Cardiac resynchronization therapy: potential for arrhythmic risk modification

Abstract

Aim. To evaluate the impact of cardiac resynchronization therapy (CRT) on the risk of sustained ventricular tachyarrhythmias (VT) in patients with heart failure (HF) with a implantable cardioverter-defibrillator (ICD) for the primary prevention of sudden cardiac death.Material and methods. This single-center prospective clinical study included 470 patients (men, 84%) with HF at the age of 57 (51-62) years with a left ventricular ejection fraction (LVEF) of 29 (25-33)%. There were following exclusion criteria: indications for cardiac surgery, known channelopathies, previously registered VT. Depending on intraventricular conduction disorders, dual-chamber ICDs (42%) or CRT-D (58%) were implanted. After ICD implantation, patients were followed up for 24 months to register the end point — a first-time sustained paroxysm of VT detected by the ICD. A positive response to CRT was established in the case of an increase in LVEF by ≥5% of the initial level.Results. A total of 388 patients underwent full postoperative follow-up. The studied arrhythmic endpoint occurred on average 21 (0,6) months after implantation in 104 patients (27%) with higher frequency in the ICD group. However, the differences in the VT rate in the study groups were statistically unreliable (30% in the ICD group versus 24% in the CRT-D group, p=0,142). It was found that the VT rate was reliably lower in CRT-responders (118 patients, 53%): 15% compared to 32% in the group of inefficient CRT. A 5% increase in the LFEF reduced the probability of VT occurrence by 3 times (odds ratio [OR]=0,34; 95% of CI: 0,13-0,86; p=002). Significant modification of arrhythmic risk was verified by increasing LFEF to 36-40% (OR=0,72; 95% CI: 0,63-0,82; p=0,04).Conclusion. The results obtained indicate that effective CRT has the potential to modify arrhythmic risk in patients with HF, especially with an increase in LVEF to the level of 36-40%.