Mitsuo Kashida

Right ventricular filling detected by pulsed Doppler echocardiography during the convalescent stage of inferior wall acute myocardial infarction

To evaluate right ventricular (RV) diastolic function in patients with inferior wall acute myocardial infarction (AMI), flow velocity patterns of the RV inflow tract were studied in patients with anterior AMI (n = 32), inferior AMI (n = 32) and angina pectoris without left ventricular asynergy (n = 10) using pulsed Doppler echocardiography. Doppler examinations were performed at least 4 weeks after the attack. Twenty-seven healthy persons served as control subjects. Three Doppler variables were measured at the RV inflow tract: the ratio of the late diastolic peak flow velocity due to atrial contraction to the rapid filling peak flow velocity in early diastole (A/E) and the acceleration time and deceleration time of the RV rapid filling wave. A/E in patients with inferior AMI (1.01 +/- 0.24, mean +/- standard deviation) was significantly greater than in those with anterior AMI (0.80 +/- 0.16, p less than 0.001) and angina pectoris (0.79 +/- 0.17, p less than 0.01) and in normal subjects (0.70 +/- 0.17, p less than 0.001). A/E in patients with inferior AMI correlated with the ratio of left ventricular to RV end-diastolic pressure (r = -0.60, p less than 0.05). A/E in inferior AMI with relatively high RV end-diastolic pressure (more than 8 mm Hg, n = 8) was significantly greater than that in those with normal pressure (8 mm Hg or less, n = 9). A/E in patients with proximal right coronary artery occlusion was significantly greater than that in those with distal occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

11C-Methionine PET of Acute Myocardial Infarction

Tissue uptake of l-[methyl-11C]-methionine (11C-methionine) has been used to monitor amino acid metabolism and protein synthesis. We examined whether 11C-methionine was retained in areas of myocardial infarction after successful reperfusion. Methods: Nine patients with infarction in the left anterior descendent region underwent percutaneous transluminal coronary artery intervention within 24 h and 201Tl SPECT, 18F-FDG PET, and 11C-methionine PET within 2 wk of infarction onset. The standardized uptake values of the infarcted area and of the normal area were measured. Results: The 11C-methionine images showed increased uptake in the infarcted area, whereas the 201Tl SPECT and 18F-FDG PET images showed decreased uptake. The highest accumulation of 11C-methionine in the infarcted area was observed during the early phase of AMI. Conclusion: 11C-methionine uptake is elevated in infarcted areas and may reflect the early acute phase of damage healing, that is, the initial process of remodeling.

Functional role of coronary collaterals with exercise in infarct-related myocardium

We evaluated the regional myocardial blood flow in collateral dependent infarct-related areas to examine the functional role of coronary collaterals. Regional myocardial blood flow was measured by positron emission tomography with 13N-ammonia at rest and during low-grade exercise (bicycle ergometer fixed at 25 W for 6.5 min). The study was performed in 24 subjects, consisting of 19 patients with prior myocardial infarction, and five normal individuals. Regional myocardial blood flow was calculated using the radioactivity in myocardial tissue measured by positron emission tomography and the radioactivity in arterial blood. Concerning the infarct related area, the exercise caused myocardial blood flow to decrease by 18.4% (P < 0.01) in the collateral-dependent areas (n = 8) of angiographically positive collaterals, and to increase by 14.4% (P = not significant) in the areas (n = 10) of negative collaterals. Four patients in whom the myocardial blood flow in all walls, including the normal areas, decreased with exercise were excluded from this evaluation. Myocardial blood flow in collateral-dependent infarct-related areas appeared to decrease transiently by low-grade exercise. Our results suggest that collaterals increase the incidence of exercise-induced ischemia, but may protect the infarct related but viable myocardium from necrosis.

Myocardial reperfusion can be predicted by myoglobin/creatine kinase ratio of a single blood sample obtained at the time of admission

To evaluate noninvasive markers for determining the reperfusion status without coronary angiography (CAG) or serial blood sampling in patients with acute myocardial infarction (AMI), two markers were examined: (1) serum myoglobin (Mb) level and (2) serum myoglobin/creatine kinase ratio (Mb/CK). Before emergency CAG a blood sample was drawn from 72 AMI patients within 6 hours after the onset of AMI. CAG revealed thrombolysis in myocardial infarction grades (TIMI) 0 to 1 in 56 and TIMI 2 to 3 in 16 patients (spontaneous reperfusion). No patients had received thrombolytic therapy before admission. TIMI 0 to 1 patients were characterized with lower Mb levels than TIMI 2 to 3 patients at admission (346 +/- 476 vs 1558 +/- 2005, mean +/- SD, p < 0.001). Furthermore, the mean Mb0/CK0 ratio in TIMI 2 to 3 patients, who had already achieved the reperfusion at admission, was significantly higher than that in patients with TIMI 0 to 1 patients (6.5 +/- 3.9 vs 2.1 +/- 1.8, mean +/- SD, p < 0.0001). When Mb0/CK0 > 5.0 was assumed to indicate the sufficient reperfusion at admission, the sensitivity, specificity, and accuracy evaluating the reperfusion status were 75%, 96%, and 92%, respectively. It can be concluded that the reperfusion status can be predicted satisfactorily by a single blood sample obtained at the time of admission without CAG.