Prognostic value of normal stress-only technetium-99m myocardial perfusion imaging protocol. Comparison with standard stress-rest protocol.

Background:  Patients with a normal stress image on technetium-99m (Tc-99m) single-photon emission computed tomography (SPECT) have a good prognosis for diagnosing coronary artery disease. However, current guidelines recommend stress and rest imaging to confirm that a stress image is normal.

Methods And Results:  We determined all-cause of cardiac events (acute coronary syndrome and sudden death) in 1,939 patients undergoing stress myocardial perfusion SPECT with Tc-99m radiotracers. Patients with an abnormal stress image were excluded, so we focused on 1,125 patients in whom the stress SPECT study was interpreted as normal. A stress-only protocol was used in 726 patients (adenosine=339; exercise=387), whereas 399 had both stress and rest imaging (adenosine=294; exercise=105). Mean follow-up was 1,252 days. At the end of follow-up, there were 39 cardiac events in the stress-only cohort and 19 in the stress-rest cohort. Kaplan-Meier analysis revealed that there were no differences for the entire cohort of cardiac events not only between the stress-only and stress-rest protocols but also for stressor modality, despite the fact that the stress-rest cohort showed higher coronary risk factors.

Conclusions:  Patients determined as having a normal SPECT on the basis of stress imaging alone have a similar cardiac event rate as those who have a normal SPECT on the basis of evaluation of both stress and rest images. This imaging strategy will significantly reduce radiation exposure in a substantial number of patients.