IntroductionThe pulmonary vasculature consists of large, elastic, extraparenchymal conduit pulmonary arteries (CPA, order 1 to 2) that arise from the sixth aortic arch and small, muscular resistance intrapulmonary arteries (RPA, ≥ 4th order), that originate from the mesenchymal lung bud by capillary plexus expansion [1]. This subdivision is associated with different response to several stimuli. While CPA dilates or fails to constrict to hypoxia, RPA is responsible for hypoxic pulmonary vasoconstriction, control the regional distribution of blood flow and largely determine pulmonary vascular resistance. This functional difference mainly depends on the distribution of electrophysiologically distinct myocytes in CPAs and RPAs arteries [1,2].Levosimendan is a positive inotropic agent (by increasing the sensitivity of troponin C to calcium) with vasodilating properties (by lowering of intracellular free Ca++, opening of different potassium channels and the inhibition of phosphodiesterase type III), also termed inodilator [3,4]. There are several animals studies in different acute pulmonary hypertension (PH) models secondary to thromboxane A2 infusion [5], endotoxemia [6], acute pulmonary embolism (PE) [7,8], and hypoxia [9] and some clinical studies that demonstrated the vasodilator effect of levosimendan on the pulmonary circulation, restoring right ventricular-arterial coupling as it increased right ventricular contractility concomitantly [10,11]. Acute PE-induced PH results from two main mechanisms:
HighlightsBackground