A Unique Pediatric Case of Left Ventricular Fatty Infiltration with Excessive Trabeculations Sparing the Right Heart (QF_TH_024)

Description of Clinical Presentation: An asymptomatic 15 year old female presented for evaluation due to maternal history of concern for long QT syndrome, cardiomyopathy with a variant of unknown significance in the MYH7 gene, and aborted cardiac arrest with ICD placement. The patient’s QTc was normal but echocardiogram demonstrated mild left ventricle (LV) dysfunction and dilation, excessive LV trabeculations, and a tiny patent ductus arteriosus. She underwent catheterization where her LV end diastolic pressure was 9mmHg; transcatheter attempt at ductus occlusion was unsuccessful. She was referred for cardiomyopathy evaluation where a genetic panel for common mutations in arrhythmogenic right ventricular cardiomyopathy was negative and Holter monitor did not demonstrate dysrhythmias.

Diagnostic Techniques and Their Most Important Findings: Cine imaging was performed to assess the myocardium, wall motion abnormalities and ventricular volumes/function. Velocity mapping was done to quantify flows. To characterize the fatty infiltration, T1-weighted imaging with and without fat saturation was performed. Standard MOLLI sequences were performed to quantify the myocardial T1 values and extracellular volumes. Motion corrected delayed enhancement imaging was performed to assess for fibrosis.

Learning Points from this Case: The LV was rounded at the apex with marked thinning of the myocardium (Figure 1). LV function was low normal with ejection fraction (EF) of 57%. Excessive trabeculations were noted primarily at the apex, with a trabeculated:compacted myocardium ratio of 2.8:1. Cine imaging demonstrated hypokinesia of the LV apex and lateral wall. These same regions contained mid- and sub-endocardial fatty infiltration seen on T1 weighted imaging (Figures 2 and 3). This was confirmed by high resolution, respiratory gated inversion recovery angiography, which showed loss of signal along the lateral wall of the LV. Fat was also noted along the LV apex. Delayed enhancement was noted in the mid-septum (Figure 1). The native T1 value was 1185ms and was 1344ms at the apex. The global extracellular volume (ECV) was mildly increased at 32%, with a peak of 41% at the apex; this was not in the region of fatty infiltration. Notably, the right ventricle was spared with no fatty infiltration or delayed enhancement and normal size and function. A small ductus arteriosus was seen narrowing to 1mm, but it was unclear if it was patent; velocity mapping demonstrated a Qp:Qs of 1:1. The patient underwent repeat CMR three years later with interval worsening of LV fatty infiltration, EF of 57% and normal LV size . Though remote infarction with lipomatous metaplasia might be entertained, age and maternal history make cardiomyopathy with fatty infiltration more likely. She was referred for a more extensive genetic evaluation. The patient’s mother has since passed away following leg surgery, presumed due to an embolic event. Although fatty infiltration is reported in adult literature as a component of arrhythmogenic cardiomyopathy, this case is unique in the degree of fatty infiltration seen, the sparing of the right ventricle, and the young age of presentation.