The effects of fasting on heart rate variability in hypertensive patients.

Heart rate variability (HRV) is an independent indicator of increased mortality in patients with myocardial infarction and congestive heart failure. The effects of fasting on the HRV are not known in hypertensive patients. Therefore, studying the effects of Ramadan fasting on hypertensive patients' HRV seems reasonable to address. We conducted a prospective study including 20 hypertensive patients with sinus rhythm. HRV was determined twice by ambulatory 24-hour Holter recordings at fasting during and after Ramadan. Subjects mean age was 55 ± 11.8 years. Sex-ratio was 1.5. When two groups compared, statistically significant differences were found in terms of SDNN (113 ± 71 vs 140 ± 38, p = 0.001), SDANN (109.7 ± 45 vs 134.8 ± 48.3, p = 0.008), T power (2368.7 ± 121.3 vs 3660.5 ± 170.9, p = 0.03) and LF (552.2 ± 31.3 vs 903.7 ± 48.9, p < 0.0001) values. HRV parameters were found to be decreased in Ramadan. Thus, Ramadan fasting enhances the activity of the sympathetic system in hypertensive patients.