A Surgical Method for Subvalvular Structure Intervention Through a Transaortic Approach in Normal Bama Pigs

This study develops a reproducible transaortic surgical method to study subvalvular interventions under clinically relevant conditions. This protocol can be applied to surgical training, histological analysis, and evaluation of subvalvular intervention strategies. After preparing the animal, make a midline incision along the sternum, extending from the suprasternal notch to approximately two centimeters below the xiphoid process.

Using an electrocautery device, incise the skin and subcutaneous tissues while maintaining an incision length of approximately 20 centimeters. Continue to separate the pectoralis major muscles and the periosteum of the sternum. Fully expose the anterior surface of the sternum.

Gently retract the lateral tissues with the help of an assistant to maintain a clear surgical field. After exposing the sternum, insert a Lebsche knife beneath the xiphoid process and apply upward traction. Using a small hammer, carefully and evenly tap the proximal end of the Lebsche knife.

Gradually split the sternum along the midline, proceeding cranially until the thoracic cavity is opened. Maintain continuous upward traction throughout the process to avoid deviation or injury to the pericardium. After completing the sternal division, place a Finochietto rib retractor.

Slowly expand the thoracic cavity bilaterally to widen the operative field, while avoiding excessive retraction to prevent pleural injury or rib fractures. Perform blunt dissection bilaterally to separate the pericardium from the mediastinal pleura and adjacent connective tissues. After completing the dissection, expose the heart under direct visualization.

Confirm clear identification of key anatomical structures, including the aorta, pulmonary artery, right atrial appendage, cardiac apex, and coronary sinus. Once adequate cardiac exposure is achieved, place a purse-string suture at the base of the right atrial appendage. Make a small incision within the suture loop and insert a venous drainage cannula obliquely downward along the axis of the right atrial appendage to establish the venous return pathway for cardiopulmonary bypass.

Advance the cannula approximately three to four centimeters to ensure that its tip enters the right atrial cavity and secure the cannula to the atrial appendage using silk sutures to prevent slippage or leakage. Insert a perfusion cannula through the right atrial appendage region into the coronary sinus to serve as the inflow pathway for cardioplegia delivery and myocardial perfusion. Activate the venous return pump to initiate partial venous drainage.

Gradually open the arterial pump to maintain perfusion pressure at 60 to 80 millimeters of mercury. Infuse cooled high potassium cardioplegia via the coronary sinus to induce cardiac arrest and record the arrest time. Apply pre-prepared sterile ice saline slush over the cardiac surface to further reduce myocardial temperature, decrease metabolic demand, and enhance myocardial protection.

After achieving cardioplegic arrest and hypothermic protection, make a transverse incision approximately one to 1.5 centimeters in length on the anterior wall of the ascending aorta. Position the incision approximately 1.5 to two centimeters above the aortic valve annulus and orient it perpendicular to the long axis of the aorta. Insert two curved sheet hooks into the aortic incision from the left dorsal and ventral sides and gently retract the incision laterally to open the aortic root and expand the surgical field.

Now, advance small curved scissors through the aortic incision along the axis of the aorta toward the left ventricular chamber. Use the traction suture to expose the target subvalvular region. Under direct visualization, orient the scissors horizontally and cut the designated subvalvular structures in a controlled manner.

Remove the resected tissue and hand it to the assistant. Finally, close the aortic incision using continuous absorbable sutures. Begin at one end of the incision and sequentially pass the needle through the intima and media using evenly-spaced stitches to ensure complete watertight closure.

Following aortic incision closure, restore cardiac perfusion and observe spontaneous cardiac rebeating. After placement of the closed drainage tubes, close the sternum with interrupted stainless steel wires and perform routine layered closure of the thoracic wall. The total operation time was approximately 2.5 to three hours.

Cardiopulmonary bypass was maintained for about 60 to 71 minutes. After restoration of cardiac perfusion, spontaneous cardiac rebeating was observed in all animals with a stable sinus rhythm. No apparent complications or adverse events were observed after the procedure.

The key challenge is achieving adequate exposure and precise resection while avoiding damage along the surgical access pathway. Following intervention, animals can undergo echocardiography, CMR, and other hemodynamic assessments to evaluate cardiac function. Future studies can explore long-term functional outcomes, optimize resection strategies, and investigate mechanisms underlying subvalvular intervention effects.