Differences in apical and non-apical types of hypertrophic cardiomyopathy: a prospective analysis of clinical, echocardiographic, and cardiac magnetic resonance findings and outcome from 350 patients.

Abstract

Apical hypertrophic cardiomyopathy (ApHCM) is thought to have a favourable clinical outcome, compared with other types of HCM. We sought to investigate the clinical and anatomical differences in cardiovascular imaging between ApHCM and non-ApHCM. A total of 350 patients diagnosed with HCM underwent cardiovascular magnetic resonance (CMR) and echocardiography. All enrolled subjects were prospectively followed up for adverse clinical outcomes. Eighty-five patients were classified as ApHCM. On CMR, the amount and proportion of late gadolinium enhancement (LGE) as well as left ventricular volumetric parameters were evaluated. Echocardiographic evaluations included diastolic function and global strain. Patients with ApHCM were less likely to present with history of syncope and have less frequency of family history of sudden cardiac death than those with non-ApHCM. Functional class was also more favourable in ApHCM [frequency of New York Heart Association (NYHA) class I; 89.4 vs. 66.8%, P < 0.001]. LGE was less frequently detected (87.1 vs. 93.9%, P = 0.04), and the amount of LGE was significantly smaller in ApHCM (7.0 ± 6.0 vs. 14.6 ± 10.5%, P < 0.001). The E/e' level and left atrial volume index were also lower in ApHCM patients (all P < 0.001). During follow-up, a composite of adverse clinical events including cardiac death, admission for heart failure, and cerebrovascular accident was higher in patients with ApHCM than those with non-ApHCM (P = 0.01). ApHCM showed a relatively small burden of myocardial fibrosis and less severe diastolic dysfunction and subsequently more favourable clinical manifestations in comparison with other HCMs. This may be one explanation of why most patients with ApHCM show a benign course of disease compared with non-ApHCM.