Apically displaced papillary muscles mimicking apical hypertrophic cardiomyopathy

AIMS: Apical hypertrophic cardiomyopathy (ApHCM) is a subtype of hypertrophic cardiomyopathy, which is clinically suspected by a characteristic giant negative T (GNT) wave on electrocardiogram (ECG) and diagnosed by demonstrating apical hypertrophy on ECG. However, GNT may not always be specific for ApHCM as in this report of apically displaced papillary muscle (ADPM). METHODS AND RESULTS: By retrospectively collecting 12-lead ECGs with a GNT wave and apical hypertrophy on 2D-ECG from 2008 to 2010, we identified 55 patients with both of these findings. ADPM was defined to be present when the base of the papillary muscle originated from the apical one-third of the left ventricle. A diagnosis of ApHCM in patients with apical hypertrophy but without evidence of ADPM was given otherwise. Careful evaluations of 2D-ECGs suggested that 20% (11/55) of all patients had an ADPM mimicking ApHCM. Baseline clinical and echocardiography data were not different between the two except for the maximal T wave on 12-lead ECG and apicoseptal hypertrophy, suggesting that the differentiation of these two groups may be subtle and difficult. In addition, patients with ADPM frequently showed abnormal insertion of papillary muscle into the left ventricular outflow tract or into the base of mitral valve leaflet. CONCLUSION: These findings suggest that ADPM may also be present with GNT on 12-lead ECG and emphasizes the careful evaluation of the left ventricular apex for proper diagnosis and discrimination of ApHCM.