P. Pezard et al., TL-201 MYOCARDIAL SCINTIGRAPHY AND LEFT-B UNDLE-BRANCH BLOCK - RELATIVE VALUES OF EXERCISE AND DIPYRIDAMOLE TESTING, Archives des maladies du coeur et des vaisseaux, 86(12), 1993, pp. 1693-1699
Stress Thallium 201 myocardial scintigraphy in patients with left bund
le branch block often shows reversible septal perfusion defects even i
n the absence of coronary artery disease. This phenomenon seems more c
ommon when the patients have tachycardia. With the working hypothesis
that dipyridamole stress testing, which does not greatly increase the
heart rate, would be more appropriate than exercise stress testing to
unmask coronary artery disease in this condition, the authors compared
the results of two Thallium 201 scintigraphies performed after exerci
se and then after dipyridamole under the same conditions three weeks l
ater, in 67 patients with complete left bundle branch block. Scintigra
phy showed one or more reversible perfusion defects in 64/67 patients
after exercise but only 32/67 patients after dipyridamole (p < 0.001).
There was poor uptake in the septal region in 59 patients (88 %) afte
r exercise and in 25 patients (37 %) after dipyridamole (p < 0.001). T
he specificity was evaluted in 23 patients estimated to have no corona
ry artery disease. If only unequi vocal perfusion defects were conside
red, the specificity after dipyridamole was higher than that after exe
rcise, increasing from : 35 % to 83 % for septal defects (p < 0.0 1);
65 % to 96 % for anterior wall defects (p < 0.05); 61 % to 87 % for in
ferior wall defects (p < 0.05); 57 % to 91 % for apical defects (p < 0
.01); 17 % to 83 % overall (p < 0.001). Lower values but with a compar
able difference were observed when all forms of hypofixation (even min
imal) were taken into account. The sensitivity of the two methods eval
uated in 14 coronary patients was equivalent (100 % after exercise 93
% after dipyridamole) and the two methods were equally valuable for pr
edicting the site of stenosis on the three main coronary arteries. The
authors conclude that in patients with complete left bundle branch bl
ock, dipyridamole stress testing would seem to be superior to exercise
stress testing when diagnostic Thallium 201 myocardial scintigraphy i
s performed. The sensitivity and specificity of scintigraphy is then c
omparable to the values observed in all other patients.