Overview of ProceduresThe procedures used to cure atrial fibrillation can be divided into two groups: – catheterization procedures and surgical procedures. Both types involve the creation of lesions on the heart wall (right and/or left atrium) in order to stop the propagation of impulses not involved in conducting the heart beat "signal" from the sino-atrial (SA) node to the atrio-ventricular (AV) node.
Catheterization procedures create the lesions from the inside via an ablation catheter threaded through the femoral vein and are performed by electrophysiologists (EPs). Surgical procedures create the lesions from the outside and access is either through incisions between the ribs or may involve open-heart surgery and the use of a heart/lung machine. Surgical procedures are carried out by cardiothoracic surgeons.
The overwhelming majority of catheterization procedures use radiofrequency (RF) energy to create the lesions, but some EPs prefer the use of nitrogen-cooled catheters (cryoablation) rather than RF-powered ones due to their reduced risk of creating pulmonary vein stenosis.
In some cases, cardiologists recommend that their patients undergo an ablation of the atrio-ventricular (AV) node accompanied by the implantation of a pacemaker. This procdure does not eliminate atrial fibrillation, but makes it substantially less noticeable. Patients who undergo AV node ablation and pacemaker implantation are entirely dependent on the pacemaker and are usually on warfarin for life. Thus this procedure is generally considered the procedure of last resort.
The original surgical procedure, the full maze or Cox procedure, used a cut-and-sew protocol for creating lesions forming a "maze" that conducted the electrical impulse from the SA to the AV node, while at the same time interrupting any "rogue" circuits. The cut-and-sew method has now largely been replaced by the use of RF-powered devices, but cryosurgery, microwave application, and high-intensity focused ultrasound (HIFU) have all been tried as well and are preferred by some surgeons.
The so-called mini-maze procedure also involves lesions on the outside of the heart wall, but access to the heart is through incisions between the ribs rather than via open-heart surgery. The mini-maze may involve the creation of the full maze set of lesions, but usually focuses on pulmonary vein isolation. The procedure does not involve the use of a heart/lung machine.
Most of the rogue electrical impulses that create afib originate in the area where the pulmonary veins join the left atrium. Thus, all catheterization procedures aimed at curing afib involve electrical isolation of the pulmonary veins from the left atrium wall. Depending on the origin of the afib, catheterization procedures may also involve ablations of the superior vena cava and coronary sinus (thoracic veins), linear ablation of the left atrial roof, and a standard cavotricuspid isthmus (right atrial flutter) ablation.
Surgical procedures, except for the full maze, also focus on isolating the pulmonary veins, but in addition may involve lesion creation at specific spots located by mapping, removal of the left atrial appendage, and disconnection of the ligaments of Marshall – a potent source of vagal input.
Catheterization Procedures (RF Ablation)A survey of over 600 afibbers who had undergone a total of 950 radio frequency ablation procedures (LAFS-12) was carried out in October 2008. The conclusions reached from that survey are presented below:
- The overall objectively-rated complete success rate (no afib without the use of antiarrhythmics) for 461 afibbers after an average of 1.5 procedures per patient was 56%, partial success was achieved in 10% of cases, and 34% of all afibbers who underwent one or more RF ablations continued to experience AF episodes.
- The subjective judgment of success by ablatees was somewhat more favourable with 64% feeling that the end result was total success, 20% claiming partial success, and 16% judging their procedures as a failure.
- The objectively rated complete success rate for a single RF ablation procedure was 34%, that of partial success 5%, and that of failure 61% when averaged over the years 1998-2008. For the more recent period 2007-2008, the complete success rate for a single RF ablation procedure averaged 48%. This remarkable improvement in single procedure success is reflected in an overall average increase in final (complete) success rate from 47% in the period 1998-2004 to 66% in the period 2007-2008.
- The average complete success rate for the 15 top-ranked RF ablation centers was 65% with a failure rate of 27% for the period 1998-2008. This compares to a complete success rate of 32%, and a failure rate of 61% at other than top-ranked institutions. This clearly indicates that the all-important factor in determining the outcome of an RF ablation is the skill and experience of the EP performing it. Techniques and outcomes have improved markedly from the period 1998-2004 to the period 2007-2008. For example, the final success rate for the three top-rated RF ablation centers (Cleveland Clinic (Ohio), Hopital Cardiologique du Haut Leveque (Bordeaux), and California Pacific Medical center (San Francisco)) has increased almost 10% to average 82% for the period 2007-2008. A very encouraging trend indeed! The average repeat rate was 30% at top-ranked institutions versus 44% at other institutions.
- Forty-one percent of 358 RF ablation procedures were accompanied by an adverse event, the most common (17%) being temporary hematoma in the thigh area. Left atrial tachycardia was also a fairly common adverse effect (12%), but resolved by itself in about 50% of cases. Stroke and TIA were rare at 0.6% and 0.8% respectively. About two-thirds of all adverse events were fully resolved at the time the survey was completed. Successful ablations were much less likely to be accompanied by an adverse event than were unsuccessful ones. NOTE: This data is from the 2006 ablation/maze survey.
- There were no significant differences in success and adverse event rates between a first and subsequent RF ablations, perhaps indicating that the technical difficulty in performing them is pretty much the same.
