Case report

A 5-month-old boy was admitted to our centre for rapid breathing, poor feeding, and failure to thrive. His body weight and height were 4750 gr and 57 cm, respectively. Physical examination revealed a resting oxygen saturation of 95%. There was no sign of desaturation either at rest or on exertion. Cardiac auscultation revealed a significant diastolic murmur at the apex and a continuous precordial murmur. Chest X-ray showed cardiomegaly and plethoric lung fields. Two-dimensional echocardiography revealed a severe mitral stenosis with a maximum of peak 28 mmHg and mean 14 mmHg gradients measured with coloured-wave doppler (Fig 1a). There were two separate papillary muscles within the mitral valve. The posterior papillary muscle was originating high on the posterior wall of the left ventricle. Both leaflets were found to adhere to the same papillary muscle. Left ventricular inflow was seen turbulent through the fenestrations of the hammock mitral valve, and moderate insufficiency was observed (Fig 1b). Mitral annulus was 18 mm, and the left atrium was measured 35 × 35 mm. Mild insufficiency of the tricuspid valve and mild dilatation of both the right and the left ventricles were detected. Biventricular systolic function was good, and there was no pericardial effusion. There was a 20 × 25 mm defect between the main pulmonary artery and the ascending aorta (Fig 1c). The aortic arch was left-sided with no coarctation. The diagnosis was confirmed as a hammock mitral valve accompanying aortopulmonary window. Depending on the clinical and echocardiographic evaluations, cardiac catheterisation was not deemed mandatory. Following median sternotomy, total excision of the thymus was performed. Pericard was opened wide enough to provide exposure of the aorta and the pulmonary arteries. Aortic and main pulmonary arterial pressure was measured directly. Aortic pressure was 75/38 (57) mmHg, while the main pulmonary arterial pressure was 74/34 (55) mmHg. A typical external fusion line was detected between the proximal ascending aorta and the main pulmonary artery (Fig 2a). Aorto-bicaval cannulation was performed. A vent was placed in the right superior pulmonary vein. Under deep hypothermic (24°C) cardiopulmonary bypass, antegrade cold blood hyperkalaemic cardioplegic arrest and an antegrade cerebral perfusion support (20 minutes), main pulmonary arteriotomy was performed and 25 × 25 mm type 1 aortopulmonary window was exposed before the pulmonary artery bifurcation. Aortopulmonary window was repaired with a transpulmonary approach by using a Dacron patch (Fig 2b). Pulmonary arteriotomy was closed primarily. Left atrial access was obtained via a right atriotomy and creation of an atrial septal defect. The mitral leaflets were developed like a membranous structure. The surface of this structure was smooth, and there were no traces of commissures. There were two separate papillary muscles. Rudimentary and short chordae arose and connected to the medial side leaflets which were originating from the posterior papillary muscle (Fig 2c). The native mitral valve was excised. We preferred to use interrupted 4/0 Ti-Cron sutures with pledgets which were directly placed into the annulus to implant the 16-mm mechanical aortic valve (Medtronic AP360) in the reverse position. The interatrial septum was closed primarily with creating a 5-mm septal defect. The right atriotomy was closed primarily. The patient was favourably weaned from the cardiopulmonary bypass without any inotropic support. Finally, the aortic pressure measurement was 102/65 (79) mmHg, whilst the main pulmonary arterial pressure measurement was 43/13 (22) mmHg after weaning from the cardiopulmonary bypass. The post-operative course was uneventful. Post-operative echocardiographic evaluations revealed neither insufficiency nor stenosis of the replaced mechanical mitral valve with a normal biventricular function (Fig 1d). Oral warfarin was started at a dose of 0.5 mg/day and uptitrated to a targeted goal international normalised ratio of 3. Heparin was continued until optimal dosing for Warfarin was obtained in an inpatient setting. Oral aspirin was administered with 5 mg/kg/day at beginning from the first post-operative day. The patient discharged on the ninth post-operative day. Follow-up echocardiogram within the first- and sixth-month outpatient clinic control revealed no evidence of mitral insufficiency or stenosis.

Figure 1.

( a ) Two-dimensional transthoracic echocardiography parasternal short-axis view showing a severe mitral stenosis with coloured-wave doppler. ( b ) Two-dimensional transthoracic echocardiography parasternal short-axis view showing left ventricular inflow with a turbulent flow through the fenestrations of the hammock mitral valve, and moderate insufficiency was observed with coloured-wave doppler. ( c ) Two-dimensional transthoracic echocardiography parasternal short-axis view showing type 1 aortopulmonary window between the proximal ascending aorta and the main pulmonary artery. ( d ) Two-dimensional transthoracic echocardiography parasternal short-axis view showing the replaced mechanical mitral valve with a 16-mm mechanical aortic valve (Medtronic AP360) in the reverse position. APW: aortopulmonary window, LA: left atrium, LPA: left pulmonary artery, LV: left ventricle, MPA: main pulmonary artery, MV: mitral valve, RPA: right pulmonary artery.

Figure 2.

( a ) Intraoperative view of the type 1 aortopulmonary window. A typical external fusion line was detected between the proximal ascending aorta and the main pulmonary artery. ( b ) Intraoperative view of a 25 × 25 mm type 1 aortopulmonary window was exposed before the pulmonary artery bifurcation. Aortopulmonary window was repaired with a transpulmonary approach by using a Dacron patch. ( c ) Intraoperative view of the excised native mitral valve. The mitral leaflets were developed like a membranous structure. The surface of this structure was smooth, and there were no traces of commissures. APW: aortopulmonary window.