Evaluating exercise challenge to validate cardiac autonomic dysfunction in lean PCOS phenotype

Background Polycystic ovary syndrome (PCOS) is frequently associated with infertility, obesity, hypertension, and diabetes mellitus. Cardiac autonomic dysfunction is well documented in long-term patients of PCOS, with impairment being proportionate to disease duration. However, there is paucity of literature on cardiac autonomic tone in the "lean" phenotype of PCOS. We used exercise challenge to probe for autonomic dysfunction, as assessed by heart rate variability (HRV), an index of cardiac autonomic tone. Methods Our study population consisted of 27 newly diagnosed PCOS patients and 25 healthy females matched by age and body mass index. Short-term HRV was assessed using time and frequency domain indices. Moderate, isotonic exercise was used as an interventional tool. Indices of both groups were compared in three bins - at baseline, immediate, and late postexercise stages. Results The groups had comparable HRV indices at baseline. However, low-frequency (LF) power was significantly reduced in PCOS patients during immediate and late postexercise phases when compared with controls (p = 0.03 and 0.03, respectively). Time domain indices also exhibited a fall postexercise, although not statistically significant. Conclusions Although "lean" phenotype PCOS patients had comparable HRV parameters as controls at baseline, the administration of exercise challenge led to reduced sympathetic drive, evident by reduced LF power in patient group. This may be due to latent autonomic dysfunction in "lean" PCOS, which is unmasked on exposure to exercise challenge. We propose that the evaluation of HRV response to exercise may serve as a sensitive screening tool to detect early cardiovascular dysfunction in newly diagnosed lean PCOS patients.