May 2005

Pulmonary Arterial Hypertension

Scientific Updates – May 2005

Complied by

United Therapeutics Corporation

In the journal scan this month there are a number of recent papers concerning various therapies (sildenafil being the hot topic) and a quite a few new papers on aspects of the basic patho-biology of PAH.

Ray Pediani - United Therapeutics

J Ky Med Assoc. 2005 Apr;103(4):138-47.

Inhaled nitric oxide in the treatment of persistent pulmonary hypertension/ hypoxic respiratory failure in neonates: an update.

Cook LN, Stewart DL.

Department of Pediatrics, University of Louisville School of Medicine, KY, USA.

Persistent pulmonary hypertension (PPHN) and subsequent hypoxic respiratory failure is seen in association with numerous diseases and conditions in the neonate. This includes infections such as group B streptococcus, meconium aspiration syndrome, perinatal asphyxia, congenital diaphragmatic hernia, congenital heart disease, and as an idiopathic phenomenon. Conventional therapy of persistent pulmonary hypertension is discussed, as well as integrated with current treatment modalities such as surfactant replacement therapy and high frequency ventilation. The molecular action of nitric oxide including its relationship to neonatal cardiopulmonary transition at birth and the human neonatal clinical experience with term infants from 1992 to the present is explored. Also, the current use of inhaled nitric oxide in preterm infants is reviewed. Additionally, the follow-up of infants treated with inhaled nitric oxide is summarized, and novel therapies including inhaled prostacyclin and other pulmonary vasodilators such as sildenafil are introduced

Biol Neonate. 2005 May 4;88(2):109-112 [Epub ahead of print]

Oral Sildenafil for Treatment of Severe Pulmonary Hypertension in an Infant.

Hon KL, Cheung KL, Siu KL, Leung TF, Yam MC, Fok TF, Ng PC.

Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, China.

We report the use of oral sildenafil in a 5-month-old preterm infant with severe bronchopulmonary dysplasia and pulmonary arterial hypertension refractory to inhaled nitric oxide treatment, maximal ventilatory support and conventional vasodilator therapy. Sildenafil was prepared as a liquid suspension by the method of trituration and administered via an orogastric tube to the patient. Forty-eight hours after sildenafil treatment, echocardiography revealed that the tricuspid incompetence was substantially diminished and the contractility of both ventricles improved, indicating a marked reduction in pulmonary arterial pressure. Oral sildenafil treatment was continued for 6 months until complete resolution of pulmonary arterial hypertension, and oxygen supplement was weaned off. There was no adverse effect during the treatment period. Oral sildenafil may be useful in reducing pulmonary vascular resistance and can be considered for treatment of severe pulmonary arterial hypertension secondary to bronchopulmonary dysplasia. Copyright (c) 2005 S. Karger AG, Basel.

J Inherit Metab Dis. 2005;28(4):603-5.

Clinical response to sildenafil in pulmonary hypertension associated with Gaucher disease.

Fernandes CJ, Jardim C, Carvalho LA, Farias AQ, Filho MT, Souza R.

Pulmonary Division, Pulmonary Hypertension Unit, Brazil.

There are few reports of pulmonary hypertension in Gaucher disease. We report a patient who showed significant clinical improvement after treatment with sildenafil.

Chest. 2005 May;127(5):1647-53.

Hemodynamic effects of sildenafil in patients with congestive heart failure and pulmonary hypertension: combined administration with inhaled nitric oxide.

Lepore JJ, Maroo A, Bigatello LM, Dec GW, Zapol WM, Bloch KD, Semigran MJ.

Cardiology Division, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.

