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1.
With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of patients suitable for transvenous system. As newer waveforms become available, the need for a flexible device may change. In addition, although it has been shown that the option of biphasic waveform may increase the defibrillation efficacy, this may depend upon the shape of the biphasic waveform used. Thirty patients undergoing transvenous defibrillator implant were included in the study. In 20 patients (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten patients (group II) testing of simultaneous monophasic shocks and biphasic waveforms with 65% and 80% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 30 patients. In group I, 50% tilt biphasic waveform consistently provided similar or better defibrillation efficacy compared to monophasic waveforms (biphasic 7.5 ±5.1 joules vs simultaneous 17 ± 7.8 joules, P < 0.01; and vs sequential 17 ± 8.4 joules, P <0.01). In group II, 65% tilt biphasic pulse required less energy for defibrillation as compared with simultaneous monophasic shocks (9.6 ± 4.5 joulesvs 15.6 ± 5.1 joules, P = 0.04). No significant difference was observed in terms of defibrillation threshold between 80% tilt biphasic shocks and simultaneous monophasic pulses (11.8 ± 6 joules vs 15.6 ±5.1 joules, P = NS). Biphasic shocks with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.  相似文献   
2.
In most reports on patients receiving implantable cardioverter defibrillators. shocks were received mainly during the first 2 to 3 years. Thus, the question had been raised as to the need for device replacement after 3 or 4 years if no shocks had been received. In order to answer this question, shock experience in 184 putients receiving the implantable cardioverter defibrillator was analyzed. Patients were followed for a mean of 24 ± 18.7 months. A patient's shock was judged to be appropriate if there was electrocardio-graphic documentation of sustained ventricular tachyarrhythmia at the time of shock or if it was preceded by sudden onset of presyncopal or syncopal symptoms. The majority of patients had coronary artery disease. In approximately two-thirds of patients, left ventricular ejection fraction was below 40%. One hundred fourteen patients had inducible sustained monomorphic ventricular tachycardia. On follow-up, there were 29 deaths, five of which were sudden. Sixty-eight patients received an appropriate shock during follow-up (37%). Over 90% of these 68 received their first shock within the 2 years after implant. The actuarial risk of receiving an appropriate shock by the fifth year after implant was 69%. Conversely, 31% of patients who survived 5 years had not received an appropriate shock. Hazard analysis indicates that there is a high incidence of first appropriate shock during the year following implant. Subsequently, the incidence dropped to a relatively steady rate with a rise in this rate during the fifth year. This analysis suggested a bimodal distribution of appropriate shocks. The results indicate that implantable cardioverter defibrillator generators should be replaced even up to the fifth year despite the fact that a patient had not received an appropriate shock.  相似文献   
3.
Implantation of a nonthoracotomy system (Medtronic PCD or CPI Endotak) was attempted in 170 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) not requiring concomitant cardiac surgery. A nonthoracotomy system could be successfully implanted in 95 of the 115 patients with the PCD system and 49 of 55 patients receiving the Endotak lead system. In 26 patients with failed nontboracotomy system because of defibrillation threshold (DFT) > 25 joules (J), an epicardial system was implanted at the same setting. Patients receiving the two lead systems were comparable with regard to age, sex, and ejection fraction. However, since tbe PCD system offers tiered therapy multiprogrammable options, all attempts were made to implant tbis lead system in patients with VT that could be pace terminated. Mean DFT(15 ± 4.7 vs 17 ± 4.6 J;P = 0.03) and implant time (2.5 ± 0.6 vs 3.3 ± 0.7 hours; P = 0.02) were less with the Endotak lead system. There was no perioperative mortality. During a mean follow-up of 20 ± 4 months, there were eight instances of lead dislodgment in patients receiving the PCD system. Tbere were four nonsudden cardiac deaths and one sudden death in the Endotak group and three nonsudden deaths in the PCD group. Sudden cardiac death and total survival using the intention-to-treat analysis during this follow-up period were 99% and 95%, respectively. In conclusion, successful implantation, perioperative mortality, and survival rate are comparable with both lead systems; however, incorporating two defibrillating electrodes in one lead minimizes lead dislodgment and reduces implant time.  相似文献   
4.
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   
5.
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   
6.
