Prognostic Significance of Ischemic Electrocardiographic Changes During Vasodilator Stress Testing in Patients with Normal SPECT Images

Background: Patients with ischemic electrocardiographic (ECG) findings during exercise stress testing but normal perfusion images generally have a low risk of cardiac death or myocardial infarction (<1% per year). During vasodilator stress testing, however, the prognostic significance of the combination of normal perfusion images and ischemic ECG changes is unknown.

Methods And Results: Among 5526 patients who underwent vasodilator stress single photon emission computed tomography (SPECT), 49 (0.9%) had normal images but ischemic ECG changes. A unique feature of this population was that 43 (88%) were women with a mean age of 67 +/- 10 years. Ischemic ECG changes occurred at a mean heart rate of 101 +/- 15 beats per minute and persisted for 6.8 +/- 4.7 minutes after termination of drug infusion. During follow-up of 28 +/- 20 months, cardiac death occurred in 2 patients and nonfatal myocardial infarction in 4 patients. The rate of cardiac death or nonfatal myocardial infarction was 4% at 1 year, 10% at 2 years, and 14% at 3 years. Of the 12 patients who underwent coronary angiography or autopsy during follow-up, 11 had multivessel coronary artery disease, indicating that these patients likely had false-negative SPECT image results. Eight patients required coronary revascularization.

Conclusions: The finding of ischemic ECG changes with normal SPECT images during vasodilator infusion is uncommon, occurs primarily in older women, and is associated with a higher subsequent cardiac event rate than is customarily associated with normal images.