Background: This study aimed to evaluate the effect of pulmonary blood flow and pulmonary hypertension on plasma endothelin-1, homocysteine and serum nitric oxide levels in patients with left-to-right shunt lesions with pulmonary hypertension and also with normal pulmonary arterial pressure.
Methods and results: Plasma endothelin-1, homocysteine and nitric oxide levels were measured in 44 patients (Group 1) with left-to-right shunt and normal pulmonary arterial pressure (Qp/Qs: 2.1), 65 patients (Group 2) with left-to-right shunt and pulmonary hypertension (Qp/Qs: 2.4), 20 healthy control subjects (Group 3), and 17 post-operative patients (Group 4). Plasma endothelin-1 and serum nitric oxide levels were significantly higher in Group 2 than in groups 1, 3, and 4 (p<0.001). Plasma homocysteine levels were significantly higher in Group 2 than in Groups 1 and 4 (p<0.001 and p<0.01, respectively).
Conclusions: The increase in serum nitric oxide levels in patients with left-to-right shunt and pulmonary hypertension may be attributed to the compensatory mechanism. However, this increase does not improve pulmonary hypertension because of increased endothelin-1 and homocysteine levels. In the light of present study, we conclude that vascular changes caused by increased homocysteine and endothelin-1 may provoke pulmonary hypertension in patients with left-to-right shunt.