Predictors of survival and arrhythmia recurrence for patients with implanted defibrillators have been reported but patients with sustained, well-tolerated ventricular tachycardia were often excluded from these trials. Arrhythmia recurrence and survival in populations including these patients have been less well studied. The purpose of the present study was to examine predictors of spontaneous ventricular arrhythmias and mortality in patients who received a tiered therapy antitachycardia pacemaker/defibrillator for ventricular tachycardia, fibrillation, or both. Three hundred thirty-seven patients who received a Ventritex CADENCE® tiered therapy antitachycardia device at one of 19 participating centers between July 11, 1989 and March 4, 1991 are included in this retrospective analysis. Diagnostic summary data and stored electrograms telemetered from the implanted device were assessed to determine characteristics of recurrent arrhythmias. Mean follow-up was 360 ± 10 (SEM) days. Thirty-three patients died during follow-up. At least one recurrent ventricular arrhythmia was observed in 205 patients (61 %). A total of 7,539 episodes were observed with a mean of 37 ± 5 per patient. Patients with recurrent ventricular arrhythmias were slightly but significantly older (64 ± 0.7 vs 59 ± 1.2 years; P < 0.001) but were not distinguished by gender or underlying structural disease. Patients whose presenting arrhythmia was monomorphic ventricular tachycardia were more likely to experience recurrent ventricular arrhythmias (69% recurrence rate) than patients presenting with ventricular fibrillation or polymorphic ventricular tachycardia (46% recurrence rate; P < 0.001). Cycle length of spontaneous tachycardia was also a predictor of arrhythmia recurrence. Patients having slower ventricular arrhythmias were less likely to remain recurrence free. Mean left ventricular ejection fraction was similar for patients with and without recurrences. Younger age and absence of arrhythmia recurrence but not presenting arrhythmia were predictors of survival. We conclude that age and presentation with monomorphic ventricular tachycardia are important predictors of arrhythmia recurrence for this patient population. Exclusion of patients with monomorphic ventricular tachycardia underestimates the rate of recurrent ventricular arrhythmias and utilization of device therapy.  相似文献   
7.
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   
8.
ICD Therapy and CABG for Sudden Death. Introduction: Previous studies have suggested that coronary artery bypass surgery is sufficient to prevent recurrence of sudden death in patients with critical coronary artery stenosis presenting with ventricular fibrillation or polymorphic ventricular tachycardia. We present our experience in patients with one or more episodes of sudden death associated with documented ventricular fibrillation or polymorphic ventricular tachycardia and severe operable coronary artery disease who underwent defibrillator implant at the time of bypass surgery. Methods and Results: Fifty-eight consecutive patients (age 63 ± 8 years) were included in this study. Eighteen of the 58 patients had no evidence of previous myocardial infarction. The mean ejection fraction was 37 ± 13%. All patients underwent electrophysiologic study before and after revascularization. At the time of first defibrillator discharge, each patient was reevaluated to exclude the presence of ischemia. The benefits of defibrillator implant were estimated comparing the projected survival based upon defibrillator discharge preceded by syncope or presyncope with survival curves generated including total death and sudden plus cardiac death. After a mean follow-up of 4.6 ± 2 years, 22 patients received appropriate shocks preceded by syncope or presyncope, and an additional 19 patients received asymptomatic shocks. At 4 years, survival free of total death was 71.2%, and the projected survival was 58.8% (P < 0.05). Multivariate analysis showed that ejection fraction lower than 30% and induction of arrhythmia with one or two extrastimuii (S2, S3) were independent predictors for defibrillator discharge. None of the remaining variables including age, gender, number of bypasses, history of myocardial infarction, and type of arrhythmias induced were predictive for death and occurrence of shocks. Conclusions: In patients with ventricular fibrillation and polymorphic ventricular tachycardia, bypass surgery does not protect from recurrence of life-threatening arrhythmias, and, as in our population, defibrillator implant may have significant impact on survival.  相似文献   
9.
Mortality in patients with cardiovascular disease is generally due to pump failure or lethal ventricular arrhythmias, In patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) and poor left ventricular (LV) function the death rate is particularly high. The overall incidence of premature arrhythmic death rate in patients with poor LV function is not totally clear. Since implantable cardioverter defibrillator (ICD) could prevent arrhythmic death in any population, we proceeded to analyze mortalities in patients with poor LV function who received ICD. Among a total of 200 consecutive patients receiving ICD at our institution, 68 (34%) had LV ejection fraction (LVEF) of < 30%. Thirty-one of these (45%) experienced appropriate ICD discharges and 17/31 (55%) had multiple shocks. Survival curves in this population revealed a 5 year projected overall survival of 11% whereas an actual survival was 60%. Even those who ultimately died from nonsudden causes, life was prolonged by ICD in a significant number of cases. Based upon these findings it is concluded that ICD has a major impact on survival in patients with poor LV function suggesting that many of these patients die prematurely from arrhythmia causes.  相似文献   
10.
Background : Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. Howevar, whether this improvement can he extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. Methods : Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60-H z alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. Results : Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 ±8.8 J vs 21.5 ±11 J; P < 0.01). Conclusion : Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.  相似文献   
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