The eco-stress of the right heart-pulmonary circulation unit: rationale and application possibilities in clinical practice

The right heart has been traditionally considered a passive conduit between the venous system and the lungs. Today, we know that a close hemodynamic interdependence exists between right ventricle, pulmonary circulation, and left ventricle, and that the right ventricle plays a key role in the ability to adapt to many super-physiological and pathological conditions. Dynamic exercise is a considerable stress for the "right heart-pulmonary circulation unit", which responds, in healthy subjects, with an increase of right ventricular contractility and cardiac output, a decrease of pulmonary vascular resistance, and a non-significant rise in pulmonary pressures. In patients affected by cardiac and/or pulmonary diseases (e.g. ischemic heart disease, heart failure, severe valvular stenosis or regurgitation, systemic sclerosis, chronic obstructive pulmonary disease, etc.) right ventricular contractile reserve may be impaired, and pulmonary artery systolic pressure may abnormally increase during exercise. From this perspective, stress echocardiography is a primary tool to evaluate right ventricle and pulmonary circulation during exercise, and can be useful in setting diagnosis, prognosis, and therapeutic timing of many cardiopulmonary diseases.