Efficacy of a tiered therapy defibrillator system used to treat recurrent ventricular arrhythmias refractory to drugs.

OBJECTIVE--To evaluate an implantable tiered therapy defibrillator system that delivered antitachycardia pacing treatment for slower well tolerated ventricular tachycardias and cardioversion or defibrillation for fast tachycardias or ventricular fibrillation. METHODS--A tiered treatment device (Ventritex Cadence V-100) was implanted in 30 patients with ventricular tachycardia that was refractory to drugs. Efficacy was evaluated by the responses of induced or spontaneous arrhythmias to the treatments delivered. RESULTS--Antitachycardia pacing successfully terminated 80% of episodes of ventricular tachycardia induced by non-invasive programmed stimulation, but acceleration was brought about by pacing in six patients in 10% of episodes. During a follow up of two to 17 (mean seven) months, 18 patients (60%) had recurrence of ventricular arrhythmias. Antitachycardia pacing terminated ventricular tachycardia in 17 of 18 patients in 87% of episodes. Twelve patients received shocks for ventricular tachycardia or fibrillation. Failure of pacing, with subsequent cardioversion, occurred in nine patients (50%) in one or more episodes. Acceleration of tachycardia by pacing occurred in 10 patients in 5% of episodes. Only two of these patients had experienced acceleration of previously induced arrhythmia. Five patients had spontaneous fast ventricular tachycardia or fibrillation treated by cardioversion or defibrillation. Spurious treatment was delivered in nine patients (30%), during atrial fibrillation in five, sinus tachycardia in two, and because of fracture of the sensing lead system in two patients. The retrieval of stored intracardiac electrograms was of clinical value in assessing spurious treatment. CONCLUSIONS--Tiered treatment was effective in terminating recurrent ventricular arrhythmias in these selected patients. Most episodes were treated successfully by pacing, and resistant tachycardias, pacing induced acceleration, or haemodynamically compromising arrhythmias were treated by shocks.     

Initial clinical experience with the pacemaker-cardioverter-defibrillator

The implantation of a new multiprogrammable pacemaker-cardioverter-defibrillator is reported in four patients suffering from drug-refractory ventricular tachycardia or fibrillation. The generator (PCD 7215; Medtronic Inc) was interfaced to the epicardium by three countershock patch electrodes and one ventricular myocardial screw-in lead for sensing/pacing. The device employs separate rate detection criteria for ventricular tachycardia and ventricular fibrillation with automatic delivery of up to four therapies per episode. Therapeutic options include: antitachycardia burst or autodecremental pacing, synchronized cardioversion, defibrillation and ventricular demand pacing at 30 to 90 beats/min. Four men and one woman (ages 29 to 75 years) underwent intraoperative implant evaluation, and the device was implanted in the four men. Over a follow-up of 1.5 to 23 months, 161 spontaneous episodes of ventricular tachycardia and nine episodes meeting ventricular fibrillation criteria (cycle length less than 280 to 290 ms) were detected and treated by the device. Ramp pacing was initially employed to terminate 140 ventricular tachycardia episodes and was successful 88.5% of the time while 10 (7.2%) required low energy epicardial cardioversion (4 to 10 J). Six (4.3%) episodes terminated spontaneously prior to therapy delivery. All nine spontaneous episodes of ventricular fibrillation were defibrillated using 10 to 15 J. Two patients continue to do well with the device functioning reliably. The device was removed at the time of heart transplant in one patient, while another patient died suddenly from drug overdose. No other complications, device malfunctions or inappropriate therapy delivery have been observed. These early results demonstrate the potential usefulness of a programmable device which provides graded therapy for ventricular tachycardia with added defibrillation and bradycardia pacing capability.     

Efficacy of automatic multimodal device therapy for ventricular tachyarrhythmias as delivered by a new implantable pacing cardioverter-defibrillator. Results of a European multicenter study of 102 implants.

