Heterogeneity in Conduction Underlies Obesity Related Atrial Fibrillation Vulnerability.

Background fibrillation (AF) but pathophysiology underlying this relation is only partly understood. The aim of this study is to compare the severity and extensiveness of conduction disorders between obese patients and non-obese patients measured at a high-resolution scale. Methods - Patients (N=212) undergoing cardiac surgery (male:161, 63+/-11years) underwent epicardial mapping of the right atrium (RA), Bachmann's bundle (BB) and left atrium (LA) during sinus rhythm. Conduction delay (CD) was defined as inter-electrode conduction time (CT) of 7-11ms and conduction block (CB) as CT >/=12ms. Prevalence of CD/CB, continuous CDCB (cCDCB), length of CD/CB/cCDCB lines, and severity of CB were analyzed. Results - In obese patients, the overall incidence of CD (3.1% versus 2.6%, p=0.002), CB (1.8% versus 1.2%, p<0.001) and cCDCB (2.6% versus 1.9%, p<0.001) was higher and CD (p=0.012) and cCDCB (p<0.001) lines are longer. There were more conduction disorders at BB and this area has a higher incidence of CD (4.4% versus 3.3%, p=0.002), CB (3.1% versus 1.6%, p<0.001), cCDCB (4.6% versus 2.7%, p<0.001) and longer CD (p<0.001) or cCDCB (p=0.017) lines. The severity of CB is also higher, particularly in the BB (p=0.008) and PV (p=0.020) areas. In addition, obese patients have a higher incidence of early de-novo post-operative AF (PoAF) (p=0.003). BMI (p=0.037) and the overall amount of CB (p=0.012) were independent predictors for incidence of early PoAF. Conclusions - Compared to non-obese patients, obese patients have higher incidences of conduction disorders which are also more extensive and more severe. These differences in heterogeneity in conduction are already present during SR and may explain the higher vulnerability to AF of obese patients.