Abstract 14840: Ability of Coronary Calcium Absence to Predict Negative Stress Test Results in Patients Considered for Flecainide Therapy

Abstract

Background: Flecainide is a useful antiarrhythmic for atrial fibrillation (AF). However, the Cardiac Arrhythmia Suppression Trial (CAST) showed an increased risk of fatal ventricular arrhythmia with flecainide use after myocardial infarction (MI). Thus, a history of MI or coronary artery disease (CAD) is a flecainide exclusion, and stress testing is used to exclude ischemia. We assessed whether absence of coronary artery calcium (CAC) can obviate the need for stress testing. Methods: We assessed ischemic burden using regadenoson Rb-82 PET/CT in 1375 AF patients (pts) ≥50 y old without clinical CAD. CAC was determined qualitatively in these pts by low dose attenuation CT (n=816) or by quantitative CT (n=559). The primary comparison was percentage of pts with ischemic burden ≥5% by CAC presence or absence. Results: Pts with CAC absent (n=433, 31.5%) were younger, heavier, with lower rates of diabetes, hypertension, and dyslipidemia. Average ischemic burden was lower in CAC-absent pts (0.8 ± 3.1 v 1.3 ± 3.7, p=0.04), and a favorable difference trend in ischemic burden ≥5% was noted that did not reach significance (7.2% v 9.7% p=0.15). CAC-absent pts showed greater coronary flow reserve (2.4 v 2.3, p=0.002) and trended to have fewer referrals for coronary angiography (1.6% v 4.0% adjusted[adj]*-p=0.10), fewer findings of obstructive CAD (1.4% v 3.5% adj-p=0.12), and lower rates of 90-day MACE (1.6% v 3.5%, adj-p=0.12); long-term MACE were fewer (5.3% v 7.0% adj-p=0.04). Conclusions: Our results support the hypothesis that an easily administered, inexpensive, low radiation CAC scan may identify a subset of flecainide candidates with a low ischemic burden on PET stress testing and that rarely need coronary angiography/intervention. CAC-absence combined with other clinical information may obviate the need for routine stress testing in selected flecainide candidates. Larger and randomized trials are indicated to confirm these findings and apply CAC use in clinical practice.