Physiology of critical pulmonary valve obstruction in the neonate

Pathophysiology and clinical presentation of paediatric heart failure related to congenital heart disease

Congenital heart disease (CHD) and cardiomyopathies represent the two most important causes of paediatric heart failure (HF) in developed countries. We made a review of the literature on pathophysiology and clinical presentation of paediatric HF in children with CHD. Two main pathophysiologic models can be identified: the 'over-circulation failure', characterised by signs and symptoms of congestion or hypoperfusion, due respectively to volume or pressure overload, and the 'pump failure'. CONCLUSIONS: The comprehension of the HF pathophysiology in paediatric patients with CHD is of paramount importance for the optimal management and for addressing the best therapeutic choices.

Alpha blocker and angiotensin-converting enzyme inhibitor in the management of severe pulmonary valve stenosis: from bench to bedside

INTRODUCTION

Neonates with severe pulmonary valve stenosis tend to remain oxygen dependent, despite resolution of the transpulmonary gradient. Alpha 2 blockers – phentolamine – and angiotensin-converting enzyme inhibitors – captopril – were reported to improve oxygen saturation.

OBJECTIVE

To describe the role of phentolamine and captopril in the treatment of these patients.

METHODS

In a retrospective cohort study, 28 neonates with severe pulmonary valve stenosis underwent balloon valvuloplasty. Among them, 20 remained oxygen or prostaglandin dependent after intervention, and were treated with phentolamine or captopril. Oxygen saturation was monitored before and after intervention and following treatment with these medications. Mean duration of hospitalisation was recorded.

RESULTS

Mean age and weight were 25.2 days and 3.1 kg, respectively. Before balloon dilation, 18/20 (90%) neonates were on prostaglandin, whereas after the procedure only 6/18 patients required it. All 20 patients required oxygen after the procedure, and nine patients (45%) were started on phentolamine. Among them, one patient with severe infundibular stenosis did not respond favourably, and 11 patients (55%) were started on captopril. After starting phentolamine or captopril treatment, prostaglandin could be discontinued after a mean time of 15.86 hours. Within <2 days, there was an increase in mean oxygen saturation from 76.6 to 93.0%.

CONCLUSION

Phentolamine and captopril seem to have therapeutic roles in neonates with severe pulmonary valve stenosis who remain oxygen dependent after balloon dilation. Both drugs led to vasodilation of the pulmonary and systemic vascularisation and facilitated inflow to the right ventricle. Right-to-left shunt across a patent foramen ovale or atrial septal defect decreased and saturation improved, leading to a significant reduction in the length of hospitalisation.

Critical pulmonary stenosis

Critical pulmonary stenosis causes cyanosis and can be potentially lethal in the neonate. Initial treatment includes general resuscitation and infusion of prostaglandin E1 to dilate the ductus. The diagnosis is usually made echocardiographically, but a right ventriculogram in the outflow tract may be necessary in some patients with only a tiny valve opening. Preformed catheters may aid in the passage of an appropriate guidewire. Valvuloplasty should be performed with a balloon approximately 1.2 times the annulus diameter. Most patients remain mildly to moderately cyanotic immediately after the procedure. With right ventricular (RV) growth and improved RV compliance, the cyanosis eventually resolves. Some patients may require prolonged prostaglandin infusion, a surgical shunt, or other mechanical means of maintaining systemic-to-pulmonary artery flow. Intermediate--to long-term results are excellent. However, only 5%-10% of patients may require surgical relief of residual valve or subvalvular stenosis. Very long-term follow-up raises concern about the significance of induced pulmonary insufficiency. Up to 30% of patients may require repeat balloon valvuloplasty.