The Effect of Polarity of the Initial Phase of a Biphasic Shock Waveform on the Defibrillation Threshold of Pectorally Implanted Defibrillators

The effect of initial phase polarity on the DFT of two pectorally implanted biphasic ICDs was tested in a randomized, prospective manner at the time of implantation. Twenty-two consecutive patients with VT or VF who received either the Medtronic PCD 7219C fewel device (10 patients) or PCD 7219D fewel device (12 patients) were studied. DFT testing was performed in a standard step-down manner. Both initial phase polarities—initial defibrillation current flowing from active can/SVC coil (± subcutaneous patch) to the RV coil (RV-) or from RV coil to active can/SVC coil (RV+)—were tested in random order. The mean DFT achieved with RV+ compared with RV- was lower for the 7219C patient group (6.6 ±3.1 vs 10.8 ± 5.5 J; P = 0.007). A similar trend was observed forthe 7219D group, though the difference did not reach statistical significance (12.0 ± 4.0 vs 16.3 ± 7.3 J; P = 0.07). Seven of the 10 patients in the 7219C group had a lower DFT with RV+, while the initial phase polarity made no difference in 3. In the 7219D group, 7 patients had a lower DFT using RV+, 2 patients had a lower DFT using RV-, and the initial phase polarity made no difference in 3. In conclusion, this study demonstrates that changing the polarity of the initial phase of a biphasic shock wave form can have a significant impact on the DFT achieved at the time of ICD implantation.     

Implantable Cardioverter Defibrillator for Prevention of Sudden Cardiac Deatb in Patients with Ventricular Tachycardia and Ventricular Fibrillation: ICD Therapy In Sudden Cardiac Death

Among the various therapy options for survivors of ventricular tachycardia-ventricular fibrillation (VT-VF), the implantable cardioverter defibrillator (ICD) seems most promising. It reliably terminates VT-VF and thus significantly impacts sudden cardiac death (SCD) survival. It is more effective than any of the known antiarrhythmic drugs in prevention of SCD, particularly among survivors of cardiac arrest. Compared to VT surgery, the ICD therapy can be offered to a larger pool of patients and can be placed at a lower surgical risk. With proper patient selection, ICD therapy is of major benefits to its recipients since it markedly reduces the chances of VT-VF relaled mortality; the main cause of premature death in this population. The ICD therapy is cost effective when compared to other medical interventions and could be more so if the implant is carried out early in the course of VT-VF management.     

Clinical Evaluation of a Dual Sensor, Rate Responsive Pacemaker

Dual sensor pacemakers should respond more appropriately during differing exercise modes than a single sensor device. The Topaz™ models 515 (QT and activity count [ACT] sensing) pacemaker shows appropriate rate response during treadmill exercise testing. We postulated that adjustments to relative sensor contribution should allow fine tuning of the onset of rate response. Eleven patients with this pacemaker were studied. Three standard exercise tests were performed with adjustment of sensor blending and activity threshold between each one. We also assessed the response to isometric exercise and a false positive activity signal. Results : Times to 100 ppm (3.7 ± 1.3, 4.4 ± 2.0, 5.3 ±1.5 mins), times to peak rate (6.1 ± 1.6, 5.6 ± 1.4, 6.5 ± 1.3 mins) and accelerations to peak (9.0 ± 2.4, 9.2 ± 5.3, 7.7 ± 2.8 ppm/min) were measured in all three different sensor settings (QT = ACT, QT 相似文献   

Functional renal reserve capacity in different stages of chronic kidney disease

Aim: There is conflict in published reports on the extent of availability of the functional renal reserve (RR) in healthy adults and in various stages of chronic kidney disease (CKD). The aim of the present study was to determine the RR in various stages of CKD. Methods: Baseline glomerular filtration rate (GFR) and ‘stimulated GFR’ following amino acid infusion were measured in 25 volunteers and 100 patients at various stages of CKD by measuring plasma clearance of Tc99m diethyl triamine pentaacetic acid. Any obtained difference between stimulated and basal GFR was considered as RR and expressed as percentage. Results The mean renal reserve was 23.4% in the healthy control group, 19.08% in CKD stage 1, 15.4% in CKD stage 2, 8.9% in CKD stage 3 and 6.7% in CKD stage 4, respectively. Conclusion: Renal reserve falls relentlessly with progression of CKD from 23.4% in normal to 6.7% in stage 4 CKD. However, RR may also get completely exhausted even with a normal or with a minimal decline basal GFR. Kidneys may retain some RR even up to the GFR level of 15 mL/min.     

