Atrial Fibrillation and Mitral Valve Repair

Angelika Jovin, MD; Dana A. Oprea, MD; Ion S. Jovin, MD; Sabet W. Hashim, MD; Jude F. Clancy, MD

Disclosures

Pacing Clin Electrophysiol. 2008;31(8):1057-1063. 

In This Article

Preoperative AF

Initially, patients in SR compared to patients in AF were thought to have significant difference in the outcome: 30 day mortality (2.0% vs 2.1%), repair failure (5.4% vs 3.6%), stroke (5.4% vs 2.2%), or endocarditis (2.3% vs 0.9%). There was a difference in age (67.2 ± 8.8 vs 61.9 ± 11.8 years), New York Heart Association (NYHA) (77.6% vs 66% in NYHA III/IV), left ventricular ejection fraction (78.8% vs 46.2%), and 3 years (83% vs 88%) mortality.[34]

Subsequently, preoperative AF was found to be the key determinant of outcome of mitral valve repair for degenerative MR, as shown in a study of 392 patients who underwent mitral valve repair due to severe MR. Death due to LV dysfunction was not frequent and cardioembolic events due to AF were the leading cause for cardiac death. Preoperative AF became a strong independent predictor of survival and morbidity. Patients with preoperative SR had excellent prognosis. The benefits of preventing cardioembolic events due to AF validate the indication of mitral valve repair for patients with high risk for AF.[35] The negative impact of preoperative AF on early and late survival was reiterated in a study including 349 patients undergoing various mitral repair procedures.[36] Moreover, in a recent study, Ngaage et al. showed again that preoperative AF is associated with increased surgical risk for patients undergoing mitral repair and also with increased postoperative morbidity. The association between perioperative AF and mortality was not statistically significant in multivariate analysis.[37]

Few data have been published on the effects of mitral valve surgery on atrial rhythm. A retrospective case note review of 92 patients with chronic MR was undertaken demonstrating that mitral valve surgery alone restored SR in only 8.5% of patients with any previous history of AF and probably concomitant antiarrhythmic procedures should be considered for all patients with AF who undergo mitral valve surgery.[38]

The superior left atrial approach to mitral valve surgery appeared to be safe as it maintains SR in a high proportion of patients postoperatively. In addition, it is not normally prone to technical complications, as shown in a study of 59 patients undergoing mitral valve surgery.[39]

Surgery for AF can be combined with mitral valve surgery without adding undue operative risk; with the maze procedure there may be a significant requirement for post-operative pacemaker implantation[40,41] because several of these patients have sinus node dysfunction. Several surgical methods for correction of AF have been devised. These methods consist of either isolation of atrial areas for excluding AF and/or channeling of particular zones for preserving unimpaired sinus rhythm. Those methods are the corridor operation, isolation of the left atrium, the maze operation, the compartment operation, and the pulmonary vein isolation.

A study of 47 patients undergoing revascularization for ischemic heart disease underwent a concomitant Cox maze III procedure, which proved to have a low operative mortality and excellent long-term efficacy in patients with ischemic heart disease.[42] The maze procedure did not appear to increase operative mortality of mitral valve surgery, was effective in eliminating AF, and reduced the risk of thromboembolic complications and the need for long-term anticoagulation after mitral valve repair or replacement with a bioprosthesis.[43] The use of unipolar radiofrequency ablation to perform a mini-maze during minimally invasive mitral valve surgery is a safe procedure and is associated with good early results concluded in a study on 103 patients in which 67.9% were in SR at 17 months and 2 years following the procedure.[44]

Other studies also confirmed that the addition of the Cox maze procedure to mitral valve repair and replacement was safe and effective for selected patients and elimination of AF significantly decreased the incidence of late stroke.[45,46] A study of a group including 72 men who had the maze procedure combined with mitral valve surgery or coronary bypass, found that 90.4% of patients were in SR (or atrial pacing) at 3 years. The preoperative symptoms were reduced: 24% had preoperative syncope; none had syncope in follow-up; 14% of patients preoperatively had cerebral or systemic emboli; and there were no perioperative or late embolic events.[47] A study of 71 patients with refractory AF concluded that left atrial reduction combined with a left atrial-only irrigated unipolar radiofrequency maze procedure is an effective treatment for patients with permanent AF undergoing concomitant mitral operations.[48] In some patients undergoing mitral valve surgery and a Cox maze procedure, AF recurs over time, mandating close, long-term follow-up of heart rhythm. Earlier operation and left atrial size reduction should be considered to improve results in selected patients. A study of 263 patients (mean left atrial diameter, 5.8 ± 1.2 cm) who underwent combined mitral valve surgery (repair in 71%) and a cut-and-sew Cox maze procedure for AF (permanent, 74%; persistent, 7%; paroxysmal, 16%) found that postoperative AF prevalence peaked at 36% at 2 weeks, decreasing to 21% at 5 years. Risk factors for higher postoperative AF prevalence varied with time and included longer duration of preoperative AF (P = 0.003), larger left atrial diameter (P = 0.01), older age (P = 0.0002), and higher left ventricular mass index (P = 0.02).[49]

Patients with mitral valve disease and AF of more than 1 year duration have a low probability of remaining in SR after valve surgery alone. Intraoperative radiofrequency ablation was used as an alternative to simplify the surgical maze procedure and is an effective and less invasive alternative to the original maze procedure.[11,13,50,51,52,53,54] This technique modifies and makes the maze procedure easier and decreases surgical time and the incidence of postoperative complications.[55] Therefore, patients may benefit from combining mitral valve surgery with a surgical approach attempting to eliminate AF. Older patients, however, with a history of AF, antiarrhythmic treatment, or an elevated pulmonary artery pressure may present with AF late after successful mitral valve repair even though SR is present preoperatively as shown in a study of 199 patients.[41]

An observational study of 114 patients from the Cleveland Clinic found that patients who undergo left atrial appendage exclusion during mitral valve surgery to reduce the risk of thromboembolism, have a significant incidence (12.3% during a follow-up of 3.6 years) of thromboembolic events, especially when warfarin therapy is not prescribed at discharge. The study authors reported 10% events in patients prescribed warfarin and 15% events in patients not prescribed warfarin.[56]

Because of the various surgical and catheter-based techniques for treatment of AF and the difficulty to compare the outcomes, several learned societies have published a consensus statement summarizing the evidence in the field regarding indications, management, and follow-up after the procedures.[57] The consensus statement summarizes the development in the field and the trials comparing surgical (stand-alone as well as combined with mitral valvular operations[58,59,60,61,62]; Table 1 ) and catheter-based procedures to no treatment.[57] Overall, both surgical and catheter-based therapies result in a lower recurrence of AF than no treatment. In a recent meta-analysis of surgical ablation for the treatment of AF, Barnett and Ad found that biatrial surgical procedures were more effective than procedures confined to the left atrium.[63] However, because of the paucity of randomized trials and because of the rapid technical evolution in the field, comparisons between various methods are difficult to make. Despite this, in a recent meta-analysis comparing surgical technique (mostly maze III) with catheter-based techniques, Khargi found minimal advantages for the maze procedure, which disappeared after adjustment for other risk factors.[64]

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