P1543 The assessment of regional myocardial strain in classifying amyloid cardiomyopathy

Background

An infiltrative cardiomyopathy is a common manifestation of AL-amyloidosis, with cardiac involvement associated with a poor prognosis. Wild-type transthyretin amyloidosis (wt-TTR), is a distinct clinical entity occurring predominantly in men > 65 yrs, that has gained interest recently due to novel treatment options. Regional strain analysis has been shown to discriminate both forms of cardiac amyloidosis from other causes of concentric left ventricular hypertrophy, with a characteristic pattern of ‘apical sparing’. Due to the significant difference in both the course of the disease and treatment options between groups, a non-invasive echocardiographic method of determining subtype would be valuable.

Aim/Method: We sought to compare traditional and novel echocardiographic parameters in a cohort of AL ( n = 80) and wild type (wt-TTR) amyloid ( n = 32) patients. All amyloid patients underwent comprehensive transthoracic echocardiography, including both conventional parameters and LV longitudinal strain. Further novel parameters were computed including the ratio of global longitudinal strain (GLS) to LV ejection fraction (LVEF), as well as GLS to indexed LV mass.

Results

wt-TTR patients had significantly greater LV mass (176 ± 59g/m2vs118 ± 37g/m2, p < 0.001), and worse diastolic dysfunction as expressed as E/E’ (21.5 ± 11vs17 ± 8, p = 0.04). LVEF was significantly lower in wt-TTR patients however remained in the normal range in both groups (53 ± 6%vs57 ± 6%, p = 0.001), whilst GLS was significantly reduced compared to AL-amyloid patients (11.5 ± 3.4%vs16.2 ± 4.6%, p < 0.001). LVEF:GLS was significantly higher in wt-TTR patients (4.93 ± 1.4vs3.87 ± 1.3, p = 0.001) reflecting a more profound reduction in strain with a relatively preserved ejection fraction. Similarly, the ratio of GLS to LV mass was significantly lower in wt-TTR amyloidosis (0.078 ± 0.05vs0.155 ± 0.07, p < 0.001), reflecting a more significant reduction in strain for a given wall thickness in wt-TTR patients. GLS:LV mass was the strongest discriminator between subtypes (AUC 0.82), with a cutoff of 0.09 giving a sensitivity and specificity of 71% and 80% respectively, for detecting wt-TTR.

Conclusion

In this cohort, patients with wt-TTR had significantly greater increase in LV wall thickness and diastolic dysfunction, which may in part reflect their increased age (77vs62). However, GLS was also significantly reduced compared to AL-amyloid, even when accounting for LV ejection fraction and LV mass, suggesting these composite parameters may have value in determining the subtype of cardiac amyloidosis.