Survival in patients with pulmonary arterial hypertension (PAH) is closely related to right ventricular (RV) function. Although pulmonary load is an important determinant of RV systolic function in PAH, there remains a significant variability in RV adaptation to pulmonary hypertension. In this report, the authors discuss the emerging concepts of right heart pathobiology in PAH. More specifically, the discussion focuses on the following questions. 1) How is right heart failure syndrome best defined? 2) What are the underlying molecular mechanisms of the failing right ventricle in PAH? 3) How are RV contractility and function and their prognostic implications best assessed? 4) What is the role of targeted RV therapy? Throughout the report, the authors highlight differences between right and left heart failure and outline key areas of future investigation.

Rationale: Transthoracic Doppler echocardiography is recommended for screening for the presence of pulmonary hypertension (PH). However, some recent studies have suggested that Doppler echocardiographic pulmonary artery pressure estimates may frequently be inaccurate. Objectives: Evaluate the accuracy of Doppler echocardiography for estimating pulmonary artery pressure and cardiac output. Methods: We conducted a prospective study on patients with various forms of PH who underwent comprehensive Doppler echocardiography within 1 hour of a clinically indicated right-heart catheterization to compare noninvasive hemodynamic estimates with invasively measured values. Measurements and Main Results: A total of 65 patients completed the study protocol. Using Bland-Altman analytic methods, the bias for the echocardiographic estimates of the pulmonary artery systolic pressure was 20.6 mm Hg with 95% limits of agreement ranging from 138.8 to 240.0 mm Hg. Doppler echocardiography was inaccurate (defined as being greater than 610 mm Hg of the invasive measurement) in 48% of cases. Overestimation and underestimation of pulmonary artery systolic pressure by Doppler echocardiography occurred with a similar frequency (16 vs. 15 instances, respectively). The magnitude of pressure underestimation was greater than overestimation (230 6 16 vs. 119 6 11 mm Hg; P 5 0.03); underestimates by Doppler also led more often to misclassification of the severity of the PH. For cardiac output measurement, the bias was 20.1 L/min with 95% limits of agreement ranging from 12.2 to 22.4 L/min. Conclusions: Doppler echocardiography may frequently be inaccurate in estimating pulmonary artery pressure and cardiac output in patients being evaluated for PH.Keywords: echocardiography; pulmonary hypertension; pulmonary systolic pressure; cardiac output; accuracy Pulmonary hypertension (PH), a syndrome characterized by increased pulmonary vascular resistance and remodeling, is associated with significant morbidity and mortality, which are directly related to cardiac function (1). Although the definitive diagnosis of PH is currently established through right-heart catheterization, accurate noninvasive assessment of pulmonary arterial pressure and cardiac output (CO) is desirable both for diagnostic purposes and to assess response to therapy.Transthoracic Doppler echocardiography (DE) is recommended as the initial noninvasive modality in the screening and evaluation of PH (2). Echocardiography can be used to evaluate right-sided chamber size and function and the presence of pericardial effusion, which are known to impact survival (3-5). Frequently, DE is used to estimate the right ventricular systolic pressure by estimating the pressure gradient between the right ventricle and the right atrium using the modified Bernoulli equation, 4v 2 , where v equals the velocity of the tricuspid regurgitant jet. An estimated right atrial pressure is added to this number to approximate the right ventricular systolic pressure, which equals the pulmonary artery systolic pres...

TAPSE powerfully reflects RV function and prognosis in PAH.