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The objective of this study was to develop an assay system that allows continuous monitoring of nitric oxide (NO) released from crystalloid perfused hearts. We utilized chemiluminescence reaction between NO and luminol-H(2)O(2) to quantify the NO level in coronary effluent. Isolated rat hearts were subjected to ordinary Langendorff's perfusion, and the right ventricle was cannulated to sample coronary effluent. After equilibration, the coronary flow rate was set constant and the hearts were paced at 300 bpm. Coronary effluent was continuously sampled and mixed with the chemiluminescent probe containing 0.018 mmol/l luminol plus 10 mmol/l H(2)O(2). Chemiluminescence from the mixture of coronary effluent and the probe was continuously measured. NO concentration was calibrated by various concentrations (0.5-400 pmol/l) of standard NO solution. The lower detection limit of NO was 1 pmol/l. Basal NO release from isolated perfused rat heart was 0.41 +/- 0.17 pmol/min/g of heart weight, and that was significantly suppressed by 0.1 mmol/l of L-NAME to 0.18 +/- 0.10 pmol/min/g of heart weight (n = 7). Application of 0.1 and 0.3 micromol/l acetylcholine increased NO level in the coronary effluent, in a concentration-dependent manner, from 6.6 +/- 1.7 in a baseline condition to 16.3 +/- 7.4 and 30.3 +/- 16.1 pmol/l at each peak, respectively. Thrombin at 1 and 10 U/ml also increased NO level from 17.6 +/- 4.3 in control to 35.5 +/- 10.4 and 48.7 +/- 8.7 pmol/l at each peak, respectively (n = 7). Thus, this assay system is applicable to the continuous real-time measurement of NO released from crystalloid perfused hearts, and it may be useful for the study of physiological or pathophysiological role of NO in coronary circulation.

Into 25 patients with heart disorders, 99mTc-tetrofosmin 555-740 MBq was injected intravenously at rest. After 40 minutes, ECG-gated myocardial perfusion SPECT was performed with a two detector gamma camera VERTEX (ADAC), setting up two detectors to form a 90-degree angle. Sixteen frames per R-R interval were acquired during a 180 degree rotation from the RAO 45 degrees to the LPO 45 degrees. A pair of data sets with standard (SDA) and rapid data acquisition (RDA) protocols was collected. In an SDA protocol, SPECT imaging was performed for 50 sec per step in 5 degree angular steps (total acquisition time; 15 minutes). An RDA protocol was conducted with 12 sec per step, 6 degree angular steps (acquisition time, 3 minutes). LVEF (%) and LVEDV (ml) quantitated automatically with a QGS program showed excellent correlations between two protocols with correlation coefficients of 0.980 (p < 0.01) and 0.983 (p < 0.01), respectively. Subsequently visual assessment of regional wall motion based on a four-point grading system was carried out with a 3-D cine LV display. High complete agreement was gained with 158 (90.3%) out of total 175 segments, so that assessment of the global and regional LV function with the RDA protocol demonstrated high reliability and feasibility.

Non-invasive assessment of ischemic heart disease requires information of both LV function and myocardial perfusion. Recently, ECG-gated myocardial SPECT with technetium-labeled radiopharma-ceuticals can provide both of them. Gated myocardial SPECT were performed in thirty-three patients with cardiac disease using a two-headed rotating gamma camera system (ADAC; VERTEX), 30-60 minutes after resting injection of 555-740 MBq of 99mTc-Tetrofosmin. Then, the SPECT data were used to determine the LV epi- and endocardial surface, and LV volume for measurement of LVEF was calculated automatically. This entire computational process required only 210 seconds per 16 frame study. Interobserver agreement of EF values obtained from gated SPECT was excellent (r = 0.996, n = 10, p < 0.01). LVEFs obtained from gated SPECT showed good correlation to those calculated from radionuclide ventriculography (MUGA) (r = 0.91, p < 0.01). In conclusion, this automatic method using gated myocardial SPECT data was considered to be useful for assessment of LV function with reproducibility.

ECG-gated dual-isotope acquisition protocol involving rest imaging with 201Tl and stress 99mTc-tetrofosmin (TF) SPECT was designed for the simultaneous assessment of rest/stress myocardial perfusion and rest ventricular systolic function. This study assessed the feasibility and diagnostic accuracy of this protocol. Forty-five patients underwent the dual-isotope SPECT protocol. Twenty minutes after resting injection of 111 MBq of 201Tl, 370 MBq of 99mTc-TF was administered at a peak exercise. The dual-isotope gated SPECT acquisition was performed 1 hour later. Then, the regional count increase rate (%WT) of 99mTc-TF from end-diastole end-systole was calculated using an automated method which was developed for quantification of regional wall thickening based on circumferential profile analysis in our laboratory. Myocardial perfusion and contractility analysis was carried out using 8 segments of left ventricle with comparison of coronary angiographical findings. The sensitivity and specificity for the detection of diseased coronary vessels (> = or 75% stenosis) were 76% and 94%, respectively. Infarcted regions showing reversible defect had significantly greater %WT as compared with those with fixed defects (63 seg; 12.7 +/- 6.1% vs. 36 seg; 8.9 +/- 7.2%, p < 0.01). In conclusion, this dual-isotope protocol has some advantages; i.e., shortening an examination time, having the exact registration of stress/rest perfusion, and simultaneous evaluation of resting regional wall thickening.

