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Location, patterns, and quantification of myocardial fibrosis identified by cardiac magnetic resonance delayed enhancement late after fontan operation

Objective

The objective of this study was to investigate the frequency, location, patterns, and quantification of myocardial fibrosis as identified by the CMR myocardial delayed enhancement (MDE) technique and describe its association with functional single ventricular ejection fraction (EF) and regional wall motion abnormalities (WMA) in patients late after the Fontan operation.

Background

MDE has been associated with adverse ventricular mechanics late after tetralogy of Fallot repair and in patients with systemic right ventricles. No studies have reported the frequency, patterns, or associations of MDE in patients late after the Fontan operation.

Methods

All patients at our center following a Fontan operation who had a CMR study with MDE from January 2002 to July 2008 were retrospectively identified. MDE was characterized by: 1) spatial location; 2) pattern; and 3) MDE quantification expressed as the MDE percent of ventricular mass (MDE %). MDE % was calculated using the histologically verified, full-width at half-maximum (FWHM) technique (Amado et al. JACC 2004; 44: 2383). Patterns of MDE were categorized as transmural, subepicardial/intramural, subendocardial, circumferential endocardial fibroelastosis (EFE), and speckled (Figure 1). Multivariate linear regression analysis with forward stepwise selection was used to investigate independent associations of functional single ventricular EF. Covariables included demographic data, cardiac diagnosis, ventricular morphology, Fontan type, surgical history, MDE locations, MDE patterns, and MDE %.

Figure 1
figure1

Arrows identify patterns of MDE. a) transmural; b) subendocardial; c) EFE; d) subepicardial/intramural.

Results

Of the 85 subjects included (65% male; median age at Fontan 4.5 [2.0, 11.2] years; mean age at CMR 23.1 ± 11.2 years), 21 (25%) had positive MDE in the ventricular myocardium. MDE was seen in the following locations: dominant ventricle free wall (n = 13, 62%), secondary ventricle free wall (n = 9, 43%), septal insertion (n = 5, 24%), ventricular septum (n = 3, 14%), apex (n = 2, 10%), previous surgical sites (n = 2, 10%), and papillary muscle (n = 2, 10%). MDE was seen in the following patterns: transmural lesion (n = 9, 43%), subepicardial/intramural (n = 5, 24%), subendocardial (n = 5, 24%), circumferential endocardial fibroelastosis (n = 4, 19%), and speckled (n = 2, 10%). Results of univariate analysis comparing patients with and without MDE, stratified by location and pattern are summarized in Table 1. Multivariate linear regression analysis demonstrated that higher MDE % (slope: -1.7, CI: -2.5 to -1.0, p < 0.0001) and age at CMR (slope: -0.6, CI: -1.0 to -0.3, p = 0.002) were independently and inversely associated with EF (R2 = 0.59).

Table 1 Univariate analysis of MDE location and pattern

Conclusion

In patients late after the Fontan operation, myocardial fibrosis was common and was associated with lower EF, higher ventricular volumes, WMA, and dyskinesis. Further studies are warranted to examine the mechanisms of myocardial fibrosis and their impact on ventricular performance.

Author information

Correspondence to Rahul H Rathod.

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Keywords

  • Ejection Fraction
  • Cardiac Magnetic Resonance
  • Myocardial Fibrosis
  • Wall Motion Abnormality
  • Regional Wall Motion