TNF and atrial fibrillation: Clearly, there are significant gaps in our knowledge (especially in canine pathology), i.e., very scant data on the frequency of true fistula formation in dogs with AF, lack of clear evidence confirming that TNF is associated with canine AF, lack of data about the role of EMT process in formation of canine fistulae, or no direct data regarding the activation of Th17 pathway in canine AF.