Introduction:
Relative apical sparing of longitudinal strain (RALS, the ratio of apical strain vs the rest of the heart) on echocardiography has been found to have high sensitivity and specificity for differentiating cardiac amyloidosis (CA) from other causes of left ventricular hypertrophy. Previous studies have shown no significant difference between amyloid subtypes, systemic light-chain amyloidosis (AL) and transthyretin amyloidosis (ATTR)
Hypothesis:
There will be a significant difference in sensitivity and specificity of RALS to detect CA across amyloid subtypes.
Methods:
A cohort of patients with either AL or ATTR amyloid was identified, with a control cohort of patients with left ventricular hypertrophy (LVH) of other etiologies. Speckle tracking echocardiography was performed on EchoPAC (GE Medical Systems) software to obtain values of basal, mid, and apical longitudinal strain for each patient; relative apical strain was then calculated.
Results:
The TTR group (n=22) was older (66.4±7.9, 76.6±11.6, p=0.001) and more likely to be female (p=0.009) than the AL group (n=30), both groups had similar rates of hypertension, diabetes mellitus, and end stage renal disease. Echocardiographic markers of diastolic function were decreased in both groups; the AL group had decreased left ventricle end diastolic volume (60.9±25.5, 94.9±50.2, p=0.012) and mean wall thickness (1.4±0.3, 1.6±0.4 p=0.017). ROC analysis using a RALS cutoff of 2 to differentiate AL and ATTR from the LVH control group revealed similar specificity (AL 85%, ATTR 85%) and sensitivity (AL 40%, ATTR 50%). Difference in area-under-curve (AUC) was not significant (p=0.2) (figure).
Conclusions:
ATTR and AL amyloid have similar specificity, but ATTR has a trend towards improved sensitivity over AL for detection of CA using RALS with the previously validated threshold of 2. This might become significant with a larger sample, work that is currently on-going..
Electrocardiographic left ventricular strain pattern, ST-segment depression and atrial fibrillation at the time of diagnosis of systemic light chain amyloidosis: Incidence and clinical significance
