Recurrent episodes of atrial fibrillation are associated with progressive left atrial substrate remodelling over time. We present an argument for early ablation in the treatment of recurrent paroxysmal atrial fibrillation prior to such deleterious changes in “left atrial electrical health”
Paramdeep S. Dhillon PhD, Department of Cardiology, St George’s Hospital, Blackshaw Road, london, UK, SW170.
A recent comprehensive review of atrial fibrillation (AF) has proposed new clinical concepts.1
However, early intervention with ablation techniques was not considered. We believe that there is now sufficient evidence to offer ablation therapy very soon after the first clinical presentations of paroxysmal AF as first line treatment. We present a simple argument which we believe is convincing. AF is currently classified as “paroxysmal” or spontaneously terminating within 7 days, or “persistent” lasting for over 7 days or requiring cardioversion to restore sinus rhythm; or “longstanding persistent” meaning present without pause for over one year; or lastly, “permanent” AF when it is accepted by the physician and the patient that no attempts should be made to convert the AF back to sinus rhythm.
It is well known that that duration of uninterrupted AF has important complex biochemical and physiological effects on the myocardium of the left atrium, otherwise known as negative electrical remodelling. This has been succinctly described as “atrial fibrillation begets atrial fibrillation”.2
In essence the “health” of the left atrium deteriorates the longer the duration of the AF. The evidence strongly suggests that patients with paroxysmal AF may, if untreated, develop more frequent and more prolonged episodes such that they develop “persistent atrial fibrillation” either as a result of duration in excess of 7 days or by requiring cardioversion. Once reclassified there is no reverting to a lesser category. The six new categories proposed,1
reflect the progressive severity of atrial negative remodelling. The evidence indicates that each category from “pre” to “permanent” is incrementally more difficult to treat whether using drugs for suppression in paroxysmal atrial fibrillation (PAF), rate control in permanent atrial fibrillation or increasingly complex modes of left atrial ablation in attempts to eliminate the substrate (the left atrial myocardium).
Atrial electrical remodelling is a complex biochemical and physiological process which has been well studied in animals3
It is manifest by changes in the microstructure of the atrium with increase in fibrosis, electrical changes including shortening of action potential duration and refractory period, slowing of conduction as a result of alterations in sodium, calcium and potassium channel functions and many other effects.3
Here we will refer collectively to these processes as deleterious changes in “left atrial electrical health”.
For paroxysmal AF there is little doubt that pulmonary vein isolation (PVI) by any technique is successful in the majority of patients.5
It is also the simplest approach and is central to almost all methods of ablation of AF. A variety of adjunctive strategies have been described for paroxysmal and persistent AF. Pappone et al,6
developed wide circumferential atrial ablation which aims to both isolate the veins and modify the atrial myocardium. Haïssaguerre et al,7
have devised a stepwise approach by adding linear ablation to conventional electrophysiological PVI. Nademanee’s group,8
targeted so-called “continuous fractionated atrial electrograms” or CFAEs. Others such as Pokushalov et al,9
have advocated specific targeting of autonomic ganglia located in clusters on the posterior left atrial wall. None of these techniques has proved superior to another and none is as effective as simple PVI for the treatment of paroxysmal AF.9,10
The success rate of ablation for persistent AF is much less than for paroxysmal AF even with several procedures.7
The implication of these observations is clear: interventional treatment with ablation should be offered as first line treatment in those patients who present with more than one episode of paroxysmal AF.
A Graphical Representation of Left Atrial Health
We recognise that AF is a heterogeneous disease, with a spectrum of left atrial substrates dependent upon underlying aetiologies. Nonetheless we present a hypothetical graph of the naturalhistory of AF in a single patient (Figure 1
). Immediately after the first onset of AF (red line at point a) negative atrial remodelling or deterioration in “left atrial electrical health” begins (y axis) and continues as long as AF is present (arbitrary time scale on x axis). When sinus rhythm is resumed either spontaneously (point b) or by cardioversion (points c and e) positive remodelling or an improvement of left atrial health occurs as a result of gradual reversal of the adverse effects of negative remodelling (point f). The longer the duration of preceding AF the longer the recovery time (blue lines). This may be interrupted by a further recurrence of AF (point d).
Hypothetical Natural History of Atrial Fibrillation Over Time
If it is accepted that the diagram fairly reflects the natural history of atrial fibrillation and “left atrial health” the implications are clear: atrial fibrillation should be treated as early as possible in its natural history. There is unanimity in the international atrial fibrillation/electrophysiology community that a single attack of AF may be just that – a one off episode that requires simple investigation (for example an echo, an ECG monitor) but no treatment other than perhaps avoidance of precipitating factors. For patients who have recurrent AF defined as 2 or more spontaneously terminating episodes PVI should be considered at an early stage, possibly as first line treatment.10
New techniques such as cryoballoon PVI are very promising.11
There are financial implications in providing early intervention in the course of atrial fibrillation,with the cost associated with increased numbers of ablation procedures. However, the initial cost of the ablation procedure may be less than that of medical management of AF in the long-term, which includes the costs of anti-arrhythmic medication, out-patient clinic attendances and most importantly hospital admissions.12
Furthermore, the prevention of persistent AF by intervention early in the course of the disease may reduce the costs associated with the treatment of strokes and exacerbations of heart failure.
The electrophysiology community may not be currently ready to provide the number of procedures required for an early interventional approach to the treatment of AF. However our interventional colleagues overcame a similar challenge in delivering wide-spread and early percutaneous coronary intervention in the treatment of coronary artery disease.