Outcome of patients with hypertrophic cardiomyopathy and a normal electrocardiogram.

Objectives: This study sought to clarify the frequency, clinical phenotype, and prognosis of those patients with hypertrophic cardiomyopathy (HCM) who present with a normal electrocardiogram (ECG).
Background: Hypertrophic cardiomyopathy is the most common cause of sudden death in young people. Screening advocates have recommended a 12-lead ECG for the early detection of HCM in athletes, yet the clinical outcomes of those presenting with a normal ECG remains to be fully delineated.
Methods: Baseline characteristic and echocardiographic data were collected on all patients with HCM who initially presented to our institution with a diagnostic echocardiogram but a normal ECG. Follow-up was obtained and compared with the prognosis of HCM patients who presented with abnormal ECGs.
Results: We compared 135 HCM patients with a normal ECG with 2,350 HCM patients with an abnormal ECG. The latter group was more likely to have worse symptoms, have higher gradients, and a greater degree of septal wall thickness than the patients with a normal ECG. Severe obstructive symptoms requiring surgical myectomy and implantation of an implantable cardioverter-defibrillator were more common in patients with abnormal ECGs. Cardiac survival was significantly better in the group with a normal ECG at presentation-none of these patients had a cardiac death at follow-up.
Conclusions: Almost 6% of patients presenting with demonstrable echocardiographic evidence of HCM had a normal ECG at the time of diagnosis. This subset of patients with normal ECG-HCM appears to exhibit a less severe phenotype with better cardiovascular outcomes.