Predictors of long-term outcomes in patients with hypertrophic cardiomyopathy undergoing cardiopulmonary stress testing and echocardiography

Background Patients with hypertrophic cardiomyopathy (HCM) have exercise intolerance due to left ventricular outflow tract (LVOT) obstruction, mitral regurgitation, and left ventricular dysfunction. We sought to study predictors of outcomes in HCM patients undergoing cardiopulmonary stress testing (CPT). Methods We studied 1,005 HCM patients (50 ± 14 years, 64% men, 77% on β-blockers) who underwent CPT with echocardiography. Clinical, echocardiographic, and exercise variables (peak oxygen consumption [VO₂] and heart rate recovery [HRR] at first minute postexercise) were recorded. End point was a composite of death, appropriate defibrillator discharges, resuscitated sudden death, stroke, and heart failure admission. Results Mean left ventricular ejection fraction (LVEF), postexercise LVOT gradient, and peak VO₂ were 62% ± 6%, 92 ± 51 mm Hg, and 21 ± 6 mL kg^-1 min^-1, respectively. Despite 789 patients (78%) being in New York Heart Association classes I to II, only 8% achieved >100% age-gender predicted peak VO₂, whereas 77% and 15% achieved 50% to 100% and <50%, respectively. Left ventricular outflow tract gradient ≥30 mm Hg was observed in 83% patients, whereas 23% had abnormal HRR. More than 5.5 ± 4 years, there were 94 (9%) events; 511 (50%) patients underwent surgery for LVOT obstruction. Multivariable Cox proportional analysis demonstrated % age-gender predicted peak VO₂ (hazard ratio [HR] 0.96 [0.93-0.98]), normal vs abnormal HRR (HR 0.48 [0.32-0.73]), higher LVEF (HR 0.96 [0.93-0.98]), surgery (0.53 [0.33-0.83]), and atrial fibrillation (HR 1.65 [1.04-2.60]) were associated with outcomes (all P <.05). Conclusions In HCM patients undergoing CPT, a higher % of achieved age-gender predicted VO₂ and surgical relief of LVOT obstruction were associated with better outcomes, whereas abnormal HRR, atrial fibrillation, and lower LVEF were associated with worse outcomes.