Global and Regional Reduction of Myocardial Perfusion in Patients with Transthyretin Type of Cardiac Amyloidosis: A Dual SPECT Study Using 99mTc Pyrophosphate and 201Thallium.

Purpose: We aimed to clarify the clinical characteristics of global and regional myocardial perfusion in patients with transthyretin type of cardiac amyloidosis (ATTR) using dual single-photon emission computed tomography (SPECT) with ^99mTc pyrophosphate (PYP) and ²⁰¹TL (TL). Methods: Consecutive 178 (mean age 78±12, male 79) patients known or suspect of ATTR who underwent PYP-TL dual SPECT were retrospectively enrolled. Patients were categorized according to the visual grading for planar PYP uptake using Perugini grading, and the patients with grade greater than or equal to 2 were analyzed. In planar analysis, the heart/contralateral ratio (H/CL) for PYP, and heart/lung ratio (H/L) for TL were obtained to evaluate global myocardial uptake. In TL-SPECT polar map analysis, the heterogeneity of myocardial uptake was evaluated using segmental mean %uptake. Cardiac function and left ventricular function and end-diastolic ventricular mass (LVmass) were measured by echocardiography. Results: Among 178 patients, 39 patients showed PYP uptake with grade 2 or 3 and H/CL >1.3 (81±5 ys, male 28). Of those, 4 patients showed significant perfusion defect in TL scan. Among 35 patients without perfusion defect, H/L showed a significant inverse correlation to H/CL, and LVmass (r=-0.3, p=0.02; r=-0.4, p=0.03. 95% confidence interval -0.4 to 0.2, and -0.7 to -0.04 for H/CL and LVmass). Polar map analysis demonstrated significantly lower mean %uptake for TL in septum compared to lateral (79.4±8.4 vs. 84.3±6.2, p=0.006 for TL in septum vs. lateral, respectively). Conclusion: In ATTR, TL uptake surrogated the reduction of global myocardial perfusion. A significant regional heterogeneity was observed with a notable reduction in septum despite the diffuse hypertrophy.