Exercise in hypertrophic cardiomyopathy is associated with sympatho-adrenal imbalance

Hypertrophic cardiomyopathy (HCM) is a genetic disease of the sarcomeric contractile proteins that is characterized by left ventricular hypertrophy and myocyte disarray. The majority of patients are limited in terms of functional capacity and a minority die suddenly. Pathogenesis of HCM has been associated with abnormalities of the sympathetic nerve-adrenergic receptor system. Epinephrine and norepinephrine are two of the catecholamines involved with the maintenance of the adrenergic system. There is limited data investigating the measurement of these catecholamines in HCM during cardiopulmonary exercise stress testing. We investigated our hypothesis that patients with HCM have an abnormal catecholamine response to exercise compared with controls. Thirteen patients with non obstructive HCM were compared with six matched controls. All participants underwent symptom limited cardiopulmonary exercise stress testing with measurement of norepinephrine and epinephrine levels performed at rest and peak exercise. All participants achieved anaerobic threshold and all stopped due to dyspnoea or fatigue. Due to the small numbers involved, non-parametric statistical testing was used. There was no significant statistical difference between the two groups for age, exercise time, max heart rate achieved, peak VO2 achieved or peak exercise norepinephrine level. Patients with HCM had a statistically significant lower level of epinephrine at peak exercise (p=0.022) in addition to an elevated ratio for the rate of change of