Due to vasodilatory properties of the NO, one of the therapeutic approaches for IPAH is oral use of nitric oxide precursors (10). Efficacy of L-arginine is well-documented in the current literature but there is paucity of data with regard to L-citrulline- malate. Hence, this study will evaluate therapeutic efficacy of L-citrulline- malate in two categories of patients with pulmonary hypertension (IPAH, and Eisenmeger syndrome). This randomized clinical trial utilizes 6-minute walk, pro BNP levels and the echocardiographic indexes an indicator of functional improvement of the patients.

Pulmonary vascular tone is maintained by the action of vasoprotective compounds including nitric oxide (NO)(1).NO can be synthesized endogenously in the body via L-arginine and NOS-independent mechanism from the anion nitrite (NO2-)(2,3).Nitric oxide (NO) causes cyclic guanosine monophosphate-mediated vasodilatation of the pulmonary vasculature. Endogenous NO is also produced from the metabolism of citrulline; an amino acid generated by the urea cycle (4). NO is critical for normal development of the pulmonary vasculature and loss of this vasodilator factor and subsequent endothelial dysfunction is proposed as one of the possible explanations for development of pulmonary hypertension (1).

From a clinical standpoint, pulmonary hypertension is a common complication of chronic obstructive pulmonary disease (COPD).Its presence is associated with shorter survival and worse clinical outcome. In a setting of COPD, pulmonary hypertension tends to be of moderate severity and progresses slowly. Recent investigations have demonstrated endothelial dysfunction and changes in the expression of endothelial-derived mediators that regulate vascular tone and cell growth in the pulmonary arteries of patients with mild disease(5). Pulmonary vascular involvement from congenital heart disease like Eisenmeger syndrome is another important category of patients with PAH. In this congenital disease pulmonary vascular involvement follows a period in which pulmonary resistance is low and pulmonary blood flow is high (6, 7, 8). Finally, Idiopathic pulmonary hypertension (IPAH) is the third category of these patients. IPAH has unknown etiology and is characterized by progressive obliteration of small and medium size pulmonary arteries; elevation in pulmonary arterial pressure, and an increase in pulmonary vascular resistance. Presence of these pathologies eventually leads to right heart failure and death (9).

Inclusion Criteria:

• all patients less than 70 years old,
• patients with a six-minute walking distance of more than 100 meters (m),
• a mean pulmonary arterial pressure (PAP) ≥ 25 mmHg at rest as assessed by right heart catheterization(RHC) (11,12).

Exclusion Criteria:

• all patients more than 70 years old,
• patients with a six-minute walking distance of less than 100 meters (m), active pulmonary or extra pulmonary infection,
• serious coronaropathy and/ or ventricular dysfunction,
• significant renal illness and/or hepatitis,
• detected immunosuppressive illnesses,
• carrier of known neoplasias,
• pregnancy,
• lack of family support,
• psychosocial problems,
• drug or alcohol abuse, and
• noncompliance with established medical protocol.