Although the risk of stroke is comparable in persistent and paroxysmal AF, the prevalence of persistent AF increases dramatically with increasing age, and thus is an overall more significant cause of morbidity and mortality. In the United States, there are currently an estimated 3.0 million adults with AF, and this number is expected to double in the next 25 years. Hospitalizations with a primary diagnosis of AF are close to half a million per year, which generates a tremendous economic burden on the health care system. When compared to health care costs of non-AF control subjects, patients with AF have greater annual healthcare costs (up to $8705 total annual incremental cost). On the basis of current prevalence data, it is estimated that AF leads to a national incremental health care cost of up to $26 billion. Inadequacy of pharmacological treatment options for persistent AF Management strategies are directed at heart rate control and stroke prevention -mere palliation- or at rhythm control. It has been shown that rhythm control strategies using antiarrhythmic drugs offer no benefit in elderly patients or patients with heart failure. Most of the lack of benefit of such rhythm control strategy is thought to be due to the adverse effects and suboptimal efficacy of antiarrhythmic drugs that can potentially augment mortality. Indeed, preservation of normal sinus rhythm is associated with decreased mortality. Dronedarone, the only antiarrhythmic drug shown to improve outcomes in nonpermanent AF compared to placebo, has been shown to double mortality, stroke and hospitalization for heart failure in the PALLAS study in patients with permanent. Thus, antiarrhythmic drugs remain suboptimal at best for the treatment of AF.
Shortcomings of catheter ablation of persistent AF Weak mechanistic rationale: Isolation of the pulmonary vein (PVs2) and adjacent LA (PV antrum) is the accepted procedural endpoint, based on the mechanistic concept that atrial extrasystoles arising from the PVs initiate paroxysmal AF. Other, non-PV triggers have been demonstrated.36 The link between PV extra systoles and AF is clear in paroxysmal AF, but not in persistent AF, in which the mechanisms of AF seem to be related more to a chronic atrial substrate than to acute triggers.4 Indeed, intramural reentry in the posterior LA seems to be particularly relevant in chronic models of AF. In persistent AF, the procedure has evolved, rather simplistically, to include additional lesions -besides isolation of the PVs, variably placed in the posterior wall, LA roof, and towards the mitral annulus, the superior vena cava,44 left atrial appendage, and other areas where complex fractionated atrial electrograms (CFAE) may be mapped. This brute force approach of simply destroying more tissue has yielded additional success, but new procedural targets with solid mechanistic bases are needed.
Suboptimal success and need for repeat procedures. Despite the additional tissue destruction, ablation success in persistent AF is with much lower than in paroxysmal AF, with single procedure success reported as low as 27%, 36%, or 49%, but up to 61% or 67%, depending on study heterogeneities in: definitions of persistent AF and of recurrence of AF, the type of AF monitoring, and ablation technique and operator experience. In order to achieve overall acceptable success rates, (which can reach up to 79%-94%), there is a consistent need for repeat procedures (sometimes up to 4) and the concomitant use of antiarrhythmic drugs. The rate of repeat procedures in experienced centers can reach up to 70 to 80%.PMF after catheter ablation of persistent AF. Clinical failures of a first ablation procedure are caused, in a significant portion of patients, by atrial flutters, rather than recurrent AF, and recurrence as flutter portends a greater chance of success in a second procedure. Such atrial flutters may be caused by perimitral reentry in up to 33-60% of the patients. Catheter ablation of PMF involves the creation of a linear lesion from the mitral annulus to the left inferior PV (the so-called mitral isthmus).Achieving a complete ablation (defined by bidirectional conduction block across the ablation line) can be very difficult, with success rates reported as 32%, 64%, or 71%. It sometimes requires ablation inside the coronary sinus (CS), in close proximity to the circumflex coronary artery, which could be damaged of note, incomplete ablation of the mitral isthmus is proarrhythmogenic, increasing the risk of recurrent flutter by up to 4 times.
