The major randomized controlled trials that demonstrated the efficacy of cardiac resynchronization therapy (CRT) excluded patients with atrial fibrillation (AF). Yet, AF occurs in one of four recipients of CRT1- 2. The prognosis of AF patients with CRT is generally worse than that of patients in sinus rhythm.3- 4 because they are at a major disadvantage 5 They exhibit loss of atrioventricular synchronicity, a higher risk for insufficient CRT delivery because of uncontrolled ventricular rates, more ICD shocks for ventricular arrhythmia, inappropriate ICD shocks, inadequate symptomatic improvement, repeated hospitalization and increased mortality. 6- 17 Furthermore AF may be associated with fusion and pseudofusion beats that represent inefficient biventricular capture (Fig 1).18, 19 Such beats render the pacing counters inaccurate for assessing true biventricular capture beats. AF represents an important cause of poor long-term CRT benefit and prognosis unless aggressive efforts are made to slow the ventricular rate. The new developments in rate control can now promote the delivery of a high percentage of biventricular paced beats to the AF patient (which was challenging in the past) so as to produce an overall response virtually similar to that seen in patients with sinus rhythm despite the persistence of atrial arrhythmia.
Credits: S. Serge Barold; Bengt Herweg