Cox-Maze IV

The authors present an open Cox-Maze IV (CMPIV) procedure using bipolar radiofrequency (RF) and cryoablation devices(1). This procedure is performed on cardiopulmonary bypass via a median sternotomy due to significant aortic insufficiency. Our ablation technique for a minimally invasive approach differs slightly with respect to the type of ablation utilized for the lesions and has been described(2). The biatrial lesion sets are performed beginning with bilateral pulmonary vein isolation. Isolation is confirmed by documenting exit block form the isolated pulmonary veins. This is followed by the right atrial lesion set which is performed on the empty, beating heart. After cross-clamping and cardioplegic arrest, the left atrial appendage is excluded, , and finally the left atrial lesion set is performed. For the pulmonary vein isolations and left atrial box lesions, we employ three sets of double ablations. For the rest of the lesions, 2 sets of double ablations are made.

The right atrial lesion set consists of a line of block from the superior down to the inferior vena cava , a right atriotomy extending from this line of block , across the right atrial free wall towards the AV groove near the free margin of the heart , and an endocardial cryoablation extending from the superior aspect of this right atriotomy, down to the tricuspid annulus at the 2 o’clock position. From the base of the right atrial appendage(RAA), an ablation line is performed down the aortic side of the RAA. A second endocardial cryoablation is made from the base fo the RAA down to the tricuspid annulus at the 10 o’clock position. Bipolar RF ablation is used for all lesions except those adjacent to the tricuspid valve. The left atrial lesion set begins with exposure of the left atrial appendage (LAA). The LAA is either amputated and oversewn, or excluded with a clip at its’ base. A connecting lesion is performed with a bipolar RF clamp, from the base of the LAA and crosses the left pulmonary vein isolation. A standard left atriotomy is then made in order to expose the posterior left atrium and the mitral valve. . Superior and inferior lesions which connect the right and left pulmonary vein isolations are performed to create a “box” lesion, isolating the entire posterior left atrium. The mitral isthmus lesion is performed using a combination of bipolar RF ablation on the atrial tissue and endocardial cryoablation for the tissue adjacent to the mitral valve and the coronary sinus. The Cox-Maze IV is completed with an epicardial cryoablation across the coronary sinus.

The outcomes for the CMPIV are excellent with 92% of patients being free of atrial tachyarrhythmias at one year and 84% at 5 years and 77% at 10 years post operatively (3).
 

References

1. Khiabani AJ, MacGregor RM, Manghelli JL, Ruaengsri C, Carter DI, Melby SJ, Schuessler RB, Damiano RJ Jr. Bipolar Radiofrequency Ablation on Explanted Human Hearts: How to Ensure Transmural Lesions. Ann Thorac Surg. 2020 Dec;110(6):1933-1939. doi: 10.1016/j.athoracsur.2020.04.079. Epub 2020 Jun 6. PMID: 32522634; PMCID: PMC7669627.
2. Lancaster TS, Melby SJ, Damiano RJ Jr. Minimally invasive surgery for atrial fibrillation. Trends Cardiovasc Med. 2016 Apr;26(3):268-77. doi: 10.1016/j.tcm.2015.07.004. Epub 2015 Jul 20. PMID: 26296538.
3. Khiabani AJ, MacGregor RM, Bakir NH, Manghelli JL, Sinn LA, Maniar HS, Moon MR, Schuessler RB, Melby SJ, Damiano RJ Jr. The long-term outcomes and durability of the Cox-Maze IV procedure for atrial fibrillation. J Thorac Cardiovasc Surg. 2020 May 5:S0022-5223(20)31065-5. doi: 10.1016/j.jtcvs.2020.04.100. Epub ahead of print. PMID: 32563577.

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