Mitral Valve Re-Replacement by Using Top-Hat Technique

Mitral valve replacement using the top-hat technique can be an option in patients with small mitral annulus or patients with patient-prosthesis mismatch. This technique can provide adequate left ventricle in-flow without a need to perform radial incisions to the mitral annulus, intraoperative balloon dilation of the mitral annulus, or aorto-mitral curtain reconstruction. 

The Patient 

A nineteen-year-old, 62kg male patient was admitted with fatigue, dyspnea on exertion, and palpitation. He had a history of congenital mitral valve stenosis, mitral insufficiency, and aortic valve stenosis. He had undergone a mitral valve replacement with a 21mm mechanical valve, an aortic valve commissurotomy at three years old, and a balloon dilation of the aortic valve at eighteen years old. 

A preoperative echocardiography revealed a mean gradient of 11mmHg in the mechanical mitral valve, a bicuspid aortic valve, a severe aortic valve stenosis (mean gradient of 45mmHg), a moderate-to-severe aortic valve insufficiency, and a dilated left atrium and left ventricle. Mitral valve replacement and aortic valve repair/replacement were planned because of his symptoms and preoperative measurements. 

The Surgery 

The mediastinum was approached through a midsternal incision. Then, aortic and bicaval cannulation was performed, and the patient was put on bypass and cooled down to 28° Celsius. After X-clamping the aorta, an aortotomy was performed. Cardioplegia (20-mL/kg del Nido cardioplegia solution) was delivered using coronary ostial cannulas. Traction sutures were then placed on both sides of the aortotomy and the aortic valve was explored. The valve looked bicuspid and severely calcified in the raphe. Thus, a left atriotomy was done. After this, multiple traction sutures were placed on the left atrium free wall and around the mitral annulus.  

Next, the mechanical valve was removed by using a clamp and 11mm scalpel. After the removal, the mitral annulus was rinsed with a saline flush, and remnants of the mechanical valve sewing ring were excised. The mitral annulus looked seriously thinned, so an insertion of a 25mm mechanical valve sizer into the mitral annulus was attempted. It barely fit into the annulus.  

After evaluating the mitral annulus, the aortic valve was explored again. The aortic valve looked injured, possibly because of previous balloon dilatation, and there was a significant tissue deficiency in the leaflet with the raphe. The decision was made to replace the valve instead of repairing it. So the aortic valve was excised, and calcified tissues were removed. Next, a 21mm mechanical valve sizer was passed through the aortic annulus. The aortic annulus looked narrow after inserting a 25mm mechanical valve sizer to the mitral annulus. Thus, additional dissection was performed for a possible aorto-mitral curtain reconstruction. Then a coronary artery branch crossing the left atrium was seen.  

Mitral annulus enlargement techniques such as radial incisions to the mitral annulus, balloon dilation of mitral valve, were discussed(1). Because of the fragile, thin mitral annulus, questionable crossing coronary artery branch, and a goal for a shorter X-clamp time, the mitral valve replacement with a mechanical valve by using a kind of top-hat technique(2) concomitant to aortic valve replacement was planned. 

A 25mm mechanical valve was inserted into a 26mm dacron tube graft. Then the valve ring was sewn into the graft using a running 4/0 Prolene stitch. The tube graft was then trimmed, and an approximately 1cm-long graft was left as a skirt for sewing. The graft was sewn in a supra-annular position with a 4/0 Prolene stitch starting from the posterior annulus. After taking a few bites, the graft was lowered into the left atrium and sewn to the supra-annular side in a running fashion. Any loose stitches were checked. The aortic valve replacement came next. AVR was performed using a 21mm HP mechanical aortic valve and pledgeted sutures in non-everting technique. Any loose stitches were checked using a nerve hook. The aortotomy and left atriotomy were closed in a double-layer fashion. After cross-clamp removal, the patient was weaned from bypass. Left atrial pressure was 10mmHg with the direct measurement using a needle. A transesophageal echocardiography showed well-functioning mechanical mitral and aortic valves and good biventricular function. 

Recovery and Follow-Up 

The patient was extubated six hours after surgery and transferred to the floor on postoperative day 1 (POD1). He had an uneventful recovery period on the floor and was discharged from the hospital on POD6. 

On the third month of his hospital discharge, a transthoracic echocardiography revealed well-functioning mechanical aortic and mitral valves with a mean gradient of 4mmHg at the mitral valve. Also, pulmonary artery pressure was 15mmHg. 

References

1. Myers PO, del Nido PJ, McElhinney DB, Khalpey Z, Lock JE, Baird CW. Annulus upsizing for mitral valve re-replacement in children. J Thorac Cardiovasc Surg. 2013 Aug;146(2):347-51.
2. Yacoub MH, Kittle CF. A new technique for replacement of the mitral valve by a semilunar valve homograft. J Thorac Cardiovasc Surg 1969;58:859–69.

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