Post-infarction ventricular tachycardia with a QRS complex narrower than 140 ms: characterization and catheter ablation

Typically, sustained monomorphic ventricular tachycardia (SMVT) in patients with a previous myocardial infarction (MI) is characterized by a wide QRS complex. However, occasionally patients present with SMVT and a narrow QRS complex (N-SMVT). We studied retrospectively the incidence of N-SMVT (i.e., QRS interval <140 ms) in patients with a previous MI and inducible SMVT who underwent electrophysiological evaluation. Of the 135 consecutive patients with inducible SMVT, 8 (5.9%) presented with inducible N-SMVT. The mean QRS complex duration in patients with N-SMVT was 126 (8) ms. Radiofrequency ablation was successful in 5 out of 6 patients (83%). One of the remaining two received an implantable defibrillator, while the other was given amiodarone. Findings during radiofrequency ablation showed that the reentry circuit was located in the left septum in 4 out of the 5 patients (80%). N-SMVT is relatively uncommon, but the success rate of radiofrequency ablation is high. The reentry circuit is most often located in the septum.