Internal Cardiac Defibrillation Threshold: Effects of Acute Ischemia

The influence of myocardial ischemia on defibrillation success was studied using two different lead orientations in halothane-anesthetized pigs. Ischemia was induced by ligating the left anterior descending artery in its distal third. Controls had loosely tied ligatures placed around the artery at the same site. Ventricular fibrillation was induced by electrical stimulation 30 minutes after coronary artery ligation. Defibrillation used a single truncated pulse of approximately 6 ms duration passed to either: a transvenous electrode catheter (Medtronic, 6880) with the cathode in the apex of the right ventricle and the anode in the superior vena cava-atrial junction region, or the cathode in the apex of the right ventricle and a mesh plaque on the epicardium of the basal lateral left ventricle as anode. Ten seconds after the onset of ventricular fibrillation, defibrillation was attempted with increasing incremental energies until defibrillation was achieved. Fibrillation episodes were repeated at 15-minute intervals until the minimum first shock was successful in defibrillating the animal (i.e., defibrillation threshold). The number of animals successfully defibrillated with a minimum energy above or below 30 J was not different between normal and ischemic animals for either electrode configuration (i.e., 3 out of 20 vs 1 out of 13 for the catheter and 5 out of 6 vs 6 out of 7 for the epicardial plaque, respectively). Also, the cumulative percent success as a function of defibrillation energy was similar in both the normal and ischemic groups. There was a significant reduction in the minimum energy necessary for defibrillation when passing current between the right ventricular apex and the left ventricular epicardial plaque. The present results indicate that, despite differences in lead orientations, acute ischemia in the anesthetized pig does not appear to influence defibrillation success.     

An investigation into whether clients and/or their respective clinicians are aware of pending service exit in the first two months of treatment admission

Introduction and Aims. When a client exits an alcohol and other drug (AOD) treatment service against clinical advice, they and their service may incur significant disadvantage. The extent of awareness by both clients and clinicians that treatment would not continue has not been examined. Accordingly, this paper presents findings from a study that sought to identify whether clients and/or their respective clinicians were aware of pending service exit that occurred within the first 2 months of treatment admission. Design and Methods. The study was set in an outpatient AOD treatment service located in Auckland, New Zealand. Data were obtained by structured questionnaire and were reported for a group of clients (n = 49), clinicians (n = 46) and matched client/clinician pairs (n = 36). Results. Overall, clients and clinicians were no more likely to accurately identify pending service exit at a rate greater than would be expected by chance alone. However, clinicians were significantly more likely to identify pending service exit as compared with their respective clients (47% vs. 25%), although a large proportion of both groups expected treatment to continue beyond what proved to be the final treatment appointment (44% and 52%, respectively). Discussion and Conclusions. These findings suggest that service exit that occurs within the first 2 months of treatment admission may be largely unpredictable and that, as a result of this unpredictability, the opportunities for a targeted response may be limited.[Pulford J, Adams P, Sheridan J. An investigation into whether clients and/or their respective clinicians are aware of pending service exit in the first two months of treatment admission. Drug Alcohol Rev 2009]     

Performance of the Lumenless 4.1‐Fr Diameter Pacing Lead Implanted at Alternative Pacing Sites in Congenital Heart: A Chronic 5‐Year Comparison

Purpose: United States approval of the Model 3830, 4.1‐French (Fr) diameter, lumenless, pacing lead (Medtronic Inc., Minneapolis, MN, USA) in patients under 17 years of age, and those with congenital heart disease (CHD), was in 2005. To date, long‐term performance at alternative pacing sites (APS) is limited and chronic efficacy comparisons with more established leads is lacking. The purpose of this study was to evaluate these factors. Methods: Implant and follow‐up data on leads were compared: group 1 (non‐3830 leads) and group 2 (Model 3830 leads). These included acute and chronic sensing and pacing, impedances, implant sites, and complications. Groups were compared using Fischer's exact test, paired, and nonpaired t‐tests, with significance defined at P < 0.05. Results: A total of 119 patients (ages 5–48 years) received 171 leads: group 1 (n = 80) and group 2 (n = 91). At implant, there were no differences in patient age, CHD, sensing, or pacing thresholds between groups. Implant lead impedances differed between groups but all were within normal values for each lead design. Chronic data showed no difference in sensing, pacing thresholds, or impedances. There were five (6%) early lead dislodgements in group 1 and one (1%) in group 2. APS were achieved in group 2 with mean 1.6 ± 1.3 minutes fluoroscopy time. Conclusion: The new 4.1‐Fr lumenless lead shows similar performance indices to established leads even at APS, yet is thinner and achieves APS with technical ease, permitting more efficient chronic pacing in children and all patients with CHD. (PACE 2010; 33:1467–1474)     

Immunoregulatory Activity, Biochemistry, and Phylogeny of Ovine Uterine Serpin

PROBLEM: During pregnancy, the endometrium of the ewe secretes a progesterone-induced member of the serpin superfamily of serine proteinase inhibitors called ovine uterine serpin (OvUS) that has immunosuppressive properties. METHOD: Review of the literature. RESULTS AND CONCLUSIONS: OvUS inhibits a wide variety of immune responses, including mixed lymphocyte reaction, mitogen-stimulated lymphocyte proliferation, and T cell-dependent antibody production. Recent data have suggested that OvUS functions by inhibiting protein kinase C and interleukin-2-mediated events. OvUS and similar genes present in cattle and pigs diverged from other serpins prior to the divergence of artiodactyls. Since this time, the serpins have apparently undergone adaptive evolution that has led to a conformational state and biological functions distinct from prototypical serpins. Thus, it is likely that these proteins have an important role in the reproductive biology of Artiodactyla. Several lines of evidence suggest that, in sheep, OvUS functions to mediate the immunosuppressive effects of progesterone and prevent immunological rejection of the fetal allograft.