Morphology of Far-Field Electrograms and Antitachycardia Pacing Effectiveness Among Fast Ventricular Tachycardias Occurring in ICD Patients: A Multicenter Study

Morphology of Far‐Field Electrograms and ATP Effectiveness Introduction Fast ventricular tachycardias (FVT) are less likely to be terminated by antitachycardia pacing (ATP). No information is available regarding the ability of far‐field electrogram (Ff‐EG) morphology (Ff‐EGm) in predicting the result of the subsequent ATP. Our objective is to determine the relationship between Ff‐EGm and ATP efficacy. Methods and Results In this multicenter study we analyzed 289 FVT (cycle length [CL]: 250–320 milliseconds) occurring consecutively in 52 ICD patients with Medtronic devices (LVEF: 37 ± 6; pacing site: right ventricular apex). FVT programming was standardized, including a single ATP burst as initial therapy. The configuration of Ff‐EG was HVA versus HVB. FVTs were classified in QFVT or non‐QFVT according to the presence or absence of a negative initial deflection in the Ff‐EG. The mean CL was 291 ± 24 milliseconds. We observed 4 Ff‐EGm: QS (n = 14, 5%), QR (n = 158, 55%), R (n = 93, 32%), and RS (n = 24, 8%). The ATP effectiveness was 80% (86% in QS, 85% in QR, 74% in R, 62% in RS). The frequency of successful ATP was higher in QFVT: 86 versus 71% (P = 0.002). By logistic regression analysis, a QFVT pattern (OR = 2.3; P = 0.015) remained as an independent predictor of effective ATP. ATP was safer in QFVTs, the frequencies of shock (14% vs 29%; P = 0.002), acceleration (5.1 vs 12.3%; P = 0.02), and syncope (4.6 vs 12.3%; P = 0.01) being lower. Conclusions Since ATP is less effective in non‐QFVTs, they are less well tolerated. Therefore, the substrate of non‐QFVTs may need a specific treatment.