Histologic Evidence of Transmurality Four Years After Bipolar Radiofrequency Cox-Maze IV

Abstract

In contrast to the cut-and-sew Cox-Maze [1Cox J.L. The surgical treatment of atrial fibrillation. IV. Surgical technique.J Thorac Cardiovasc Surg. 1991; 101: 584-592Abstract Full Text PDF PubMed Google Scholar], durable transmurality of the ablation lines in the Cox-Maze IV (CM-IV) relies on coagulative and apoptotic phenomena after the ablative energy is applied. Achieving transmurality, defined as complete atrial wall thickness of fibrotic changes, is of paramount importance for procedure success and explains the evolving use of different energy sources during the last years, in the search for reliable and durable scar lesions. Presently, CM-IV procedures are mostly performed using radiofrequency and cryothermy [2Lall S.C. Melby S.J. Voeller R.K. et al.The effect of ablation technology on surgical outcomes after the Cox-maze: propensity analysis.J Thorac Cardiovasc Surg. 2007; 133: 389-396Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar]. We report the histologic studies 4 years after a CM-IV using bipolar radiofrequency. A 69 year-old female underwent mitral valve repair and CM-IV with bipolar radiofrequency; mitral and tricuspid lines were completed at the annulus by monopolar radiofrequency. Sinus rhythm was thereafter confirmed annually. Four years later, progressive residual mitral regurgitation becoming severe required reintervention. During valve replacement, scar lines from the previous Maze were evident on epicardial and endocardial aspects (Fig 1A, white arrow). Ten samples from pulmonary veins and different points at both atria were studied with Masson’s trichrome. A fibrous band affecting the complete width was shown in all samples (Fig 1B, Fig 1C, white arrows; Fig 1D), with normal atrial tissue surrounding. This is the first histologic report in human myocardium confirming medium-term transmurality after bipolar radiofrequency CM-IV.