Relationship between Right Atrial Pressure and Inferior Vena Cava Dimensions in Pediatric Post Heart Transplant Patients

Abstract

The correlation between a low right atrial pressure (RAP) and increased respiratory collapsibility of the inferior vena cava (IVC) is well studied in adults. There is limited data in the pediatric population, especially in the pediatric heart transplant population. This study aims to assess the relationship between non invasive imaging of both IVC dimensions and collapsibility to invasive RAP measurement. A retrospective review of the pediatric transplant patient data between 2015-2017 was performed. Seventy-six patients had cardiac catheterization and echocardiogram within a maximum two weeks of each other. Clinical data, including mean RAP during cath and N-terminal pro b-type natriuretic peptide (NTproBNP) were collected. Echos were reviewed on two separate occasions by a single reviewer for intra-observer variability. IVC diameter in long axis in inspiration and expiration, IVC collapsibility index, left ventricular remodeling index (LVRI) and tricuspid regurgitant (TR) velocity were reviewed. A higher IVC collapsibility index correlated with a lower RAP (r = -0.25, p = 0.03) and a larger IVC diameter in expiration (indexed to body surface area (BSA)) correlated with a higher RAP (r = +0.24, p = 0.04) (Figure 1A, 1B). There was a correlation between elevated NTproBNP and IVC collapsibility (r = -0.39, p = 0.0007), IVC expiratory diameter/BSA (r = 0.34, p = 0.0003), and RAP (r = 0.7, p = 0.0001)(Figure 1C, 1D, 1E). Secondary outcomes of TR velocity and LVRI had no correlation with RAP. Our study showed a correlation between both IVC collapsibility and IVC expiratory diameter (indexed to BSA) to mean RAP in pediatric heart transplant patients. Non invasive imaging of the IVC offers indirect data on right sided cardiac filling and intravascular volume status.