Case report

The patient is an 8-year-old male who was born with pulmonary atresia with an intact ventricular septum. He underwent a right modified Blalock–Taussig shunt as a neonate, followed by the hemi-Fontan procedure with bilateral pulmonary artery patch angioplasty, atrial septectomy, and ligation of the modified Blalock–Taussig shunt at the age of 7 months. He underwent completion of lateral tunnel, fenestrated Fontan procedure at the age of 2.5 years. The peak and mean preoperative pressure gradients across the left ventricular outflow tract prior to the Fontan procedure were 14 mmHg and 7 mmHg, respectively. At the time of discharge, the peak and mean pressure gradients on the echocardiogram were 7 mmHg and 3 mmHg, respectively.

Approximately 6 months after the Fontan procedure, a routine follow-up echocardiogram revealed a peak pressure gradient of 42 mmHg (mean 18 mmHg) across the left ventricular outflow tract. A prominent muscle ridge of the ventricular septum and chordal attachments from the mitral valve caused dynamic obstruction (Fig 1a, 1b). There was also a systolic anterior motion of the anterior mitral valve leaflet (supplementary video). There was associated development of mild mitral valve regurgitation. He was asymptomatic and observed without intervention at that time.

Figure 1.

(a ) Apical three-chamber view of transthoracic echocardiography during his follow-up. There was a systemic ventricular outflow tract obstruction with a prominent muscle ridge of ventricular septum (*) and chordal attachments from the mitral valve (arrow). (b ) Doppler echocardiogram across SVOT. There was a peak pressure gradient of 42 mmHg.

Over the next 5 years, the gradient gradually increased across the left ventricular outflow tract (range 40–80 mmHg) (Fig 2a–2f) with stable mild mitral regurgitation. Despite the increase in gradient, he remained clinically asymptomatic.

Figure 2.

Longitudinal changes in Doppler echocardiogram across systemic ventricular outflow tract. (a ) pre-Fontan procedure (a peak pressure gradient of 13 mmHg), (b ) at the time of discharge after FP (6 mmHg), (c ) 3 months after FP (2 mmHg), (d ) 6 months after FP (50 mmHg), (e ) at 4 years of age (71 mmHg), (f ) at 5 years of age (120 mmHg).

At 8 years old, he started to complain of fatigue and difficulty in keeping up with his siblings. The echocardiogram showed a peak pressure gradient of 145 mmHg (mean gradient 60–70 mmHg) across the left ventricular outflow tract. There was moderate mitral valve regurgitation with normal left ventricular systolic function. The Fontan pathway was widely patent. Since his significant systemic ventricular outflow tract gradient coupled with his clinical symptoms, he underwent surgical repair to relieve his left ventricular outflow tract obstruction. Operative findings showed a discrete subaortic membrane, abnormal accessory tissue of the anterior leaflet of the mitral valve with abnormal attachment to the ventricular septum, and abnormal attachment of the anterior papillary muscle to the septum. He underwent resection of the subaortic membrane and resection of abnormal accessory tissue of the anterior mitral valve leaflets with a detachment of abnormal attachment to the ventricular septum. Separation of the anterior papillary muscle of the interventricular septum to the base of the papillary muscle with debulking the papillary muscle was also performed. The post-operative left ventricular outflow tract pressure gradient on the echocardiogram was 40 mmHg. He was discharged on post-operative day 15. The mitral valve regurgitation improved to mild and left ventricular systolic function remained normal. At his 2 months follow-up visit, there was no residual gradient across the left ventricular outflow tract with a peak gradient of 12 mmHg and a mean of 5 mmHg. He is clinically doing better and has no complaint of fatigue.