This review focuses on right ventricular anatomy and function and the significance of ventricular interdependence in the response of the right ventricle to an increase in afterload. This is followed by a discussion of the pathophysiology of right ventricular failure in pulmonary arterial hypertension as well as in other clinical syndromes of pulmonary hypertension. Pulmonary hypertension is common in critically ill children and is associated with several conditions. Regardless of the etiology, an increase in right ventricular afterload leads to a number of compensatory changes in cardiovascular physiology. These changes are not altogether intuitive and require an understanding of right ventricular physiology and ventricular interdependence to optimize the care of these patients.