심근허혈의 지표로서 운동부하 심전도에서 PR 절 경사의 의의 = The Significance of PR Segment Slope in the Evaluation of Exercise - induced RT Depression as an Indicator of Myocardial Ischemia

다국어 초록 (Multilingual Abstract)

Objectives: It was postulated that exaggerated atrial repolarization waves seen during exercise may extend from the PR segment into the ST segment and T wave, and thus can produce ST segment depressions mimicking myocardial ischemia. The aim of this study is to investigate whether or not there is any association between P-R segment slope and ST segment depression in exercise ECG for predicting accuracy of myocardial ischemia. Method: The treadmill exercise test was performed using the modified Bruce Protocol (Korea University Hospital Protocol) in 62 patients with chest pain. The P wave amplitude, PR segment slope and duration, the ST segment duration, and the J point depression were studied in Lead II and V5 in 39 patients whose exercise ECG suggested myocardial ischemia. The PR segment slope was determined by measuring the velocity of descent in mm/sec. Coronary arteriography was performed in all patients, and≥50% stenosis in a major cornary artery was considered a significant lesion. Results: The overall sensitivity and specificity of the exercise test in 62 patients was 74% and 43%, respectively. The exercise test results in 10 patients were deemed false positive because of normal coronary arteriograms and left ventricular function. The false positive group was characterized by more marked downsloping PR segments in Lead II at peak exercise (15.9±9.3 mm/ sec vs 4.8±5.6mm/sec, p<0.05) and more rapid peak exercise heart rates than those of the true positive group (151±26 vs 131±25, p<0.05). The sensitivity and specificity of exercise-induced ST depression for CAD were changed as following if positive exercise test with increased PR segment slope is considered as false positive test: 1) with PR segment is slope over 5mm/s: snsitivity 78%, specificity 39% 2) with PR segment slope over 10 mm/s: sensitivity 83%, specificity 45% 3) with PR segment slope over 15 mm/s: sensitivity 79%, specificity 46%. Conclusion: These findings suggest that markedly downsloping PR segment seen in otherwise positive exercise test by ST segment depression criteria is a sign predicting false positive exercise test.