The inconvenient truth of elevated left atrial pressure and AF recurrence despite catheter ablation

A Compelling Case for Less Aggressive Arrhythmia Management in Patients With Chronic Heart Failure and Long-Standing Atrial Fibrillation

BACKGROUND AND METHODS

Atrial fibrillation (AF) is common in chronic heart failure, and some have advocated intensive rate and/or rhythm control strategies for these patients. However, the loss of atrial systole and irregularity of the ventricular response has not been shown to contribute to the progression of heart failure, and the presence or rate of long-standing AF in patients with chronic heart failure does not have prognostic significance.

RESULTS

In randomized clinical trials, pharmacological rhythm control has not been shown to be superior to rate-control in influencing long-term outcomes, but the use of membrane-active antiarrhythmic drugs can increase the risk of both pump failure and arrhythmic deaths in patients with heart failure. Additionally, intensive efforts to slow the ventricular rate in AF can potentially cause clinically inapparent bradyarrhythmias, which can trigger rate-dependent lethal rhythm disturbances or hemodynamic abnormalities. In patients with AF, a more stringent approach to rate control (target rate <80/min) is not superior to a more lenient strategy (target rate <110/min) on the risk of major events. Little is known about the effects of catheter ablation of long-standing AF in established heart failure, particularly in patients with a preserved or a meaningfully reduced ejection fraction, but ablation can add to the fibrotic burden of the left atrium and impair its capacitance functions.

CONCLUSIONS

For all of these reasons, the management of heart failure and long-standing AF should be primarily directed to slowing of the progression of their underlying cardiomyopathic process rather than the treatment of the arrhythmia. In addition, patients should receive long-term oral anticoagulation with non-vitamin K-antagonist oral anticoagulants to reduce the risk of thromboembolic events. The utility of intensive rate and rhythm control interventions for long-standing AF in patients with established heart failure requires further study.

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

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.

Histopathological Study of Left and Right Atria in Isolated Rheumatic Mitral Stenosis With and Without Atrial Fibrillation

BACKGROUND

Mitral stenosis (MS) has the highest incidence of atrial fibrillation (AF) in chronic rheumatic valvular disease. There are very few studies in isolated MS comparing histopathological changes in patients with sinus rhythm (SR) and AF.

OBJECTIVES

To analyze the histological changes associated with isolated MS and compare between changes in AF and SR.

METHODS

This was a prospective study in patients undergoing valve replacement surgery for symptomatic isolated MS who were divided into 2 groups, Group I AF (n = 13) and Group II SR (n = 10). Intra-operative biopsies performed from 5 different sites from both atria were analyzed for 10 histopathologic changes commonly associated with AF.

RESULTS

On multivariate analysis, myocytolysis (odds ratio [OR]: 1.48, P = 0.05) was found to be associated with AF, whereas myocyte hypertrophy (OR: 0.21, P = 0.003), and glycogen deposition (OR: 0.43, P = 0.002) was associated with SR. Interstitial fibrosis the commonest change was uniformly distributed across both atria irrespective of the rhythm.

CONCLUSION

In rheumatic MS, SR is associated with myocyte hypertrophy whereas AF is associated with myocytolysis. Endocardial inflammation is more common in left atrial appendage irrespective of rhythm. Interstitial fibrosis is seen in >90% of patients distributed in both the atria and is independent of the rhythm. Amyloid and Aschoff bodies are uncommon and the rest of the changes are uniformly distributed across both the atria.