Promise or peril: the ECG in HCM

Abstract

Abstract Introduction Hypertrophic cardiomyopathy is a complex disease of the myocardium characterised by left ventricular hypertrophy >15mm in any one segment, in the absence of loading conditions. The phenotypic variability and inhomogeneous nature of the condition have resulted in difficulties with diagnosis. Despite the significant progression in cardiac imaging and genetics, the electrocardiogram (ECG) remains the cornerstone of initial evaluation of patients with HCM and in the screening of families. Moreover, the ECG is in widespread use for pre-participation sports screening. Purpose Original and contemporary studies indicate that the ECG is normal in only 6–10% of patients with echocardiographic evidence of HCM. We hypothesised that the ECG may be normal in a significant proportion of HCM patients. This study sought to reassess the ECG as a screening tool in a HCM cohort. Methods 112 patients were selected randomly from the database of a specialist cardiomyopathy clinic. Their most recent ECG, clinical and imaging data were reviewed. All patients had echocardiographic HCM and were carriers of pathogenic sarcomere gene mutations. Patients with phenocopies were excluded. ECG data for 100 age and sex-matched controls was also analysed. ECG interpretation was performed using international criteria. Results 18% of patients with a clinical diagnosis of HCM by conventional diagnostic standards (LV wall thickness >15mm) had a normal ECG. A further 7% had a normal ECG with a mild HCM phenotype (LV wall thickness of 13–14mm). The most common abnormality observed was T wave inversion (TWI) in 28%. An additional unexpected finding in the HCM group was isolated TWI in lead aVL. This occurred in 27% of patients in the absence of any other repolarisation abnormalities, compared with 1% of controls. The significance of this finding is unclear. 27% of HCM patients displayed voltage criteria for left ventricular hypertrophy by either Cornell or Sokolow-Lyon criteria, with just 4% meeting criteria for both. 13% of HCM patients had corrected QT prolongation, in the absence of medications responsible for this. Conclusion The ECG continues to play a pivotal role in HCM diagnosis but its sensitivity to detect disease has been over-estimated. Up to a quarter of patients with HCM have a normal ECG. This is significantly higher than previously reported. The ECG in isolation therefore is not a reliable tool for screening for HCM in the general population and especially unreliable in at-risk subjects. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Mater Foundation