Right heart imaging in patients with heart failure: a tale of two ventricles

Abstract

Purpose of review: The purpose is to describe the recent advances made in imaging of the right heart, including deformation imaging, tissue, and flow characterization by MRI, and molecular imaging.

Recent findings: Recent developments have been made in the field of deformation imaging of the right heart, which may improve risk stratification of patients with heart failure and pulmonary hypertension. In addition, more attention has been given to load adaptability metrics of the right heart; these simplified indices, however, still face challenges from a conceptual point of view. The emergence of novel MRI sequences, such as native T1 mapping, allows better detection and quantification of myocardial fibrosis and could allow better prediction of postsurgical recovery of the right heart. Other advances in MRI include four-dimensional flow imaging, which may be particularly useful in congenital heart disease or for the detection of early stages of pulmonary vascular disease.

Summary: The review will place the recent developments in right heart imaging in the context of clinical care and research.

Figure 1. Simplified representation of the “unfolded circulation”: right atrium (RA), right ventricle (RV), lungs, left atrium (LA), left ventricle (LV) and systemic organs

Concepts related to coupling and matching between different physiological and anatomical entities are represented. V/Q: ventilation/perfusion. (Reproduced with permission from Laboratory of Surgical Research of the Marie Lannelongue Hospital and Springer International Publishing Switzerland).

Figure 2. Myocardial deformation and velocity imaging of the right heart

A: Superposed RV speckle tracking tracing with numbers representing segmental peak strain. Example from Philips tracking (developed for LV and applied to RV); specific RV tracking has also been developed by other vendors. B: Strain-time curve of the different signals. ApL indicates apex lateral; ApS, apex septum; BIS, basal interventricular septum; BL, basal lateral; GLS, global longitudinal strain; MIS, mid interventricular septum; and ML, mid lateral. (Adapted from Vonk Noordegraaf et al. Circulation 2015) (1).

Figure 3. Relationships between right ventricular function (A) or end-systolic size (B) and ventricular afterload

Based on the literature, this figure schematically represents the curvilinear fit (usually logarithmic fit) of the relationships between RV function or end-systolic dimension, and afterload (such as pressure, resistance, capacitance or estimation of the RV wall stress). Estimation of the wall stress is more challenging, but better reflects the force opposing ventricular function. The shape of the fit would be inversed if capacitance is used as afterload. Two examples are depicted on this figure (patient 1 and patient 2). Despite similar moderate right ventricular function, patients 1 and 2 differ in terms of RV adaptation. Patient 1 has a disproportional dysfunction as the function is worse than what would be expected for the mild increase in afterload compared to patient 2.

Figure 4. Four-dimensional flow MR imaging of a patient with pulmonary valvular disease (left); patients with pulmonary hypertension compared to a healthy control (right panel). Left panel

Flow pattern of a patient with both pulmonary regurgitation (A and B, acquired during diastole) and pulmonary stenosis (D and C, acquired during systole). PA indicates main pulmonary artery; PV, pulmonary valve; and RV, right ventricle. Right panel: Typical flow patterns in the RV outflow tract at different cardiac phases for a patient with manifest PH (A, D, and G), a patient with latent PH (B, E, and H), and a normal subject (C, F, and I). At maximum outflow (A through C), flow profiles were distributed homogenously across the cross sections of the main pulmonary artery in manifest PH (A), latent PH (B), and normal (C). In later systole (D through F), a vortex was formed in manifest PH (D). No such vortex could be found in latent PH (E) or normal (F). After pulmonary valve closure (G through I), the vortex in patients with PH persisted for some time. In all cases, continuous diastolic blood flow upward along the anterior wall of the main pulmonary artery could be observed. Although this phenomenon disappeared quickly in controls (I), it was observed significantly longer in latent PH (H) and manifest PH (G). (Right panel adapted from Reiter et al. Circ Cardiovasc Imaging, 2008 (74)).

Figure 5. Right ventricular pressure (RVP), right atrial pressure (RAP), hepatic venous flow (HVF) and portal venous flow (PoVF) in normal patients (A,D,G,J) and typical patterns commonly observed in patients with mild (B,E,H,K) and severe (C,F,I,L) right ventricular dysfunction

AR, atrial reversal HVF velocity; D, diastolic HVF Doppler velocity; Ppa, pulmonary artery pressure; Prv, right ventricular pressure, S, systolic HVF velocity. (Adapted from Haddad et al. Curr Opin Anaesthesiol, 2016 (3)).