Although 99mTc-pyrophosphate (PYP) myocardial scintigraphy has so far been widely used for the diagnosis of right ventricular infarction, PYP accumulation disappears within one week or so. To evaluate the myocardial condition of the right ventricle alternatively, myocardial SPECT with 99mTc-MIBI was performed in 16 patients with acute inferior left ventricular infarction, and ECG-gated myocardial SPECT data acquisition was accompanied in 14 of 16 patients. Right ventricular perfusion defect was observed in 4 of 16 patients (RVI (+) group), and the remains were negative (RVI (-) group). Then, right ventricular count increase rate (RV %WT) of MIBI from end-diastole to end-systole was calculated using an automated method which was developed for quantification of wall thickening in our laboratory. The RV %WT was conceived to be an objective index representing right ventricular contractility. RVI (+) group (n = 3) as compared with RVI (-) group (n = 11) had significant lower RV %WT (26.7 +/- 3.2 vs. 49.6 +/- 14.2; p < 0.01). In conclusion, ECG-gated myocardial SPECT with MIBI was considered to be useful for assessment of myocardial perfusion and contractility of right ventricle.

Simultaneous dual-isotope SPECT with 99mTc-methoxy isobutyl isonitrile (MIBI) and 123I-beta-methyl iodophenyl-pentadecanoic acid (BMIPP) was performed in 25 patients with ischemic heart disease. ECG-gated myocardial SPECT was acquired following the injection of MIBI (555 MBq) and BMIPP (148 MBq). Both MIBI and BMIPP scans provided high-quality myocardial images. Then, myocardial count increase rate (%WT = ES-ED/ED x 100) was calculated as an index of left ventricular contraction using MIBI gated SPECT data. The %WT was well correlated with severity scores of both MIBI image (r = -0.70) and BMIPP image (r = -0.72). Thus, ECG-gated dual-isotope SPECT with MIBI and BMIPP was considered to be useful method for assessment of left ventricular contraction as well as myocardial perfusion and fatty acid metabolism.

Although 201TlCl myocardial scintigraphy has so far been widely used for the evaluation of the viability of the myocardial infarcted area, functional evaluation using low dose dobutamine (DOB) loaded echography also became recently available. We performed 99mTc-mIBI gated SPECT on eight cases of myocardial infarction at rest and low dose (4-6 micrograms/kg/min) DOB-loading and related data were collected. Next, we calculated myocardial count increase rate (% WT = ES-ED/ED x 100) with left ventricular contraction from end-diastolic (ED) and end-systolic (ES) pictures in short-axial image, and made a comparative examination of regional contractilities at rest and DOB-loading. DOB-loaded echography performed on the same cases at the same dose revealed 15 segments as infarcted area (WM (+)) presenting improvement in wall movement at loading and 5 segments as infarcted area (WM (-)) presenting no such improvement, and %WT at rest and loading were 29.1 +/- 6.2 and 33.2 +/- 2.4 for (WM (-)) and 26.8 +/- 9.8 and 40.0 +/- 12.3 for (WM (+)), indicating a significant increase (p < 0.05) at loading. Contractility analysis using MIBI gated SPECT in combined use of DOB-loading was considered as a useful method of examination in view of its reflectability in the evaluation of the wall movement in DOB-loaded echography and of its high quantitativity.

Restoration of blood flow to the ischemic myocardium prevents continuing cell necrosis, but reperfusion may cause irreversible damage to potentially salvable tissue, possibly through the generation of toxic reactive oxygen species. Intracellular calcium overload, secondary to membrane lipid peroxidation, has been proposed as a general pathogenic mechanism. However, using the photosensitisation of rose bengal to generate singlet oxygen and superoxide radicals, we demonstrate a direct effect of reactive oxygen species on the cardiac sarcoplasmic reticulum calcium-release channel. Exposure of heavy sarcoplasmic reticulum vesicles to reactive oxygen species in vitro resulted in the progressive loss of specific [3H]ryanodine binding and the degradation of high molecular weight proteins identified by polyacrylamide gel electrophoresis. The gating of single channels incorporated into artificial planar phospholipid bilayers was modified during the exposure to reactive oxygen species: an initial increase in open probability being followed by irreversible loss of channel function. Degradation by reactive oxygen species of specific proteins, such as the calcium-release channel, may contribute to in vivo reperfusion injury.

