Hypertrophic cardiomyopathy in patients with a normal electrocardiogram: A view from the east side of the Atlantic Ocean

Background: Although the 12‑lead electrocardiogram (ECG) is abnormal in most patients with hypertrophic cardiomyopathy (HCM), some present normal ECG. This study aimed to analyse the baseline characteristics, clinical presentation and outcomes of HCM patients with normal ECG and to compare them with those with abnormal ECG.

Methods and results: Baseline characteristics, clinical presentation, data from complementary exams and clinical outcomes of 1070 consecutive patients included in the Portuguese Registry of HCM (Pro-HCM registry) were compared between two groups of patients: normal Vs. abnormal ECG. Among this population, 98 (9.2%) patients had normal ECG at presentation; they were significantly younger and had lower frequency of hypertension, symptoms at presentation, heart failure, angina, cardiac and non-cardiac diseases. ESC and AHA risk scores for Sudden Cardiac Death (SCD) were not significantly different between the two groups. Patients with normal ECG had higher prevalence of family history of SCD and lower degree of left ventricular (LV) hypertrophy, LV systolic dysfunction, LV outflow tract obstruction and myocardial fibrosis. The combined endpoint of cardiac death, SCD, cardiac arrest, appropriate ICD shocks or evolution to systolic dysfunction, during a mean follow-up of 5 years was significantly less frequent in patients with normal ECG (2.1% Vs. 6.5%; p = 0.043).

Conclusions: A normal ECG is not a marker of an overall benign profile in HCM patients. Though a normal ECG at presentation is associated with a less severe phenotype and a lower probability of evolution to heart failure at 5-years, this finding did not show a protective effect in other clinical outcomes.