Some Surgical Aspectsof Atrial Fibrillation

Vincent A. Gaudiani, MD

Luis J. Castro, MD

Audrey L. Fisher, MPH

The Nature of Surgical Intervention

Demands a Simplified Model of What May Be a Complex Problem

Conceptual strip of atrium with normal depolarization

Initial impulse

Impulse travels

Impulse completes circuit while tissue is still depolarized

Tissue repolarizes – ready for next impulse

Yellow tissue is repolarized and ready to conduct.Green tissue is depolarized and cannot currently conduct.

Each macro-reentrant pathway must have a conduction time sufficiently long to permit initially depolarized muscle to repolarize before the depolarizing wavefront returns. This will depend on the:

• Physical length of the pathway• Conductance of the pathway

Macro-reentrant pathways

Normal Abnormally Long

Abnormally Slow

Macro-reentrant pathways

N

Normal Long Slow

Initial impulse

Impulse travels: farther in long circuit and at slwoer speed in slow circuit. Both of these circuits allow for tissue to repolarize by the

time the impulse completes the circuit.

Circuit complete: normal circuit tissue is still depolarized and unable to conduct again. The time delay in long and slow

circuits creates tissue that is repolarized by the time the circuit is complete, and the

impulse can be conducted again and again.

N

Normal SlowLong

N

Normal Long Slow

Yellow tissue is repolarized and ready to conduct.Green tissue is depolarized and cannot currently conduct.

Cox and his colleagues demonstrated that atrial fibrillation may be seen as the

result of the interaction of a finite number of macro-reentrant pathways

ANDthat each pathway correlated with an

anatomic feature of the atria.

Cox reasoned that surgical interdiction of each of these pathways would preclude

sustained atrial fibrillation.

The likely Anatomic Pathways are around the right atrium:

Venae Cavae

Atrial Septum

Tricuspid Valve

Right Atrial Appendage

The likely Anatomic Pathways are around the left atrium:

Pulmonary Veins

Mitral Valve

Atrial Septum

Left Atrial Appendage

Surprisingly, other research has shown that atrial fibrillation is frequently initiated within the cuff of tissue

comprised by the pulmonary veins and the local atrial tissue around them.

- Perhaps 70-80% of atrial fibrillation can be prevented solely by isolating this

tissue from the rest of the atrium.

Optimum Therapy of AF demands:

• Ablation of AF• Restoration of AV Synchrony• Restoration of AV Transport

Optimum therapy corrects the clinical problems associated with AF:

• Atrial thrombus formation

• Decreased cardiac efficiency

• Palpitations

• Need for anticoagulation

Surgical incisions in the right atrium

• Excise right atrial appendage

• Extend from right atrial appendage totricuspid valve

• SVC to IVC straight line incision

• Extend from caval incision to tricuspid

Surgical incisions in the left atrium

Excise left atrial appendageExtend from appendage to epvExtend from mitral annulus to epvCut atrial septum through fossa

ovalis

Left atriotomy

Encircle pulmonary veins

(epv)

The Cox/Maze III operation restores AV synchrony and transport in > 70-80% of patients by isolating the pulmonary vein

cuff and placing surgical incisions through each of the major macro-reentrant circuits.

Every segment of the atria, except the pulmonary vein cuff, remains in electrical

contact with the SA node.

Maze Results I

From October 1997 through December 2003 we performed 162 Maze operations as follows:

•Maze Only 11

•Maze and Mitral Valve Only 74

•Maze and Any Other 77

Maze Results II

In the entire series of 162 cases, there were three operative mortalities (1.9%). These occurred in high-risk patients. There have not been any deaths in reasonable or low risk patients.

Maze Results IIIWe follow up with our Maze patients on an annual basis. Our follow up of August 2003 included 133 patients from between three months to over five years out from the time of operation. The percentage of patients in normal rhythm at 2003 follow up was:

•Maze Only 91% (10/11)•Maze and Mitral Valve Only 92% (55/60)•Maze and Any Other 89% (55/62)

Conclusion

The Cox/Maze procedure is an effective treatment for atrial fibrillation

for some patients who require cardiac operations.