Abstract P188: “False Positive” Stress Testing: Does Endothelial Vascular Dysfunction Explain ST-Segment Depression in the Absence of Clinical Coronary Artery Disease in Women?

Abstract

Background: Current guidelines do not endorse exercise electrocardiography (Ex-ECG) screening in asymptomatic adults due to poor diagnostic accuracy for clinical coronary artery disease (CAD), however Ex-ECG combined with other variables paradoxically has strong prognostic accuracy for cardiovascular mortality. Ex-ECG ST segment depression “false positive” results are common in women, who have higher rates of vascular dysfunction such as Raynaud’s and migraines compared to men. We hypothesized that ST segment depression indicates endothelial vascular dysfunction, which is known to predict an adverse prognosis. To test this hypothesis, we evaluated the relationship between Ex-ECG and peripheral endothelial vascular function in asymptomatic women. Methods: Asymptomatic women with no cardiac risk factors and normal resting ECG underwent maximal Bruce protocol Ex-ECG testing (GE Healthcare). Computer-generated Ex-ECG ST segment values were independently verified by 2 cardiologists. Based on established methods, endothelial vascular function was assessed by calculating reactive hyperemia index (RHI) using peripheral vascular testing (Endopat, Itamar). As established previously, RHI <1.68 is abnormal and indicates endothelial vascular dysfunction. Results: Among 35 women, mean age 54±8 years and BMI 24±4, there were 5 (14%) women with abnormal RHI. Women with abnormal RHI had a greater (more abnormal) ST/HR slope, a trend toward greater peak ST depression, and achieved lower METs than women with normal RHI (Table 1). Conclusion: Among asymptomatic women, endothelial vascular dysfunction was associated with abnormal Ex-ECG results characterized by greater ST/HR slope, greater ST depression, and lower exercise capacity. These findings suggest that “false positive” ST-segment depression in the absence of clinical CAD in women may be explained by endothelial vascular dysfunction. Our study further suggests that endothelial vascular dysfunction may explain the Ex-ECG diagnostic/prognostic paradox.