Management of atrial arrhythmias

Device: Management of atrial arrhythmias

1. Basic concepts

RESYNCHRONIZATION AND ATRIAL FIBRILLATION

There is a vicious circle between heart failure and atrial fibrillation, one favoring the other and vice versa. The prevalence of atrial fibrillation in CRT candidates is high and increases with the functional class: approximately, 5% for patients in NYHA class I, 10 to 25% for patients in class II and III, 50% for patients in NYHA class IV. The presence atrial fibrillation reduces the probability of positive response after resynchronization, the complete and permanent biventricular capture (an essential prerequisite), being impaired in some patients with atrial fibrillation. A certain number of patients with atrial fibrillation present a rapid and irregular ventricular rhythm incompatible with a permanent LV capture. In addition, patients with atrial fibrillation are not resynchronized at the atrioventricular level that also contribute to the lower prevalence of positive results after resynchronization when compared to patients in sinus rhythm.
In a resynchronized patient, it is necessary to be relatively aggressive in the therapeutic approach to maintain the sinus rhythm as long as possible or to control the ventricular response.
The different therapeutic options include 1) the introduction of a loading dose of amiodarone and/or the electrical cardioversion of the patient; 2) treatment with amiodarone or ablation of the pulmonary veins and the left atrial substrate to maintain the sinus rhythm 3) introduction of rate control agents to maintain the heart rate as low as possible and promote biventricular pacing 4) programming specific algorithms forcing the stimulation on a detected ventricular activity and 5) ablation of the His bundle to suppress any competition between spontaneous rhythm and paced rhythm. The radiofrequency ablation of the atrioventricular junction is a well-validated treatment for restoring an adapted heart rate and a permanent biventricular pacing at rest as during exercise (with the programming of a rate responsive function).
The programming of algorithms forcing the ventricular stimulation on a detected ventricular event  (pseudo-VVT mode) in a patient with AF seems poorly efficient because the heart rate remains high and progressive fusion with the spontaneous ventricular activity remains incomplete or absent (pseudo-fusion).
The ablation of the pulmonary veins and the left atrial substrate has been proposed even though the results in patients with heart failure and enlarged left atrium are sometimes imperfect.
Therefore, it seems logical to try first to restore and maintain the sinus rhythm to preserve atrial contribution to the LV filling and maintain a physiological rate at rest and during exercise. If this strategy fails, we prefer to control the ventricular response with a beta-blocker. In case of unsatisfactory results, we do not hesitate to propose the ablation of the His bundle since patients with a preserved AV conduction and low percentage of stimulation do not benefit from the resynchronization therapy.
It is also possible to program a number of algorithms that aim to prevent the occurrence of atrial fibrillation by using different mechanisms: increasing the percentage of atrial pacing, reducing the post-PVC pauses, non-competitive atrial pacing. There is yet no evidence of the effectiveness of these types of algorithms in CRT patients. 

RESYNCHRONIZATION AND DEFIBRILLATION FUNCTION

For more informations, refer to chapters specificities by manufacturers.

2. Specificities by company