Atrial fibrillation (AF) affects more than two million Americans, a number that continues to increase as the population ages. While not fatal in itself, patients who suffer from atrial fibrillation are at increased risk of stroke and congestive heart failure. Many patients have shortness of breath, chest pain, fatigue and feelings of anxiety.
Traditional treatment for symptomatic AF involves anti-arrhythmic medication, though the success rate remains low and side effects are common. Observations that paroxysmal AF is often initiated from high-frequency electrical activation in or near the pulmonary veins have led to development of the pulmonary vein isolation (PVI) procedure. This procedure is largely performed with meticulous unipolar radiofrequency ablation from the endocardium, with the goal of electrically disconnecting the pulmonary veins from the atrium. In a randomized trial of patients with paroxysmal AF who failed an anti-arrhythmic medication, PVI was associated with better rates of maintaining sinus rhythm than a second anti-arrhythmic medication.1
Unfortunately, the PVI procedure is not perfect. The main limitations of the procedure are related to patient safety and procedural success. With the goal of building a better, safer procedure, we critically evaluated the various components of a PVI procedure.
Arrhythmia-free survival for the PVI procedure approaches 70% for patients with paroxysmal AF. Recurrences are thought to be due to recovery of electrical conduction across previous ablation sites. Reasons for recovery are unclear, though the two most obvious reasons are incomplete ablation across the entire atrial myocardium (non-transmural lesion) and gaps between adjacent ablations during the initial procedure (non-linear lesion). These observations have led to intense investigation for an ablation modality that creates a more durable, transmural lesion. In a rigorous study of various energy sources, bipolar radiofrequency ablation performed the best, with transmural, durable lesions.2 This type of energy is commonly used during a surgical Maze procedure, which is performed on an arrested heart. If recurrences are largely due to recovery of conduction across ablation lines, then an ideal procedure should use bipolar linear ablation to provide more durable lesions.
The one-year success rates of the PVI procedure are significantly lower for patients with persistent AF (<50%). This is thought to be driven by electrical, molecular and structural changes that occur with the various disease conditions leading to AF, as well as the direct contribution of AF toward the remodeling process. This has led operators toward a larger lesion set, mimicking the lesion set produced in a surgical Maze procedure (one-year success rate ~90%). However, ablation of persistent AF can become a long procedure, and incomplete linear ablations can be a source for atrial reentrant tachycardias. If we seek to replicate Maze-like results, then an ideal procedure should provide an extensive Maze-like lesion set.
Finally, endpoints of the procedure should be rigorously tested. During surgical ablation for AF, pacing can be performed on the pulmonary veins to assess for exit block, but access to these sites is often limited to one location in each vein. Therefore, in an ideal procedure, accurate electrical testing for PV entrance/exit block and bidirectional block of linear ablation should be performed to assess for gaps.
As reported in an international registry,3 complication rates related to PVI range from 2–4%. The most common complication is related to vascular access, which is largely treatable. Life-threatening complications are rare. Pericardial effusion and tamponade are often recognized and treated in the EP lab. However, the delayed presentation and high mortality associated with esophageal fistula make this the most feared complication.
Compared to catheter ablation, the surgical Maze procedure carries a substantial recovery time and procedural risk. Published follow up of patients undergoing the Maze procedure (with and without concomitant cardiac surgery) shows the risk of adverse events ranging from 10–15%, which includes the need for a pacemaker for sinoatrial node dysfunction.4
An ideal AF procedure would improve upon the current safety profiles of both procedures. It would avoid the risk of cardiopulmonary bypass and be performed on a beating heart. It should allow for the direct visualization of ablation location, avoiding collateral damage (such as to the esophagus). Additionally, it should address the left atrial appendage, which is thought to reduce the risk of stroke.
The HYBRID-AF Procedure
Several centers across the world have begun to address these procedural shortcomings as described above. At Washington University, we have developed our HYBRID-AF procedure with the goal of combining the success rates of the Maze procedure with the minimally invasive nature and shorter recovery times associated with catheter ablation. This allows patients with atrial fibrillation to be treated more effectively with a single procedure.
We perform our procedure in the EP lab, with a full surgical team and cardiopulmonary bypass available in the room. The patient is positioned, prepped, and draped widely. Venous and arterial access is obtained, and catheters are placed into the coronary sinus and right ventricle by the electrophysiologist. The surgeon then performs a thoracoscopic-guided dissection through 3–4 small “ports” in the right chest. Ultimately, a bipolar ablation clamp is fashioned around the right PV antrum, and RF ablation is performed. Additional epicardial linear ablation can be initiated at this time toward the left PVs. Our lab typically performs a superior (roof) line and an inferior (floor) line. Then the surgeon moves to the left side, and a similar bipolar ablation clamp is used around the left PV antrum. The roof and floor lines are then completed. Depending on the location of the left circumflex artery, a mitral isthmus line can be started from the epicardial aspect of the left atrium. Finally, for the surgeon, the left atrial appendage is occluded or removed.
The electrophysiologist then gains access to the left atrium and performs detailed endocardial mapping, testing for entrance and exit block of the PVs. Because the roof/floor lines are performed only from the epicardium, additional endocardial ablation is often used along these lines to improve the chance of full-thickness ablation. With PV isolation and intact linear ablation, the entire posterior left atrium is electrically isolated, and pacing from this location will fail to capture the atrium. Additional right atrial ablation can be performed at the operator’s discretion. An example of endocardial mapping after epicardial ablation is shown in Figure 1.
After the procedure, the patient has bilateral chest tubes and is observed in an intensive care unit setting overnight. The chest tubes are generally removed the following day, and typical recovery time in the hospital after the procedure has been three days. A video of one patient’s experience is provided online at: http://news.wustl.edu/news/Pages/22454.aspx
Currently, at Washington University, the HYBRID-AF procedure is being offered to patients with symptomatic drug-refractory AF who are high risk for AF recurrence. This includes patients with persistent AF, particularly with a large left atrium, or patients who have failed catheter ablation. Whether a combined epicardial-endocardial approach will lead to more favorable outcomes than other treatment options remains to be determined. The HYBRID-AF procedure is an attempt to build on the successes and limitations of current treatment options. As such, it may represent an important step forward in the management of difficult atrial fibrillation.
- Wilber DJ, Pappone C, Neuzil P, et al. Comparison of antiarrhythmic drug therapy and radiofrequency catheter ablation in patients with paroxysmal atrial fibrillation: A randomized controlled trial. JAMA 2010;303:333–340.
- Prasad SM, Maniar HS, Scheussler RB, Damiano RJ Jr. Chronic transmural atrial ablation by using bipolar radiofrequency energy on the beating heart. J Thorac Cardiovasc Surg 2002;124:708–713.
- Cappato R, Calkins H, Chen SA, et al. Updated worldwide survey on the methods, efficacy, and safety of catheter ablation for human atrial fibrillation. Circ Arrhythm Electrophysiol 2010;3:32–38.
- Prasad SM, Maniar HS, Camillo CJ, et al. The Cox maze III procedure for atrial fibrillation: Long-term efficacy in patients undergoing lone versus concomitant procedures. J Thorac Cardiovasc Surg 2003;126:1822–1828.