False positive ST-segment depression during exercise in subjects with short PR segment and angiographically normal coronaries: correlation with exercise-induced ST depression in subjects with normal PR and normal coronaries.

The aim of this study was to investigate exercise-induced ST-segment depression in subjects with a 120-ms or shorter PR segment and normal coronary arteries. A population of 86 individuals who demonstrated ST-segment depression of 1.5 mm or more on treadmill testing and had a subsequent normal coronary arteriography was classified into two groups. Group A (n = 71) comprised those with a normal PR interval on baseline electrocardiogram 160.9 +/- 14.8 ms (mean +/- 1 SD), and group B (n = 15) comprised those with a 120-ms or shorter PR interval 113 +/- 8.8 ms (mean +/- 1 SD). All subjects had undergone a symptom-limited treadmill test by the standard Bruce protocol (mainly for evaluation of chest pain or angina-like pain), during which they demonstrated ST depression of 1.5 mm or more in either lead II, lead V2, or lead V5. All had normal or near normal coronary arteries on angiography. In the subjects with short PR segments and angiographically normal coronaries, a trend of greater ST-segment depression during treadmill testing as compared with control subjects was observed in lead V5. In the same group, ST-segment depression at the 9th minute of exercise was more prevalent in lead V5 than in lead II or V2.