Calculation of myocardial strain and of %normal myocardium by fast-SENC

The fast-SENC method uses out-of-plane phase encoding gradients along the slice-selected direction and thus longitudinal strain was extracted from the three short axes acquisitions using a 16-segment model, whereas circumferential strain was measured from three long axes views using a 21-segment model [14]. The global longitudinal strain (GLS) and global circumferential strain (GCS) values for myocardial strain were calculated as an average of the 16 and 21 segments, respectively.

In concordance with previous studies, we considered a value for either longitudinal or circumferential strain in any segment ≤ −17% as normal [15, 16]. We then measured the percentage of normal myocardium in each patient as the ratio between the total number of segments expressing normal myocardium, i.e. longitudinal strain ≤ −17% (out of n = 16) and circumferential ≤ −17% (out of n = 21) and then dividing this number by the total number of segments analysed (37 segments in total), as follows [17]:

The number of segments with diagnostic image quality, enabling the assessment of myocardial strain by fast-SENC was assessed in 80 randomly selected patients (n = 2960 segments).

In addition, we calculated a relative regional ratio of the average of the apical segmental strain divided by the sum of the average basal and mid-ventricular segmental strain, to differentiate between amyloidosis and HCM, as previously described [18].

To avoid confusion and in keeping with most of the literature on the subject, the strain parameters will be interpreted in their absolute values (i.e., more “negative” strain meaning better strain).