Multimodality Imaging–Based Phenotyping and Prognostic Implications of Right Ventricular Involvement in Apical Hypertrophic Cardiomyopathy

BACKGROUND: Right ventricular (RV) involvement is a potential high-risk marker in hypertrophic cardiomyopathy (HCM); however, its prognostic relevance in apical HCM remains unclear. OBJECTIVES: This study aimed to evaluate the prognostic significance of RV involvement in apical HCM and the incremental value of imaging-based phenotyping. METHODS: We retrospectively analyzed 289 patients with apical HCM who underwent cardiovascular magnetic resonance and strain echocardiography. Patients were classified into 3 morphological subtypes-purely apical, mixed, and RV involvement. The primary outcome was a composite of cardiovascular (CV) events. RESULTS: In total, 117 patients (40.5%) had purely apical HCM, 102 (35.3%) had mixed apical HCM, and 70 (24.2%) had RV involvement. During a median follow-up of 7.7 years, 35 (12.1%) patients experienced CV events. RV involvement was associated with a higher risk of CV events (adjusted HR: 2.59; 95% CI: 1.02-6.60; P = 0.046). Imaging-based clustering identified 2 distinct phenotypic subgroups: Cluster 1 (n = 200) and cluster 2 (n = 89). Cluster 2 was characterized by greater hypertrophy, more fibrosis, and impaired systolic/diastolic function, and was associated with a higher risk of CV events (adjusted HR: 2.31; 95% CI: 1.04-5.13; P = 0.039). When stratified into 4 groups according to cluster and RV involvement, patients in cluster 2 with RV involvement exhibited the highest risk (adjusted HR: 4.02; 95% CI: 1.44-11.19; P = 0.008). CONCLUSIONS: RV involvement is associated with adverse prognosis in apical HCM, and imaging-based clustering further identifies high-risk phenotypes. Combined risk stratification incorporating imaging-derived clusters and RV morphology may enhance individualized risk assessment in this population.