Heart Rate Variability Is Associated with Exercise Capacity in Patients with Cardiac Syndrome X

• Published in: PloS one Vol. 11; no. 1; p. e0144935
• Main Authors: Lu, Dai-Yin, Yang, Albert C., Cheng, Hao-Min, Lu, Tse-Min, Yu, Wen-Chung, Chen, Chen-Huan, Sung, Shih-Hsien
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.01.2016; Public Library of Science (PLoS)
• Subjects: Acute coronary syndrome; Adults; Age; Aged; Algorithms; Angina pectoris; Autonomic nervous system; Biology and Life Sciences; Body mass; Body mass index; Body size; Cardiac arrhythmia; Cardiac patients; Cardiology; Cardiovascular disease; Care and treatment; Clinical medicine; Complications and side effects; Diagnosis; Exercise; Exercise - physiology; Family medical history; Female; Fitness equipment; Fitness training programs; Health education; Heart diseases; Heart failure; Heart rate; Heart Rate - physiology; Hospitals; Humans; Ischemia; Logistic Models; Low frequencies; Male; Measurement; Medical prognosis; Medicine; Medicine and Health Sciences; Microvascular Angina - physiopathology; Middle Aged; Patients; Physical fitness; Physical training; Physiological aspects; Physiology; Population studies; Prospective Studies; Public health; Research and Analysis Methods; Review boards; Sinuses; Spectrum analysis; Subpopulations; Variability; Very Low Frequencies; Taiwan; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0144935

Heart rate variability (HRV) reflects the healthiness of autonomic nervous system, which is associated with exercise capacity. We therefore investigated whether HRV could predict the exercise capacity in the adults with cardiac syndrome X (CSX). A total of 238 subjects (57±12 years, 67.8% men), who were diagnosed as CSX by the positive exercise stress test and nearly normal coronary angiogram were enrolled. Power spectrum from the 24-hour recording of heart rate was analyzed in frequency domain using total power (TP) and spectral components of the very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges. Among the study population, 129 subjects with impaired exercise capacity during the treadmill test had significantly lower HRV indices than those with preserved exercise capacity (≥90% of the age predicted maximal heart rate). After accounting for age, sex, and baseline SBP and heart rate, VLF (odds ratio per 1SD and 95% CI: 2.02, 1.19-3.42), LF (1.67, 1.10-2.55), and TP (1.82, 1.17-2.83) remained significantly associated with preserved exercise capacity. In addition, increased HRV indices were also associated with increased exercise duration, rate-pressure product, and heart rate recovery, independent of age, body mass index, and baseline SBP and heart rate. In subgroup analysis, HRV indices demonstrated similar predictive values related to exercise capacity across various subpopulations, especially in the young. In patients with CSX, HRV was independently associated with exercise capacity, especially in young subjects. The healthiness of autonomic nervous system may have a role in modulating the exercise capacity in patients with CSX.