Hot Topics: Procedural Complications, Rehospitalizations, and Repeat Procedures After Catheter Ablation for AFib
April 26, 2012
Atrial fibrillation (AF) ablation has become a popular treatment strategy in the management of this arrhythmia. However, the procedure utilizes multiple intracardiac catheters and requires a significant degree of “invasiveness” while maintaining high levels of anticoagulation, all of which make possible the occurrence of various potentially life threatening complications. In the two world-wide surveys involving over 80 centers internationally, that were conducted by Cappato et al. between 1995-2002 and 2003-2006, despite doubling of patients undergoing AF ablation (from approximately 8,000 to >16,000), the overall complication rates observed during the procedure remained relatively constant (4% versus 4.5%). Amongst the various complications reported, roughly 1/3rd of these were related to vascular access and were not life threatening. The more serious complications associated with the procedure were seen in approximately 3% of patients and these included cardiac tamponade, pneumo/hemothorax, diaphragmatic paralysis, valve damage, atrio-esophageal fistula, cerebro-vascular events, PV stenosis, septicemia, etc. It is also important to point out that amongst the more serious complications encountered during AF ablation, fatality rates for some complications is higher. These include atrio-esophageal fistula, acute respiratory distress syndrome, septicemia and myocardial infarction. This is the likely explanation why, despite the relative infrequency of their occurrence, operator vigilance for these potentially fatal complications is expectedly high. It is also important to note that complications during AF ablation may be more common in older patients and females. As can be expected with any complex procedure, complication rates during AF ablation are higher in hospitals that have less experience doing these. In general the majority of complications associated with AF ablation are typically encountered early (during or within 48 hours of completing the procedure), although some (PV stenosis, esophageal fistula) may occur beyond the index hospitalization. Similarly, while the majority of these complications manifest dramatic symptoms and distinct physical signs, a few of them can have an insidious onset and / or remain completely asymptomatic (PV stenosis). The majority of complications encountered during AF ablation can be avoided using tools that can better define cardiac anatomy and monitor online energy delivery/lesion creation. Should they occur, careful attention to alterations in the patient’s clinical profile (both peri and post procedure) combined with sophisticated imaging techniques can facilitate their early recognition which is critical in preventing fatality from these complications.
Since its original description in 1998, the technique of catheter based AF ablation has undergone several modifications. Currently, many operators utilize an anatomical approach consisting of circumferential lesions encircling individual or ipsilateral pulmonary veins (PVs) with additional empiric left atrial (LA) ablations (lines) whereas others perform a more PV specific approach utilizing entrance / exit block to validate isolation, deferring any additional non-PV lesions unless clinically indicated. Despite these differences in technique, there remain remarkable consistencies in the AF outcome data between centers, with overall single procedure efficacy of ≥70% in achieving long-term arrhythmia control for patients with paroxysmal AF but significantly lesser success rates in achieving a similar outcome for patients with persistent or long persistent AF. These observations imply that the mechanism(s) underlying persistent / long persistent AF may be different from paroxysmal AF. It has been posited that in the persistent stage, AF is maintained by the underlying substrate rather than triggers. Although this hypothesis remains to be proven, it has nevertheless resulted in the development of adjunctive substrate modification strategies for patients with more established forms of AF. These include linear lesions across potential reentrant channels, targeting complex fractionated electrograms (CFEs), ablating ganglionated plexi, etc. Currently the most prevalent approach for ablating persistent AF involves PV isolation followed by extensive targeting of CFE sites (in both atria and coronary sinus) with the intention of terminating the arrhythmia. However, AF termination using this approach is a rarity (10%) and in the majority of cases it transforms into an organized rhythm which requires more mapping, more ablation and eventually in the majority of instances external cardioversion to finally restore sinus rhythm. Despite such extensive ablation, the majority of these patients (~60%) require a second procedure for arrhythmia recurrences and in the majority of instances these arrhythmias are not AF but organized atrial arrhythmias (OAT). Investigators favoring extensive ablation strategies argue that recurrent arrhythmias in their series being OAT and not AF imply that they have successfully modified the AF substrate. However, it can be argued that such an extensive ablation strategy may be pro-arrhythmic for OAT. Moreover, from the patient’s perspective, OAT can be symptomatically just as debilitating as AF and repeat ablation for these can be just as time consuming as a redo AF ablation. Other concerns with such extensive ablation strategies include risk of collateral damage to surrounding structures (circumflex coronary artery, phrenic nerve, etc) as well as its long-term impact on atrial transport function and CS patency. In this context it is important to point out that the single procedure efficacy of a more limited approach targeting PVs and only documented non-PV triggers of AF can achieve long term arrhythmia control in up to 50% of patients with persistent AF. Importantly when these patients experience arrhythmia recurrence, the majority of times it is attributable to reconnection of the previously isolated veins and re-isolating these on the 2nd attempt translates into long term arrhythmia control rates of ≥80% which is comparable to the long term results of the more extensive ablation strategies.
With the growth in the AF ablation volume, there has been a push to reducing the length of hospitalization involved with the procedure. One of the major developments towards this end has been the ability of operators to now perform AF ablation on fully anticoagulated patients (with therapeutic INRs). With the advent of this approach, index hospitalization in patients undergoing AF ablation has been reduced to 1-2 days. Nevertheless, re-hospitalizations after the index AF ablation procedure are not uncommon and can occur in as many as 10% of patients within 30 days of the index ablation and in 20% of the patients within the 1st year. The majority of these re-hospitalizations are on account of arrhythmia recurrences although in some instances, especially early on after the ablation these can be attributed to procedure related complications. Regardless of the cause, it is important to note that readmission rates following AF ablation are still lower than those in patients undergoing percutaneous coronary intervention (14%) and half the readmission rates observed in Medicare beneficiaries with heart failure (20%) after their index hospitalization.