Computed Tomographic Diagnosis of Myocardial Fat Deposits in Sarcoidosis

Lipomatous Metaplasia Is Associated With Ventricular Tachycardia Recurrence Following Ablation in Patients With Nonischemic Cardiomyopathy

BACKGROUND

Ventricular tachycardia (VT) recurrence rates remain high following ablation among patients with nonischemic cardiomyopathy (NICM).

OBJECTIVES

This study sought to define the prevalence of lipomatous metaplasia (LM) in patients with NICM and VT and its association with postablation VT recurrence.

METHODS

From patients who had ablation of left ventricular VT, we retrospectively identified 113 consecutive NICM patients with preprocedural contrast-enhanced cardiac computed tomography (CECT), from which LM was segmented. Nested within this cohort were 62 patients that prospectively underwent CECT and cardiac magnetic resonance from which myocardial border zone and dense late gadolinium enhancement (LGE) were segmented. A control arm of 30 NICM patients without VT with CECT was identified.

RESULTS

LM was identified among 57% of control patients without VT vs 83% of patients without VT recurrence and 100% of patients with VT recurrence following ablation. In multivariable analyses, LM extent was the only independent predictor of VT recurrence, with an adjusted HR per 1-g LM increase of 1.1 (P < 0.001). Patients with LM extent ≥2.5 g had 4.9-fold higher hazard of VT recurrence than those with LM <2.5 g (P < 0.001). In the nested cohort with 32 VT recurrences, LM extent was independently associated with VT recurrence after adjustment for border zone and LGE extent (HR per 1 g increase: 1.1; P = 0.036).

CONCLUSIONS

Myocardial LM is prevalent in patients with NICM of a variety of etiologies, and its extent is associated with postablation VT recurrence independent of the degree of fibrosis.

PDGFRb+ mesenchymal cells, but not NG2+ mural cells, contribute to cardiac fat

Understanding cellular origins of cardiac adipocytes (CAs) can offer important implications for the treatment of fat-associated cardiovascular diseases. Here, we perform lineage tracing studies by using various genetic models and find that cardiac mesenchymal cells (MCs) contribute to CAs in postnatal development and adult homeostasis. Although PDGFRa⁺ and PDGFRb⁺ MCs both give rise to intramyocardial adipocytes, PDGFRb⁺ MCs are demonstrated to be the major source of intramyocardial adipocytes. Moreover, we find that PDGFRb⁺ cells are heterogenous, as PDGFRb is expressed not only in pericytes and smooth muscle cells (SMCs) but also in some subendocardial, pericapillary, or adventitial PDGFRa⁺ fibroblasts. Dual-recombinase-mediated intersectional genetic lineage tracing reveals that PDGFRa⁺PDGFRb⁺ double-positive periendothelial fibroblasts contribute to intramyocardial adipocytes. In contrast, SMCs and NG2⁺ pericytes do not contribute to CAs. These in vivo findings demonstrate that PDGFRb⁺ MCs, but not NG2⁺ coronary vascular mural cells, are the major source of intramyocardial adipocytes.

Presence of Intramyocardial Fat Tissue in the Right Atrium and Right Ventricle - Postmortem Human Analysis

Histologic and radiologic studies describe intramyocardial fat tissue as a normal finding or as part of cardiac pathology. The role of fat cells within the myocardium is not fully understood. The aim of this study was to assess fat tissue distribution in the myocardium of right atrium (RA) and right ventricle (RV) and age differences in subjects free from cardiac disease. The study included 10 males without cardiac disease divided into two groups according to age (below/above 50 years). Three cross sections were performed (RV free wall and apex and RA free wall) with histomorphological analysis on digital photographs. The shares of total myocardial fat (TMF), peri-vascular fat (PVF) and non-perivascular (nPVF) fat were calculated. Samples from the older group had larger amounts of fat in the epicardium and myocardium, without statistically significant differ-ence (TMF p=0.847, PVF p=0.4 and nPVF p=0.4). The largest quantities of fat tissue were found in the RV apex samples (14.9%), followed by RV free wall (7.5%) and RA (4.5%), where total apical RV fat share was significantly larger than in RA sample (p=0.044). Intramyocardial fat cells were present within the non-diseased RA and RV in all samples, mostly in the apex. Further investigations on age difference, effect of visceral obesity and sex differences are needed.