Mesenteric blood flow velocities in the newborn with single-ventricle physiology: modified Blalock-Taussig shunt versus right ventricle-pulmonary artery conduit.

BACKGROUND: Neonates with ductal-dependent single-ventricle congenital heart disease palliated with a modified Blalock-Taussig shunt (mBTS) commonly have retrograde diastolic flow in the aorta, which may place them at increased risk of mesenteric ischemia. Recently, palliation with a right ventricle-to-pulmonary artery conduit, known as the Sano procedure, has been shown to eliminate retrograde diastolic flow, theoretically leading to better systemic perfusion. OBJECTIVE: To compare the changes in superior mesenteric artery (SMA) and celiac artery velocities and flow after a bolus enteral feed in patients with single-ventricle congenital heart disease palliated with an mBTS vs. those palliated with the right ventricle-to-pulmonary artery conduit. DESIGN: Prospective clinical study. SETTING: Cardiothoracic intensive care unit and pediatric ward of a tertiary care children's hospital. PATIENTS: A total of 27 patients with single-ventricle congenital heart disease (15 with mBTS, 12 with Sano) after stage-1 palliation. INTERVENTION: Doppler ultrasound of the SMA and celiac artery was performed 30 mins before and after a bolus enteral feed. MEASUREMENTS AND MAIN RESULTS: SMA and celiac artery peak systolic flow velocity, mean flow velocity, and time-velocity integral were measured. After a bolus enteral feed, 8 of 15 infants palliated with an mBTS had retrograde diastolic flow through the SMA yet demonstrated significant increases in all variables of both the SMA and celiac artery flow velocities (SMA peak systolic flow velocity: 0.96 +/- 0.33 vs. 1.2 +/- 0.4 m/sec, p = .01). Those palliated with the Sano procedure did not demonstrate SMA retrograde diastolic flow but also did not have any significant changes in their mesenteric flow variables (SMA peak systolic flow velocity: 0.79 +/- 0.16 vs. 0.89 +/- 0.26 m/sec, p = .2). CONCLUSION: Postprandial retrograde diastolic flow was observed in the majority of patients palliated with an mBTS vs. none of the patients in the Sano group. However, contrary to expectations, postprandial mesenteric blood flow velocities in those palliated with an mBTS are significantly higher than in Sano patients, although the increase is not as high as that historically seen in normal neonates. This may place this population at risk for mesenteric ischemia and feeding intolerance in the postoperative period, and the risk may be even greater for those neonates palliated with a right ventricle-to-pulmonary artery conduit.