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Background— Low-pressure cardiac tamponade is a form of cardiac tamponade in which a comparatively low pericardial pressure results in cardiac compression because of low filling pressure. This syndrome is poorly characterized because only isolated cases have been reported. We conducted a study of its clinical and hemodynamic profiles. Methods and Results— From 1986 through 2004, we evaluated all patients at our institution with combined pericardiocentesis and cardiac catheterization. We identified those patients who fulfilled catheterization-based criteria of low-pressure cardiac tamponade and compared their clinical and catheterization data with those of patients with classic tamponade. A total of 1429 patients with pericarditis were evaluated, 279 of whom underwent combined pericardiocentesis and catheterization. Criteria of low-pressure cardiac tamponade were met in 29, whereas 114 had criteria of classic cardiac tamponade. Patients with low-pressure tamponade less frequently had clinical signs of tamponade, but the rate of constitutional symptoms, use of diuretics, and echocardiographic findings of tamponade were similar in both groups. Patients with low-pressure tamponade showed a significant increase in cardiac output after pericardiocentesis, but they usually had less severe cardiac tamponade compared with patients with classic tamponade. Prognosis was related mainly to the underlying disease. Conclusions— Low-pressure cardiac tamponade was identified in 20% of patients with catheterization-based criteria of tamponade. Clinical recognition may be difficult because of the absence of typical physical findings of tamponade in most patients. Although some patients are critically ill, most show a stable clinical condition. However, these patients obtain a clear benefit from pericardiocentesis.

Background— ST-segment elevation in lead aVR has been associated with severe coronary artery lesions in patients with acute coronary syndromes, but the prognostic significance of this finding is unknown. Methods and Results— We analyzed the initial ECG in 775 consecutive patients admitted to our center with a first acute myocardial infarction without ST-segment elevation in leads other than aVR or V 1 . The rates of in-hospital death in patients without (n=525) and with 0.05 to 0.1 mV (n=116) or ≥0.1 mV (n=134) of ST-segment elevation in lead aVR were 1.3%, 8.6%, and 19.4%, respectively ( P P Conclusions— Lead aVR contains important short-term prognostic information in patients with a first non–ST-segment elevation acute myocardial infarction. Because the poorer outcome predicted by ST-segment elevation in lead aVR seems to be related to a more severe coronary artery disease, an early invasive approach might be especially beneficial in patients presenting with this finding.

Background Myocardial ischemia increases tissue electrical resistivity leading to cell-to-cell uncoupling, and this effect is delayed by ischemic preconditioning in isolated myocardium. Alterations in myocardial resistivity elicited by ischemia in vivo may influence arrhythmogenesis and local ST-segment changes, but this is not well known. Methods and Results Myocardial impedance (resistivity [Ω · cm] and phase angle [°]), epicardial ST segment, and ventricular arrhythmias were analyzed during 4 hours of coronary artery occlusion in 11 anesthetized open-chest pigs; these were compared with 13 other pigs submitted to a similar coronary occlusion preceded by ischemic preconditioning. Myocardial resistivity rose slowly during the first 34±7 minutes of occlusion (237±41 to 359±59 Ω · cm), increased rapidly to 488±100 Ω · cm at 60 minutes, and reached a plateau value (718±266 Ω · cm, ANOVA; P P Conclusions A rapid impairment of myocardial impedance occurs after 30 minutes of coronary occlusion, and its onset is better defined by shift in phase angle than by rise in tissue resistivity. Phase 1b arrhythmias are associated with marked impedance changes, and both are delayed by preconditioning. Reversion of ST-segment elevation is partially associated with impairment of myocardial impedance, but other factors play a role as well.

Background— Aortic intramural hematoma (IMH) evolves very dynamically in the short-term to regression, dissection, or aortic rupture. The aim of the present study was to assess the long-term clinical and morphological evolution of medically treated IMH. Methods and Results— Fifty of 68 consecutive patients with aortic IMH monitored clinically and by imaging techniques at 3, 6, and 12 months and annually thereafter were prospectively studied. Mean follow-up was 45±31 months. In the first 6 months, total IMH regression was observed in 14 and progression to aortic dissection in 18 patients; in 14 of these, the dissection was localized, and 12 later developed pseudoaneurysm. At the end of follow-up, the IMH had regressed completely without dilatation in 17 patients (34%), progressed to classical dissection in 6 (12%), evolved to fusiform aneurysm in 11 (22%), evolved to saccular aneurysm in 4 (8%), and evolved to pseudoaneurysm in 12 (24%). Evolution to dissection was related to echolucency ( P P Conclusions— The most frequent long-term evolution of IMH is to aortic aneurysm or pseudoaneurysm. Complete regression without changes in aorta size is observed in one third of cases, and progression to classical dissection is less common. A normal aortic diameter in the acute phase is the best predictor of IMH regression without complications, and absence of echolucent areas and atherosclerotic ulcerated plaque are associated with evolution to aortic aneurysm.

