Abstract 19953: Pulmonary Blood Flow is Systematically Underestimated at Cardiac Catheterization in Single Ventricle Patients after Superior Cavo-pulmonary Connection Due to the Presence of Systemic-pulmonary Collateral Flow
Introduction: Systemic-pulmonary collateral flow (SPCF) is common in patients with single ventricle heart disease after superior cavo-pulmonary connection (SCPC), although its implications are unclear. As estimating pulmonary blood flow (Qp) by Fick is challenging in this population, we have recently described a novel method to objectively quantify SPCF as well as Qp and systemic blood flow (Qs) by cardiac magnetic resonance (CMR).
Hypothesis: SPCF is a major contributor to Qp after SCPC, and consequently oximetric data from cardiac catheterization (CC) systematically underestimate Qp after SCPC.
Methods: We retrospectively compared Qp and Qs by CC (Fick) and CMR (Qp=total pulmonary venous flow, Qs=total caval flow, SPCF=average of aortic minus caval and pulmonary venous minus pulmonary arterial flow) among SCPC patients who had both studies within 6 months. We tested for associations between other variables and SPCF quantified by CMR.
Results: Subjects were studied after bidirectional Glenn (n=16) or hemi-Fontan (n=5) 1.6 ± 0.9 years after SCPC (age 2.2 ± 0.9 years). CMR-measured SPCF was 1.7 ± 0.8 L/min/m2 accounting for 53 ± 26% of total pulmonary flow and 36 ± 16% of total aortic flow. CC-measured Qp was lower than total Qp measured by CMR (2.3 ± 0.6 v. 3.2 ± 0.8 L/min/m2, p<0.0001). Qs by CC was higher than Qs by CMR (3.8 ± 1.2 v. 3.0 ± 1.0 L/min/m2, p=0.002). There was, however, a moderately strong correlation for each variable between modalities (r=0.68 for Qp and 0.53 for Qs, p=0.0007 and 0.01). Qp:Qs at CC was therefore lower than by CMR (0.61 ± 0.12 v. 1.2 ± 0.4, p<0.0001). SPCF was negatively associated with hemoglobin concentration (p=0.012). When taken as a percentage of total Qp, there was a positive association between SPCF and mean pressures throughout the cavo-pulmonary circuit (p=0.03). Patients with a bidirectional Glenn had a lower percentage of total Qp represented by SPCF compared to those with a hemi-Fontan (44.9 ± 23 v. 77 ± 18%, p=0.01).
Conclusions: We conclude that SPCF is responsible for a large percentage of Qp after SCPC. Oximetric data systematically underestimate Qp and overestimate PVR in these patients. Accurate assessment of Qp and PVR after SCPC by combining CC and CMR may be important in prognosis after Fontan completion.
- © 2010 by American Heart Association, Inc.