Phenotypic differences between electrocardiographic and echocardiographic determination of hypertrophic cardiomyopathy in genetically affected subjects.

ABSTRACT

OBJECTIVES: In the molecular era, two types of phenotypic differences are recognized between electrocardiography (ECG) and echocardiography in hypertrophic cardiomyopathy (HCM); ECG abnormalities in carriers without left ventricular hypertrophy (LVH), and normal ECG patterns in carriers with LVH. The goal of this study was to evaluate the diagnostic value of ECG for detecting carriers without LVH, and also to assess normal ECG patterns in carriers with LVH from the genetic standpoint of HCM. SETTING: A matched case-control study in a university hospital and general hospitals in Japan. PATIENTS AND DESIGN: ECG and echocardiographic findings were analysed in 173 genotyped subjects (107 genetically affected, 66 unaffected) from families with disease-causing mutations in four genes. RESULTS: ECG abnormalities were found in 18 (54.5%) of 33 nonhypertrophic carriers, but only nine (13.6%) of 66 noncarriers (P < 0.001). For detecting nonhypertrophic carriers, ST-T abnormalities showed the highest accuracy amongst the three major ECG criteria. In contrast, normal ECG patterns were found in eight (10.8%) of 74 carriers with LVH. The sensitivity of ECG for detecting carriers with LVH in families with the cardiac myosin-binding protein C, cardiac troponin T and cardiac troponin I gene mutations was 83%, 88% and 94% respectively. CONCLUSION: These findings suggest that ECG may have favourable diagnostic value even for detecting nonhypertrophic carriers. Furthermore, diagnostic value of ECG may differ according to the genes involved. Our data may contribute to interpretation of phenotypic differences between ECG and echocardiography from the viewpoint of molecular genetics of HCM.