Parasympathetic dysfunction in hypertrophic cardiomyopathy assessed by heart rate variability: comparison between short‐term and 24‐h measurements

In this study, we evaluate cardiac autonomic function in hypertrophic cardiomyopathy (HCM) by assessing heart rate variability (HRV), comparing a short‐term laboratory method with an ambulatory (24‐h) method, in patients with and without beta‐blockade. Reduced HRV is a risk factor for adverse events in some cardiac diseases, but is not a proven risk indicator in HCM. Analysis of HRV has been based on either short‐ or long‐term electrocardiographic recordings and previous studies in HCM have shown conflicting results. There is no consensus on which method to prefer, and we evaluate, for the first time, both short‐ and long‐term analyses in patients with HCM. Long‐ and short‐term HRV analyses were performed in 43 patients with HCM. They were divided in two groups, 22 patients on beta‐blockade and 21 non‐treated patients. As controls, 121 healthy subjects were used. Young patients without beta‐blockade showed a reduction in HRV parameters reflecting parasympathetic function, both in the short‐ and long‐term registrations, which was attenuated by beta‐blockade. Parasympathetic autonomic regulation was found to be impaired in young patients with HCM. This may be of clinical relevance as abnormal autonomic function might be a substrate for malignant dysrhythmias. The impairment was attenuated by beta‐blockade, which might indicate a clinically useful effect. We also show that short‐ and long‐term methods yield similar results, suggesting that a short‐term registration might be sufficient to assess HRV in patients with HCM.