Assessment of myocardial fibrosis using T1-mapping and extracellular volume measurement on cardiac magnetic resonance imaging for the diagnosis of radiation-induced cardiomyopathy

Abstract

Radiation-induced heart disease (RIHD) is a serious side effect of thoracic radiation therapy (RT) and is associated with significant morbidity and mortality. Radiation-induced cardiomyopathy (RICM) is one of the manifestations of RIHD, which represents with left ventricular (LV) systolic and diastolic dysfunction due to myocardial fibrosis. Although the diagnosis of RIHD is challenging and is generally an exclusion diagnosis, multimodality imaging including echocardiography, cardiac computed tomography and cardiac magnetic resonance (CMR) imaging could help the diagnosis. Herein, we report a case of 70-years-old male, who had been treated with chemo-radiation therapy for early esophageal cancer, was suffered from medically refractory heart failure due to severely reduced LV systolic function and constrictive pericarditis 8 years after chemo-radiation therapy. Although no gadolinium-enhancement (LGE) was detected on CMR, T1 mapping depicted increased extracellular matrix volumes of 45%, which suggested global myocardial fibrosis. Histopathological analysis by endomyocardial biopsy (EBM) revealed marked degeneration of myocytes and interstitial fibrosis, while vacuolation in myocytes which is characteristics of chemotherapy induced cardiomyopathy was not specific by electron microscopy. Therefore, we diagnosed that the present case was likely to the RICM. <Learning objective: RICM is characterized by inflammation followed by the development of a diffuse, patchy interstitial fibrosis of the myocardium, which is usually obtained either by EBM or at autopsy. Native and post-contrast T1-mapping by CMR enables to estimate extracellular volume (ECV), which is believed to be increased as a result of diffuse myocardial fibrosis. The assessment of myocardial fibrosis using ECV should be useful for early detection of myocardial damage due to RT, and which probably taking place of EBM.>.

Keywords: Myocardial fibrosis; Onco-cardiology; Radiation-induced heart disease.

Fig. 1

(Upper) Electrocardiogram (ECG) and (Lower) chest X-ray before and after chemo-radiation therapy. Before chemo-radiation therapy (A), both ECG and chest X-ray showed no definite abnormality. On this admission (B), ECG showed low voltage in the extremity leads and poor R progression in the chest leads. Cardiomegaly and bilateral pleural effusion (left dominant) were revealed in the chest X-ray.

Fig. 2

Cardiac magnetic resonance (CMR) imaging. Cine CMR imaging (A) showed severely reduced left ventricular (LV) systolic function without LV dilatation (end-diastolic volume index, 66 ml/m², end-systolic volume index, 53 ml/m²), and ejection fraction of 19%. In addition, the pericardium thickness was up to 3–4 mm (normal range <2–3 mm), and small pericardial and pleural effusion existed. T2 weighted imaging showed no high-intensity lesion which suggests myocardial edema. Late gadolinium enhancement (LGE) images in short-axis view did not show definite enhancement in the LV wall (B). However, extracellular volume (ECV) maps with T1 mapping (C) showed increased ECV of 45% (reference value: 20–30%), in the whole myocardium, which suggested global myocardial fibrosis.

Fig. 3

Histopathological analysis of the resected myocardium. (A) Histopathologically, interstitial fibrosis (yellow arrow) and myocardial degeneration such as irregular arrangement (white arrow) or vacuolar changes (blue arrow) are seen. Masson trichrome stain ×200. (B) Myofibrillary loss (red arrow), dilatation of sarcoplasmic reticulum (asterisks), and proliferation of small sized mitochondria (yellow arrows) are recognized by electron microscopy ×500.