Lesional tachycardias related to mitral valve surgery.

Objectives: The purpose of this study was to define the anatomic distribution of electrically abnormal atrial tissue and mechanisms of atrial tachycardia (AT) after mitral valve (MV) surgery.

Background: Atrial tachycardia is a well-recognized long-term complication of MV surgery. Because atrial incisions from repair of congenital heart defects provide a substrate for re-entrant arrhythmias in the late postoperative setting, we hypothesized that atriotomies or cannulation sites during MV surgery also contributed to postoperative arrhythmias.

Methods: In 10 patients with prior MV surgery, electroanatomic maps were constructed of 11 tachycardias (6 right atrium [RA], 4 left atrium [LA] and 1 biatrial). Activation and voltage maps were used to identify areas of low voltage, double potentials and conduction block.

Results: Lesions were present in the lateral wall of the RA (six of seven maps) and in the LA along the septum adjacent to the right pulmonary veins (four of five maps). In 8 of 10 patients, these findings corresponded to atrial incisions or cannulation sites. Arrhythmia mechanisms were identified for 9 of 11 tachycardias. A macro-re-entrant circuit was mapped in six cases, three involving lesions in the lateral wall of the RA and three involving the LA septum and right pulmonary veins. In three of these cases figure-of-eight re-entry was demonstrated, and in the other three a single macro-re-entrant circuit was observed. In three other cases, a focal origin was identified adjacent to abnormal tissue in the RA (two cases) or within a pulmonary vein (one case).

Conclusions: Surgical incisions for MV surgery provide a substrate for atrial arrhythmias. Both macro-re-entrant and focal mechanisms contribute to AT after MV surgery.