45 minutes of reperfusion, ATP levels recovered to 33 +/- 9% of control in group 1, to 71 +/- 9% in group 2 and to 86 +/- 6% in group 3. Although there were no differences between groups in the content of creatine phosphate after 60 minutes of ischemia, the rates of creatine phosphate decline were dissimilar. Further, during the early reflow period, a marked overshoot in tissue creatine phosphate was detected, especially in groups 1 and 2. Histologic damage assessed by light microscopy correlated with the metabolic data, confirming that multidose cardioplegia provided the best preservation of cellular morphology. These results demonstrate that the magnitude of intracellular acidosis and the associated increase in inorganic phosphate correlate inversely with recovery of postischemic ventricular structure and function. ATP, but not creatine phosphate, content correlates with return of contractile performance after reperfusion. The overshoot in creatine phosphate during early reperfusion might impede optimal restoration of ATP content and, as a result, optimal recovery of cell functions.

Reperfusion of ischemic myocardium has been postulated to result in a specific oxygen radical-mediated component of tissue injury. In a previous study we demonstrated improved recovery of ventricular function and metabolism when the superoxide radical scavenger superoxide dismutase was administered at the time of postischemic reflow. Studies in vitro, have suggested that superoxide toxicity might be mediated via the generation of more reactive hydroxyl radicals in an iron-catalyzed reaction. The present study was designed to test the hypothesis that myocardial reperfusion injury might be reduced by administration of the iron chelator deferoxamine at the time of reflow, most likely by preventing hydroxyl radical formation. Sixteen isolated Langendorff rabbit hearts, perfused within the bore of a superconducting magnet, were subjected to 30 min of normothermic (37 degrees C) total global ischemia followed by 45 min of reperfusion. At reflow eight treated hearts received a 10 ml bolus containing 50 mumol of deferoxamine followed by an infusion of 11 mumol/min for the first 15 min of reflow. The hearts were then perfused with standard perfusate for an additional 30 min. Eight untreated control hearts received a similar bolus of perfusate followed by 45 min of standard reperfusion. Serial 5 min 31P nuclear magnetic resonance spectra were recorded. Myocardial phosphocreatine (PCr) content fell to 5% to 7% of control during ischemia in both groups of hearts. Deferoxamine-treated hearts recovered 99 +/- 10% of control PCr content, while untreated hearts recovered 60 +/- 16% (p less than .05). Intracellular pH fell to 5.9 during ischemia in both groups, before showing more rapid and complete recovery in treated hearts (p less than .01). Recovery of developed pressure reached 70 +/- 6% of control in treated hearts compared with 35 +/- 10% in untreated hearts (p less than .05). Iron content of the perfusate was 7 microM, and by electron paramagnetic resonance spectroscopy was in the form of Fe3+-EDTA complexes. In the effluent of treated hearts iron was in the form of Fe3+-deferoxamine chelates. In summary, administration of the iron chelator deferoxamine at the time of postischemic reflow results in greater recovery of myocardial function and energy metabolism, which supports the hypothesis that iron plays an important role in the pathogenesis of reperfusion injury.

Several lines of evidence point to a major role of oxygen free radicals in the pathogenesis of cell death or dysfunction in a variety of disease processes. Recent studies from this as well as other laboratories have demonstrated that oxygen free radicals play a major role in the pathogenesis of post-ischemic reperfusion injury in the heart. We have recently developed methods for direct measurement of radical species and/or specific byproducts of radical injury. Timely administration of oxygen radical scavengers reduced the quantity of free radicals generated following reperfusion and in addition improved recovery of post-ischemic ventricular function and metabolism. In a regionally ischemic model the free radical scavenger recombinant human superoxide dismutase also administered at the time of reflow was shown to limit infarct size. In this article we review the biophysical and molecular mechanisms of oxygen free radical generation that are viewed as contributing to post-ischemic reperfusion injury. We also discuss the mechanisms by which the body defends against free radical attack and the interrelationships of free radical injury to other mechanisms of tissue injury.

An oxygenated perfluorocarbon cardioplegic solution was examined, utilizing a blood-perfused canine model. Twenty-one animals were divided into three equal groups, and each animal received Fluosol cardioplegia at one of three infusion temperatures: 20 degrees C, or 4 degrees C. All hearts underwent 90 minutes of ischemia, during which time 150 ml of the cardioplegic solution was infused every 30 minutes. Myocardial oxygen and carbon dioxide tensions (PmO2 and PmCO2) were monitored continually using mass spectrometry, and myocardial oxygen consumption was calculated with each cardioplegic injection. The mean increase in PmO2 was 7.1 +/- 0.9 mm Hg with 20 degrees C Fluosol infusions, 31.1 +/- 4.7 mm Hg with 10 degrees C Fluosol injections, and 22.2 +/- 4.7 mm Hg with infusions of 4 degrees C Fluosol. Average myocardial oxygen consumptioN, expressed as cubic centimeters of oxygen per 100 gm of left ventricle (wet weight), was 21.2 +/- 0.5 with 20 degrees C Fluosol, 22.8 +/- 1.3 for 10 degrees C Fluosol, and 19.6 +/- 1.0 for 4 degrees C Fluosol. Mean myocardial temperatures with infusions of 20 degrees C, 10 degrees C, and 4 degrees C solutions were 21.4 +/- 0.1 degree C, 16.9 +/- 0.4 degree C, and 15.9 +/- 0.5 degree C, respectively. After 45 minutes of reperfusion, maximum rate of rise of left ventricular pressure, expressed as percentage of preischemic control, was 70.9 +/- 3.9% for 20 degrees C Fluosol, 90.9 +/- 3.2% for 10 degrees C Fluosol, and 90.4 +/- 2.3% for 4 degrees C Fluosol (p less than 0.005, 20 degrees C versus 10 degrees C, 4 degrees C Fluosol). In addition, the 10 degrees C and 4 degrees C Fluosol hearts had essentially normal structure by light and electron microscopy. These data demonstrate tht Fluosol cardioplegia results in near optimal myocardial protection when infused at cold temperatures (4 degrees C to 10 degree C). The increases intramyocardial oxygen and myocardial oxygen consumption with each injection demonstrate that there is enhanced oxygen delivery and utilization, which may account for the improved functional recovery observed in these hearts.