PROGNOSTIC VALUE OF VASODILATOR MYOCARDIAL PERFUSION IMAGING IN PATIENTS WITH LEFT-BUNDLE-BRANCH BLOCK

Background-The prognostic value of tomographic myocardial perfusion im aging with dipyridamole or adenosine in patients with left bundle-bran ch block has not been established. Methods and Results-The study group consisted of 245 patients with left bundle-branch block who underwent tomographic (single photon emission tomography) myocardial perfusion imaging with thallium-201 (n=173) or technetium-99m sestamibi (n=72) a nd either dipyridamole (n=153) or adenosine (n=92) stress. Patients we re prospectively classified into two groups. Patients were classified as ''high risk'' if they had (1) a large severe fixed defect (n=28), ( 2) a large reversible defect (n=36), or (3) cardiac enlargement and ei ther increased pulmonary uptake (thallium) or a decreased resting ejec tion fraction (sestamibi) (n=20). The remaining 161 patients (66% of t he study group) were at ''low risk.'' Follow-up was 99% complete at 3 +/- 1.4 years. Three-year overall survival was 57% in the high-risk gr oup compared with 87% in the low-risk group (P<.0001). Survival free o f cardiac death/nonfatal myocardial infarction/cardiac transplantation was 55% in the high-risk group and 93% in the low-risk group (P<.0001 ). The presence of a high-risk scan had significant incremental progno stic value after adjustment for age, sex, diabetes, and previous myoca rdial infarction (P<.0001). Patients with a low-risk scan had an overa ll survival that was not significantly different from that of a US age -matched population (P=.86). Conclusions-Tomographic myocardial perfus ion imaging with adenosine or dipyridamole stress provides important p rognostic information in patients with left bundle-branch block, which is incremental to clinical assessment.