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 ± I 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.