The heart and lungs support the metabolic functions of other vital organs in a human body. Their development begins in the early gestational period and relies on the complex process of cellular differentiation and formation of the immature fetal circulatory system. The transition from “in-parallel” fetal to extra-uterine “in-series” circulation is the key to establishing viability of life. Left ventricular (LV) function is the main determinant of systemic hemodynamics. Under normal conditions, LV preload is approximated by end diastolic volume, and its function is governed by the Frank-Starling Law. LV compliance and afterload may also influence myocardial work as represented in pressure-volume loops. The right ventricle (RV) is volume dependent and load sensitive. Its preload is determined mainly by end-diastolic volume, but also influenced by pulmonary vascular resistance, impedance, and compliance. Pulmonary hypertension comprises different pathological states, leading to direct alterations of normal gas exchange and RV hemodynamics. One of the most widely used tools to assess RV hemodynamics is the pulmonary artery catheter. LV and RV interdependence highlights the importance of hemodynamic optimization through biventricular synchrony.