Early Repolarization Associated With Ventricular Fibrillation

Description

Electrocardiographic (ECG) early repolarization, defined as an elevation of the QRS-ST junction (J-point) of at least 1.0 mm (0.1 mV) from baseline in the inferior or lateral lead, manifest as QRS slurring or notching, is a common ECG finding that is generally considered to be benign but may be associated with ventricular fibrillation in some patients (summary by Haissaguerre et al., 2008).

Clinical Features

Haissaguerre et al. (2008) reviewed data from 206 patients who were resuscitated after cardiac arrest due to idiopathic ventricular fibrillation, compared to 412 age-, sex-, race-, and physical activity-matched controls without heart disease. Patients with short or long QT intervals (see 609620 and 192500, respectively) or Brugada syndrome (see 601144) were excluded from the study. Early repolarization occurred in 64 (31%) of 206 patients compared to 21 (5%) of 412 controls (p less than 0.001). The magnitude of early repolarization was also greater in patients than in controls, with a J-point elevation of approximately 2.0 mm versus 1.2 mm, respectively (p less than 0.001). After adjustment for age, sex, race, and level of physical activity, the odds ratio for the presence of early repolarization in patients compared to controls was 10.9 (95% confidence interval, 6.3 to 18.9). Patients with early repolarization were more likely to be male (p = 0.007), to have experienced symptoms during sleep (p = 0.03), and to have a shorter QTc interval (p = 0.01) than those without early repolarization. All patients received an implantable cardioverter-defibrillator (ICD) device. Arrhythmic recurrences were more frequent in patients with early repolarization than in those without such repolarization (41% vs. 23%, respectively), with a hazard ratio for recurrence of 2.1 (p = 0.008). The 3 patients with the highest J-point elevations (greater than 5.0 mm) had more than 50 episodes of ventricular fibrillation, leading to death in 1 of the patients. Of the 64 patients with early repolarization, 10 had a family history of sudden cardiac arrest. Haissaguerre et al. (2008) concluded that among patients with a history of idiopathic ventricular fibrillation, there is an increased prevalence of early repolarization.

Commenting on the study by Haissaguerre et al. (2008), Myerburg and Castellanos (2008) noted that case-control associations do not prove causality, and stated that until prospective population data were available, physicians should continue to view this common ECG variant as generally benign. They suggested, however, that careful attention be paid to patients with early repolarization and J-point elevations greater than 2.0 mm, particularly in patients with otherwise unexplained arrhythmias or a family history of unexplained sudden death.

Molecular Genetics

Associations Pending Confirmation

For discussion of a possible association between ventricular fibrillation with early repolarization and variation in the KCNJ8 gene, see 600935.0001.