Selective Pulmonary Vasodilation Improves Ventriculovascular Coupling and Gas Exchange in a Patient with Unrepaired Single‐Ventricle Physiology

Abstract

We describe a 63-year-old patient with unrepaired tricuspid valve atresia and a hypoplastic right ventricle (single-ventricle physiology) who presented with progressive symptomatic hypoxia. Her anatomy resulted in parallel pulmonary and systemic circulations, pulmonary arterial hypertension, and uncoupling of the ventricle/pulmonary artery. Hemodynamic and coupling data were obtained before and after pulmonary vasoactive treatment, first inhaled nitric oxide and later inhaled treprostinil. The coupling ratio (ratio of ventricular to vascular elastance) shunt fractions and dead space ventilation were calculated before and after treatment. Treatment resulted in improvement of the coupling ratio between the ventricle and the vasculature with optimization of stroke work, equalization of pulmonary and systolic flows, a decrease in dead space ventilation from 75% to 55%, and a significant increase in 6-minute walk distance and improved hypoxia. Inhaled treprostinil significantly increased 6-minute walk distance and improved hypoxia. This is the first report to show that pulmonary vasoactive treatment can be used in a patient with unrepaired single-ventricle anatomy and describes the hemodynamic effects of inhaled therapy on ventriculovascular coupling and gas exchange in the pulmonary circulation in this unique physiology.Keywords: pulmonary hypertension, ventricular/vascular coupling hemodynamics, congenital heart disease, treatment effect. Pulmonary arterial hypertension (PAH) is a progressive disease defined by severe pulmonary vasculopathy resulting in high right ventricular (RV) afterload. Although treatment focus is often on the pulmonary vasculopathy, mortality in this disease is most specifically indicated by RV load adaptation. 1 Therefore, there has been recent research emphasis on methods directed toward recognition of early pump dysfunction. One such method is ventriculovascular coupling, a method that describes the hydraulic transfer of energy from the ventricle to the vasculature. 2 This method is not generally thought of in the context of the "coupling" of gas exchange. Functional improvements with therapy are attributed to a combination of improvements in gas exchange and RV function. However, the extent to which each component contributes is unknown.Ventriculovascular coupling is most often described by the coupling ratio, the numeric ratio of ventricular elastance (Ees) to vascular elastance (Ea). Ees is often termed contractility and thought of as a component that is independent of acute changes in preload and afterload, or Ea. The RV increases contractility as an adaptation to sustained increases in afterload. 3 The degree of adaptation of the ventriculovascular unit is typically indicated by the coupling ratio, Ees/Ea. While stroke work is optimized at a coupling ratio of 1.0, 4 studies of experimental PAH indicate that the system is coupled under normal conditions to maximum work for minimum energy cost (efficiency) at a coupling ratio of approximately 1.5-2.0. 5 Pulmonary gas exchange ...

Pulmonary arterial hypertension related to congenital heart disease with a left-to-right shunt: phenotypic spectrum and approach to management

“…In patients with more severe PVD but still with predominant left-right shunting (i.e., not yet fulfilling Eisenmenger criteria), a treat-and-repair strategy is less likely to be successful; repairing a defect in a patient who requires very aggressive PAH therapy to achieve hemodynamic criteria for operability may not be wise and the benefits in terms of abolishing the left-right shunt may not outweigh the risks of the intervention and likelihood of progressive severe PVD after repair of the defect. There may, however, be merits in using pulmonary vasodilators in an attempt to improve ventriculo-vascular and gas exchange coupling, optimizing RV stroke volume and improving pulmonary blood flow through better distribution to relatively normal V/Q units ( 46 ). In this setting, PAH therapies can lower PVR and RV afterload, though it is likely that the left-right shunt and ventricular volume overload will increase.…”