Abstract 2617: Importance of Atrial Surface Area and Refractory Period in Sustaining Atrial Fibrillation: Testing the Critical Mass Hypothesis in vivo
Purpose: The critical mass hypothesis for atrial fibrillation (AF) was proposed in 1914; however, there are no studies precisely defining the relationship between atrial surface area and AF in an in vivo model. The purpose of this study was to evaluate the effect of tissue area and effective refractory period (ERP) on the probability of sustaining AF.
Methods: Domestic pigs (n=8) weighing 60–85kg underwent median sternotomy. Epicardial activation maps were obtained using electrode-embedded silicone patches placed on the atria. Baseline ERPs were obtained using single extra-stimulus pacing. ERP was lowered with continuous infusion of acetylcholine (0.005–0.04 mg/kg/min) until AF could be sustained after burst pacing. The atria were then partitioned using bipolar radiofrequency ablation. ERPs were lowered with increasing doses of acetylcholine until AF could be sustained in each subdivision of atrial tissue. Each section of tissue was further divided until AF was no longer inducible. ERPs were measured after each ablation. At study completion, the heart was excised and the surface area of each section was measured.
Results: Over a range of ERPs from 75 to 250ms, the probability of AF was found to be correlated with tissue area (range 19.5 to 105 cm2) and ERP as shown in the figure⇓. Logistic regression analysis identified shorter ERP and larger area as factors predictive of an increased probability of sustained AF. (AUC of ROC = 0.752, p<0.05)
Conclusion: The probability of sustained AF was significantly associated with increasing tissue area and decreasing ERP. These data may lead to a greater understanding of the mechanism of AF and help to design better interventional procedures.