Prediction of sudden death risk in obstructive hypertrophic cardiomyopathy: Potential for refinement of current criteria

Background: In patients with hypertrophic cardiomyopathy (HCM), the use of an implantable cardioverter defibrillator (ICD) can prevent sudden cardiac death (SCD). In patients with obstructive HCM, we sought to determine the prognostic utility of European Society of Cardiology (ESC) SCD risk score and to evaluate whether additional factors modulate SCD risk. Methods: We studied 1809 consecutive patients with obstructive HCM (mean age, 50 ± 14 years; 63% males; mean maximal outflow tract gradient, 93 ± 40 mm Hg). Major SCD risk factors were recorded (0, 1, or ≥2) and % 5-year ESC SCD risk score was calculated. The need for surgical myectomy and a composite endpoint (SCD and/or appropriate ICD discharge) were recorded. Results: The distribution of major SCD risk factors was 0 in 65% of the patients, 1 in 26%, and ≥2 in 8%. The 5-year ESC risk was low (<4%) in 65% of the patients, intermediate (4%-6%) in 18%, and high (>6%) in 17%. Surgery was performed in 1160 patients (64%), and 361 (20%) had AF. At a mean of 8.8 ± 4 years, 169 patients had a composite event (154 SCDs). At 5 years, despite a wide range of expected events (2.5%-9%), the observed events ranged from 4.6% to 5% across 3 SCD risk categories (Hosmer–Lemeshow P =.32). On multivariable competing-risk analysis, myectomy (subdistribution hazard ratio [sHR], 0.69; 95% confidence interval [CI], 0.47-0.83) was associated with lower risk of longer-term composite events (P <.01), whereas ESC SCD risk score was not (sHR, 1.31; 95% CI, 0.75-2.25; P =.36). Conclusions: In patients with obstructive HCM, despite a wide range of expected 5-year primary event rate, the observed primary events were similar across the 3 ESC SCD risk categories, with myectomy mitigating SCD risk. In patients with obstructive HCM, SCD risk may need to be refined for patients following myectomy.