Heart rate variability as a predictive factor for coronary artery disease

Background and Objective: Heart rate variability (HRV) is the amount of heart rate fluctuations around the mean heart rate and can be used as a mirror of the cardiorespiratory control system. It is a valuable tool to investigate the sympathetic and parasympathetic functions of the autonomic nervous system. This variation during respiration is called respiratory sinus arrhythmia (RSA). RSA reflects heart rate control system, especially a cardiac parasympathetic activity which can be evaluated by some proper tests such as standing test. Researches show HRV alters among patients with coronary artery diseases (CAD). Materials and Methods: In this study, we intended to calculate amount of HRV in patients with chest pain before diagnostic exercise stress test (EST) and to compare the obtained results with EST results. 66 (19 women and 47 men) with chest pain. Volunteers and unknown CAD referred for EST with a mean age of 50 years were participated in this study. Each volunteer underwent deep breathing (6 breaths/minute) and standing up tests prior to EST for HRV measurements. Results: There was less variation in heart rate during both deep breathing and standing up tests in patients with positive result of EST than in patients with negative result of EST. Conclusion: Our study suggests that HRV is depressed in individuals who have unknown coronary artery disease with an immediate positive EST result.