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

Atrial Fibrillation

Atrial fibrillation (AF) is characterized by rapid and irregular activation of the atrium. It may be recurrent (paroxysmal) or permanent (chronic).[1] During AF, atrial cells fire at rates of 400-600 times per minute. The filtering function of the atrioventricular node prevents the conduction to the ventricles and therefore results in ineffective cardiac contraction.[2] The overall prevalence of AF in the population is increasing. The occurrence of AF increases with age, gender, and underlying disease. The incidence of AF doubles with each decade of adult life. Diabetes, hypertension, congestive heart failure, and valve disease are significantly associated with increased risk for AF in both sexes.[3]

AF is associated with the loss of the atrial contribution to ventricular filling. This may result in a decrease in ventricular stroke volume and hemodynamic impairment.[4] If the patient is hemodynamically unstable electrical cardioversion is recommended. Restoration of sinus rhythm (SR) is also considered when the patient is symptomatic despite rate control. Otherwise, rate control is an acceptable alternative.[5,6] Only 20% to 30% of patients who are successfully cardioverted maintain SR for more than 1 year without chronic antiarrhythmic therapy.[7,8,9]

The application of radiofrequency energy at the site of ectopic foci within the pulmonary veins or the electrical isolation of the pulmonary vein from the atrium leads to a reduction in spontaneous atrial ectopy and the abolition of AF in certain populations.[10] The maze procedure, introduced 1987 by Cox and colleagues, is a surgical procedure in which the atrial appendages are excised and the pulmonary veins are isolated. The incisions are placed so that the critical atrial mass necessary to sustain multiple reentrant circuits and thus AF cannot occur. Several dead-end alleyways create maze-like pathways and permit the depolarization of all the atrial tissue, in an attempt to maintain mechanical contraction.[11] A modified maze procedure, which also better preserves atrial function, is more commonly used nowadays, because of the requirement of cardiopulmonary bypass and a chronotropic as well as technical issues with of the initial maze procedures.[12] The sinus node, a strip of atrial tissue, and the atrioventricular node are isolated from the rest of the atria. While allowing SR to be sustained this does not reestablish atrial transport or atrioventricular synchrony, like the maze operation.[2,8,11] The surgical therapy of AF, especially in the setting of mitral operations, has been recently reviewed.[13,14,15] Implantable defibrillators can be programmed to terminate AF by means of an internal shock in selected patients.[4,16,17]

Systemic embolization in the setting of paroxysmal or chronic AF, spontaneously or in association with cardioversion, results in increased stroke severity and a greater mortality rate than in non-AF strokes.[18] Warfarin with a goal international normalized ratio of 2-3 is the treatment of choice in patients in whom the risk of thromboembolism is greater than the risk of bleeding complications from anticoagulation.[19,20]

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