Surgery for Atrial Fibrillation

The Maze procedure was developed and modified by Dr. James Cox and has proved to be effective for treating atrial fibrillation associated with valvular and ischemic heart disease and isolated atrial fibrillation refractory to medical therapy. The Cox-Maze III cut and sew technique is the gold standard against which modifications should be measured because of its greater than 95% cure of atrial fibrillation. However, this procedure adds significantly to the aortic clamp time and incurs the risk of serious bleeding from the back of the heart. Several different energy sources have been used to ablate atrial tissue, creating the same lesion pattern as the Maze III operation in less time and with less bleeding potential. The ideal energy source for performing a full or partial Maze procedure should be fast and produce a transmural lesion without causing damage to surrounding structures. It would be advantageous if it could be applied through a minimally invasive approach without the use of cardiopulmonary bypass. Radiofrequency systems heat tissue, causing thermal injury and conduction block. Unipolar systems have been modified by adding irrigation to minimize the surface charring, which can lead to thrombus formation, and to prevent injury to adjacent structures, particularly the esophagus. Bipolar radiofrequency clamps can be used epicardially, assure transmural lesions, and avoid damage to surrounding tissue. However, not all of the Maze lesions can be performed with the bipolar device. Cryoablation is performed with a nitrous oxide-cooled probe. Its advantage is the lack of tissue vaporization, resulting in a smooth tissue surface. It takes 2 to 3 minutes to produce each transmural lesion. Microwave produces conduction block by thermal injury, but unlike radiofrequency, it does not cause surface charring. It is also more likely to produce a transmural lesion because of greater tissue penetration. Focused ultrasonography results in deep heating and coagulati on necrosis, and can be delivered through tubular or planar transducers. Both the Nd:YAG laser and infrared coagulator produce transmural photocoagulation necrosis at relatively low tissue temperatures with no tissue vaporization. We have used a combination of bipolar radiofrequency clamp and a cryoprobe to recreate the lesions of Cox-Maze III procedure (which is called Cox-Maze IV procedure). This procedure can also be performed using a combination of other energy sources. Patients with chronic atrial fibrillation undergoing mitral valve surgery are candidates for this procedure, which adds approximately 20 minutes to the cross-clamp time.

TECHNIQUE

A median sternotomy is used, and standard bicaval cannulation is performed. The initial right atrial incisions and lesions are accomplished on cardiopulmonary bypass with a beating heart.

We first encircle right and left pulmonary veins. Using the radiofrequency clamp, we create transmural lesions around the pulmonary veins (Fig. 13.1). After tightening the caval tourniquets, the right atrial appendage is excised. Using the radiofrequency clamp passed through the right atrial appendage opening, a linear lesion is created toward SVC, on the aortic side of the appendage (Fig. 13.2). We then perform a vertical incision on the right atrial free wall. Using the bipolar clamp, linear lesions are created up to SVC and down to IVC (Fig. 13.3).

FIG. 13.1 The bipolar clamp is used to create lesions around the right and left pulmonary veins.

FIG. 13.2 Excision of the right atrial appendage and lesion line on the aortic side of SVC.

With the atrial free wall retracted, linear endocardial lesions are created from the superior aspect of atriotomy to 2 o’clock and 10 o’clock positions of the tricuspid vale annulus (Fig. 13.4). These two lesion sets are usually performed with bipolar radiofrequency clamp on the free wall to save time. The segment near AV groove needs to be performed endocardially with cryoprobe.

Omitting Right Atrial Ablation Lines

It is generally agreed that most of the right-sided lesions are not required in most patients. However, the ablation line from the coronary sinus inferiorly into the inferior vena cava should probably be included to prevent right atrial flutter (Fig. 13.5).

After placing a retrograde cardioplegia catheter, we then close the right atriotomy and start the left-sided lesion set. Aorta is cross-clamped and heart is arrested. Left atrial appendage is amputated and through the opening, a lesion is created between the left atrial appendage opening and left superior pulmonary vein (Fig. 13.6). Left atrial appendage base closed. We then mark the coronary sinus with a marking pen between the right and left coronary artery circulations. A standard left atriotomy is performed, with extension superiorly into the dome of left atrium or inferiorly around the right inferior pulmonary vein. Using the bipolar clamp, a lesion is created from the inferior aspect of the atriotomy to the inferior left pulmonary vein. Similarly, another lesion is created toward the mitral valve annulus and across the coronary sinus (Fig. 13.7). We then use the cryoprobe to create endocardial lesions connecting the PV lesions and to connect the left PV lesion set to the annulus of the mitral valve (Fig. 13.8). Lastly, the epicardial cryoablation of the coronary sinus is performed to complete the mitral isthmus ablation.

FIG. 13.3 Linear lesions are created through the atriotomy up the SVC and down to IVC.

FIG. 13.4 Radiofrequency lesions from the amputated appendage to the tricuspid valve annulus and from the atriotomy free wall to the tricuspid annulus.

Only gold members can continue reading. Log In or Register to continue