Noninvasive Imaging in the Assessment of the Cardiopulmonary Vascular Unit

Abstract

899N oninvasive imaging plays a key role in both the diagnosis and management of patients with pulmonary hypertension (PH). In recent years, there have been 2 major changes in perspective of imaging in PH. The first was the realization that imaging should focus on the evaluation of not only the pulmonary pressures but also the cardiopulmonary unit ( Figure 1). 1,2The second was the emergence of multimodality imaging with a complementary role for echocardiography, magnetic resonance (MRI), computed tomography, and positron emission tomography (PET).2-7 These techniques not only help in the diagnosis of PH but also help identify factors that determine risk and prognosis and gauge therapeutic effects on right ventricular (RV) function in patients with pulmonary arterial hypertension (PAH). Although echocardiography is the mainstay in the assessment of hemodynamic and ventricular function in PH, MRI has emerged as the gold standard for quantifying volumes, function, and flow in the right side of the heart. 2-7 PET is also offering novel insights into perfusion and blood flow, metabolism, neurohormonal activation, and other molecular processes in the right side of the heart but is used mainly for research at this time. Catheterization of the right side of the heart remains the gold standard for defining PH and assessing hemodynamics both at rest and with exercise. Invasive assessment of cardiac output (CO) may, however, have limited accuracy when assumed instead of measured oxygen consumption is used to derive CO (eg, using the Fick method) or when thermodilution is used in the setting of a low-CO state. [8][9][10] This review covers RV imaging studies performed in the field of PH and discusses recent advances in echocardiography and cardiac MRI and PET imaging for detailed assessment of RV function. The review starts with a discussion of important physiological considerations and unmet needs in imaging research of the right side of the heart in PH. Computed tomography angiography, which plays an important role in evaluating chronic thromboembolic PH, is not discussed extensively in this review. Physiological ConsiderationsAlthough PH is a syndrome affecting the pulmonary vasculature, survival of patients with PH is closely related to RV function. 1,[11][12][13][14] The RV initially adapts to the increased afterload by increasing its wall thickness and contractility. These mechanisms are, however, often insufficient, and RV dysfunction eventually occurs. After the recent Fifth World Symposium on Pulmonary Hypertension, a definition of failure of the right side of the heart secondary to PH was adopted: "Right heart failure in the setting of PH can be defined as a complex clinical syndrome due to a suboptimal delivery of blood or elevated systemic venous pressure at rest or exercise as a consequence of elevated RV afterload."2 The proposed definition takes into account both the systolic and diastolic characteristics of function of the right side of the heart, as well as physiological demands such as exercise.In underst...

Ambrisentan and Tadalafil Up-front Combination Therapy in Scleroderma-associated Pulmonary Arterial Hypertension

“…RVEF improved significantly with therapy from 46% at baseline to 57% at Week 36 ( Figure 2B), which also indicates that one or several factors that affect RVEF, such as preload, afterload, contractility, and ventricular synchrony (36), improved after 36 weeks of therapy. This average 11% absolute improvement in RVEF is particularly relevant, considering an estimated meaningful treatment effect of 3-5% in cardiac CMR imaging-based RCTs (37) and in light of a recent study demonstrating that stability and/or improvement in RVEF by CMR imaging after therapy indicated better survival than decreased RVEF after therapy in a large cohort of patients with PAH (38).…”

Right heart imaging in patients with heart failure

“…In addition to interventricular interactions, a comprehensive understanding of RV function should also consider the cardiopulmonary unit (1). As shown in Figure 1, this includes a better assessment of ventriculoarterial coupling (matching between RV contractility and afterload), ventilation perfusion matching, as well as atrioventricular coupling.…”

“…The concept of ventriculoarterial coupling has been developed to describe matching between RV contractility and afterload; a ventricle that can increase its contractility in response to the increase in afterload usually stays well compensated. In PAH for example, RV contractility is increased but insufficient to match the increase in load, thus RV dysfunction ensues (1,45). This is an important distinction, as RV contractility is not decreased in PAH, as illustrated by the RV recovery post- lung transplantation in those patients.…”

“…One of the most important changes has been the greater awareness given to right heart function in both clinical and research settings (1). In this review, we will highlight recent innovations in the field of right heart imaging, including myocardial deformation imaging, 3D and 4D flow magnetic resonance imaging (MRI), as well as molecular imaging.…”

Fluid therapy in critically ill patients: perspectives from the right heart

“…The low-pressure system ensures myocardial perfusion both during diastole and systole [4]. The right heart is connected to the left heart serially and shares with it the interatrial and interventricular septa and the pericardial space, causing marked ventricular interdependence [5].…”