Relationship between the Duration of the Basal QRS Complex and Electrical Therapies for Ventricular Tachycardias among ICD Patients

Background: In implantable cardioverter‐defibrillators (ICD) patients, the duration of the basal QRS complex (QRSd) is not associated with a greater risk of developing ventricular tachyarrhythmias. QRSd could be inversely related to the effectiveness of antitachycardia pacing (ATP) because it may be associated with longer conduction times of the paced‐impulses and hence, with a greater propensity to require shocks to terminate ventricular tachycardias (VTs). Methods: We followed 216 ICD patients (pacing site: right ventricular apex; QRSd ≤ 100: 34%) for 21 ± 12 months. ICD programming was standardized. QRSd was determined on the electrocardiogram (50 mm/s) at device implantation. Results: Five hundred and fifty‐one VTs (cycle length: 329 ± 35 ms) occurred in 67 patients (36% had a QRSd ≤ 100 ms). ATP terminated 86% of VTs and 11% needed shocks. Mean ATP efficiency per patient was 83%. QRSd was significantly correlated with the probability of successful ATP (C‐coefficient: 0.66), the best cut‐off point being 100 (sensitivity and specificity of 91% and 49%). Patients with QRSd ≤ 100 had a higher ATP effectiveness (98% vs 75%; P = 0.003) and fewer VTs terminated by shocks (1% vs 23%; P = 0.003). By logistic regression, QRSd > 100 remained as an independent predictor of receiving shocks to terminate VTs (P = 0.01). According to Kaplan‐Meier analysis, the occurrence of VTs was similar regardless of the QRSd (30% vs 38%; P = 0.2), but the incidence of shock due to VTs was higher in patients with a QRSd > 100 (19% vs 7%; P = 0.01). Conclusion: Since QRSd is a negative and independent predictor of effective ATP, ICD patients with QRSd > 100 ms require shocks more frequently to terminate VTs. (PACE 2010; 596–604)