Right Ventricular Dysfunction in Pulmonary Hypertension

Abstract

We now know that there are many key differences between the right ventricle (RV) and the left ventricle (LV), ranging from embryological origin, structure, function (metabolism and perfusion), neurohormonal activation and response to increased afterload. Although the role of the RV in the low-pressure normal pulmonary circulation may not be critical, its critical role may become apparent in the diseased pulmonary circulation (e.g. pulmonary hypertension, PHT) or in high-altitude environments. Similarly, although in utero the RV is hypertrophied, within a few weeks after birth, its metabolism and structure is switching to the adult phenotype. Thus, the RV may be designed to be more "plastic." However, its dynamic responses to physiologic or nonphysiologic triggers increase the risk of maladaptation. We now know that a maladaptive, failed RV is the most important factor in the morbidity and mortality in PHT, regardless of its specific cause. Right ventricular dysfunction is also a very strong predictor of outcome in patients with heart failure due to left ventricular dysfunction. Yet, at this time, few studies have focused on the RV, without extrapolating concepts form the LV. Thus, the concept of RV-specific therapies remains embryonic. In 2006, the NIH formed a task force focusing on increasing awareness and promoting RV studies specifically. Here we review the basic principles of right ventricular dysfunction, clinical diagnosis, as well as therapy, introducing the concept of RV-specific therapies. However, the biggest question in this field, i.e. what is the difference between the adapted RV (for example, the RV in a patient with severe PHT due to congenital heart disease that offers the patient decades-long survival) and the maladaptive RV [for example, the RV in a patient with idiopathic pulmonary arterial hypertension (PAH) of similar magnitude, which fails relatively quickly and allows only a few years of survival], remains unknown. It is hoped that the next edition of this textbook will provide some answers to this critical question.