The Right Ventricle under Pressure: Evaluating the Adaptive and Maladaptive Changes in the Right Ventricle in Pulmonary Arterial Hypertension using Echocardiography (2013 Grover Conference Series)

Abstract

The importance of the right ventricle (RV) in pulmonary arterial hypertension (PAH) has been gaining increased recognition. This has included a reconceptualization of the RV as part of an RV-pulmonary circulation interrelated unit and the observation that RV function is a major determinant of prognosis in PAH. Noninvasive imaging of RV size and function is critical to the longitudinal management of patients with PAH, and continued understanding of the pathophysiology of pulmonary vascular disease relies on the response of the RV to pulmonary vascular remodeling. Echocardiography, in particular the newer echocardiographic measurements and techniques, allows easy, readily accessible means to assess and follow RV size and function.Keywords: imaging, three-dimensional echocardiography, tricuspid annular plane systolic excursion, right heart failure, right ventricular function. Pulmonary arterial hypertension (PAH) is characterized by severe remodeling of distal pulmonary arterioles due to a complex interplay between genetic and molecular factors.1,2 This remodeling is characterized by intimal hyperplasia, vasoconstriction, medial hypertrophy, and the development of plexiform lesions, all of which contribute to and result in higher pulmonary artery pressure. The prevalence of PAH is 7-15 individuals per million people. 3,4 A diagnosis of PAH is initially suggested by symptoms including dyspnea, syncope, and exertional intolerance and is usually evaluated first with echocardiography. 5 Echocardiography may suggest elevated pulmonary artery pressures (PAPs) and help formulate a working hypothesis regarding the etiology of the presumed pulmonary hypertension (PH), but right heart catheterization remains essential to provide final hemodynamic classification of PH and, with that knowledge in hand, to guide appropriate World Health Organization (WHO) PH group-specific therapy. 6 Once the diagnosis of PAH is established (mean PAP ≥ 25 mmHg and pulmonary capillary wedge pressure ≤ 15 mmHg), most clinicians rely on a combination of frequent clinical evaluations and echocardiography to follow therapeutic response and to give insight into the effects of elevated PAP on the structure and function of the right ventricle (RV). The right ventricle's adaptation or maladaptation to the increased afterload is often a sign of the severity of PH. 7The relevance of the relationship between the RV and the pulmonary circulation in PAH has been gaining increased recognition.8 As a pump, the RV generates the same stroke volume as the left ventricle (LV) with onefourth the stroke work because of the lower resistance of the normal pulmonary vasculature. 9 The RV is thin walled, with the free wall measuring 2-5 mm, and contains onesixth the muscle mass of the LV. 9 It is a crescent-shaped chamber with a high capacitance and a greater ability to handle changes in preload than in afterload. When chronically exposed to increased afterload, the RV can adapt with myocardial hypertrophy, since increase in wall pressure leads to increase in ...

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“…The presence of RV hypertrophy has been implicated as both adaptive and maladaptive in PAH. 15 Thus, although the RV mid-ventricular free wall thickness was increased somewhat in SSc-PAH compared to iPAH patients in this study, attributing impaired RV performance in SSc-PAH to this finding in the absence of differences in RV mass or other geometric indices does not seem justified. Similarly, the authors’ observation that SSc-PAH patients exhibit a decrease in RV recirculation fraction, which is an indirect measure of calcium cycling in the cardiomyocyte sarcoplasmic reticulum, is consistent with recent reports identifying involvement of SERCA2a, phospholamban, and other calcium handling proteins in the RV myocardium to the pathogenesis of PAH.…”

Serial assessment of right ventricular systolic function in patients with precapillary pulmonary hypertension using simple echocardiographic parameters: A comparison with cardiac magnetic resonance imaging

“…Several simple and rapidly quantifiable echo-derived parameters of RV systolic function are available [8] and provide important prognostic information in precapillary PH [9,10].…”

Imaging the right heart pulmonary circulation unit: Insights from advanced ultrasound techniques

“…The right ventricle (RV) can adapt to increased afterload by hypertrophy and increased contractility (LaPlace's law) . However, these mechanisms are often insufficient and maladaptive changes can subsequently occur, leading to RV dilatation and decreased contractility up to progressive RV failure, disability, and death …”

“…6,7 However, these mechanisms are often insufficient and maladaptive changes can subsequently occur, leading to RV dilatation and decreased contractility up to progressive RV failure, disability, and death. 6,[8][9][10] Although right heart catheterization (RHC) remains the "gold standard" for confirming diagnosis and supporting treatment decisions, especially in the case of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH), 2 cardiovascular ultrasound assessment is an essential step in the diagnostic-prognostic clinical pathway of patients with suspect or overt pulmonary hypertension (PH). [11][12][13] We discuss the current clinical applications of standard transthoracic Doppler echocardiography (TDE) and stress echocardiography (SE) and present novel insights from advanced ultrasound techniques (strain, three-dimensional echocardiography, and lung ultrasound) in imaging the RH-PCU.…”