Comprehensive Invasive and Noninvasive Approach to the Right Ventricle–Pulmonary Circulation Unit

Abstract

… And I ask, as the lungs are so close at hand, and in continual motion, and the vessel that supplies them is of such dimensions, what is the use or meaning of this pulse of the right ventricle? And why was nature reduced to the necessity of adding another ventricle for the sole purpose of nourishing the lungs? — —William Harvey, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, 1628 There is still no answer to William Harvey’s rhetorical question. He included the right ventricle (RV), its “pulse,” the large pulmonary arteries (PAs), and the lungs in the same sentence, emphasizing the concept of a “unit.” Although Harvey realized the importance of the RV and its interactions with the pulmonary circulation, 4 centuries later, the RV is largely understudied. At the same time, there has been significant progress in our understanding of the pathology of pulmonary vascular disease and, over the past few years, an explosion of clinical therapeutic trials for PA hypertension (PAH).1 This unbalanced approach has generated a number of problems and controversies. For example, it is now becoming apparent that even if experimental therapies improve or reverse PAH pathology, this does not necessarily lead to clinical improvement and prolonged survival unless accompanied by a parallel improvement in RV function. The degree of pulmonary hypertension (ie, PA pressure [PAP]) does not strongly correlate with symptoms or survival, whereas RV mass and size and right atrial pressure reflect functional status and are strong predictors of survival.2 The 6-minute walk test, used as the primary end point in most PAH clinical trials, correlates better with RV function (ie, cardiac output) than with the degree of pulmonary pressure elevation. However, this test is being heavily criticized because of multiple inherent problems and the fact that it does …