Apical sparing pattern of left ventricular myocardial 99m Tc-HMDP uptake inpatients with transthyretin-related cardiac amyloidosis

Objective A decreased longitudinal strain in basal segments with a base-to-apex gradient has been described inpatients with cardiac amyloidosis (CA). Aim of the study was to investigate the left ventricular (LV) regional distribution of early-phase 99mTc-hydroxymethylene diphosphonate (HMDP) uptake inpatients with transthyretin-related cardiac amyloidosis (TTR-CA). Methods All patients underwent a whole-body planar 99mTc-HMDP scintigraphy acquired at 10 min postinjection (early-phase) followed by a thorax SPECT/CT. The relative segmental uptake % was investigated on AHA 17-segment model and 3-segment model (basal, mid-cavity, apical). Results Sixty-one TTR-CA patients were included of whom; 29 were wild-type (wt-TTR-CA) and 32 had hereditary TTR-CA (m-TTR-CA). Early myocardial 99mTc-HMDP uptake occurred in all TTR-CA. In all patients, segmental analysis of the LV myocardial distribution of 99mTc-HMDP uptake showed an increased median uptake (interquartile range) in basal/mid-cavity segments compared to the lowest median uptake of apical segments (respectively 79 [72–86] vs. 72 [64–81]; P −6 ). This pattern was similar in wt-TTR-CA group (78 [70–84] vs. 70 [61–81]; P −6 ), in m-TTR-CA group (80 [74–86] vs. 73 [66–82]; P −7 ) and remains constant independently of the TTR mutationu0027s subtype with P ranging 10–5 to 0.03. Conclusions Early-phase myocardial scintigraphy identified regional distribution of 99mTc-HMDP uptake characterized by a base-to-apex gradient, corroborating echocardiographic and cardiac magnetic resonance findings. This relative “apical sparing” pattern was similar across TTR-CA and TTR mutations’ subtypes.