Objective To evaluate the diagnostic value of MRI in combination of late gadolinium-enhanced imaging in the identification of restrictive cardiomyopathy (RCM).
Methods 116 patients with RCM underwent ECG, x-ray, Echocardiography and MRI. The final diagnosis was made on comprehensive evaluation in consideration of patients' history, clinical symptom and sign, imaging modalities. All patients had objective evidence of impaired cardiac filling and were referred to rule out pericardial thickening. Five histologically proven cases with RCM included heart transplantation in four patients with RCM, endomyocardial biopsy in one patient with RCM. Fifty-five normal subjects were used for reference. All patients were divided into two groups according to contrast-enhanced MRI: RCM with delayed enhancement (RCM with DE, n=35) and RCM without delayed enhancement (RCM without DE, n=81). Quantitative measurement of bi-atrial and bi-ventricular size, ventricular septal and left free wall thickness were done. A paired t-test was used for statistic analysis and a p value of less than 0.05 was considered significant. Qualitative assessment of segmental wall motion, in this present study.
Results The parameters, such as bi-atrial size, right ventricular diastolic diameter (RVDD), ventricular septal and left free wall thickness were significantly larger in 116 patients with RCM than in normal subjects (p<0.05). However, there were no statistical differences between the two groups in left ventricular diastolic diameter (LVDD). Visual observation showed that mild mitral regurgitation (43%), moderate mitral regurgitation (21%), mild tricuspid regurgitation (28%) and severe tricuspid regurgitation (40%) were noted, respectively. 35 RCM with DE was further divided into diffuse and segmental enhancement. RCM with diffuse delayed enhancement was 15 cases, of which 12 cases showed powdery enhancement, and three showed petaline enhancement. Three cases with powdery enhancement were histologically proven as myocardial amyloidosis. RCM with segmental enhancement was 20 cases. Ventricular septum was the most vulnerable segment. Six cases presented subendocardial enhancement that corresponded to apical obliteration, of which one case was confirmed as hypereosinophilia with use of marrow examination. The other 14 cases didn't present any regular enhancement. 81 RCM without DE, of which histologically proven non-specific findings were in two cases, had marked bi-atrial dilation, near-normal ventricular chambers and near-normal ventricular thickness.
Conclusions MRI is an excellent imaging modality to identify restrictive cardiomyopathy. Primary RCM presents marked bi-atrial dilation with nonhypertrophied and nondilated ventricles. Diffuse left ventricular thickening associated with powdery enhancement indicates myocardial amyloidosis. Apical obliteration associated with subendocardial enhancement corresponds to endomyocardial fibrosis.