Abstract 2132: Beta-Blocker Therapy and Effectiveness of Antitachycardia Pacing among ICD Patients: A Dose-Dependent Effect
Beta-blockers (BB) increase the efficacy of antitachycardia pacing (ATP) in terminating slow and monomorphic ventricular tachycardias (MVT) in ICD patients. Whether this effect occurs in fast MVT and whether it is dose-dependent it is unknown. Our aim is to determine the relationship between the indexed dose equivalents (IDE) of beta-blockers (BB-IDE) with the effectiveness of ATP in terminating MVT. In this prospective study we included 200 ICD patients (LVEF: 31±11). Detection and ATP therapies for VT were programmed as follows: Fast-VT zone (Cycle Length [CL]: 250 –320 ms; 1 burst of 5 pulses at 84% of CL); slow-VT zone (CL: 321–390 ms; 3 bursts of 15 pulses at 91%). In each patient we determined the BB-IDE at MVT presentation. Dose equivalents (DE) were defined with atenolol used as reference. IDE were calculated by dividing DE by body surface area (mg*m2/day). During a follow-up of 602±368 days, 546 MVT (CL: 329±35 ms; 41% fast-VT; 22 % no BB treatment; median of BB-IDE: 26 mg*m2/day) were recorded. Success rate of APT was 87%. BB-IDE was higher in the cases of successful ATP (S-ATP): 22±18 vs. 15±16 (p=0.001). Classifying the events into three groups according to the BB-IDE: no BB, low IDE (BB-IDE<median) and high IDE (BB-IDE≥median), the frequency of S-ATP increased with the BB-IDE: 78 vs. 84 vs. 94% (all MVTs; p<0.001 for the trend) and 47 vs. 84 vs. 97% (fast-MVTs; p<0.001, for the trend). In a multivariate analysis (logistic regression), BB-IDE (mg*m2/day) remained as a significant predictor of S-ATP: OR: 1.03 (95% CI: 1.01–1.05; p=0.001). The incidences of MVT-related symptoms and appropriate discharges were lower in higher values of BB-IDE. Table⇓. Among ICD patients, BB therapy increases the likelihood of ATP terminating MVTs, especially in fast MVTs. This effect is dose-dependent: the higher the IDE, the more probable the S-ATP. Thus, BB improves MVT clinical tolerance.