Mechanical cardiopulmonary interactions during exercise in health and disease

The heart and lungs are anatomically coupled through the pulmonary circulation and coexist within the sealed thoracic cavity, making the function of these systems highly interdependent. Understanding of the complex mechanical interactions between cardiac and pulmonary systems has evolved over the last century to appreciate that changes in respiratory mechanics significantly impact pulmonary hemodynamics and ventricular filling and ejection. Furthermore, given that the left and right heart share a common septum and are surrounded by the nondistensible pericardium, direct ventricular interaction is an important mediator of both diastolic and systolic performance. Although it is generally considered that cardiopulmonary interaction in healthy individuals at rest minimally affects hemodynamics, the significance during exercise is less clear. Adverse heart-lung interaction in respiratory disease is of growing interest as it may contribute to the pathogenesis of comorbid cardiovascular dysfunction and exercise intolerance in these patients. Similarly, heart failure represents a pathological uncoupling of the cardiovascular and pulmonary systems, whereby cardiac function may be impaired by the normal ventilatory response to exercise. Despite significant research contributions to this complex area, the mechanisms of cardiopulmonary interaction in the intact human and the clinical consequences of adverse interactions in common respiratory and cardiovascular diseases, particularly during exercise, remain incompletely understood. The purpose of this review is to present the key physiological principles of cardiopulmonary interaction as they pertain to resting and exercising hemodynamics in healthy humans and the clinical implications of adverse cardiopulmonary interaction during exercise in chronic obstructive pulmonary disease (COPD), pulmonary hypertension, and heart failure.