Phenotypic overlap in hypertrophic cardiomyopathy: apical hypertrophy, midventricular obstruction, and apical aneurysm.

BACKGROUND: Within the diverse phenotypic spectrum of hypertrophic cardiomyopathy (HCM), subgroups of patients with apical hypertrophy (APH), midventricular obstruction (MVO), and apical aneurysm (APA) have emerged. While previous studies have suggested the existence of considerable overlap between APH, MVO, and APA, there are still many unanswered questions. Therefore, we attempted to clarify the relationship of the above three phenotypes of HCM with respect to prevalence, overlap, and outcomes. METHODS: Among the 544 study HCM patients (mean follow-up period: 11.6±7.4 years), 170 with APH (31.3%), 51 with MVO (9.4%), and 24 with APA (4.4%) were examined. RESULTS: There was phenotypic overlap between APH and MVO in 17 patients, APH and APA in 14 patients, and MVO and APA in 14 patients. Furthermore, a combination of APH, MVO, and APA was observed in eight patients. Detailed analysis of the relationship between overlapping phenotypes and the prognosis showed that APA patients without a history of APH had an extremely poor outcome (probability of the combined endpoint of sudden death and potentially lethal arrhythmic events ≥50%). Conversely, APH patients without MVO had a strikingly good outcome (probability of the combined endpoint <5%). Other patients had an intermediate outcome (probability of the combined endpoint 10-40%). CONCLUSIONS: Our results suggest that overlap between these three forms of HCM is substantial, and that detailed classification of the overlapping phenotypes is clinically meaningful.