Few studies found that coronary microvascular dysfunction was highly prevalent in subjects with cardiac transthyretin amyloidosis (ATTR), even in the absence of epicardial coronary artery disease (CAD). The aim of this preliminary report is to confirm the coronary microvascular dysfunction using dynamic cardiac SPECT.

Adult patients with confirmed ATTR cardiomyopathy were included before Tafamidis treatment in a multicentric, prospective, observational cohort study (AMYTRE study, NCT05103943). Dynamic cardiac SPECT data were acquired on CZT-based pinhole cardiac cameras in listmode using a stress (249±13MBq)/rest (506±17MBq) one-day 99mTc-tetrofosmin protocol. Kinetic analysis was done with Corridor4DMTM software using a 1-tissue-compartment model and converted to myocardial blood flow using a previously determined extraction fraction correction. Myocardial flow reserve (MFR) was defined as the ratio between stress and rest myocardial blood flow.

Thirteen (9 male, 4 female) patients were prospectively included. Mean age was 77±18; mean BMI was 28±8.1. ATTR was diagnosed on 99mTc-HDP bone scintigraphy (8 grade 2 and 5 grade 3). LVEF was preserved, mean 57±7.5%. Twelve patients had normal perfusion imaging, without ischemia; 1 patient had moderate infero-basal ischemia (5–10% extent). MFR was significantly reduced both globally (1.5±0.35) and in all territories (1.5±0.34 for left anterior descending, 1.6±0.39 for left circumflex, and 1.6±0.45 for right coronary).

In this preliminary report, MFR is significantly reduced in all territories in patients with ATTR cardiomyopathy, undergoing cardiac dynamic SPECT. This confirms potential coronary microvascular dysfunction.