Usefulness of ST segment depression limited to the recovery phase of exercise stress test.

Abstract

To determine the diagnostic value of ST segment depression limited to recovery phase of Exercise Tolerance Test (ETT). An observational cross-sectional study. The study was carried out at Punjab Institute of Cardiology, Lahore, from March to August 2007 for a period of 6 months. In this study, 100 patients were selected with purposive non-probability sampling technique and were divided into two groups, group A having ST segment depression during exercise phase of ETT, and group B having ST segment depression only in recovery phase after undergoing ETT according to Bruce protocol. The patients were subjected to coronary angiography later on. The chi-square or Fischer's exact test of significance was applied at 0.05 level of significance to compare the coronary angiographic finding between two groups. Diagnostic value of ST segment depression was computed keeping angiographic finding as Gold standard. There were no major differences between the two groups regarding angiographic finding. Significant coronary artery stenosis (> 50% narrowing) was found in 68 (93%) patients of group A and 23 (85%) patients of group B (p=0.18). Three vessel disease was found in 30 (41%) patients in group A and 7 (26%) patients in group B (p=0.08). Left main stem disease was found in 5 (6.8%) patients of group A and 1 (3.7%) patient of group B. Normal coronaries were found in 6% of patients among group A and 14% of patients among group B (p=0.12). Specificity, sensitivity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of ST segment depression in recovery phase was 55, 25, 85 and 6 percent respectively (95% CI; 1.16 - 2.25). In patients undergoing exercise stress test, ST segment depression occurring only in recovery phase of ETT has a diagnostic value largely comparable with that of ST segment depression induced during exercise phase of ETT. Thus careful evaluation of ST segment depression occurring only in recovery phase may add significantly to the clinical information derived from the results of ETT.