The Clinical Trajectory of NYHA Functional Class I Patients With Obstructive Hypertrophic Cardiomyopathy

Background: 

An improved understanding of the natural history in NYHA functional class I patients with obstructive hypertrophic cardiomyopathy (oHCM) is needed. 

Objectives: 

Using a multicenter registry (SHaRe [Sarcomeric Human Cardiomyopathy Registry]), this study described the natural history in patients with oHCM who were classified as NYHA functional class I at the initial visit compared with patients classified as NYHA functional class II and reported baseline characteristics associated with incident clinical events. Methods: Incident events assessed included a composite of NYHA functional class III to IV symptoms, left ventricular ejection fraction <50%, atrial fibrillation, stroke, ventricular arrhythmias, septal reduction therapy, ventricular assist device or transplantation, or death. Factors associated with incident events were determined using Kaplan-Meier, Cox proportional hazards, and restricted cubic spline models. 

Results: 

Of 7,964 patients with HCM in SHaRe, 1,239 patients with oHCM met inclusion criteria; 598 were in NYHA functional class I at the initial visit (age 48 ± 17 years; 31.1% female; peak gradient, 75 ± 40 mm Hg). At 5-year follow-up, the composite event rate of NYHA functional class I patients was 28% compared with 44% (P < 0.001) in 641 NYHA functional class II patients with oHCM (age 54 ± 16 years; 46.5% female; peak gradient, 83 ± 39 mm Hg). Left atrial (LA) diameter ≥45 mm (HR: 1.56 [95% CI: 1.14-2.12]; P = 0.005), female sex (HR: 1.61 [95% CI: 1.16-2.24]; P = 0.003), and older age (HR: 1.21 per 10 years [95% CI: 1.09-1.34]; P < 0.001), but not the magnitude of left ventricular outflow tract obstruction, were associated with a higher risk of the composite outcome in NYHA functional class I patients.

Conclusions: 

Although NYHA functional class I patients with oHCM fared better than NYHA functional class II patients, more than one-fourth experienced adverse events over 5-year follow-up, especially if they were older, female, and/or had LA enlargement. Strategies to reduce the rate of clinical outcomes in NYHA functional class I patients warrant further study.