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Ann Thorac Surg 1997;64:244-247
© 1997 The Society of Thoracic Surgeons
Department of Cardiovascular Surgery, Faculty of Medicine, Kyoto University, Kyoto, Japan
Accepted for publication February 21, 1997.
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We report a case of aortic stenosis, preductal coarctation, and severe PH that was caused by the excessive medial thickening of the pulmonary arterioles in which, however, the clinical presentation was not that of PPHN. The patient is alive about 5 years after the operation, but the PH remains.
A 7-month-old female infant was referred to our department for heart failure and growth retardation. Her mother had been involved in two traffic accidents during this pregnancy. The patient was born at 37 weeks of gestational age by spontaneous normal delivery. The Apgar score was 10 at birth. She showed heart failure at 1 week of age. She was treated medically. She was diagnosed as having aortic stenosis, preductal aortic coarctation, severe PH, and Turner's syndrome. Doppler echocardiography revealed that the pressure gradient across the aortic valve was about 90 mm Hg and that across the coarctation was about 40 mm Hg. There were no shunts at the atrial, ventricular, or arterial level. The mitral valve was normal, and the volume and contraction of the left ventricle were within the normal range. Right heart catheterization and retrograde radial arteriography were performed when she was 7 months old. The catheter did not enter in the left atrium. The pulmonary arterial pressure (PAP) was 100/38 mm Hg (mean, 66 mm Hg). Retrograde radial arteriography disclosed that a preductal coarctation was present. Pulmonary arteriography revealed almost normal volume and contraction of the left ventricle, dilatation of the ascending aorta, and slightly hypoplastic distal aortic arch.
Operation was performed in July 1991. With the patient in the right semilateral position, a left anterolateral thoracotomy was made through the fourth intercostal space, and the sternum was transected. Two arterial cannulas were inserted into the ascending and descending aorta. One venous cannula was inserted into the right atrium via the appendage. After valvotomy of the bicuspid aortic valve, coarctectomy was performed with an extended aortic arch anastomosis. She was easily weaned from the extracorporeal circulation under catecholamine support. Biopsy of the lung was performed before the thoracotomy was closed.
Pulmonary arterial pressure was monitored for 4 days. It varied between about three fourths and one half of the systemic arterial pressure with infusion of prostaglandin E1. She was successfully extubated on the 14th postoperative day. She needed catecholamine support for 3 weeks. As she became restless and took less milk while breathing room air, she was kept in an oxygen box.
The histopathologic examination revealed marked medial thickening of the pulmonary arterioles (Figs 1
, 2). The smooth muscle of the intraacinar pulmonary arterioles extended into smaller, peripheral, normally nonmuscular vessels. The endothelium was thin-layered and intact. These findings are compatible with PPHN.
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In the first group, examination of the pulmonary vascular bed demonstrates normal anatomic development. In these infants, the syndrome is precipitated by intense pulmonary vasoconstriction, occurring in infants with, for example, meconium aspiration, birth asphyxia, or low Apgar score. Although multiple factors may be responsible for pulmonary vasoconstriction, hypoxia or acidosis is generally considered to be the primary stimulus [1].
In the second group, examination of the pulmonary vascular bed demonstrates increased medial wall thickness in intraacinar pulmonary arterioles, with extension of smooth muscle into smaller, peripheral, normally nonmuscular vessels. Chronic intrauterine hypoxia is thought to stimulate medial hypertrophy of pulmonary arterioles. Goldberg and associates [3] produced medial hypertrophy in the pulmonary arterioles of neonatal rats in which chronic intrauterine hypoxemia had been maintained throughout late gestation by lowering the oxygen content in the mothers' chamber to 13% to 15%. Drummond and Bissonnette [4] produced medial hypertrophy in fetal sheep by partially infarcting the placenta with microspheres during the latter part of gestation.
Pulmonary hypertension during fetal development can also cause medial hypertrophy. Intake of a prostaglandin synthesis inhibitor, eg, indomethacin [5], during pregnancy causes ductal vasoconstriction and elevates pulmonary pressure, and it is one of the causes of PPHN.
Luciani and colleagues [6] recently reported successful surgical repair of 2 cases of transposition of the great arteries and intact ventricular septum (TGA/IVS) with persistent PH. Persistent PH was diagnosed after right-to-left shunting via the ductus arteriosus, which was demonstrated by Doppler echocardiography. Luciani and colleagues employed inhaled nitric oxide and rapid arterial switching operation, and they used extracorporeal membrane oxygenation support preoperatively and postoperatively in 1 patient with biventricular dysfunction. They described that the fundamental pathology in TGA/IVS/persistent PH had been shown to be increased thickness of the wall of the pulmonary arterioles, due to extension of smooth muscle to the peripheral vessels. The PAP in both patients, however, was normalized even 2 or 3 days after cessation of nitric oxide administration. In both patients the mechanism could be considered to have been the same as that in the first group of PPHN described by Rudolph [2]. If the atrial communication is too small or perinatal stress exists, the infants with TGA/IVS show hypoxia, acidosis, or both. Hypoxia can cause pulmonary vasoconstriction, which will result in PH exceeding systemic pressure in some patients with TGA/IVS even after adequate balloon atrial septostomy. Once ductal shunting occurs, this results in a decrease of "effective" pulmonary and systemic flow [6]. This causes metabolic acidosis, which exacerbates the pulmonary vasoconstriction. If pulmonary vasoconstriction disappears after surgical repair of TGA/IVS/persistent PH, PAP would be normalized.
Our patient did not show the presentation of PPHN clinically, but she did have the histopathology distinctive of PPHN. Medial thickening is also seen in patients with congenital cardiac defects in the Heath-Edwards classification grades I and II [7]. Intimal hypertrophy is also seen. Our patient, however, had no cardiac defects and no shunts. The endothelium was thin-layered and intact. After we distinguished the medial hypertrophy in the pulmonary arterioles histopathologically, we reappraised the history. It was only then that her mother told us for the first time that she had been involved in two traffic accidents. These might have caused the slight abruptions of the placenta that can lead to intrauterine hypoxia, and this line of thought is also suggested by the experimental results presented by Drummond and Bissonnette [4].
Pulmonary hypertension in the fetal circulation, secondary to ductal vasoconstriction by prostaglandin synthesis inhibitor, causes medial hypertrophy and results in PPHN [5]. Haworth and Reid [8] reported that medial hypertrophy of the lungs was seen in newborns who had died of aortic atresia or stenosis, and that it was more severe in aortic atresia. They suggested that, in fetuses with aortic atresia or stenosis, PAP could be elevated to maintain systemic and placental perfusion, and that this would be a cause of medial hypertrophy [8]. Furthermore, in fetuses with aortic stenosis and preductal aortic coarctation, PAP would be elevated more so than in fetuses with aortic stenosis to maintain cerebral perfusion. However, aortic atresia and preductal aortic coarctation are two components of hypoplastic left heart syndrome. The newborns with hypoplastic left heart syndrome undergo Norwood's operation, and the survivors undergo Fontan-type operation. Therefore, it seems rare that medial hypertrophy in patients with aortic stenosis/aortic coarctation without left heart hypoplasia results in PH that remains about 5 years after operation. We strongly suspect that our patient had been exposed to intrauterine hypoxia.
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This article has been cited by other articles:
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  S. Yamaki, A. Abe, M. Endo, T. Tanaka, K. Tabayashi, and T. Takahashi Surgical indication for congenital heart disease with extremely thickened media of small pulmonary arteries Ann. Thorac. Surg., November 1, 1998; 66(5): 1560 - 1564. [Abstract] [Full Text] [PDF]
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