Cardiac resynchronization therapy ( CRT ) is an effective therapy in symptomatic, drug-refractory heart failure ( HF ) patients with prolonged QRS and low ejection fraction ( EF ). Long-term results of CRT on exercise tolerance and disease progression as evaluated by reversal of maladaptive remodeling process are rather limited, and mostly reported in patients with sinus rhythm ( SR ).
Permanent atrial fibrillation (AF) is a rather common supraventricular arrhythmia in heart failure patients and is associated with increased morbidity and mortality.
Some studies have reported significant acute benefits but short-term data of CRT in atrial fibrillation patients are conflicting. The importance of atrioventricular junction ( AVJ ) ablation in order to optimize CRT in patients with permanent atrial fibrillation has been investigated at minimum extent. This approach appears to maximize CRT delivery yielding a resynchronization effect which translates into significant long-term improvements of both ejection fraction and reversal of maladaptive remodeling; such reversal remodeling effect has been previously correlated with improved survival in heart failure patients with normal sinus rhythm.

The goal of the study was: first to investigate the effect of CRT on long-term survival in heart failure patients with permanent atrial fibrillation compared to SR patients; second to evaluate within an ample atrial fibrillation population treated with CRT the impact of AV junction ablation on long-term survival.

The question was addressed using data included into the Multicenter Longitudinal Observational Study ( MILOS ). This registry included, using a prospectively pre-defined registry protocol, 1305 consecutive patients undergoing CRT pacemaker ( CRT-P ) or CRT defibrillator ( CRT-D ) device implant between August 1st 1995 and August 1st 2004 from 2 centers in Italy and 2 in Germany.

The MILOS results have shown for the first time the importance of AVJ ablation on long-term survival in atrial fibrillation patients treated with CRT.
The long-term overall survival of drug-refractory heart failure patients with permanent atrial fibrillation and left ventricular conduction delay treated with CRT was similar to that of SR patients. However, in heart failure patients with permanent atrial fibrillation, AVJ ablation in addition to CRT significantly improves long-term overall mortality, compared to CRT alone, primarily by reducing HF death.

AVJ ablation appears to be of paramount relevance in order to ensure adequate CRT delivery and thus reducing mortality in patients with permanent atrial fibrillation.

Source: European Society of cardiology ( ESC ) – Congress, 2007

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