Effects of medical therapy on outcome assessment using exercise thallium-201 single photon emission computed tomography imaging: evidence of a protective effect of beta-blocking antianginal medications.

Objectives: The purpose of this study was to determine whether antianginal medications modify the prognostic significance of exercise single photon emission computed tomography (SPECT) ischemia.
Background: Antianginal medications (especially beta-adrenergic blocking agents) limit exercise SPECT ischemia, but it is not known whether such medications also modify the prognostic effect of exercise SPECT ischemia.
Methods: We included 352 patients with coronary heart disease, who had exercise Tl-201 SPECT and coronary angiography, and who were initially treated medically. Survival Cox models were applied in patients for whom classes of antianginal medications taken at exercise SPECT were the same as those prescribed for follow-up (GI; n = 136), and in patients for whom new classes of antianginal medications, including beta-blockers (GII; n = 79) or not including beta-blockers (GIII; n = 113), were added for follow-up.
Results: During a mean 5.3+/-1.6 years of follow-up, 45 patients had cardiac death or myocardial infarction. Variables reflecting necrosis (irreversible defect extent, left ventricular ejection fraction) and those from coronary angiography provided equivalent prognostic information in the three groups. In contrast, the SPECT variable reflecting ischemia (reversible defect extent), which provided comparable prognostic information in GI (p = 0.005) and GIII (p = 0.004), lost its prognostic significance (p = 0.54) in GII, and was associated with a lower relative risk in GII than in GI or GIII (both p < 0.05).
Conclusions: In patients with coronary heart disease, the introduction of antianginal medications, when including beta-blockers, appears to have a favorable effect on the deleterious prognostic effect of exercise ischemia.