Exercise-induced silent myocardial ischemia in single vessel coronary artery disease associated with Q wave infarction. Assessment by thallium 201 single-photon emission computed tomography.

PURPOSE

To examine the relationship between the symptom of ischemia and the amount of abnormally perfused myocardium, coronary arteriography and exercise and redistribution thallium 201 single-photon emission computed tomography (SPECT) were analyzed.

MATERIALS AND METHODS

The study group consisted of 153 patients with single-vessel coronary artery disease; 53 patients had no pathologic Q waves (group 1) and 100 patients had pathologic Q waves consistent with the area supplied by the diseased vessel (group 2). Twenty normal subjects were used as control subjects. The apical, mid, and basal left ventricular levels of the short-axis view and apical portion of the long-axis view were divided into 20 segments, and segmental images were scored blindly on a 0 (normal) to 4 (severely reduced uptake) scale. The redistribution score was defined as the thallium 201 defect score of exercise subtracted from that of the redistribution image and was used as a measure of the amount of ischemic myocardium.

RESULTS

The redistribution score in 20 control subjects was 0.20 +/- 2.06, and the upper limit of normal redistribution score was defined as mean + 2 x SD (4.32). In group 1, 40 of 53 patients had a redistribution score above the normal range. In group 2, 34 of 100 patients had a redistribution score above the normal range. Of 40 patients in group 1, angina during exercise was observed in 22 patients (55 percent). Twenty-two patients who had angina had a redistribution score of 15.2 +/- 6.7, while those who did not have angina had a score of 13.7 +/- 5.2 (p = NS). Of 34 patients in group 2, angina was observed in 10 patients (29 percent) during exercise. Ten patients with angina had a redistribution score of 10.1 +/- 4.4, and those without angina had a score of 9.9 +/- 3.4 (p = NS).

CONCLUSION

Thus, the incidence of silent ischemia without the Q wave infarct zone was found to be higher than that within the ischemic zone without Q wave. Patients with silent and symptomatic ischemia during exercise have similar amounts of ischemic myocardium demonstrated by tomographic thallium 201 imaging; this was found in patients who had Q wave infarction and in those who did not.