Cardiac dysfunction in severe pediatric acute respiratory distress syndrome: the right ventricle in search of the right therapy

Abstract

Severe acute respiratory distress syndrome in children, or PARDS, carries a high risk of morbidity and mortality that is not fully explained by PARDS severity alone. Right ventricular (RV) dysfunction can be an insidious and often under-recognized complication of severe PARDS that may contribute to its untoward outcomes. Indeed, recent evidence suggest significantly worse outcomes in children who develop RV failure in their course of PARDS. However, in this narrative review, we highlight the dearth of evidence regarding the incidence of and risk factors for PARDS-associated RV dysfunction. While we wish to draw attention to the absence of available evidence that would inform recommendations around surveillance and treatment of RV dysfunction during severe PARDS, we leverage available evidence to glean insights into potentially helpful surveillance strategies and therapeutic approaches.

Keywords: children; echocardiography (Echo); extracorporeal membrane oxygenation (ECMO); pediatric acute respiratory distress syndrome (PARDS); right ventricular (RV) dysfunction.

Figure 1

Pulmonary vascular resistance (PVR) changes in severe pediatric acute respiratory distress syndrome (PARDS). (A) Schematic representation of total PVR as a function of lung volume in a healthy pediatric lung. PVR is lowest at functional residual capacity (FRC) and highest either at residual capacity (RV) where PVR is elevated due to resistive changes in extra-alveolar vasculature or total lung capacity (TLC) where PVR is elevated due to resistive changes in alveolar vasculature. (B) In severe PARDS, PVR is globally elevated secondary to a complex combination of the following: (1) lung architectural heterogeneity from regional atelectasis, alveolar overdistention, or parenchymal cystic changes; (2) hypoxia-, hypercapnia-, and acidemia-mediated vasoconstriction; (3) parenchymal inflammatory changes with associated pulmonary edema.

Figure 2

Pathophysiologic changes in right ventricular (RV) systolic and diastolic function during severe pediatric acute respiratory distress syndrome (PARDS). (A) Normal RV end-systolic and end-diastolic pressure-volume relationships (ESPVR and EDPVR, respectively) in a healthy child as a function of pulmonary arteriolar (PA) elastance that generates a given stroke volume (difference in RV end-systolic and end-diastolic volumes, or RVESV and RVEDV). Adapted from Brener et al. (22). (B) After the first several months of life, the RVEDP is significantly lower than the LVEDP in a healthy child, leading to the RV taking a more crescentic shape around the LV (cartoon transverse cross-section of a situs solitus heart with D-looped ventricles). (C) In severe PARDS, increases in PVR result in higher RV afterload that, in a developing heart, can precipitate RV systolic dysfunction that manifests with impaired contractility. The result of these pathologic changes result in higher RVEDP and RVEDV; however, stroke volume (SV) is preserved. (D) Elevated RVEDP and RVEDV begins to dilate the RV and compete against LVEDP, leading to ventricular septal flattening. (E) In the setting of RV failure, the RV does not adapt to the higher RVEDV and begins to manifest lower stroke volumes. (F) The much higher RVEDP begins to reach or surpass LVEDP and impose upon LVEDV. The diminished LV preload from both a reduction in RV output and RV compression can compromise systemic cardiac output and coronary artery perfusion. RV ballooning will also result in tricuspid regurgitation and elevated systemic venous pressures, compromising perfusion pressures of end-organs.