Association of Histologic Findings With Long-Term Outcomes in Symptomatic Obstructive Hypertrophic Cardiomyopathy Patients Undergoing Surgical Myectomy.

Background: In hypertrophic cardiomyopathy, histologic findings like myocyte hypertrophy and disarray, interstitial fibrosis (IF), and small intramural coronary artery dysplasia (SICAD) result in left ventricular hypertrophy, diastolic dysfunction, arrhythmogenicity, and microvascular ischemia.

Objectives: The authors sought to evaluate the association between histology and outcomes in obstructive hypertrophic cardiomyopathy (oHCM) patients undergoing surgical myectomy (SM).

Methods: The study included 1,722 symptomatic oHCM patients (mean age: 56 ± 14 years; 948 [55%] men) who underwent SM at a tertiary center between 2005 and 2018. The SM specimen was analyzed for presence and severity of: 1) myocyte hypertrophy; 2) myocyte disarray; 3) IF; and 4) SICAD. Histologic findings were graded as 0-3 (none, mild, moderate, and severe) and a score from 0-12 was calculated. Primary endpoint was a composite of death, appropriate defibrillator discharge, or cardiac transplantation during follow-up.

Results: Moderate and severe histologic findings were distributed as follows: myocyte hypertrophy (1,341 [78%]); disarray (237 [14%]); IF (448 [26%]); and SICAD (258 [15%]). The mean total histologic score was 5.1 ± 1.4. At 5.1 ± 5.2 years, there were 352 (20%) primary events (317 [18%] deaths). On spline analysis, a total histology score of >5 was associated with primary events. On Kaplan-Meier analysis, patients with a histology score >5 had greater events vs those with a score ≤5 (147/598 [25%] vs 205/1124 [18%]; log-rank P value = 0.002). On multivariable Cox analysis, total histology score >5 (HR: 1.24 [95% CI: 1.03-1.54]; P = 0.03) was independently associated with higher primary events.

Conclusions: In symptomatic oHCM patients undergoing SM, a higher histologic score was independently associated with long-term outcomes.