Apical sparing pattern of left ventricular myocardial ^99mTc-HMDP uptake in patients with transthyretin cardiac amyloidosis

Background

A decreased longitudinal strain in basal segments with a base-to-apex gradient has been described in patients with cardiac amyloidosis (CA).

Objectives

Aim was to investigate the left ventricular (LV) regional distribution of early-phase ^99mTc-Hydroxymethylene diphosphonate (^99mTc-HMDP) uptake in patients with transthyretin-related cardiac amyloidosis (TTR-CA).

Methods

All patients underwent a whole-body planar ^99mTc-HMDP scintigraphy acquired at 10-min post-injection (early-phase) followed by a thorax SPECT/CT. The segmental uptake (expressed as % of maximal myocardial HMDP uptake) was investigated on the 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 < 10⁻⁶). This pattern was similar in wt-TTR-CA group (78% [70%-84%] vs. 70% [61%-81%]; P < 10⁻⁶), in m-TTR-CA group (80% [74%-86%] vs. 73 [66%-82%]; P < 10⁻⁷) and remained constant independently of the TTR mutation 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 apical sparing pattern was similar across TTR-CA and TTR mutation subtypes.