Myocardial strain pattern in patients with cardiac amyloidosis secondary to multiple myeloma: a cardiac MRI feature tracking study

Cardiac MRI is frequently used in the diagnosis of cardiac amyloidosis. Feature tracking is a novel method of analyzing myocardial strain at the myocardial borders. We investigated myocardial deformation mechanics of both the right and left ventricles in patients with multiple myeloma with suspected cardiac amyloidosis. Comprehensive strain analysis was performed in 43 patients with multiple myeloma and suspected cardiac amyloidosis. MRI strain by feature tracking was measured using 2D cardiac performance analysis MR software (Tomtec, Germany). Global longitudinal (GLS) and global circumferential (GLC) strain were calculated in endo and epicardium. In addition, right ventricular longitudinal strain was measured in the endocardium only. All patients later underwent endomyocardial biopsy. Average wall thickness in biopsy proven cardiac amyloidosis group (22 patients) was 1.4 +/- 0.4 cm with wall thickness <= 1.2 cm in 36 %. LGE was present in all patients with biopsy confirmed disease. There was significantly decreased global longitudinal strain and strain rate in the epicardial and endocardial layers. Global circumferential strain was significantly reduced in the epicardial layer but not the endocardium. GLS was significantly decreased at the base in both layers compared to the mid and apical regions of the myocardium. However, the base to apex GLS gradient was suggestive of apical sparing in the endocardial layer among patients with amyloidosis (-8.2 +/- 2 vs. -2.7 +/- 1; p = 0.001) but not the epicardial layer. Apical sparing was evident even in those with normal thickness CA. This feature tracking MRI analysis sheds light on strain mechanics in a cohort of multiple myeloma associated cardiac amyloidosis with a significant number of cases with normal LV wall thickness and explains mechanism of apical sparing effect.