CA-532-02 ATRIAL UPTAKE OF TECHNETIUM-99M-PYROPHOSPHATE IS ASSOCIATED WITH INCREASED ARRHYTHMIA RECURRENCE FOLLOWING AF ABLATION

Atrial amyloidosis is an arrhythmogenic substrate for atrial fibrillation (AF). Technetrium-99m-pyrophosphate (99mTc-Pyp), known to bind calcium, was originally developed as a bone tracer. It was subsequently demonstrated that 99mTc-Pyp correlated with areas of calcium deposition in injured and necrotic myocytes. Assessment of atrial uptake (AU) of 99mTc-Pyp is currently not utilized clinically but may provide important insights into the likelihood of success of rhythm control strategies among individuals with AF. To examine the association between AU on 99mTc-Pyp scan and maintenance of normal sinus rhythm following AF ablation. We studied 620 patients who were referred for a 99mTc-Pyp scan for suspected transthyretin cardiac amyloidosis between January 2012 and September 2019. Of these patients, 55 subsequently underwent AF ablation and were included in our final analyses. Presence or absence of AU was assessed using Corridor 4DM® software and Syngo Via® using fused/co-registered computed tomographysingle photon emission computed tomography imaging in all cases. AU was defined as qualitative uptake in the atrial walls distinct from the blood pool. A representative example of AU is shown in Figure 1b. A 2-sided p-value <0.05 was considered statistically significant. Baseline characteristics are shown in Figure 1a and were similar between those with and without AU. Following ablation, 34/55 (62%) developed recurrent arrhythmia and the mean time to recurrence was 28 months. Among those with AU on 99mTc-Pyp scan, 21/25 (84%) experienced arrhythmia recurrence, compared to 13/30 (43%) of those without AU (Figure 1c, log-rank 5.4, p=0.02). On multivariable models adjusting for AF type, the presence or absence of cardiac amyloidosis, and left ventricular ejection fraction, AU was a significant predictor of recurrent arrhythmia (HR 2.6, 95% CI 1.2-5.3, p=0.016). Atrial myopathy is the result of a variety of factors that lead to structural and electrical remodeling in the atrium and portends a poorer prognosis with respect to rhythm control among patients with AF. AU of 99mTc-Pyp may identify patients at higher risk for arrhythmia recurrence following AF ablation.