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Atrial fibrillation is the most common
arrhythmia with a prevalence varying from 0.04 to 5% according to age. It is present in
almost all cardiac diseases, causes the loss of left and right atrial kick and irregular rate
with worsening of the whole cardiac function. In the long period it predisposes the atrial
surfaces to clotting and growth of thrombi1. The physiopathology of atrial fibrillation is
complex. Garey in 1924 hypotized that a “critical mass” of atrial myocardium was
necessary to sustain atrial fibrillation2. More recently, Moe demonstrated that in the
human atrial tissue atrial fibrillation is formed by multiple wavelets with various
directions and amplitude and of unpredictable durability, distribution and extension3.
On the basis of these observations, it is possible to formulate a unitary hypothesis
according to which the arrhythmia is caused by multiple reentrant circuits originated in
the proximity of anatomical or functional barriers (venous orifices, valvular annuli, atrial
appendages) and sustained by structural alteration of the muscular wall4. In patients
with mitral disease requiring surgical intervention, atrial fibrillation is present in about
60% of cases and more prevalent in cases with enlarged atrial cavities5. After mitral
valve surgery atrial fibrillation rarely converts to sinus rhythm thank to valve surgery
alone due to the persistence of atria with increased diameter, altered hystological
structure and electrophysiologic properties6. In the past decade several attempts to
associate the treatment of the valve disesase toghether with that of the associated
arrhythmia have been performed, namely left atrial isolation7
and maze procedure8, with its
variations9. Both technique are efficacious but present some limitations.
Left atrial isolation (Fig. 1) leaves a left atrial surface with no contracting properties and
potential thrombotic risk. The maze procedure (Fig. 2) carries long sutures along the
atria, with risk of postoperative bleeding, sinus node or atrioventricular node
disfunction and limited atrial pump function. The use of radiofrequency energy instead
of surgical incisions has considerabily improved the technical aspects of the maze
procedure, although the rate of the recurrence of AF is variable among the various
series10,11. Moreover there are different protocols of maze procedure and lines of
radiofrequency ablation, so that it is sometimes difficult to correctly analizing the
results. On the basis of our experience with a modified maze operation on a series
of 26 patients, we discuss the indications, the limitations and the possible future
perspectives of the treatment of AF associated with mitral disease.
Fig. 1: Operative scheme of left atrial isolation.
Fig.2: Operative scheme of "Maze" procedure.
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