Issue 16

R. Laczkó et alii, Frattura ed Integrità Strutturale, 16 (2011) 28-33; DOI: 10.3221/IGF-ESIS.16.03 29 electrode in a way it may break and the tip may be left in the vessel or the coating may be damaged. It is also important to consider the type and size of the stent in order ensure the most appropriate fixation. The aim of our article is to examine the damages the electrode explantation may cause to the electrodes and stents and to find the most convenient stent for electrode fixation. Figure 1 : X-ray picture of an implanted pacemaker and electrodes [5]. Figure 2 : The head of a pacemaker electrode M ETHODS special curve was shaped to model the bend of the outer surface of the left ventricle. The curve was formed in a sheet made from foamed polystyrene show in Fig. 3. The sheet was 50 mm long, 30 mm wide and 30 mm thick. The Left Ventricular Diastolic Diameter (LVDD) is typically about 70 mm and the representative wall thickness of the left ventriculum of patients receiving cardiac resynchronization therapy is 10 to 20 mm [3]. Accordingly, the radius of the test curve was 90 mm. A silicon tube was inserted into the curve and the electrodes were stabilized with coronary stents in the tube. Figure 3 : curve to model the bend of the left ventriculum where the lead is implanted. The first step of the procedure was to fill the tube with physiological saline. Since the electrode is surrounded by blood in the ventricle, similar wet conditions had to be ensured in order to minimize the friction between the stent and the electrode. It was achieved by filling the tube with physiologic solution. Secondly, the electrode was led up to the end of the tube and coronary stents attached to a balloon were used to fix the electrode. The stents were expanded with an indeflator. The indeflator is a pump complete with a pressure meter and is filled with Ringer’s solution. Since maximum pressure is normally used to expand stents in practice, the same pressure (26 bar) was chosen in our experiments. Our aim was to achieve the maximum available diameter of stents with this method. After the electrode was fixed with the expanded stent, the guide wire and balloon catheter were removed. Finally the electrode was slowly and carefully extracted. The procedure was monitored with stereomicroscope. The indeflator was filled with a turquoise liquid for better visibility because polymer tube modelling the vein is not completely transparent. This method makes it possible to follow the process of the expansion more precisely: in the picture the silhouette is sharp. A