Epidural Lead Fracture Caused by Material Processing Fault

Fracture of the epidural lead (Pisces Quad 3487) is documented in four out of eight patients with an implanted Itrel pacing system for treatment of peripheral vascular disease. In two patients, lead fracture was established during x-ray fluoroscopy. In the remaining two patients, x-ray examination did not reveal any fracture, due to proximity of the fragments. Microscopic examination of the extracted lead, however, confirmed lead fracture, as well as the presence of tissue fluid and thrombus between the two ends of the spiral shaped lead, but no insulation defect was observed. A cross-sectional area on the fracture line of the broken lead was examined using scanning electron microscopy. It was found, by tracing the radial marks to their point of convergence, that the initial microcrack started from a large inclusion of the calcium-silicon type at the lead surface. The initial microcrack was propagated by the fatigue mechanism. The presence of a large inclusion at the surface suggests that the main cause of the failure of the investigated epidural leads could be improper fabrication of the material. The high incidence of epidural lead fracture in our group suggests that this complication should be considered as a possible cause of epidural spinal electrical stimulation pacing system dysfunction.     

Efficiency,Safety, and Long‐Term Follow‐up of Retrograde Approach for CTO Recanalization: Initial (Belgrade) Experience with International Proctorship

Background: Retrograde approach increases the success rate for percutaneous recanalization of complex chronic total occlusion (CTO) of coronary arteries. Objectives: The purpose of this study was to describe our initial experience of retrograde percutaneous coronary intervention for CTO program, focusing on its safety and feasibility, and long‐term clinical follow‐up. Methods: The study was a single center retrospective registry which included a total of 40 patients, of 590 CTO treated patients (6.7%), between January 2008 and October 2011, who underwent retrograde approach for CTO recanalization. Results: Mean occlusion duration was 37.8 ± 40.3 months. Overall success recanalization rate was 87.5% (35/40). Septal collaterals were used to access the occlusion in all cases (100%). Retrograde guidewire crossing of collateral channels was successful in 36/40 (90.0%) patients with success rate of CTO recanalization in these patients of 97.2%. Retrograde approach as the primary strategy was applied in 23/40 (57.5%) patients, retrograde approach immediately after antegrade failure attempt was performed in 8/40 (20.0%) patients, and retrograde approach as elective procedure, after previously failed antegrade attempt, was performed in 9/40 (22.5%) patients. The success rate of these strategies was: 87.0% (20/23 patients) for primary, 87.5% (7/8 patients) for retrograde immediately after antegrade failure, and 88.9% (8/9 patients) for retrograde after previous failed antegrade attempt, respectively. Total in‐hospital major adverse cardiac events (MACE) rate was 5.0% (2 non‐Q‐wave myocardial infarctions). The MACE free survival at median follow‐up of 20 months was 89% (95% CI: 78–100%). Conclusions: This study has demonstrated that adequate training and international proctorship for this complex and demanding technique is a necessity and prerequisite to achieve high overall success rates, with acceptable complication rates and excellent long‐term survival rate. (J Interven Cardiol 2012;25:540–548).     

The Etiology of Syncope in Pacemaker Patients

A total of 46 patients with syncopal episodes after VVI pacemaker implantation were studied. Of these, 92% had one to three syncopal episodes and 8% more than three. All underwent a thorough clinical examination, which included chest X ray, echocardiogram, neurological exam, and the following protocol: 24-hour Holter monitoring, EEG, blood pressure (BP) measurement in three positions, Doppler exam of the carotid vessels, fasting blood glucose, and head-up tilt table test (60 minutes, 60 degrees). Holter monitoring showed exit block in two patients (4.3%) and failed sensing in one (2.1%). In two patients there was unilateral slowing on EEG. Orthostatic hypotension was found in four patients (8.6%), and hypoglycemia in three insulin-dependent diabetics. An occlusive atherosclerotic plaque in the carotid artery was found in three patients (6.5%). Syncope was induced in 17 patients (36.9%) by the tilt table test, after a mean standing time of 47 +/- 11 minutes. The mean resting systolic BP of these patients was 140 +/- 24 mmHg, and fell to a mean level of 56 +/- 8 mmHg (mean systolic BP drop was 79 +/- 8 mmHg). Sixteen of these 17 patients with positive tilt table were being paced at the time of syncope and one had a spontaneous heart rate of 73 beats/min. In 14 cases (30.4%) the cause of syncopal episodes after this extensive workup remained unexplained. These results indicate that pacemaker dysfunction is not a major cause of syncopal episodes in pacemaker patients and that these are most often due to vasovagal syncope. Long-term follow-up is warranted to determine the prognostic significance of various types of syncope in pacemaker patients.     

Target Lead—Low Threshold Electrode

Acute and chronic threshold measurements were compared for three different electrodes: the Medtronic * Target Tip model 4011, the Medtronic Ring Tip Model 6971 and the Siemens-Elema ** Carbon Tip Model 412S. The results of this study show that acute thresholds are lower with the Target Tip lead as compared to the other two, This finding applies to chronic thresholds as well. The results of this study favor programming to lower output energies while maintaining adequate safety margins with this lead system.     

Interspecies pharmacokinetic scaling of some iodinated organic acids

We have investigated the possibility of interspecies scaling of relationships between the structure and total plasma clearance in a group of nine organic acids (iododerivatives of benzoic, phenylacetic and hippuric acids) in rabbits, rats and mice. The intercompound comparison established the dependence of total plasma clearance predominantly on the molecular structure in all the animals under study, but the dependence on drug lipophilicity was also meaningful. For interspecies scaling of total plasma clearance, the use of a biological clock with an effective renal plasma flow as the unit seemed most suitable and is probably connected with the principal role of the kidney in the elimination of the compounds under study.     

Association Between Stimulated QT Interval and Ventricular Rhythm Disturbances: Influence of Autonomic Nervous System

To examine the association between ventricular rhythm disturbances and changes in the pacemaker-induced stimulated T interval (STIM-T interval), we compared findings from monitoring of two patient groups. The first group consisted of 15 patients with QTX microprocessor pacemakers and the second group consisted of 198 patients with documented ventricular rhythm disturbances and coronary artery disease (CAD). In the first group, which was free of ventricular rhythm disturbances and manifest coronary artery disease, the STIM-T interval was measured every 4 hours over a 36-hour period at four pacemaker frequency settings (70, 80, 90, and 100) in order to observe the circadian variation of the STIM-T interval as a function of changes in autonomic nervous system (ANS) tone. The second group was comprised of patients with CAD and over 30 VES/hrs (Lown grade classification 1–5), and taking no antiarrhythmic medication. These patients were followed using 24-hour Holter monitoring over a minimum of 23 hours and with less than 5% artifact/recording. Information regarding mean hourly heart rate, total number of VES, VES pairs, VT runs, and ischemic episodes in this group was compared with changes in the STIM-T interval in the first group. The STIM-T interval was found to be shorter during the day and longer at night at all heart rate settings. The total frequency of VES, of VES pairs, VT runs, and ischemic episodes in the second group varies in a similar circadian fashion. The greatest total number of VES, of VES pairs, VT runs, and ischemic episodes was recorded in the waking hours, at the same time when the STIM-T interval is the shortest, while this number was significantly lower during sleep, when the STIM-T interval of the first group is the longest. This coincidence of circadian variation pattern between STIM-T interval in group I, and ventricular arrhythmias and ischemic episodes in group II, suggests that alterations in ANS tone reflected in the STIM-T interval may be an important factor in the occurrence of these untoward events.