THROMBOEMBOLISM IN THE ADULT FONTAN POPULATION: A MARKER OF FONTAN CIRCULATORY DYSFUNCTION?

Abstract

The reported incidence of clinical and/or silent thromboembolism (TE) in Fontan patients varies in the literature from 10-35%. Clinical TE has been shown to be associated with increased mortality in the Fontan population. It is unknown whether clinical and/or silent TE is a marker of Fontan circulatory dysfunction or occurs in isolation and is of minimal clinical consequence. Our objective was to determine: 1) prevalence of clinical and silent Fontan or pulmonary artery thromboembolism (TE) in an adult Fontan population and its’ relationship with adverse cardiac events; and 2) the association of Fontan TE with extra-cardiac organ dysfunction. A retrospective study of adult Fontan patients actively followed at St. Paul’s Hospital, who underwent definitive assessment for TE with either cardiac CT or MRI between 2000 and 2018. Adverse cardiac event were defined as death, heart transplantation or surgery for Fontan conversion or atrioventricular valve replacement. Sixty seven patients were included. TE was present in 15 (22%) patients, of which 8 (53%) were silent. TE was present in 41% (7/17) with a classic Fontan and 16% (8/50) with a total cavopulmonary connection (TCPC). TE was associated with increased rates of adverse cardiac event compared to those without [27% (4/15) vs.8% (4/52), p=0.02]. There was also a lower albeit normal eGFR in the TE group (p=0.02). Liver enzymes, VAST score and protein losing enteropathy was similar between the two groups. The incidence of TE is higher in the classic Fontan compared with TCPC. TE is associated with more adverse cardiac events, although it appears to be a marker rather than a cause of abnormal cardiac hemodynamics. No clear relationship was seen between TE and extracardiac organ dysfunction, suggesting that TE is likely not a marker of overall Fontan circulatory dysfunction. Nearly half of the TE detected in our cohort was clinically silent, highlighting the need to consider regular screening of the Fontan circuit with multimodality imaging.