A burst of free oxygen radical production has been demonstrated during the early moments of reperfusion, coincident with the onset of reperfusion arrhythmias, which can be attenuated by antioxidants. We have investigated whether a sudden burst of oxidant stress, superimposed on that occurring during reperfusion, can exacerbate reperfusion arrhythmias. Rat hearts (n = 12/group) were subjected to 12 minutes of aerobic perfusion; during the last 2 minutes, rose bengal (1 mumol/l) was added to the perfusion fluid. Then, regional ischemia was induced, and rose bengal-free perfusion was restored. After 5 minutes of ischemia, reperfusion was initiated for 5 minutes, and during the first 30 seconds of reperfusion, hearts were uniformly illuminated (8,500 lux) with green light (530-590 nm). The photoactivation of rose bengal trapped in the tissue, producing singlet oxygen and superoxide, resulted in an exacerbation of reperfusion arrhythmias. Thus, 92% of hearts developed ventricular premature beats, 83% ventricular tachycardia, and 33% ventricular fibrillation. In contrast, hearts with regional ischemia and reperfusion in the absence of rose bengal and/or illumination did not develop ventricular fibrillation; only one heart exhibited ventricular tachycardia, and the incidence of ventricular premature beats was lower (42-50%). Furthermore, the burst of oxidant stress shortened the time to onset of ventricular premature beats from 21.7 +/- 5.6 to 9.9 +/- 2.1 seconds. Additional studies revealed that rose bengal photoactivation without reperfusion was less arrhythmogenic compared with the combination of reperfusion plus photoactivation. These results demonstrate that a sudden burst of oxidant stress during the early moments of reperfusion can exacerbate the vulnerability to reperfusion arrhythmias.

In order to evaluate the clinical significance of 201Tl lung uptake, 201Tl myocardial scintigraphy was performed in 675 cases with various cardiac diseases. The lung uptake ratio of 201Tl (L/T) was calculated by ratio of the total radioactivity of the unilateral lung to the injected dose of 201Tl in 69 cases. Using both 201Tl scintigraphy and cardiac pool scintigraphy with 99mTc-human serum albumin, images of 201Tl of the intravascular space and extravascular space were obtained in 14 cases. The image of 201Tl of the extravascular space was almost the same as the original 201Tl image as regards the pattern of 201Tl-distribution, and the lung uptake ratio of the former was 95.7 +/- 2.8% of that of the latter. The mean values of L/T of the right and left lung were 1.5 +/- 0.9%, 1.2 +/- 0.6% in the healthy lungs, 2.8 +/- 1.4% and 1.4 +/- 0.7% in heart diseases without left heart failure, and 4.4 +/- 1.8% and 2.6 +/- 1.2% in those with left heart failure, respectively. Increased lung uptake ratio of 201Tl, which was related to post-capillary pulmonary hypertension, prolonged pulmonary circulation time and findings of left heart failure, was observed more frequently in mitral valvular diseases (72.2%) and dilated cardiomyopathies (60.0%). Increased lung uptake of 201Tl was associated with normal or increased pulmonary perfusion in many cases or areas, but with pulmonary hypoperfusion in some cases with post-capillary pulmonary hypertension, in whom both increased lung uptake of 201Tl and pulmonary hypoperfusion were shown in the lower lung fields.(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to determine whether reactive oxygen intermediates (e.g., singlet oxygen and the superoxide radical) can rapidly induce electrophysiological disturbances leading to the genesis of arrhythmias, even in the absence of ischemia and reperfusion. Rat hearts (n = 6 per group) were perfused aerobically at 37 degrees C for 10 minutes without rose bengal and for 5 minutes with rose bengal (250 nmol/l), during which time no changes in coronary flow or heart rate were observed. Hearts were then uniformly illuminated for 20 minutes with green light (530-590 nm) from 200 fiber optic cables. With light and without rose bengal, or vice versa, all hearts remained stable. However, in the illuminated rose bengal group, electrophysiological changes (inversion of the terminal portion of the T wave and an increase in Q-T interval) were observed within 11.8 +/- 2.1 seconds (i.e., less than 60 beats). All hearts exhibited ventricular premature beats (within 2.2 +/- 0.7 minutes) and ventricular tachycardia (within 2.8 +/- 0.7 minutes) before the occurrence of complete atrioventricular block (within 5.5 +/- 0.9 minutes). During the illumination period, coronary flow progressively fell in the rose bengal-perfused hearts from 11.6 +/- 0.5 ml/min to 2.0 +/- 0.4 ml/min (p less than 0.05 when compared with any control group). When a similar progressive reduction in coronary flow was mimicked (with or without rose bengal), no arrhythmias occurred.(ABSTRACT TRUNCATED AT 250 WORDS)