Increased myocardial energy expenditure in cardiac syndrome X: More work, more pain

Objective: The aim of this study was to assess the myocardial energy expenditure (MEE) in patients with cardiac syndrome X (CSX) and to examine its association with exercise electrocardiogram (ECG) parameters. Methods: A total of 99 patients who underwent coronary angiography and who were diagnosed as having normal coronary arteries were included. The patients were divided into 2 groups based on symptoms and exercise ECG parameters: 56 CSX patients and 43 control patients with a negative stress test. MEE was calculated using transthoracic echocardiography-derived parameters: circumferential end-systolic stress, left ventricular ejection time, and stroke volume. Results: In patients with CSX, the MEE at rest was 28% higher in than the control group (89.2+-36.3 vs. 69.8+-17.2 cal/minute). Correlation analysis revealed a moderately negative correlation between MEE and the Duke treadmill score (DTS) (β: -0.456; p