The Influence of Atrial Fibrillation on Cardiac Resynchronization Therapy

Abstract

More successful recognition and treatment of cardiovascular risk factors and diseases continues to decrease mortality and increase the proportion of elderly population. Therefore, there are more people with increased risk of developing heart failure and atrial fibrillation (AF) in the course of their lives. The prevalence of AF, in patients with heart failure, increases with the severity of the disease, reaching up to 40% in advanced cases. In these patients with heart failure, AF is an independent predictor of morbidity and mortality increasing the risk of death and hospitalization. Despite the excellent results obtained with different drugs, the optimal medical treatment can fail in the intention to improve symptoms and quality of life of patients with severe heart failure. Thus, the necessity to use cardiac devices emerges facing the failure of optimal medical treatment in order to achieve hemodynamic improvement. The simultaneous electric stimulation of both ventricles with Cardiac Resynchronization Therapy (CRT) results in a significant hemodynamic improvement restoring a more homogeneous contraction pattern. However, CRT is interrupted in over 30% of patients after successful implantation of a CRT device, and the most common reasons for interruption of CRT are the development of AF (18%) and loss of left ventricular capture (10%). Therefore, there should be a strong effort with different maneuvers to prevent AF, since it would significantly improve the ability to deliver CRT in patients with heart failure. The search for better pharmacological maneuvers should continue to provide the help needed to cardiac devices. The incorporation of the AF suppression algorhythm to CRT devices may be very useful in eliminating AF, allowing a better performance of the CRT device without interruption. Sinus rhythm is associated with a long-term improvement in left ventricular systolic function after AF ablation. Therefore, AF ablation may have a primary role as a rhythm control strategy in the definite treatment of AF in patients with HF.

The Deleterious Effect of Atrial Fibrillation and Its Association with Mortality in Non-Responders to Cardiac Resynchronization Therapy

“…It promotes an atrial stimulation with adequate rates for the patient. It dynamically adjusts the stimulation rates in manner that stimulates the heart slightly over the intrinsic atrial rate regardless of the activity status [20][21][22][23][24]. Because patients with slower heart rates are more likely to develop AF, a dual-chamber rate-modulated pacing mode may reduce interruptions of CRT.…”

The Influence of Hyperthyroidism in the Electrophysiological Properties of the Atrial Muscle in Paroxysmal Atrial Fibrillation

“…On the other hand, the slowing in conduction of the atrial impulses may set the background for reentry to occur [1][2][3][4][5]. Although an increase of 20 ms or more in the atrial conduction time in response to early extra-stimuli appears to be a physiological response of the normal atrium, patients with PAF show longer IACD zones and maximum IACDs than control subjects without atrial arrhythmias [15][16][17][18]. Thus, the IACD zone and maximum IACD are believed to be good indices of a tendency to develop AF.…”

“…The atrial vulnerability of the atrial myocardium in patients with PAF can be easily exposed in the electrophysiology laboratory. Abnormal responses of the atrial muscle can be elicited by programmed atrial stimulation during the electrophysiological study [15][16][17][18]. Certain parameters of atrial vulnerability, namely, repetitive atrial firing, fragmented atrial activity, and intraatrial conduction delay (IACD) can be induced by atrial stimulation.…”