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(Circulation. 2003;108:II-167.)
© 2003 American Heart Association, Inc.

Surgery for Congenital Heart Disease

Intravenous Sildenafil Is a Potent Pulmonary Vasodilator in Children With Congenital Heart Disease

Ingram Schulze-Neick, MD; Paulina Hartenstein, BSc; Jia Li, MD; Brigitte Stiller, MD; Nicole Nagdyman, MD; Michael Hübler, MD; Ghazwan Butrous, MD; Andy Petros, MD; Peter Lange, MD; Andrew N. Redington, MD

From the Abteilung für Angeborene Herzfehler, Deutsches Herzzentrum Berlin, Berlin, Germany; Pfizer Ltd, Sandwich, UK; Cardiothoracic Unit, and Pediatric Intensive Care, Great Ormond Street Hospital, London, UK; Division of Cardiology, The Hospital for Sick Children, Toronto, Canada.

Correspondence to Dr Andrew N. Redington, Head, Division of Cardiology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8 Canada. Phone: 416-813-6135, Fax: 416-813-7547. E-mail: Andrew.redington{at}sickkids.ca

Background— Increased pulmonary vascular resistance (PVR) because of congenital heart disease (CHD) may be caused by a dysfunction in endogenous pulmonary endothelial nitric oxide (NO) production. In other forms of pulmonary vascular disease with increased PVR, an elevated activity of a phosphodiesterase type 5 (PDE-5), responsible for the degradation of cyclic guanidine monophosphate (cGMP), the second messenger of endothelially produced NO, has been demonstrated. This study compares the effects of inhaled NO before and after the specific inhibition of the PDE-5 by intravenous sildenafil (Viagra^TM) in pre- and postoperative children with increased PVR because of CHD.

Methods and Results— 12 children with congenital heart disease (age 0.2 to 15.7 years, median 2.4 years) and increased mean pulmonary arterial pressure, and 12 postoperative children (age 0.11 to 0.65 years, median 0.32 years) with increased PVR (8.3±1.0 Wood Units*m²) were studied during cardiac catheterization ("cath laboratory"), or within 2 hours after return from cardiac surgery ("post op"), respectively. All were sedated, tracheally intubated and paralyzed. During alveolar hyperoxygenation (F_iO₂=0.65), the effects of inhaled NO (20 ppm) were compared before and after the stepwise infusion of sildenafil ("cath laboratory", 1 mg/kg; post op, 0.25 mg/kg). Intravenous sildenafil more effectively reduced PVR than NO (11.5% versus 4.3% in the "cath laboratory" patient group, P<0.05, and 25.8% versus 14.6% in the post op patient group, P=0.09. The increase in cGMP in response to NO was potentiated (2- to 2.4-fold) by PDE-5 inhibition. While the vasodilating effects of sildenafil showed pulmonary selectivity, its infusion was associated with increased intrapulmonary shunting in the postoperative patients (Q_s/Q_t=16.5±4.7% to 25.5±18.2% P=0.04).

Conclusions— Intravenous sildenafil is as effective as inhaled NO as a pulmonary vasodilator in children with congenital heart disease. Although clinically insignificant in this study, increased intrapulmonary shunting with sildenafil may be disadvantageous in some patients after CHD surgery.

Key Words: heart defects • congenital • heart surgery • pulmonary circulation • hypertension • pulmonary • nitric oxide • sildenafil