Mitral Valve Re-Replacement by Using Top-Hat Technique
A 19-years-old, 62 kg male patient was admitted to Siyami Ersek Thoracic and Cardiovascular Surgery Training and Research Hospital pediatric cardiac surgery clinic 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 mitral valve replacement with a 21 mm mechanical valve, aortic valve commissurotomy at 3 years old, and balloon dilation of the aortic valve at 18 years old.
Preoperative echocardiography revealed a mean gradient of 11 mmHg in the mechanical mitral valve, a bicuspid aortic valve, severe aortic valve stenosis (mean gradient of 45 mmHg), moderate-to-severe aortic valve insufficiency, a dilated left atrium, and left ventricle. Mitral valve replacement and aortic valve repair/replacement were planned due to his symptoms and preoperative measurements.
The mediastinum was approached through a midsternal incision. Aortic and bicaval cannulation was done. The patient was put on bypass and cooled down to 28° Celcius. After X-clamping the aorta, aortotomy was done. Cardioplegia (20-mL/kg Del Nido cardioplegia solution) was delivered by using coronary ostial cannulas. Traction sutures were placed on both sides of the aortotomy. The aortic valve was explored. It looked bicuspid and severely calcified in the raphe. Left atriotomy was done. Multiple traction sutures were placed on the left atrium free wall and around the mitral annulus. The mechanical valve was removed by using a clamp and 11 mm scalpel. Mitral annulus was rinsed with saline flush, and remnants of the mechanical valve sewing ring were excised. The mitral annulus looked seriously thinned. A 25 mm mechanical valve sizer was attempted to insert into the mitral annulus. It barely fitted into the annulus. After evaluating the mitral annulus, the aortic valve was explored again. The aortic valve looked injured, possibly due to 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 repair it. The aortic valve was excised, and calcified tissues were removed. A 21 mm 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. Additional dissection was done for possible aorto-mitral curtain reconstruction. 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) Due to the fragile, thin mitral annulus, questionable crossing coronary artery branch, and a goal for a shorter X-clamp time, mitral valve replacement with a mechanical valve by using a kind of top-hat technique(2) concomitant to aortic valve replacement was planned.
A 25 mm mechanical valve was inserted into a 26 mm dacron tube graft. The valve ring was sawn into the graft by using a running 4/0 prolene stitch. The tube graft was trimmed, and an approximately 1 cm long graft was left as a skirt for sewing. The graft was sewn in a supra-annular position by 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. We proceeded with aortic valve replacement. AVR was done using a 21 mm HP mechanical aortic valve and pledgeted sutures in non-everting technique. Any loose stitches were checked by using a nerve hook. Aortotomy and left atriotomy were closed in a double-layer fashion. After the cross-clamp removal, the patient was weaned from bypass. Left atrial pressure was 10 mmHg with the direct measurement using a needle. Transesophageal echocardiography showed well-functioning mechanical mitral and aortic valves, good biventricular function.
The patient was extubated 6 hours after surgery and transferred to the floor on POD 1. He had an uneventful recovery period on the floor and was discharged from the hospital on postoperative day 6.
On the 3rd month of his hospital discharge, transthoracic echocardiography revealed well-functioning mechanical aortic and mitral valves with a mean gradient of 4 mm Hg at the mitral valve. Pulmonary artery pressure was 15 mmHg.
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 for performing radial incisions to the mitral annulus, intraoperative balloon dilation of the mitral annulus, or aorto-mitral curtain reconstruction.
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.