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

Abstract

The myocardial washout rate of thallium-201 was studied in 85 subjects with a <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 ° and 85 ° 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 < 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 < 0.05 vs group I), 31 ± 13% in group IIB (p ± 0.05 vs group I) and 54 ± 11% in group III (p < 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. The mean washout rate in group IIA was not significantly different from that in group IIB. The lower washout rates with dipyridamole than with exercise indicate that normal limits of thallium-201 washout rate, specific for this test, are required for clinical purposes. Administration of aminophylline does not appear to affect the washout rate of thallium-201 after dipyridamole infusion.