Positron emission tomography demonstrates that coronary sinus retroperfusion can restore regional myocardial perfusion and preserve metabolism.

Positron emission tomography was used to image blood flow and metabolic tracers in risk zone myocardium after left anterior descending coronary artery occlusion during synchronized coronary venous retroperfusion. Six control and seven intervention open chest dogs had occlusion of the mid left anterior descending coronary artery. Synchronized retroperfusion commenced 25 min later. Flow tracers (rubidium-82 and nitrogen-13 ammonia) were injected retrogradely. Three hours after coronary occlusion, fluorine-18 (F-18) deoxyglucose uptake in the control and treatment groups was compared. At 200 min of occlusion, infarct size was assessed. Retrograde flow tracer uptake was observed in the risk zone in the seven intervention dogs. Fluorine-18 deoxyglucose uptake in the risk zone was increased in five of the six intervention dogs but was reduced in five of the six control dogs. The risk zone to normal zone F-18 deoxyglucose count ratio was higher in the intervention than the control group (1.13 +/- 0.39 vs. 0.59 +/- 0.51; p less than 0.05). The endocardial subsegment risk zone to normal zone F-18 deoxyglucose count ratio was also significantly higher in the intervention group. Percent infarction in the risk zone was 70% lower in the group treated with synchronized retroperfusion than in the control group (18.4 +/- 22.6% vs. 61.2 +/- 25.4%; p less than 0.02). Thus, positron emission tomography revealed that retroperfusion could deliver oxygenated blood and maintain metabolism in risk zone myocardium. Infarct size was limited to 30% of that of control. In acute closure of the left anterior descending coronary artery, synchronized retroperfusion might be considered for maintaining viability of the jeopardized myocardium if the artery cannot be reopened rapidly.

Comparison of myocardial washout rate of thallium-201 between rest, dipyridamole with and without aminophylline, and exercise states in normal subjects.

The myocardial washout rate of thallium-201 was studied in 85 subjects with a less than 5% likelihood of coronary artery disease undergoing rest (group I, n = 12), dipyridamole (group II, n = 24) and exercise (group III, n = 49) stress thallium-201 scintigraphy. Subjects receiving dipyridamole were subdivided into group IIA (n = 11), who received an aminophylline injection 10 minutes after dipyridamole infusion, and group IIB (n = 13), who did not. The mean and highest washout rate values in each of 3 segments in the anterior, 45 degrees and 85 degrees left anterior oblique views were calculated. In group II the mean washout rate of thallium-201 was similar in all segments of each view and the overall mean washout rate did not differ between the 3 views studied. There was a good correlation between the mean and highest washout rate values in individual subjects (r = 0.98, p less than 0.001). The mean +/- standard deviation myocardial 4-hour washout rate of thallium-201 (anterior view) was 10 +/- 6% in group I compared with 40 +/- 14% in group IIA (p less than 0.05 vs group I), 31 +/- 13% in group IIB (p less than 0.05 vs group I) and 54 +/- 11% in group III (p less than 0.05 each vs group IIA and group IIB, respectively). There was a wide variation in mean washout rate values in group II (range 12 to 58%), and this variation was not altered by aminophylline administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic criteria to distinguish reversible from irreversible myocardial ischaemia.

This treatise reviews two-dimensional echocardiographic criteria which have been developed to describe and distinguish reversible vs irreversible myocardial ischaemia. It also discusses the new pathophysiologic concepts such as 'hibernating' and 'decapitated' myocardium, and also 'reperfusion injury' and 'stunned' myocardium, complications which may supervene following reperfusion of jeopardized ischaemic myocardium. Computerized regional and global wall-motion analysis is now usually measured from enhanced endocardial edges. Provocative interventions can contribute information regarding viability of jeopardized ischaemic regions by testing contractile response of the myocardium to afterload reducing agents such as nitroglycerine or nitroprusside. They can also validate viability by demonstrating that post-extrasystolic beats can still cause potentiation. Ultrasonic contrast washout half-life of the myocardium which is compromised by stenotic coronary arteries provides a promising method for supplying information about the coronary perfusion defects and flow reserve. The decrease in global or regional ejection fraction following exercise echocardiography may show if jeopardized ischaemic myocardium is irreversibly damaged. A new hypercontractility phenomenon is described following brief coronary occlusions such as during percutaneous transluminal angioplasty, or after sudden release of angiospasm, and this should be considered a sign of viability. Increase in end-diastolic wall thickness and echo amplitudes immediately after reperfusion of ischaemic segments is often associated with reversibly damaged myocardium.