STUDY OBJECTIVES: In patients with pulmonary hypertension (PH) secondary to congestive heart failure, inhaled nitric oxide (NO) increases pulmonary vascular smooth-muscle intracellular cyclic guanosine monophosphate (cGMP) concentration, thereby decreasing pulmonary vascular resistance (PVR) and increasing cardiac index (CI). However, these beneficial effects of inhaled NO are limited in magnitude and duration, at least in part due to cGMP hydrolysis by the type 5 isoform of phosphodiesterase (PDE5). The goal of this study was to determine the acute pulmonary and systemic hemodynamic effects of the selective PDE5 inhibitor, sildenafil, administered alone or in combination with inhaled NO in patients with congestive heart failure and PH. DESIGN: Single center, case series, pharmacohemodynamic study. SETTING: Cardiac catheterization laboratory of a tertiary care academic teaching hospital. PATIENTS: We studied 11 patients with left ventricular systolic dysfunction due to coronary artery disease or idiopathic dilated cardiomyopathy who had PH. INTERVENTIONS: We administered oral sildenafil (50 mg), inhaled NO (80 ppm), and the combination of sildenafil and inhaled NO during right-heart and micromanometer left-heart catheterization. MEASUREMENTS AND RESULTS: Sildenafil administered alone decreased mean pulmonary artery pressure by 12 +/- 5%, PVR by 12 +/- 5%, systemic vascular resistance (SVR) by 13 +/- 6%, and pulmonary capillary wedge pressure by 12 +/- 7%, and increased CI by 14 +/- 5% (all p < 0.05) [+/- SEM]. The combination of inhaled NO and sildenafil decreased PVR by 50 +/- 4%, decreased SVR by 24 +/- 3%, and increased CI by 30 +/- 4% (all p < 0.01). These effects were greater than those observed with either agent alone (p < 0.05). In addition, sildenafil prolonged the pulmonary vasodilator effect of inhaled NO. Administration of sildenafil alone or in combination with inhaled NO did not change systemic arterial pressure or indexes of myocardial systolic or diastolic function. CONCLUSIONS: PDE5 inhibition with sildenafil improves cardiac output by balanced pulmonary and systemic vasodilation, and augments and prolongs the hemodynamic effects of inhaled NO in patients with chronic congestive heart failure and PH.

Respir Med. 2005 May 9; [Epub ahead of print]

Acute and chronic effects of sildenafil in patients with pulmonary arterial hypertension.

Preston IR, Klinger JR, Houtches J, Nelson D, Farber HW, Hill NS.

Department of Pulmonary, Critical Care and Sleep, Tufts-New England Medical Center, 750 Washington Street, Box #257, Boston, MA 0211, USA.

Sildenafil and inhaled nitric oxide (iNO) relax smooth muscle by inhibiting the degradation and stimulating the production of cyclic guanosine monophosphate, respectively. We compared the acute pulmonary vasodilator effects of sildenafil, iNO, and epoprostenol and asked whether the combination of iNO with sildenafil had additive pulmonary vasodilator effects. We assessed the effects of extended use of sildenafil in a small cohort of patients. Twenty patients with pulmonary arterial hypertension underwent an acute vasodilator trial with sildenafil (all patients), iNO and iNO plus sildenafil (11), and epoprostenol (19). We also provided sildenafil to patients who were ineligible for, or had clinical deterioration on epoprostenol, treprostinil, or bosentan. Mean+/-se pulmonary artery pressure dropped by 13+/-3%, 19+/-4%, 14+/-3%, and 26+/-4% with epoprostenol, iNO, sildenafil, and iNO+sildenafil, respectively. Cardiac index increased with epoprostenol and sildenafil. A correlation was found between the effects of iNO and epoprostenol. Nine out of ten patients who were started on long-term sildenafil treatment alone or in combination with other vasodilators had symptomatic improvement. Three died of right heart failure. In conclusion, sildenafil is a potent acute pulmonary vasodilator, an effect that is potentiated by combination with iNO. Long-term therapy of pulmonary hypertension with sildenafil alone or in combination with other agents appears to be safe and well tolerated.

Ann Pharmacother. 2005 May;39(5):869-84. Epub 2005 Apr 12.

Sildenafil for pulmonary hypertension.

Lee AJ, Chiao TB, Tsang MP.

