Hypertrophic cardiomyopathy (HCM) is an inherited cardiomyopathy that affects 1 in 500 adults worldwide, with up to 50% of patients have device-detected atrial fibrillation (AF). In patients with HCM, loss of atrial kicking with new-onset AF at high left ventricular end diastolic pressure results in reduced ventricular filling, which affects cardiac output. These patients eventually progress to heart failure, which is associated with worsening symptoms and decreased quality of life.

Previous studies have shown that catheter ablation for AF in patients with HCM is safe but less effective than in patients without HCM. Many AF patients required repeat ablation and post-procedure anti-arrhythmic drug (AAD) therapy to maintain sinus rhythm. However, if the procedure for AF is successful, heart failure symptoms are significantly improved. Theories have been proposed to explain these findings, including the non-pulmonary vein foci, cellular-level alterations in myocardial proteins, mitral regurgitation, progressive atrial dilatation, and atrial scar in patients with HCM.

Data regarding symptom improvement after successful catheter ablation in patients with AF with HCM are lacking. Although the number of studies is small, symptom improvement after successful ablation is evident. The better filling of the less compliant left ventricle improved cardiac output. It can improve symptoms in HCM patients. However, this was only seen in patients whose AF did not recur after the procedure, and conversely, there was no improvement in symptoms in patients whose procedure failed. Therefore, strategy for successful ablation is important.

Successful ablation in patients with AF with HCM is challenging, but desirable outcomes can be achieved if sinus rhythm is maintained. The EAST-AFNET 4 trial supports early rhythm control with AAD therapy or ablation. Early rhythm control in HCM patients may be hopeful to prevent progressive atrial remodeling.

Figure 1. Mechanisms of developing atrial fibrillation in patients with hypertrophic cardiomyopathy.

LV: left ventricle, LVOT: left ventricular outflow tract