Background —Previous natural history studies in broad populations of heart failure patients have associated female gender with improved survival, particularly in patients with a nonischemic etiology of ventricular dysfunction. This study investigates whether a similar survival advantage for women would be evident among patients with advanced heart failure. Methods and Results —The study analysis is based on the Flolan International Randomized Survival Trial (FIRST) study which enrolled 471 patients (359 men and 112 women) who had evidence of end-stage heart failure with marked symptoms (60% NYHA class IV) and severe left ventricular dysfunction (left ventricular ejection fraction 18±4.9%). A Cox proportional-hazards model, adjusted for age, gender, 6-minute walk, dobutamine use at randomization, mean pulmonary artery blood pressure, and treatment assignment, showed a significant association between female gender and better survival (relative risk of death for men versus women was 2.18, 95% CI 1.39 to 3.41; P P =0.275), among patients with a nonischemic etiology of heart failure, the relative risk of death for men versus women was 3.08 (95% CI 1.56 to 6.09, P =0.001), whereas among those with ischemic heart disease, the relative risk of death for men versus women was 1.64 (95% CI 0.87 to 3.09, P =0.127). Conclusions —Women with advanced heart failure appear to have better survival than men. Subgroup analysis suggests this finding is strongest among patients with a nonischemic etiology of heart failure.

Background The objective of this study was to test the hypothesis that chemical interaction through gap junctions may result in cell-to-cell progression of hypercontracture and that this phenomenon contributes to the final extent of reperfused infarcts. Methods and Results Cell-to-cell transmission of hypercontracture was studied in pairs of freshly isolated adult rat cardiomyocytes. Hypercontracture induced by microinjection of a solution containing 1 mmol/L Ca 2+ and 2% lucifer yellow (LY) was transmitted to the adjacent cell (11 of 11 pairs), and the gap junction uncoupler heptanol (2 mmol/L) prevented transmission in 6 of 8 pairs ( P =.003), with a perfect association between passage of the LY and transmission of hypercontracture. In the isolated, perfused rat heart submitted to 30 minutes of hypoxia, addition of heptanol to the perfusion media during the first 15 minutes of reoxygenation had a dose-related protective effect against the oxygen paradox, as demonstrated by a reduction of diastolic pressure and marked recovery of developed pressure ( P P P P P =.04), and modified infarct geometry with a characteristic fragmentation of the area of necrosis. Heptanol at 1 mmol/L had no significant effect on contractility of nonischemic myocardium. Conclusions These results demonstrate that hypercontracture may be transmitted to adjacent myocytes through gap junctions and that heptanol may interfere with this transmission and reduce the final extent of myocardial necrosis during reoxygenation or reperfusion. These findings are consistent with the hypothesis tested and open a new approach to limitation of infarct size by pharmacological control of gap junction conductance.

Echocardiographic characteristics of the interventricular septum (IVS) have been studied in eight patients with chronic constrictive pericarditis (CP). Values of septal thickening (ST) were clearly below normal in all cases. Interventricular septal systolic motion (IVSSM) was normal in four cases, hypokinetic in three and paradoxical in one. In seven out of the eight patients, an early interventricular septal diastolic motion (IVSDM) consisting of a sudden anterior displacement followed by a brisk posterior rebound was recorded. The beginning of this anomalous movement was coincident with the pericardial knock in the phonocardiogram and its peak was coincident with the simultaneously recorded deep "y" trough in the jugular pulse tracing. The tendency toward normality of IVSDM observed after pericardiectomy in six out of seven patients suggests that this peculiar interventricular septal systolic motion may be a frequent and probably specific echocardiographic finding in constrictive pericarditis.

Twenty-nine consecutive spontaneous attacks of paroxysmal supraventricular tachycardia (PSVT) in 14 infants (mean age 4.4 months) were treated with verapamil. No infant had associated heart disease. Verapamil 1-2 mg i.v was administered over 30 seconds. The dosage varied according to the weight of the infant. Within 60 seconds sinus rhythm was obtained in 28 instances (96.5%). No significant complications were observed. The high effectiveness, rapid action and lack of undesirable side effects observed in this series suggest that verapamil is the drug of choice in the treatment of PSVT in infants without underlying heart disease.

Incidence and significance of pericardial effusion in patients with acute myocardial infarction (AMI) have not been established. To evaluate these issues, we studied prospectively 138 consecutive patients with AMI. An echocardiogram was obtained in each 1, 3, and 10 days and 3 and 6 months after admission. Fifty four patients with unstable angina and 57 without heart disease were studied as controls. Echocardiographic diagnostic criteria of pericardial effusion were established from 33 additional patients undergoing surgery. Pericardial effusion was found in 28% of patients with AMI. Twenty-five percent of patients with AMI had pericardial effusion on the third day, vs 8% of patients with unstable angina (p less than .02) and 5% of patients without heart disease (p less than .01). At 1, 3, and 10 days and 3 and 6 months prevalence of pericardial effusion was 17%, 25%, 21%, 11%, and 8%, respectively. There was no case of tamponade. Pericardial effusion was more common in anterior AMI (p less than .02) and in patients with heart failure (p less than .05) but it was not significantly associated with early pericarditis, peak creatine kinase-MB, the level of anticoagulation, or mortality. Thus, pericardial effusion is a common event in patients with AMI (incidence of 28%), but does not result in specific complications. The reabsorption rate of pericardial effusion is slow and, in our experience, mild or moderate pericardial effusion does not preclude heparin therapy.

Two patients who had a huge pericardial effusion of at least 9 and 14 years' duration caused by cardiac toxoplasmosis are reported. Toxoplasma gondii were seen in the pericardial fluid, and serologic evidence also demonstrated the activity of the infection. These cases illustrate both the need to exclude toxoplasmosis in chronic pericardial effusion of unknown cause and the possibility of seeing toxoplasma in the pericardial fluid of patients with active toxoplasmic pericarditis. Moreover, in endemic areas, cardiac toxoplasmosis may not be an exceptional cause of chronic pericardial effusion.