Systemic-to-Pulmonary Collateral Flow Correlates with Clinical Condition Late After the Fontan Procedure

In the Fontan circulation, there is a substantial degree of systemic-to-pulmonary collateral flow (SPCF), which can be measured by cardiac magnetic resonance (CMR). However, the correlation between the degree of SPCF and long-term outcomes is not fully understood. We retrospectively studied 321 patients who underwent the Fontan procedure and CMR at a single center. Using CMR, we calculated SPCF as pulmonary blood flow - systemic blood flow. %SPCF was defined as SPCF ÷ pulmonary blood flow. The mean age of patients at CMR was 14.3 ± 7.5 years. The average %SPCF was 13.0% ± 11.0%. With a multivariate analysis, %SPCF was significantly correlated with time (i.e., the longer the time period since the Fontan procedure, the lower the %SPCF) (p = 0.006), previous total anomalous pulmonary vein drainage (p = 0.007), a low pulmonary artery index (Nakata index) before the Fontan procedure (p = 0.04), and older age at the time of the Fontan procedure (p = 0.002). Regarding the findings after the Fontan procedure, %SPCF was significantly correlated with ventricular end-diastolic volume (p < 0.001), ventricular end-systolic volume (p < 0.001), central venous pressure (p < 0.001), plasma brain natriuretic peptide concentration (p < 0.001), hemoptysis (p = 0.009), and poor New York Heart Association functional class (p = 0.007). SPCF was correlated with clinical condition after the Fontan procedure. The importance of sufficient growth of the pulmonary vascular bed should be emphasized because the development of SPCF is believed to result from the poor condition of the pulmonary circulation.