Long-Term Results of the First Clinical Application of Stereotactic Radioablation Using a Linear Electron Accelerator for the Treatment of Ventricular Tachycardia.

We present the first clinical application of non-invasive stereotaxic radioablation of ventricular tachycardia (VT) refractory to medical and surgical treatment. Based on the results of invasive navigational activation mapping, a pericicatrical zone in the interventricular septum associated with VT was verified. Radiosurgical irradiation of the target in the region of the interventricular septum and the posterior apical segment of the left ventricle was performed on a TrueBeam linear electron accelerator (Varian) in accordance with the segmental scheme of the left ventricle. Irradiation doses for 95% of the internal target volume (ITV, 17 cm3) and planned target volume (PTV, 46 cm3) (31.2 and 25 Gy, respectively) were delivered by two full coplanar arches in 1 session. Irradiation was performed during expiration using a respiratory control system. The loading dose to critical structures was within tolerance. The planned follow-up period is 6 months. According to remote monitoring, the intensity of VT paroxysms over 48 days after treatment was from daily to 2-3 per day. Then, the incidence of VT paroxysms decreased (1-3 per week), and from the 64th to the 185th day (the end of the observation period), no VT paroxysms were recorded, which suggests that the impact was highly precise, conformal, and involved the total wall thickness. No undesirable effects and damage to adjacent organs were observed.

Development of Noninvasive Technology of Stereotaxic Radioablation Using Linear Accelerators for the Treatment of Life-Threatening Ventricular Tachycardias in Experiment.

We developed a new technique of noninvasive stereotactic radioablation for the treatment of life-threatening tachyrhythmias. The study is performed on pigs (Sus scrofa domesticus). The zones of planned exposure were atrioventricular node (heart loading dose 40 Gy) and the apex of the left ventricle with a part of the interventricular septum (35 Gy) in animal No. 1 and atrioventricular node (45 Gy) and free wall of the left ventricle (40 Gy) in animal No. 2. The study was conducted on the Varian TrueBeam linear accelerator. The planned follow-up duration was 6 months. Delivery of 40 Gy to the atrioventricular node did not lead to persistent electrophysiological effect due to the development of transient third-degree atrioventricular block. The dose of 45 Gy resulted in permanent third-degree atrioventricular block followed by development of ventricular standstill on day 21 of observation. Histological examination confirmed transmurality and high precision of performed intervention.

Assessment of Biocompatibility and Local Action of Biomaterial for Production of an Envelope for Implanted Heart Electronic Devices.

We studied a biomaterial for a new domestic product, a biological envelope for implantation of cardiac electronic devices. The product is designed to prevent complications after pacemaker implantation and to facilitate the reimplantation procedure. By chemical and biological processing of raw materials (submucosa of porcine small intestine), an acellular extracellular collagen matrix was obtained. The biocompatibility of the material was tested in vitro using stem cell cultures. The biomaterial for fabrication of the envelope is not cytotoxic, biocompatible, and represents a suitable substrate for attachment, growth, and reproduction of stem cells. The biological effect of the material was studied in vivo on the model of heterotopic implantation in small laboratory animals. The biomaterial did not induce inflammation and tissue reaction and was completely transformed into healthy vascularized tissue without scars in 90 days after implantation.

Isolated Atrial Amyloidosis in Patients with Various Types of Atrial Fibrillation.

The myocardium of the right and left atrial appendages (auricles) in patients with paroxysmal, persistent, and permanent forms of atrial fibrillation was examined by histological methods and electron microscopy. Isolated atrial amyloidosis was detected in the left (50.0-56.3% patients) and in the right (45.0-55.6% patients) atrial appendages. In all cases, immunohistochemistry revealed atrial natriuretic peptide in fibrillary amyloid deposits. Ultrastructurally, amyloid masses formed clusters of myofibrils 8-10 nm in diameter. They were chaotically located in the extracellular space along the sarcolemma as well as in membrane invaginations, dilated tubules of cardiomyocyte T-tubular system, and vascular walls. Amyloidosis was predominantly observed in women; its degree positively correlated with age of patients and duration of atrial fibrillation but negatively correlated with atrial fibrosis. The study revealed positive (in permanent atrial fibrillation) and negative (in paroxysmal atrial fibrillation) correlation of amyloidosis with myofibril content in atrial cardiomyocytes.