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11.
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.  相似文献   
12.
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.  相似文献   
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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.  相似文献   
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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.  相似文献   
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The purpose of this investigation is to define whether the antiarrhythmic drug moricizine has beneficial or adverse effects on currently used antitachycardia and antifibrillatory devices. These studies were performed in a dog model of sustained monomorphic ventricular tachycardia (VT). In 11 dogs, the left anterior descending artery and all surrounding epicardial collateral feeder vessels were ligated. Defibrillator patches were implanted and the dogs were allowed to recover. After a 7-day recovery period, effective refractory period (ERP), end diastolic threshold (EDT), VT induction, and VT and ventricular fibrillation (VF) termination data were collected before and after moricizine infusion (2 mg/kg). In this experimental model, moricizine caused the folIowing electrophysiological changes: a prolongation of the ERP from 173 ± 14 to 182 ± 15 fP < 0.02) with no significant effect on the EDT for pacing; a prolongation of the VT cycle length from 175 ± 18 to 201 ± 23 msec (P < 0.003); an increased cycle length required for overdrive pacing from 136 ± 20 to 157 ± 22 msec (P < 0.01); no effect on the energy required to cardiovert VT; an increase in the defibrillation threshold from 7.5 ±4 to 9.4 ± 4 joules (P < 0.006) and; in 5 of the 8 dogs with VT, theVT could be initiated with somewhat less aggressive stimulation. Significant beneficial electrophysiological effects were noted on theVT cycle length, including a proportionately prolonged overdrive pacing cycle length for VT termination. These changes were contrasted by the significant increase in the VF conversion energy required and the ease with which the VT could be induced postmoricizine. These findings suggest a possible proarrhythmic effect of moricizine.  相似文献   
18.
The effect of initial phase polarity (IPP) reversal using biphasic shocks on DFT at the time of implantation of implantable cardioverter defibrillator and the reproducibility of this effect during predischarge testing was evaluated in a randomized fashion. Twenty-two patients with ventricular tachycardia or ventricular fibrillation (VF) who received either the Medtronic 7219D (7 patients), 7219C (12 patients), 7223 (1 patient), or CPI Ventak MINI (2 patients) were studied. The DFT was determined in a randomized fashion at implantation and during predischarge testing using a binary search protocol. Initial shock was delivered at 12 J. If successful, subsequent shock was delivered at 6 J, following which the shock was incremented or decremented by 3 J depending upon the success. The DFT for right ventricular (RV)-and RV + IPP was 10.9 ± 4.1 J and 11.1 ± 4.0 J, respectively, at implant (P = ns) and 9.7 ± 4.3 J and 8.4 ± 6 J, respectively, (P = ns) at predischarge testing. Of the six patients who had better DFT with RV+ at implantation, only one patient maintained the benefit during predischarge testing. The differences observed in IPP in individual patients may not be demonstrable during repeated testing. These findings may have implications on how these devices should be programmed.  相似文献   
19.
Wide QRS Complexes. Wide QRS complex tachycardia is a commonly encountered arrhythmia and its appropriate diagnosis often poses a challenge to most physicians. The origin of a wide QRS complex is either supraventricular with abnormal ventricular activation or ventricular. This review addresses the main electrophysiologic mechanisms involved in the genesis of a wide QRS complex and its maintenance as a sustained arrhythmia. (J Cardiovasc Electrophysiol, Vol. 3, pp. 365–393, August 1992)  相似文献   
20.
Objective: The goal of this study was to assess if tilt bears any impact on defibrillation efficacy of biphasic shocks. Background: Although it has been shown that hiphasic waveform may increase the defibrillation efficacy, this pulsing method has not been as extensively studied in patients, and information regarding the effect of different tilts is lacking. Methods: This study consisted of two similar but distinct protocols including 33 patients undergoing transvenous defibriilator implant. In 17 patients (Part I) defibrillation threshold was obtained delivering biphasic waveforms with 50%, 65%, and 80% tilt in random fashion. Similarly, in 16 patients (Part II) testing of biphasic waveform with 40%, 50%, and 65% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 33 patients. Results: In Part I, tilt of 50% demonstrated a defibrillation threshold significantly lower than 65% tilt (7.5 ± 4.3 J vs 9.7 ± 5.0 J; P = 0.04) and 80% tilt (7.5 ± 4.3) vs 11.7 ± 5.9 J; P < 0.01). Similarly, 65% tilt provided a lower defibrillation threshold than 80% tilt (9.7 ± 5.0 J vs 11.7 ± 5.9 J; P = 0.02). In Part II, no significant difference was observed in terms of defibriilation threshold between 40% tilt and the two tilts of 50% and 65%. However, as in Part I, 50% tilt provided a significant reduction of the energy to defibrillate as compared to 65% tilt (6.3 ± 3.6 J vs 9.0 ± 4.8 J; P < 0.01). The 50% tilt resulted in better defibrillation efficacy than 65% tilt independent of the lead system used for testing (Medtronic Transvene and CPI Endotak-C). Conclusions: Biphasic shocks with 50% tilt required less energy for defibrillation than 40%, 65%, and 80% tilts. However, in the clinical setting a programmable tilt may be preferable to account for some patient-to-patient variability.  相似文献   
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