Predictors of Atrial Fibrillation in Hypertrophic Cardiomyopathy

Nov 29, 2021
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Authors:
Kramer CM, DiMarco JP, Kolm P, et al.
Citation:
Predictors of Major Atrial Fibrillation Endpoints in the National Heart, Lung, and Blood Institute HCMR. JACC Clin Electrophysiol 2021;7:1376-1386.
Summary By:
Supriya Shore, MD

Quick Takes

  • Among 2,631 hypertrophic cardiomyopathy (HCM) patients, predictors of major, clinically relevant atrial fibrillation (AF) events included age, BMI, history of arrhythmia, echo-derived moderate or severe mitral regurgitation, and MRI-derived LA volume and LA mechanical function.
  • Obesity was a predictor for major AF events in younger patients; LA volume and LA mechanical function were predictors in middle-aged and older HCM patients.
  • Female sex, sarcomeric mutations, LVOT gradient, and prior history of AF were not predictors of major AF events.

Study Questions:

What are predictors of major clinically important atrial fibrillation (AF) in patients with hypertrophic cardiomyopathy (HCM)?

Methods:

This study included patients with HCM enrolled across 44 sites in six countries from the HCM Registry (HCMR). Data were collected from clinical questionnaires, cardiac magnetic resonance imaging (MRI), biomarkers, and genetic analyses. Patients with persistent or permanent AF at study entry were excluded, as they were clinically stable. Major AF endpoints were defined as AF needing electrical cardioversion or ablation, needing hospitalization >24 hours, or clinical decision to accept permanent AF in patients previously in sinus rhythm. Atrial flutter was considered equivalent to AF. Stroke or thromboembolic events were not included as they could not always be attributed to AF.

Results:

The study included 2,631 HCM patients with a mean follow-up of 33.5 ± 12.4 months. There were 127 major AF endpoints in 96 patients and 24 deaths. The final prediction model for time to first AF event included age, BMI, history of arrhythmia, cardiac MRI-derived index, left atrial volume (LAV), LA contractile percent, and echo-derived moderate or severe mitral regurgitation (MR). Model discrimination was high with excellent calibration for predicting first and multiple AF events. Age had a significant interaction with several other predictors including BMI, LAV, and LA contractile percent. Higher BMI was a predictor for younger patients and higher LAV, and lower LA contractile percent were predictors for middle-aged and older patients. Female sex, prior history of AF, left ventricular outflow tract (LVOT) gradients, and sarcomeric mutations were not identified as predictors of AF.

Conclusions:

In a large cohort of HCM patients, predictors of time to major AF endpoints (i.e., needing cardioversion/ablation/hospitalization or new permanent AF) included age, high BMI, history of arrhythmia, moderate or severe MR, increased LAV, and reduced LA mechanical function.

Perspective:

AF is commonly encountered in HCM patients and associated with worse outcomes. While several prior studies have assessed predictors of incident AF, the current study assessed predictors of clinically significant AF—defined as AF needing cardioversion, ablation, or hospitalization or a new diagnosis of permanent AF. The study also used data collected from cardiac MRIs to capture alterations in cardiac structure and function as predictors. Important takeaways include the prominent role age plays as a predictor for major AF events in HCM patients—not only was age a significant predictor in itself, effect of several other predictive variables were age-dependent. Among other variables identified as predictors, only obesity can be modified and increasing data support benefit of exercise in HCM patients. While reducing LAV, improving LA function, and decreasing MR may help in reducing major AF in HCM patients, studies addressing such interventions need to be conducted.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Valvular Heart Disease, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Magnetic Resonance Imaging, Mitral Regurgitation

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Atrial Flutter, Biomarkers, Body Mass Index, Calibration, Cardiomyopathy, Hypertrophic, Catheter Ablation, Electric Countershock, Heart Failure, Magnetic Resonance Imaging, Middle Aged, Mitral Valve Insufficiency, Mutation, Obesity, Primary Prevention, Stroke


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