The strain-8 study: a multimodal scan-rescan assessment of myocardial strain repeatability

Myocardial strain is a powerful, non-invasive diagnostic and prognostic marker in patients with heart disease. However, its applicability is hindered by uncertain repeatability, particularly for segmental values. This study measures the repeatability of myocardial strain across eight imaging methods.

In this prospective study, 20 healthy volunteers (aged 34 $\pm$ 8, 14 men) were recruited and scanned twice with eight strain imaging protocols: cardiac magnetic resonance (CMR) at 1.5T and 3T with cine, tagging, and displacement encoding with stimulated echoes (DENSE) sequences, and 2D and 3D echocardiography (Echo). Global and segmental strains were quantified from each scan. Inter-scan repeatability was assessed with the coefficient of variation (CoV), intraclass correlation coefficient, and Bland-Altman analysis.

Inter-scan repeatability of global strains ranged from excellent to fair (CoV ≤ 20%) depending on protocol. Using CMR feature tracking at 1.5T, relative global longitudinal strain (GLS) changes exceeding 11.2% are unlikely to be caused by measurement variability alone; this figure is 5.5% for 2D echocardiography. Segmental strain values frequently had poor repeatability (CoV > 20%), particularly for longitudinal and radial strains.

Imaging protocols including CMR and Echo can measure global strain parameters with fair repeatability, but segmental strain values are unreliable. Future work should aim to improve the repeatability of segmental strain values, particularly longitudinal strain.