Ann Thorac Surg 1998;65:1764-1765
© 1998 The Society of Thoracic Surgeons
Case Reports
Temporary Aorto–Pulmonary Shunt for Pulmonary Hypertension After Truncus Arteriosus Repair
Takahiro Katsumata, MDa,
Amihay Shinfeld, MDa,
Stephen Westaby, FRCSa
a Department of Cardiac Surgery, Oxford Heart Centre, John Radcliffe Hospital, Oxford, England, United Kingdom
Accepted for publication December 12, 1998.
Address reprint requests to Mr Westaby, Department of Cardiac Surgery, Oxford Heart Centre, John Radcliffe Hospital, Oxford OX3 9DU, England
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Abstract
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We describe successful management of pulmonary hypertension with a reversible aorto–pulmonary (central) shunt and inhaled nitric oxide gas after truncus arteriosus repair. A temporary central shunt may provide a lifeline in those cases refractory to pharmacologic pulmonary vasodilation as long as marginal systemic oxygenation can be maintained.
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Introduction
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Neonatal primary repair is recognized as the optimal treatment for truncus arteriosus [1, 2]. Although early primary repair is unlikely to be associated with fixed elevated pulmonary vascular resistance [3, 4], the immediate results of the operation still depend on pulmonary vascular reactivity. We describe successful salvage after failure to wean from cardiopulmonary bypass during a pulmonary hypertensive crisis. A reversed aorto–pulmonary shunt was constructed when nitric oxide treatment failed. The shunt was reversed when the pulmonary artery pressure fell.
A 2.83-kg male infant with DiGeorge syndrome presented with heart failure on the second day of life. The respiratory rate was 60 per minute, with an oxygen saturation of 90% on room air and arterial oxygen tension of 82 mm Hg. Echocardiography showed type 1 truncus arteriosus with normal systemic and pulmonary venous drainage. There was a small left-to-right shunt at the atrial level. Treatment with digoxin and diuretics was commenced immediately, and surgical correction was undertaken on his 34th day of life. With mechanical ventilation, oxygen saturation was 86% with an inspired oxygen fraction of 0.5. The pulmonary arteries were mobilized from the truncus, and the ventricular septal defect was repaired in the usual way. Right ventricular–pulmonary artery continuity was established with an 11-mm antibiotic-treated aortic homograft. The proximal anastomosis of the homograft conduit was completed with a hood of autologous pericardium. A large atrial septal defect was closed directly during a short period of total circulatory arrest at 22°C.
Despite vigorous left ventricular contraction, initial attempts to wean the patient from cardiopulmonary bypass failed, with unexpectedly low oxygen saturation (66%) and distention of the right ventricle. Direct pressure measurements showed suprasystemic pressure (78 mm Hg) in the central pulmonary artery beyond the homograft anastomosis, with a systemic arterial pressure of 30 mm Hg. Cardiopulmonary bypass was recommenced and the elevated pulmonary vascular resistance was treated with additional narcotic analgesia (fentanyl), isoproterenol hydrochloride, alkalinization of the blood, and hyperventilation (inspired oxygen fraction of 1.0). Despite these maneuvers, the pulmonary arterial pressure and right ventricular motion did not improve and the infant remained hypoxic (arterial oxygen tension of 42 mm Hg). Inhalational nitric oxide therapy was provided at a concentration of 30 to 40 ppm via the endotracheal tube after an abortive second attempt to wean the patient from bypass. This provided an immediate increase in the oxygen tension to 105 mm Hg (oxygen saturation, 94%) and a marginal increase in systemic arterial pressure to 40 mm Hg. Pulmonary arterial pressure remained suprasystemic (68 mm Hg) and the right ventricle remained distended.
In an attempt to rectify hemodynamics incompatible with life, we constructed an aorto–pulmonary shunt during cardiopulmonary bypass with a 10-mm segment of homograft innominate artery 6 mm in diameter from the same donor (Fig 1). We performed the end-to-side homograft-to-pulmonary artery anastomosis and then used a side clamp on the ascending aorta to create a reversible aorto–pulmonary window.
