[Indications and potential benefits of implantable automatic defibrillator endowed with biventricular pacing]

Heart failure (HF) is associated with a poor long-term survival due to progressive refractory heart dysfunction and sudden cardiac death. Cardiac resynchronization through three-chambered atriobiventricular pacing has been introduced to treat patients with drug-refractory HF and unsynchronized ventricular activation due to left bundle branch block (LBBB). The technique is aimed to overcome inter- and intraventricular conduction delays leading to a ventricular dyssynchrony, characterized by paradoxical septal wall motion, presystolic mitral regurgitation, and reduction in diastolic filling times. Acute studies demonstrated that biventricular pacing (and maybe left ventricular pacing alone) may improve both systolic and diastolic function. First studies on chronically paced patients consistently showed that the QRS shortening was associated with a significant improvement in symptoms, NYHA functional class, left ventricular ejection fraction (LVEF), exercise tolerance, and quality of life. As far as sudden cardiac death prevention in HF is concerned, the implantable cardioverter-defibrillator (ICD) has been demonstrated to be the most effective therapy in patients with prior cardiac arrest due to ventricular fibrillation or poorly tolerated ventricular tachycardia. Low LVEF, unsustained ventricular tachycardia and inducibility at electrophysiological study also may identify high risk patients requiring ICD implantation. Further studies are needed in evaluating the impact of cardiac resynchronization on hard endpoints, such as survival and long-term clinical outcome, as well as in upgrading risk stratification criteria to be used in candidate selection to ICD implantation. However, HF patients with prior cardiac arrest and LBBB should be considered as the optimal candidates to the "ICD implantation combined with biventricular pacing". Conversely, HF patients with LBBB, but without cardiac arrest, could be considered for "biventricular pacing combined with an ICD". The selection criteria for this novel non-pharmacological therapy still have to be defined. The authors emphasize the main indication to ICD implantation combined with biventricular pacing, i.e. HF patients with prior cardiac arrest and LBBB; controversially, while they discuss the other indications to biventricular pacing combined with an ICD.