提高认知能力的印度传统草药土丁桂

土丁桂属草药是作用于中枢神经系统的印度传统药物，特别是对促进记忆和改善智力有较好疗效。从印度传统医学和梵语文献中提取的大量信息提示，冠以土丁桂属草药名称的植物类别共4种：旋花科田旋花、旋花科土丁桂、蝶形花科蝴蝶花豆和龙胆科穿心草。这些草药名称均在古代文献中有所记载，可单独使用或与其他药材组合成各种草药处方。本文就现有的科学信息，如土丁桂属不同植物来源物种的生药学特征、化学成分、药理作用、临床前及临床应用等方面进行述评，以期为科学地应用土丁桂提供依据。此外，还可根据不同植物来源土丁桂属草药的不同功效进行鉴别应用。     

Ablation of Left Free-Wall Accessory Pathways Using Radiofrequency Energy at the Atrial Insertion Site:

Transseptal versus Transaortic Ablation. Introduction: Transcatheter ablation of the left free-wall atrioventricular accessory pathways (AP) by delivery of radiofrequency current at the ventricular insertion site has been shown to be effective. The efficacy of such a technique targeting the atrial insertion site of the AP was evaluated.
Methods and Results: One hundred consecutive patients with left free-wall APs and symptomatic supraventricular tachyarrhythmias were included. APs were manifest in 55 patients and concealed in 45. There were 55 men and 45 women with a mean age of 35 years. A total of 107 left free-wall APs were identified in these patients. In these 100 patients, successful ablation was accomplished in all by using a transseptal (45 patients) or transaortic (54 patients) technique. In one patient, ablation was accomplished from within the coronary sinus. Seven patients required a repeat ablative procedure, which was performed successfully. During 107 ablative procedures, six were associated with nonfatal complications including pericardial effusion (hemopericardium) in two patients, mild mitral regurgitation in two patients, swelling of the left arm in one patient, and staphylococcal bacteremia in one patient. Eighty-two (82%) patients underwent a repeat electrophysiologic study 6 to 8 weeks after successful ablation and were found to have no functioning AP or inducible supraventricular tachycardia. During a mean follow-up of 20 ± 8 months, none of the 100 patients had a recurrence of tachyarrhythmias.
Conclusion: These data indicate that the atrial insertion site of the AP can be successfully ablated in the majority of patients with left free-wall APs by using cither a transseptal or transaortic approach. Furthermore, both techniques are associated with minimal morbidity and no mortality.     

Catheter Ablation of the Left Bundle Branch for the Treatment of Sustained Bundle Branch Reentrant Ventricular Tachycardia

Sustained Bundle Branch Reentrant VT. Radiofrequency catheter ablation of the left bundle branch (LBB) was attempted in a patient with sustained bundle branch reentry. During sinus rhythm, the QRS had a complete LBB block pattern, and the LBB was activated retrogradely (transseptal). Ablation of the LBB eliminated inducibility of the tachycardia, while the QRS complex and the duration of the HV interval (70 msec) remained unchanged. Successful ablation of the LBB eliminated bundle branch reentry and yet maintained the anterograde conduction properties of the His-Purkinje system, obviating implantation of a permanent pacemaker.     

Reliable Models of Severe Coronary Stenosis in Porcine Coronary Arteries: Lesion Induction by High Temperature or Copper Stent

Severe, chronic, and nonfatal stenoses in coronary arteries have been difficult to induce consistently in large animals. Availability of such a model would have practical applications, including understanding the pathophysiology of coronary stenoses and testing new interventional devices. Current methods of producing stenosis typically require an open chest preparation, are time-consuming, and expensive. The purpose of this study was to report two reliable methods for creating severely stenotic lesions percutaneously in a porcine model without the need for an atherogenic diet. Two methods for producing severe coronary stenoses in pigs were found: (1) thermal balloon angioplasty at high temperature (80°C), and (2) implantation of elemental copper stents. Both were performed using a carotid artery cutdown. Pigs were euthanized, the hearts perfusion fixed, and arteries examined histologically. Thermal balloon angioplasty injury produced lesions with mean histopathological stenosis of 67%± 27% and mean angiographic stenosis of 70%± 21%. Histopathological examination showed medial necrosis, adventitial fibrosis, and occasional calcification of the external elastic lamina. Copper stent deployment created a mean histopathological stenosis of 81%± 22% and mean angiographic stenosis of 84%± 17%. Histopathological evaluation revealed inflammatory lesions with destruction of the elastic laminas and gross enlargement of vessel diameter. Two practical methods that reliably create severe coronary artery stenoses use intracoronary heat or copper stent implant. These lesions can be used for testing coronary interventional and diagnostic devices. These models generate lesions that form rapidly, use standard percutaneous techniques, and do not require intrathoracic surgery or atherogenic diets.