Morphological assessment of radio-frequency ablation lines of the myocardium of the left atrial appendage in patients with atrial fibrillation

The using in clinical practice of devices for radiofrequency ablation of the atrial myocardium significantly reduced the trauma of the operation and reduced the time of its execution. At the same time, radiofrequency ablation does not violate the integrity of the atrial walls, and the isolation effect is achieved only due to structural damage to the myocardium. The study was carried out on biopsies of the left atrial appendages, resected in patients (n=18) suffering from ischemic heart disease and non-paroxysmal atrial fibrillation. The histological structure of ablation lines formed on the myocardium by two different radiofrequency devices was studied. Bioptats of the left atrial appendages were fixed in a 10% buffered formalin solution, then their fragments were performed in a Microm STP120 histoprocessor, which were embedded in Histo-mix paraffin using the Tissue TekR Tek 5 modular system. Paraffin sections 3-5 pm thick were stained using routine histological methods and embedded in Bio Mount medium. Microscopic examination of the preparations and their photographic recording were carried out on a hardware-software complex Nic-Elements AR 4.12.00 on the basis of a research microscope Nicon 50S with a digital camera Nicon DS-Fi. The formation of ablation lines was carried out by: 1) applying one radio frequency exposure; 2) three radio frequency exposures; 3) application of radiofrequency exposure to a persistent reduction in the time to achieve transmurality. The histological study of the results of exposure to the myocardium of the left ears of the heart was carried out in a double-blind manner. The envelope, which contained data on the method of formation of ablation lines, was opened after receiving the results of the histological examination. As a result of the study, it was found that the priority criterion for the usefulness of the formed ablation lines under radiofrequency exposure to the left atrium in patients with non-valvular fibrillation should be recognized as a persistent decrease in the time to achieve transmurality. Based on this criterion, it is possible to obtain ablation lines with a complete absence of viable cardiomyocytes in their zone.