ECG analysis
We evaluated ECGs recorded in the 3rd and 4th ICSs in the absence of antiarrhythmic drugs during sinus rhythm in all study subjects. J point elevation in the right precordial leads was defined as upward/downward notching or downward slurring with an amplitude ≥ 0.1 mV at the end of QRS to early ST segment in any of the right precordial leads (V1 and V2) in the 3rd or 4th ICS (Figure 1). Inferolateral early repolarization (ER) was defined as the presence of a positive J wave, which is a slurring or notch at the QRS terminal that is ≥ 0.1 mV above the isoelectric line in ≥ 2 contiguous leads in any of the inferior leads (II, III, and aVF), the lateral leads (I, aVL, and V4–V6), or both.4 All ECGs were manually evaluated separately by two independent cardiologists who were blinded to the patient status (VF patients or healthy controls).