Positive Stress Electrocardiography in Patients With Non-obstructive Coronary Disease

Introduction The episodes of myocardial ischemia in patients with non-obstructive coronary disease are extremely variable in provoking factors and presentation. Purpose We investigated the significance of coronary blood flow velocity and epicardial diameter as correlates of a positive electrocardiographic exercise stress test (ExECG) in hospitalized patients with unstable angina and non-obstructive coronary artery disease. Methods The study was a single-center cohort retrospective. ExECG was performed and analyzed in a group of 79 patients with non-obstructive coronary disease (coronary stenoses < 50%). Thirty-one percent of the patients (n=25) were diagnosed with slow coronary flow phenomenon, SCFP; 40.5% (n=32) - patients with hypertensive disease, left ventricular hypertrophy (LVH), and slow epicardial flow; 27.8% (n=22) with hypertension, left ventricular hypertrophy and normal coronary flow. The patients were hospitalized in University Hospital "Alexandrovska," Sofia in the period 2006-2008. Results The frequency of positive ExECG is increased as a trend was associated with smaller epicardial diameters and pronounced delay in epicardial coronary flow. In the subgroup with SCFP, the risk for a positive ExECG test was determined by slower coronary flow (36.5±7.7 frames vs. 30.3±4.4 frames, p=0.044) and borderline significant by epicardial lumen diameters (3.3±0.8 mm vs. 4.1±1.0 mm, p=0.051) and greater myocardial mass (92.8±12.6 g/m² vs. 82.9±8.6 g/m², p=0.054). In cases of left ventricular hypertrophy, which included both patients with the normal and slow epicardial flow, there were no statistically significant correlates of an abnormal exercise stress ECG test. Conclusions In patients with non-obstructive coronary atherosclerosis and predominantly slow epicardial coronary flow, the provoking of ischemia at an electrocardiographic exercise stress test is associated with the lower epicardial flow velocity at rest and with the smaller epicardial diameter. In SCFP, the risk for an abnormal stress test is determined by slower coronary flow, smaller epicardial lumen diameter, and greater myocardial mass. The presence and size of the plaque burden are not associated with a greater risk of a positive ExECG in these patients.