The role of the left ventricle (LV) in ICU patients with circulatory shock has long been considered. However, acute right ventricle (RV) dysfunction causes and exacerbates many common critical illnesses (e.g., acute respiratory distress syndrome (ARDS), pulmonary embolism (PE), inferior acute myocardial infarction, and postoperative cardiac surgery). There is a variety of definitions for acute RV dysfunction (RVD), RV failure (RVF), and right heart failure (RHF) in the literature that must be clarified and not used interchangeably. RHF can be defined by a clinical syndrome due to an alteration of structure and/or function of the right heart circulatory system (comprised from the systemic veins up to the pulmonary capillaries) that reduces the ability to propel blood to the pulmonary circuit and/or high systemic venous pressures at rest or with effort [1]. Failure of the RV is a frequent component of RHF but not a mandatory feature of the RHF syndrome. Acute RVD is defined as at least one of the following (Table 1) [2, 3]: (i) Acute occurrence of RV systolic dysfunction by measuring the longitudinal systolic displacement and dilation [4–۶] (ii) Unexplained increase of natriuretic peptides in the absence of LV or renal disease (iii) Electrocardiographic (ECG) RV strain patterns which are strong markers of moderate-to-severe RV strain. While specific, they are limited by a lack of sensitivity. Evidence of cardiomyocyte death (elevation of troponin ? > 0.4 ng/mL, troponin ? > 0.1 ng/mL) predicts severe RVD. Although evidence of cardiomyocyte death can be seen in the absence of RVD, such patients are at risk for progression to circulatory collapse. Acute cor pulmonale (ACP) is a form of RVD due to an acute increase in RV afterload. Acute RVF is defined as acute RVD plus low cardiac output (CO) and hypoperfusion with the consequent multiorgan dysfunction/failure. RVF occurs when the RV fails to provide enough blood flow to the pulmonary circulation to accomplish adequate LV filling [7] (Figure 1). It can be suspected whenever the ratio of the right atrial pressure to the pulmonary arterial occlusion pressure ≥ ۰٫۸–۱٫۰ with a reduction in the cardiac index. In the present work, we will focus on the epidemiology, pathophysiology, diagnosis, and treatment of acute RVD/ RVF.