Abstract 2751: Correlation of Left Atrial Voltage Maps with Cardiovascular MR Provides Evidence of Pre-existent Scar in Atrial Fibrillation Patients

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Introduction: There is increasing evidence for and interest in detecting electrically silent left atrial (LA) myocardium which may be the substrate of atrial fibrillation (AF). Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) might detect these areas of pre-existent scar as high signal in the LA wall. We sought to correlate the extent low-voltage areas in AF patients with clinical parameters of LA volume and type of AF, and to correlate areas of low voltage with areas of high signal on LGE CMR, indicating areas of scarred tissue. Methods: Twenty-two patients with AF underwent high resolution atrial LGE CMR on a 1.5 T CMR scanner and bipolar voltage electroanatomic mapping (Carto, Biosense Webster). The number of the LA mapping points with low (< 0.1mV) voltage was calculated for each patient. LA systolic volume was measured, indexed to BSA. Using the voltage maps, blood-LA contrast to noise ratio (CNR) was measured on the LGE CMR images in two areas, low and high voltage areas (N=10). Hypothesis testing used t-tests and p<0.05. Results: The average extent of LA low voltage was 8 % of the LA. Four (18%) patients had no low voltage regions. The extent of low voltage for patients with non-paroxysmal vs. paroxysmal AF was 11 ± 13% vs. 4 % ± 5 % (p=0.08). The extent of low voltage for patients with larger than median LA volumes vs. smaller LA volumes was 12 ± 13% vs. 1 ± 1 % (p=0.027). In 10 patients in which LGE was measured in low and high voltage regions, the CNR was 10 vs. 6 (p=0.016). Conclusions: Patients with extensive low voltage regions in the LA have larger LA volumes. The CNR is higher in low-voltage regions, suggesting that such regions of possible scar can be identified by LGE CMR. This research has received full or partial funding support from the American Heart Association, AHA National Center.