Abstract 14359: Systemic to Pulmonary Collateral Flow Increases as a Fraction of Aortic Flow After Fontan Completion
Background: We recently described a method of quantifying systemic to pulmonary collateral (SPC) flow in patients with superior (S2) and total (S3) cavopulmonary connections using magnetic resonance phase contrast velocity mapping (PC-MRI). We wished to examine changes in physiology and SPC flow from S2 to S3 by comparing serial PC-MRI data. We hypothesized that SPC flow decreases after S3 compared to S2.
Methods: We retrospectively reviewed MRI data to identify patients who had collateral flow quantified at both S2 and S3. SPC flow, systemic blood flow (Qs = total caval flow), and pulmonary blood flow (Qp = total pulmonary vein flow) were quantified as previously described. Fenestration flow was quantified in S3 by the difference in flow in the Fontan baffle above and below the fenestration.
Results: We identified 10 patients who had SPC flow quantified at 0.3±0.4 yrs before and 0.6±0.3 yrs after S3. Indexed SPC flow was 1.2±0.6 L/min/m2 at S2 and 1.7±09 L/min/m2 at S3 (p=0.06). This represented a significantly higher fraction of aortic flow in S3 compared to S2 (35±13% vs. 28±12%, p=0.04). As a result, while indexed aortic flow did not change (4.4±0.7 L/min/m2 at S2 vs. 4.5 L/min/m2 at S3), there was a significant decrease in Qs from 3.2±0.8 L/min/m2 at S2 to 2.8±0.6 L/min/m2 at S3 (p=0.04). Fenestration flow averaged 46±32% of the inferior vena caval (IVC) flow at S3, with a decrease in right to left shunt from 1.7 at S2 to 0.5 L/min/m2 at S3 (p<0.001). Qp increased significantly at S3 compared to S2, primarily from a reduction in the right to left shunt. There was a resulting significant increase in Qp/Qs ratio at S3.
Conclusions: Indexed SPC flow does not appear to decrease significantly in the short term after S3 and trends toward increasing. While the indexed aortic flow does not change, SPC flow expressed as a fraction of aortic flow increases significantly at S3, resulting in a significantly lower Qs at S3.
- © 2011 by American Heart Association, Inc.