Prognostic Value of 99mtechnetium-PYP SPECT Visual Grade in Patients with Transthyretin Cardiac Amyloidosis on Stabilization Therapy.

Objective: The aim of our study was to evaluate the prognostic value of amyloid burden estimated by 99mTechnetium-pyrophosphate SPECT (99mTc-PYP-SPECT) visual grade in patients with transthyretin amyloid cardiomyopathy (ATTR-CM) receiving transthyretin (TTR) stabilization therapy.

Methods: Our retrospective cohort study included 344 ATTR-CM participants receiving TTR stabilization therapy. 99mTc-PYP-SPECT myocardial uptake was graded as 0, 1, 2 or 3, based on myocardial uptake that was either absent, less than, equal to, or greater than rib uptake, respectively. National Amyloidosis Center (NAC) stage was defined by NTpro-BNP (≤3000 pg/ml) and estimated glomerular filtration rate (≥45 mL/min/1.73m2) levels. The primary outcome was all-cause mortality. Kaplan-Meier survival and multivariable Cox regression analyses were performed.

Results: Of 344 participants (median age 80 years), 88% were men, and 98% had 99mTc-PYP-SPECT visual grade uptake 2 or 3. 76 participants (22.1%) died during follow-up (median 27 months). In Cox regression analysis adjusted for age, NAC stage, NYHA class, left ventricular (LV) mass index, LV ejection fraction, and 99mTc-PYP-SPECT visual grade, only NAC stage (HR 4.01, p-value <0.001) and NYHA class (HR: 5.22, p-value = 0.011) strongly predicted mortality.

Conclusions: In patients with ATTR-CM receiving TTR stabilization therapy, organ dysfunction evidenced by NAC stage and NYHA class, but not by amyloid burden on 99mTc-PYP-SPECT visual grade, are strong predictors of mortality. Our results support a revision to 99mTc-PYP visual grading 2 and 3 into a single grade positive. Future work is needed to evaluate whether amyloid burden measured by quantitative 99mTc-PYP-SPECT offers prognostic value in ATTR-CM.