Valve Exposure, Intraoperative Valve Analysis, and Reconstruction

MITRAL VALVE EXPOSURE

After extracorporeal circulation has been instituted, adequate exposure of the mitral valve is mandatory to perform a safe and effective operation. Pericardial adhesions, if present, are released up to the apex.

The interatrial approach is used in most instances ( Fig. 7-1 ). It provides better access to the mitral valve than the classic direct atrial approach and less damage than Dubost's biatrial transseptal approach. The interatrial groove is dissected and the two atria are divided up to the fossa ovalis (a) . This dissection exposes the roof of the left atrium, which is incised after the heart has been arrested by cardioplegia (b) . The incision is extended superiorly to 1 cm from the superior vena cava, and inferiorly to midway between the right inferior pulmonary vein and the inferior vena cava (c, d) . If the right atrium is opened inadvertently, it is closed later when left atrial closure is performed.

Maximal exposure of the left atrium is obtained using the self-retaining sternal retractor ( Fig. 7-2 ). The upper blade is positioned first. Its curvature is pushed upwards with the right thumb while the left hand hooks the blade to the sternal retractor. The lower blade is then positioned by pushing its curvature upwards with the left thumb while its straight portion is hooked using the right hand. A lateral blade is available to improve the exposure of the posterior aspect of the mitral valve if necessary.

If exposure of the mitral valve remains suboptimal, several additional maneuvers may be useful:

• All pericardial adhesions are released.

• The vena cavae are dissected from the pericardial tissue and upwards traction is placed on the caval tapes.

• The left atrial incision is extended between the inferior vena cava and the right inferior pulmonary vein.

• A 1-cm incision perpendicular to the atrial incision is added involving the right atrium vertically and the septum transversally up to the fossa ovalis (insets) . This adjunct technique replaces the classic Dubost biatrial incision ( Fig. 7-1, e, insets ).

Once the atrium is fully opened and the mitral valve exposed, a left atrial vent is placed to drain the pulmonary venous return.

To obtain optimal exposure, a transseptal approach may be indicated in cases with previous aortic valve replacement, a small left atrium, or the presense of severe adhesions between the right atrium and the pericardium ( Fig. 7-3 ). This approach is also favored in patients with a giant left atrium to obtain easier access to the mitral valve and to position the incision in an area of high-velocity blood flow, thus minimizing the risk of clot formation. After a craniocaudal (longitudinal) right atriotomy (a) , the septum is incised through the fossa ovalis toward the space between the coronary sinus and the orifice of the inferior vena cava (b) . Inverted mattress sutures are placed to hold the septal edge (c) , which is then retracted with blades (d) .