IMPORTANCE OF DONOR SELECTION IN RENAL TRANSPLANTATION

Renal transplantation has become a treatment of choice for patients with end stage renal disease. A successful transplant is the result of a combination of several factors acting synergistically, such as the degree of HLA compatibility between donor and the recipient, pretransplant blood transfusions, the recipient''s state of immunoreactivity and sensitization, immunosuppressive therapy given in post operative period etc. Donor selection appears to be the most critical factor for the long term success of the organ graft. In this brief review, some of the important parameters of donor selection in renal transplantation are highlighted.KEY WORDS: Histocompatibility (HLA) matching, Cross match, Sensitization     

Review article: Managing bone complications after kidney transplantation

Chronic kidney disease mineral and bone disorder (CKD-MBD) describes the laboratory, bone and vascular abnormalities that exist in patients with CKD stages 3–5D and that may persist after transplantation. Persisting abnormalities of bone turnover and abnormal mineralization, together with bone mineral density (BMD) loss from glucocorticoids, may all predispose to a loss of structural integrity and increased fracture risk in kidney and kidney pancreas recipients. Vitamin D, calcitriol, calcitonin and bisphosphonates have all been used to preserve BMD following transplantation, despite a lack of safety data and the potential for some of these drugs to cause harm. A limited number of post-transplant studies utilizing these drugs have not yet documented improved fracture prevention or fracture-related mortality and have not considered allocation based on risk factors for fracture or markers of bone turnover. Targeted allocation of the available therapies based on a stratification of risk appears warranted. This might be achieved using an algorithm incorporating BMD, X-ray evaluation, laboratory investigations including bone turnover markers and the assessment of standard fracture risk factors at the time of and soon after transplantation. This approach, which is similar to protocols used in the general population, may result in more effective management of patients and fewer adverse effects such as adynamic bone disease. Although BMD is a surrogate for fracture risk in the general population it is not validated in this transplant population. Consequently, such an approach should be confirmed by studies that include bone biopsy data and an evaluation of patient level outcomes.     

Prospective Randomized Comparison of Biphasic Waveform Tilt Using a Unipolar Defibrillation System

Background: A unipolar defihrillation system using a single right ventricular (RV) electrode and the active shell or container of an implantable cardioverter defibrillator situated in a left infraclavicular pocket has been shown to be as efficient in defibrillation as an epicardial lead system. Additional improvements in this system would have favorable practice implications and could derive from alterations in pulse waveform shape. The specific purpose of this study is to determine whether defibrillation efficacy can be improved further in humans by lowering biphasic waveform tilt. Methods: We prospectively and randomly compared the defibrillation efficacy of a 50% and a 65% tilt asymmetric biphasic waveform using the unipolar defibrillation system in 15 consecutive cardiac arrest survivors prior to implantation of a presently available standard transvenous defibrillation system. The RV defibrillation electrode has a 5-cm coil located on a 10.5 French lead and was used as the anode. The system cathode was the active 108 cm² surface area shell (or “CAN”) of a prototype titanium alloy pulse generator placed in the left infraclavicular pocket. The defibrillation pulse derived from a 120-μF capacitor and was delivered from RV ± CAN, with RV positive with respect to the CAN during the initial portion of the cycle. Defibrillation threshold (DFT) stored energy, delivered energy, leading edge voltage and current, pulse resistance, and pulse width were measured for both tilts examined. Results: The unipolar single lead system, RV ± CAN, using a 65% tilt biphasic pulse resulted in a stored energy DFT of 8.7 ± 5.7 J and a delivered energy DFT of 7.6 ± 5.0 J. In ail 15 patients, stored and delivered energy DFTs were < 20 J. The 50% tilt biphasic pulse resulted in a stored energy DFT of 8.2 ± 5.4 J and a delivered energy DFT of 6.1 ± 4.0 J;P = 0.69 and 0.17, respectively. As with the 65% tilt pulse, all 15 patients had stored and delivered energy DFTs < 20 J. Conclusion: The unipolar single lead transvenous defibrillation system provides defibrillation at energy levels comparable to that reported with epicardial lead systems. This system is not improved by use of a 50% tilt biphasic waveform instead of a standard 65% tilt biphasic pulse. (PACE 1995; 18:1369–1373)     

Defining Patients at High Risk for Gastrointestinal Hemorrhage after Drug‐Eluting Stent Placement: A Cost Utility Analysis

Introduction: The study goal was to evaluate the cost‐effectiveness of drug‐eluting stent (DES) placement with consideration of gastrointestinal (GI) bleeding risk. DES reduce the need for future coronary revascularization, but require prolonged dual anti‐platelet (DAT) therapy, which may increase the risk for GI bleeding. While DES have been found to be cost‐effective in patients at average risk for GI bleeding, they may not be the most cost‐effective strategy in higher risk patients. Methods: A Markov model was created to compare DES with bare metal stents (BMS). Patients were a hypothetical cohort of 60‐year‐old individuals with coronary artery stenosis that required nonemergent percutaneous coronary revascularization (PCI). The primary outcomes were the threshold incremental risks of GI bleeding from DAT based on willingness to pay (WTP) of $50,000, $100,000, and $150,000 per quality adjusted life year (QALY) gained. Results: For a WTP of $100,000, the relative risk of GI bleeding from DAT could be as high as 10.8 (when compared to aspirin alone) before DES would no longer be cost‐effective. In patients with two risk factors for GI bleeding, the threshold relative risk could be as low as 1.6. Conclusion: In average‐risk patients, the risk of GI bleeding from DAT can be substantial without affecting the cost‐effectiveness of DES. However, DES are unlikely to be cost‐effective in patients with two or more risk factors for GI bleeding. (J Interven Cardiol 2010;23:179‐187)     