Thomas J Long School of Pharmacy, University of the Pacific; Clinical Specialist, Internal Medicine, Veterans Affairs Medical Center, San Francisco, CA.

OBJECTIVE: To evaluate the efficacy of sildenafil for treatment of pulmonary hypertension. DATA SOURCES: Literature retrieval was accessed through MEDLINE (1977-March 2005), Cochrane Library, and International Pharmaceutical Abstracts (1977-March 2005) using the terms sildenafil and pulmonary hypertension. In addition, reference citations from publications identified were reviewed. STUDY SELECTION AND DATA EXTRACTION: All articles in English identified from the data sources were evaluated. Studies including >5 patients with primarily adult populations were included in the review. DATA SYNTHESIS: The treatment of pulmonary hypertension is challenging. Sildenafil has recently been studied as monotherapy and in combination with other vasodilators in the management of pulmonary hypertension. Eight hemodynamic studies and 12 clinical trials were reviewed (1 retrospective, 3 double-blind, 8 open-label). Sildenafil reduced pulmonary arterial hypertension and pulmonary vascular resistance/peripheral vascular resistance index and tended to increase cardiac output/cardiac index compared with baseline. Sildenafil was comparable to nitric oxide and at least as effective as iloprost or epoprostenol in terms of its pulmonary vasoreactivity. Combination therapy with iloprost, nitric oxide, or epoprostenol resulted in enhanced and prolonged pulmonary vascular effects. Clinical trials suggest that sildenafil improves exercise tolerance and New York Heart Association functional class, but large, randomized controlled trials are needed to confirm these findings. Overall, sildenafil was well tolerated. CONCLUSIONS: Overall, sildenafil is a promising and well-tolerated agent for management of pulmonary hypertension. Further well-designed trials are warranted to establish its place in the treatment of pulmonary hypertension.

Echocardiography. 2005 May;22(5):374-9.

Correlation between Right Ventricular Indices and Clinical Improvement in Epoprostenol Treated Pulmonary Hypertension Patients.

Nath J, Demarco T, Hourigan L, Heidenreich PA, Foster E.

University of Kansas Medical Center, Kansas City, Kansas.

The aim of this study was to evaluate which parameter of right ventricular (RV) echocardiographic best mirrors the clinical status of patients with pulmonary arterial hypertension. Patients with pulmonary arterial hypertension on epoprostenol therapy were identified via hospital registry. Twenty patients, (16 females, 4 males) were included in the study, 9 with primary pulmonary hypertension and 11 with other diseases. Echocardiograms before therapy and at 22.7 (+/-9.3) months into therapy were compared. The right ventricular myocardial performance index (RVMPI) was measured as the sum of the isometric contraction time and the isometric relaxation time divided by right ventricular ejection time. Other measures included peak tricuspid regurgitation jet velocity (TRV), pulmonary artery systolic pressure (PASP), pulmonary valve velocity time integral (PVVTI), PASP/PVVTI (as an index of total pulmonary resistance) and symptoms by New York Heart Association (NYHA) functional class. Echo parameters of right ventricular function were analyzed in patients, before and during therapy. There was significant improvement of NYHA class in patients following epoprostenol therapy (P < 0.0001). Peak tricuspid regurgitant jet velocity (pre 4.2 +/- 0.6 m/sec, post 3.8 +/- 0.7 m/sec, P = 0.02) and PASP/PVVTI (pre 6.7 +/- 3.3 mmHg/m per second, post 4.8 +/- 2.2 mmHg/m per second, P < 0.0001) were significantly improved during treatment. RVMPI did not improve (pre 0.6 +/- 0.3, post 0.6 +/- 0.3, P = 0.54). Changes in NYHA class did not correlate with changes in RVMPI (P = 0.33) or changes in PASP/PVVTI (P = 0.58). Despite significant improvements in TRV, PASP/PVVTI, and NYHA class, there was no significant change in RVMPI on epoprostenol therapy. Changes in right ventricular indices were not correlated with changes in NYHA class. (ECHOCARDIOGRAPHY, Volume 22, May 2005).