Thallium-201 uptake in variant angina: probable demonstration of myocardial reactive hyperemia in man.

Abstract

SUMMARY Myocardial thallium scintigraphy was performed in four subjects with variant angina and in one subject with isolated, fixed coronary obstruction. Three subjects with variant angina had short episodes of ischemic ST-segment elevation that lasted seconds. Thallium scintigrams demonstrated excess uptake in regions judged to be ischemic by angiographic and electrocardiographic criteria. Two subjects, one with variant angina and the other with a fixed coronary lesion, had prolonged episodes of ischemia that lasted 390-900 seconds. Both had reduced thallium uptake in the ischemic regions. We conclude that myocardial reactive hyperemia is the cause of excess thallium uptake in patients with variant angina who have short episodes of myocardial ischemia.MYOCARDIAL reactive hyperemia occurs after transient coronary occlusion.' The hyperemic response produces a considerable increase in flow in the normal coronary bed after release of an occlusion. However, with severe coronary stenosis, vasodilatory reserve is exhausted and reactive hyperemia is abolished. Myocardial thallium-201 (201TI) uptake is related to myocardial blood flow,5' 6 and in canine studies, regional myocardial thallium uptake is high when the isotope is injected in the hyperemic state.69Patients with variant angina have episodes of transient myocardial ischemia due to transient coronary artery occlusion.'0'" The cause of these occlusions is uncertain,'2-14 but it seemed likely that these patients might demonstrate reactive hyperemia on 201TI scintigrams. However, previous studies have revealed perfusion defects rather than excess uptake.1'69 We suspected that the timing of the 20'Tl injection and the duration of the ischemia might affect the pattern of uptake. Accordingly, we examined myocardial perfusion in patients with variant angina, studying the time of injection and the length of the ischemic period. sion at this site. There were only minimal irregularities of the other coronary arteries, and none demonstrated spontaneous vasomotion. Ergonovine was not given. Continuous two-channel electrocardiographic recording was begun using an ICR recorder for simultaneous evaluation of an anterior and an inferior lead. For this patient and the others, 20'Tl images were collected using an Ohio Nuclear Series 120 mobile scintillation camera, a high-resolution collimator, the 80-keV 20'Tl photopeak, a 25% window, and 300,000 counts per image, recorded on Polaroid film. Collection of the initial image of this patient was begun 91/2 minutes after injection and was completed 20 minutes after the onset of pain. The image demonstrated high 20'Tl uptake in the interventricular septum compared with the posterior wall, instead of the expected septal perfusion defect ( fig. 2). Serial images showed a trend toward equalizing uptake in the septum and posterior wall.With calcium-antagonist therapy, the patient became asymptomatic and was discharged. One month later, he discontinued his medications and suffered an acute anterior myocardial infarction. A repeat 201Tl sc...

Clinical usefulness of myocardial scintigraphy in patients with vasospastic angina

“…Myocardial Tl uptake is related to myocardial blood flow and exercise-Tl and pharmacologic stress-Tl scintigraphy is widely used to diagnose the presence of coronary artery disease [10,11]. Tl myocardial scintigraphy can also noninvasively detect the regional perfusion abnormality due to coronary spasm [12][13][14]. Myocardial scintigraphy is more useful to detect some ischemic findings than just exercise test.…”