- The majority (79%) of respondents experienced AF episodes at least weekly prior to their ablation. [From 2007 survey]
- There was no evidence that age at diagnosis and ablation, gender, years of afib, or type of paroxysmal afib affected the outcome to a significant degree. However, more frequent episodes were associated with a lower success rate. [From 2007 survey]
- The most successful procedure for the period 2005-2008 was the pulmonary vein antrum isolation procedure (Natale method) with a single procedure complete success rate of 62% (paroxysmal, persistent and permanent combined). The segmental PVI (Haissaguerre method) was the second-most successful procedure with an average complete success rate of 42%.
- A significant majority (69%) of afibbers who had a completely successful ablation experienced no AF episodes at all after the procedure. Only 8% of those "doomed to failure" experienced no episodes at all after their procedure. Only 2% of completely successful ablatees experienced episodes for more than 3 months after the procedure, while 56% of unsuccessful ablatees did so. Thus, if AF episodes continue beyond 3 months the procedure is almost certainly a failure. On the other hand, if no AF episodes occur during the first month then the procedure is likely to be a success. [From 2007 survey]
- Almost 60% of ablatees recovered fully in less than 2 months, but 24% took longer than 3 months to return to their pre-ablation level of stamina. NOTE: This data is from the 2006 ablation/maze survey.
- Most (96%) of afibbers who had a completely successful ablation did not continue with warfarin, but 13% of them continued to use natural stroke prevention remedies such as fish oil, nattokinase, vitamin E and ginkgo biloba. Seventeen percent took a daily aspirin for stroke prevention. In contrast, 36% of ablatees with a failed procedure continued on warfarin. [From 2007 survey]
- While 79% of successful ablatees no longer needed to avoid previous triggers, only 23% of those having undergone an unsuccessful ablation were so lucky. Nevertheless, it would seem that any ablation, whether successful or not, does help to reduce trigger sensitivity.
- The incidence of post-procedure ectopics (PACs and PVCs) even 6 months or more following the procedure was high at 50% for completely successful ablations and 71% for failed procedures, a difference that is statistically significant. There was no indication that having undergone a right atrial flutter ablation prior to or during the left atrium ablation reduced the incidence of ectopics.
- The incidence of post-procedure tachycardia (SVT and inappropriate sinus tachycardia) was 12% for completely successful and 44% for failed ablations. Having undergone a right atrial flutter ablation as part of or prior to the left atrium ablation did not affect the incidence of post-procedure tachycardia.
- The incidence of post-procedure flutter was 7% for a completely successful ablation and 41% for an unsuccessful one. Having undergone a prior right atrial flutter ablation made no difference to the post-procedure incidence of flutter perhaps indicating that most of the post-procedure flutter was left atrial flutter.
- Even an unsuccessful ablation resulted in a significant reduction in episode frequency in 74% of cases and in 75% of cases was associated with a significant decrease in episode duration. Overall, 70% of unsuccessfully ablated patients experienced a 50% or better decrease in their afib burden. [From 2007 survey]
- Considering a 50% or greater reduction in afib burden (frequency x duration) as an indicator of improvement, it is estimated that close to 90% of RF ablations were ultimately successful in improving quality of life. [From 2007 survey]
- A post-ablation increase in heart rate was a common occurrence. This phenomenon was more prevalent among successful ablatees (67%) than among those whose ablation had failed (41%). This may indicate that a more aggressive approach (increased destruction of vagal nerve endings) is associated with a better outcome. [From 2007 survey]
Cryoablation, AV Node Ablation, and Surgical ProceduresA survey of 87 afibbers who had undergone a total of 94 procedures other than RF ablation procedures (LAFS-12) was carried out in October 2008. The conclusions reached from that survey are presented below.
For details of RF ablation procedures please see the December 2008 issue of The AFIB Report (by subscription).
- The outcome (at least 6 months after procedure) was known for 12 cryoablation procedures. Four (33%) were fully successful and one (9%) was partly successful. The average single procedure complete success rate of cryoablation is thus 33%, not significantly different from the average single procedure complete success rate of PVI procedures at 34%. There is insufficient data to say what the final success rate would be after repeated cryoablations.
- It is not possible, based on a small sample, to evaluate the success rate of an AV node + pacemaker implantation since it, at best, provides symptomatic relief only. Eighty percent of respondents felt (subjectively) that their procedure had been a success, while the remaining 20% felt that it has been partially successful. Thus, based on a small sample of 14 respondents it would appear that AV node ablation + pacemaker implantation is usually a successful procedure and provides significant symptomatic relief even though it does not eliminate the fibrillation of the atria. Nevertheless, it is still the procedure of last resort.
- The full maze procedure performed by a top-ranked cardiac surgeon provides the best chance of being cured of afib with one single procedure (complete success rate of 88%). However, full maze procedures performed by less skilled surgeons tend to be considerably less successful. This, combined with the potential for significant adverse events (especially associated with the use of the heart/lung machine), would lead one to the conclusion that it may be "overkill" for a paroxysmal afibbers, with no underlying heart disease, to select the full maze over a conventional RF ablation or mini-maze procedure.
- A mini-maze procedure performed by a top-ranked cardiac surgeon provides the second-best chance of being cured of afib with one single procedure. It is also likely that even a mini-maze performed by a less than top-ranked surgeon will have a substantially better outcome than a single standard RF ablation performed by a less than top-ranked EP. However, the risk of adverse effects accompanying the mini-maze procedure is somewhat higher than for RF ablations.
For details of cryoablation, AV node ablation and surgical procedures please see the upcoming February 2009 issue of The AFIB Report (by subscription).