Effect of catheter ablation on pre-existing abnormalities of left atrial systolic, diastolic, and neurohormonal functions in patients with chronic heart failure and atrial fibrillation

Abstract

The critical role of the left atrium (LA) in cardiovascular homoeostasis is mediated by its reservoir, conduit, systolic, and neurohormonal functions. Atrial fibrillation is generally a reflection of underlying disease of the LA, especially in patients with heart failure. Disease-related LA remodelling leads to a decline in both atrial contractility and distensibility along with an impairment in the control of neurohormonal systems that regulate intravascular volume. Catheter ablation can lead to further injury to the atrial myocardium, as evidenced by post-procedural troponin release and tissue oedema. The cardiomyocyte loss leads to replacement fibrosis, which may affect up to 30-35% of the LA wall. These alterations further impair atrial force generation and neurohormonal functions; the additional loss of atrial distensibility can lead to a 'stiff LA syndrome', and the fibrotic response predisposes to recurrence of the atrial arrhythmia. Although it intends to restore LA systole, catheter ablation often decreases the chamber's transport functions. This is particularly likely in patients with long-standing atrial fibrillation and pre-existing LA fibrosis, especially those with increased epicardial adipose tissue (e.g. patients with obesity, diabetes and/or heart failure with a preserved ejection fraction). Although the fibrotic LA in these individuals is an ideal substrate for the development of atrial fibrillation, it may be a suboptimal substrate for catheter ablation. Such patients are not likely to experience long-term restoration of sinus rhythm, and catheter ablation has the potential to worsen their haemodynamic and clinical status. Further studies in this vulnerable group of patients are needed.

Keywords: Atrial fibrillation; Catheter ablation; Heart failure; Left atrium.

Figure 1

Impairment of left atrium function in atrial fibrillation and heart failure. Left atrium electrical and mechanical remodelling impairs the chamber’s contractility, distensibility and modulation of neurohormonal systems, leading to deranged volume control, sympathetic activation, and a limited ability of left atrium systole to enhance left ventricular ejection.

Take home figure

Potential risks of catheter ablation in patients with long-standing atrial fibrillation and pre-existing left atrium fibrosis. With long-standing atrial fibrillation and meaningful left atrium fibrosis, the loss of cardiomyocytes and scar formation following ablation can exacerbate the pre-existing impairment of atrial contractility and distensibility. These sequelae are less likely in patients with relatively healthy atria and only paroxysmal atrial fibrillation.