Clinical Experience with a Dual-Chamber Implantable Cardioverter Defibrillator to Treat Atrial Tachyarrhythmias

INTRODUCTION: This study evaluated the safety and efficacy of a new dual-chamber implantable cardioverter defibrillator (ICD) to detect and treat atrial tachyarrhythmias in patients with drug-refractory atrial fibrillation (AF) and no indication for a ventricular ICD. METHODS AND RESULTS: A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 144 of 146 patients. The device discriminates atrial tachycardia from AF based on cycle length and regularity, and uses atrial overdrive pacing as well as shocks to terminate tachyarrhythmia episodes. Patients were followed for an average of 12.6+/-6.2 months. Use of antiarrhythmic drugs was 63% at baseline and did not change over time. Kaplan-Meier estimates of 12-month complication-free survival, device therapy survival, and patient survival were 85%, 91%, and 98%, respectively. Positive predictive accuracy of spontaneous atrial tachyarrhythmia detection was 99%, while atrial overdrive pacing and shocks terminated 40% and 87% of treated episodes, respectively. Median duration of successfully treated episodes was 8.9 minutes versus 144 minutes for the therapy failures. There was no reduction in the use of patient-activated shock therapy over time; at the 12-month follow-up evaluation, 94% of patients were in sinus rhythm. Ventricular tachyarrhythmias (67 episodes) were detected and appropriately treated in 7.6% of patients. CONCLUSION: This dual-chamber ICD appears to be safe and well tolerated in patients with drug-refractory symptomatic atrial tachyarrhythmias. The device, used in combination with drugs, effectively treats atrial tachyarrhythmias with pacing and/or shock therapies and decreases the median episode duration. In addition, the device protects from ventricular tachyarrhythmias in patients with AF and structural heart disease.     

Lead Fixation in Dogs Achieved with RF Energy

Lead Fixation in Dogs Achieved with RF Energy. Introduction : The purpose of this study was to test whether radiofrequency (RF) energy could be used to fixate leads to the endocardium.
Methods and Results : In six dogs we measured the dislodgment force and pacing threshold before and after RF Fixation in the coronary sinus (CS) and right ventricle (RV). RF fixation was achieved with a CardioRhythm Atakr* ablation unit. The dislodgment force of CS leads fixed with RF energy was 1.63 ± 0.65 oz, compared with < 0.1 oz for similar leads placed in the CS of six separate dogs. In the RV, leads fixed with RF energy had a dislodgment force of 1.29 ± 0.27 oz, compared with 0.48 ± 0.28 oz. for urethane ( P < 0.01) and 1.01 ± 0.21 oz for silicone ( P = 0.41) tined leads. In the CS, the pacing threshold for RF fixed leads increased significantly from 2.2 ± 1.1 V (0.5 msec) before fixation to 4.2 ± 1.3 V after fixation ( P < 0.01), while in the RV, the pacing threshold increased from 0.41 ± 0.05 V (0.5 msec) before fixation to a mean of 2.03 ± 0.44 V after fixation ( P < 0.01). In another group of six dogs studied for 12 weeks. 5 of 6 RF fixed CS leads remained attached, as did 8 of 10 RF fixed RV leads. For the RV leads, the mean pacing threshold was 0.90 ± 0.35 V, compared with 0.53 ± 0.18 V (0.5 msec) for similar tined leads ( P = 0.02) and 1.2 ± 0.30 V (0.5 msec) for screw leads ( P = 0.18) in the RV.
Conclusion : We conclude that RF energy can be used to attach leads to the RV and CS endocardium. While the RV pacing thresholds increased acutely, the mean chronic thresholds were not significantly different for RF fixed leads and standard tined or screw leads.     

Antecedent caloric intake and glucose excursion following a subsequent meal in Type 1 diabetes

Background: In the present study, we tested the hypothesis that calories consumed at a prior meal (lunch) may impair glycemic control after a subsequent meal (supper) even if the pre‐supper glucose did not differ regardless of the size of the lunch meal. Methods: Nine subjects with Type 1 diabetes using continuous subcutaneous (s.c.) insulin infusion (CSII) therapy were studied on two separate days. Lunch (1200 h) was randomly assigned as 25% or 50% of the usual daily intake on alternate study days. The CSII was stopped at 1000 h on the day of the study and glucose was controlled until supper by adjusting the rate of intravenous (i.v.) insulin based on glucose measurements every 15 min. The CSII was restarted 1 h before supper and i.v. insulin discontinued 15 min before the first bite of supper. An identical supper meal and pre‐supper s.c. bolus of short‐acting insulin were administered on both visits. Results: Pre‐supper glycemia was nearly identical on each of the two study days. However, the post‐supper glucose area under the curve was 27.5% greater on the day of the antecedent large lunch compared with the small lunch (P = 0.0039). Conclusions: For optimal postprandial glucose control, people with Type 1 diabetes may need to consider not only anticipated meal calories, but also prior food intake, a practice not commonly recommended based on currently used insulin dosing algorithms.