Quick Fire Session
SCMR 22nd Annual Scientific Sessions
Extracellular volume (ECV) fraction, a marker of tissue remodeling due to excessive collagen deposition, can be calculated using contrast-enhanced T1 mapping with cardiac magnetic resonance. Liver ECV can be measured on cardiac studies without requiring additional imaging. We hypothesized that patients with a Fontan palliation have higher liver ECV, reflecting a higher degree of liver fibrosis or congestion.
Using a 3T cardiac scanner (Siemens Tim Trio), adult Fontan patients prospectively underwent cardiac MRI including T1 mapping of the myocardium in a single short axis plane. These images also contain a section of the left lobe of the liver. Thus, a region of interest of the liver, excluding blood vessels, was contoured to quantify T1 before and 3 minutes, 7 minutes, and 15 minutes after gadolinium administration. ECV fraction was calculated using T1 values and hematocrit values collected at the time of the MRI. Cardiac catheterization was performed in all patients following the MRI. For comparison, liver ECV was also calculated using identical methods in patients with cancer (n=8), hypertrophic cardiomyopathy (HCM; n=12), tetralogy of Fallot (ToF; n=14), and healthy control subjects (n=11) who had undergone similar cardiac MRI at either 3T or 1.5T.
A total of 17 Fontan patients participated (mean age 28.5±7.4 years, 7 [41%] female). The mean liver ECV fraction for Fontan patients was 45.9±6.4%. Using one-way ANOVA, the mean liver ECV was significantly higher (p<0.001) in Fontan patients compared to all other patient groups (31.5±3.3% for healthy control subjects, 32.2±5.3% for cancer patients, 32.7±6.0% for HCM patients, and 30.7±5.5% for ToF patients, FIGURE). By Bonferroni post-hoc analysis, Fontan liver ECV was significantly higher than all other groups, whereas there was no statistically significant difference in mean liver ECV between the other patients groups. Fontan patients were younger than the other clinical groups studied. Amongst Fontan patients, hepatic ECV correlated with cardiac ECV (R=0.542, p=0.025), but was not associated with age, PA pressure, or ventricular end-diastolic pressure.
Calculated liver ECV using contrast-enhanced T1 mapping obtained for cardiac ECV measurement is convenient to obtain and significantly higher in patients with a Fontan palliation as compared to controls without liver disease. This is consistent with a higher degree of hepatic fibrosis and/or congestion. Liver ECV may be an alternative method of fibrosis detection, though further studies are needed to determine its clinical utility in liver health surveillance.