BACKGROUND: Two-dimensional speckle-tracking strain echocardiography (2D STE) in cardiac amyloidosis (CA) patients has shown relatively preserved left ventricle apical systolic function as measured by longitudinal strain (LS). Technetium-99m pyrophosphate ( 99mTc-PYP) myocardial imaging has gained favor in diagnosis of transthyretin amyloidosis. Since 99mTc-PYP binds amyloid fibrils, we hypothesized this technique can elucidate relative distribution of amyloid in the heart.
METHODS: We identified 9 patients with CA diagnosis who had had 2D STE and 9mTc-PYP scans. Segmental LS was measured by 2D STE as a measure of systolic function. Segmental uptake of 99mTc-PYP was measured using a 17-segment model as a measure of CA burden in the specific segment. If uptake was 100% of maximum, it was categorized as 0% defect.
Results: Mean LS was markedly decreased in CA patients (-8.3) and much lower in normal patients. Strain increased from base to apex on 2D STE (average basal strain [-3.3] vs. mid strain [-8.3] vs. apical strain [-14]); p\u3c0.01 for all comparisons. Percent defect increased gradually from base to mid to apex (10%, 38%, 60% defect, respectively) in CA patients; p\u3c0.0001 for all comparisons. Apical cap percent defect was not significant from apex (48.7 vs 59.5; p=0.7547).
CONCLUSIONS: These data provide the first insight into relative distribution of amyloid in the ventricle and suggest the relative apical sparing of systolic strain may be a function of amyloid deposition of the ventricular base
