[Clinical implications of diffuse slow washout of thallium-201 in exercise stress myocardial SPECT]

Clinical implications of diffuse slow washout of thallium-201 (DSWO) in exercise-redistribution myocardial SPECT were studied. Thallium-201 washout rate was calculated by Bull's-eye method. DSWO was defined as having abnormal thallium-201 washout rate (less than 30% per 3 hours) in more than two thirds of each coronary artery (CA) area. OF 974 patients whose exercise heart rate exceeded 120/min, 51 (5.2%) showed DSWO and coronary angiography was performed in 43. Twenty-three patients (53%) showed triple vessel disease (3VD), 8 (19%) showed single or double vessel disease (1VD/2VD) and 12 (28%) showed normal CA. Patients with normal CA consisted of 6 patients with hypertrophic cardiomyopathy (HCM), 5 with hypertension (HT) and one with electrocardiographic abnormality only. The causes of DSWO were assessed from the history of effort angina (EA) and congestive heart failure (CHF), delayed fill-in of the perfusion defect and the ratio of lung to heart thallium-201 activity (L/M) at exercise as an indicator of the left ventricular (LV) function. High prevalence of EA (74%), high incidence of scintigraphic delayed fill-in (83%) and normal L/M suggested diffuse LV ischemia as the cause of DSWO in 3VD. On the other hand in patients with 1VD/2VD, LV dysfunction at exercise was considered as the cause of DSWO because of low prevalence of EA (13%) and scintigraphic delayed fill-in (13%) (p less than 0.01, p less than 0.005 each vs 3VD), and high L/M (p less than 0.001 vs 3VD) and high prevalence of CHF (38%, NS).(ABSTRACT TRUNCATED AT 250 WORDS)