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Fig 1. (A) Thoracic aortic homograft from 9-month-old donor. The aortic root was used for right ventricular outflow tract reconstruction. (B) The innominate artery was used as an aorto–pulmonary shunt when pulmonary hypertension prevented separation from cardiopulmonary bypass.
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The patient was then weaned with equal pulmonary arterial and systemic pressures (56 mm Hg), a central venous pressure of 10 mm Hg, and mild desaturation of the arterial blood (arterial oxygen tension, 90 mm Hg; oxygen saturation, 86%) without inotropic support. Echocardiography showed unidirectional (right to left) flow in the shunt immediately after the operation. With continued deep sedation and a reduced concentration of nitric oxide (16 ppm), repeated echocardiography showed a gradual decrease of the right-to-left shunt. By 4 hours in the intensive care unit, the flow was bidirectional but predominantly left to right. The chest was then reopened and the aorto–pulmonary shunt was clipped to increase the diastolic pressure and myocardial blood flow. The oxygen saturation was restored to 95% on an inspired oxygen fraction of 1.0. Systemic arterial pressure increased from 55 to 65 mm Hg with the pulmonary arterial pressure remaining at 52 mm Hg. The patient remained hemodynamically stable, and nitric oxide administration was discontinued 24 hours later. Echocardiography showed resolution of right ventricular distention (now approximately 70% of the systemic pressure).
The infant was extubated on the seventh postoperative day and made an otherwise uneventful recovery. At follow-up 3 months later, the infant is thriving and fully saturated without medication for heart failure.
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Comment
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The central aorta-to-main pulmonary artery shunt with an interposition conduit is a widely used palliative procedure for cyanotic congenital heart disease. A major advantage of this procedure is simplicity and ease of reversal. Instead of increasing pulmonary blood flow, the central shunt can also be applied to offload the rightventricle during a pulmonary hypertensive crisis. Although fenestration of the ventricular septal defect patch or the atrial septum is the conventional maneuver to rescue the right ventricle after failed attempts to reduce pulmonary vascular resistance, this requires repeat cardiotomy. In the event of resultant improvement of right ventricular function, a second operation to close the ventricular septal defect is usually necessary for persistent left-to-right shunt with a propensity for endocarditis. The fact that the "rescue" central shunting compromises systemic oxygenation and reduces diastolic blood pressure and coronary flow should be considered before its application. A number of centers have reported successful reversal of intractable pulmonary hypertension with low-dose inhalational nitric oxide or extracorporeal membrane oxygenation after operations for congenital heart disease [5–8].
In our patient, administration of nitric oxide reduced pulmonary vascular resistance and provided some improvement of gas exchange, presumably because of a reduction in ventilation-perfusion mismatch. Nevertheless, pulmonary arterial pressure remained at suprasystemic levels with declining right ventricular function. The central shunt equalized ventricular pressures and, by offloading the right side, allowed the septum to shift back to the right, thereby improving function in both ventricles. Pulmonary hypertension subsided in a few hours, after which the shunt was detrimental through lowering of aortic diastolic pressure with a reduced coronary blood flow. A clip on the artificial ductus arteriosus immediately corrected this situation, and the infant survived.
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Acknowledgments
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We thank the staff of the Oxford Heart Valve Bank for their invaluable technical assistance, and Miss Katherine L. Ely for editorial assistance.
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References
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- Hanley F.L., Heinemann M.K., Jonas R.A., et al. Repair of truncus arteriosus in the neonate. J Thorac Cardiovasc Surg 1993;105:1047-1056.[Abstract]
- Bove E.L., Lupinetti F.M., Pridjian A.K., et al. Results of a policy of primary repair of truncus arteriosus in the neonate. J Thorac Cardiovasc Surg 1993;105:1057-1066.[Abstract]
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Abstract
Introduction
