Prevalence and characteristics of normal electrocardiograms in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic heart disease characterized by left ventricular hypertrophy (LVH) in the absence of other causes. More than 90% of patients exhibit abnormalities such as T wave inversion, Q waves, or LVH voltage criteria. However, a small subgroup with milder disease may present with a normal electrocardiogram (ECG), which can delay diagnosis. This study aimed to determine the prevalence and clinical characteristics of HCM patients with a normal ECG and their relationship with indicators of disease severity.

Patients diagnosed with HCM according to European Society of Cardiology (ESC) guideline criteria were retrospectively evaluated. Those with alternative causes of LVH or infiltrative/storage cardiomyopathies were excluded. Abnormal ECG was defined by the presence of atrial fibrillation, conduction block, pathological Q waves, repolarization changes, LVH voltage, low voltage, QTc >460 ms, or QRS >120 ms.

Among 682 patients, 11 (1.6%) had completely normal ECGs. The most frequent abnormalities were repolarization changes (82.6%) and LVH voltage criteria (70.2%). Normal ECGs were associated with lower NT-proBNP, lower pulmonary artery pressudre, better right ventricular function, and less frequent late gadolinium enhancement on cardiac magnetic resonance imaging (CMR). The number of ECG abnormalities correlated positively with wall thickness, NT-proBNP, left atrial diameter, pulmonary pressures, and sudden cardiac death (SCD) risk score, but negatively with right ventricular functionand left ventricular ejection fraction.

A completely normal ECG was observed in only 1.6% of patients with hypertrophic cardiomyopathy. While a normal ECG substantially lowers the likelihood of HCM, it does not exclude the diagnosis. Despite advances in imaging, the ECG remains a simple, accessible, and indispensable screening tool for early detection.