BACKGROUND. Third-generation implantable cardioverter-defibrillators are devices designed to treat ventricular tachycardia (VT) and ventricular fibrillation (VF) by means of overdrive pacing, cardioversion, or defibrillation. So far, the efficacy of tiered therapy has been documented only in small series. Therefore, a European multicenter clinical evaluation study of a new tachyarrhythmia control device, the Medtronic PCD pacer-cardioverter-defibrillator with epicardial patch-lead configuration, was undertaken. METHODS AND RESULTS. We report on 102 patients (mean age, 55 +/- 13 years) from 11 European centers. PCD devices implanted between May 1989 and February 1991 were included. The patients suffered from hemodynamically significant ventricular tachyarrhythmias not suppressed by antiarrhythmic drug therapy and unrelated to acute myocardial infarction; one patient had nonsustained VT and severely depressed left ventricular function. Seventy patients had coronary artery disease with old myocardial infarctions, 23 had cardiomyopathies of various etiologies, and nine patients had no detectable heart disease. Mean ejection fraction was 36 +/- 14% (range, 10-76%). Mean intraoperative defibrillation threshold (51 patients) was 10.6 +/- 5.1 J (range, 2-18 J). The documented follow-up ranged from 1 to 21 months (mean, 9.4 +/- 5.8 months), or 79.9 cumulative patient-years. Perioperative mortality was 3.9%. The actuarial survival rate at 12 months was 91%. One sudden arrhythmic death occurred. Sixty patients (58%) received device therapy. Seventeen patients had therapies only for "VF" episodes, 16 patients only for VT, and 28 patients for VT and "VF" episodes. Based on device memory data, 1,235 spontaneous VT episodes were detected and treated in 43 patients. Twelve hundred four of these VT episodes received painless initial antitachycardia pacing therapy, restoring sinus rhythm in 91%. The 108 ongoing episodes received 209 multiple therapeutic attempts. Eighty-five additional overdrive pacing therapies restored sinus rhythm in 30%. Initial ineffective antitachycardia pacing therapies received 51 cardioversion pulses. The success rate was 61%. Seventy-three additional cardioversion pulses were delivered to backup ineffective pacing therapy as well as ineffective secondary cardioversion pulses. Their success rate was only 40%. Two hundred eighty-six spontaneous episodes were detected in 44 patients as "VF." Overall defibrillation efficacy was 97.6%. CONCLUSIONS. The implanted device nearly eliminates sudden arrhythmic death in patients with documented, potentially fatal ventricular tachyarrhythmias. Automatic tiered therapy is highly effective to restore sinus rhythm, provided that an integrated two-zone tachycardia detection algorithm is used, assigning lower tachycardia rates to overdrive pacing and/or cardioversion and higher tachycardia rates to defibrillation. In general, spontaneous VTs can be terminated by automatic overdrive pacing, and painful or disturbing countershock therapies are not required to terminate the majority of spontaneous VT episodes.     

The contribution of artificial pacemaking to understanding the pathogenesis of arrhythmias

Right atrial or ventricular pacing was performed on 36 occasions in 26 patients in an attempt to terminate a variety of tachyarrhythmias. Of 16 episodes of atrial flutter, 13 were terminated successfully; in 9 of the 13, sinus rhythm or the patient's pre-flutter rhythm was restored immediately, whereas in 4 patients, intervening atrial fibrillation or unstable atrial flutter occurred. Pacing terminated paroxysmal atrioventricular junctional or paroxysmal atrial tachycardia on 3 occasions; in a fourth patient, this tachyarrhythmia terminated during catheter manipulation. Six episodes of pacemaker-induced ventricular tachycardia were abolished by ventricular pacing. In 2 patients, atrial tachycardia was only transiently suppressed, and in 1 of these patients, d-c cardioversion produced a similar effect. Atrial fibrillation, spontaneously converting to atrial flutter, resulted during pacing for atrial tachycardia with block; the latter arrhythmia returned when the atrial flutter was terminated. Atrial fibrillation in 7 patients remained unaffected by atrial pacing. Based on the different electrophysiologic mechanisms responsible for reentrant excitation and automatic pacemaker discharge, an attempt has been made to determine the pathogenesis of the tachyarrhythmia by its response to pacing.     

Permanent radiofrequency ventricular pacing for management of drug-resistant ventricular tachycardia

Three patients with frequent episodes of symptomatic, sustained ventricular tachycardia that often required physician intervention were treated with a permanent patient-activated radiofrequency ventricular pacemaker for self-termination of ventricular tachycardia. Before pacemaker implantation, electrophysiologic testing revealed the tachycardia to be resistant to all approved and several investigational antiarrhythmic drugs. In all three patients, ventricular tachycardia was reliably and reproducibly terminated with brief bursts of rapid right ventricular apical pacing over several hundred trials. No patient had rapid ventricular pacing-induced acceleration of ventricular tachycardia or pacing-induced ventricular fibrillation. Since the implantation of a radiofrequency ventricular pacemaker an average of 13.7 months ago, all episodes of ventricular tachycardia (average 43/patient) have been terminated successfully by radiofrequency pacing, and no patient has required hospitalization for an arrhythmia-related problem.     

Termination of ventricular tachycardia with bursts of rapid ventricular pacing

Bursts of rapid ventricular pacing used during 573 episodes of ventricular tachycardia in 23 patients terminated 5 12 episodes (89 percent), with burst rates averaging 56 beats/min above the ventricular tachycardia rate, for 5 to 10 captures. Tachycardia was accelerated by pacing bursts to rates below 300 beats/min in 16 episodes (3 percent); 10 of these terminated spontaneously or responded to further bursts. Acceleration of heart rate to more than 300 beats/min or ventricular fibrillation occurred six times (1 percent), each episode requiring direct current cardioversion. Pacing bursts had no effect in 38 instances (7 percent), mostly in patients with terminal cardiogenic shock. Implantable pacemakers delivering bursts of rapid ventricular pacing were placed in two patients who have used these units at home. No deaths were associated with bursts of rapid ventricular pacing, which is an effective, rapid, pleasant alternative to repeated direct current cardioversion and a useful tool during electrophysiologic testing in patients with recurrent tachycardia.     

埋藏式心脏复律除颤器治疗恶性室性心律失常的随访观察

对２２例埋置了埋藏式心脏复律除颤器（ＩＣＤ）的有晕厥史的恶性室性心律失常患者进行了随访，观察ＩＣＤ的治疗效果。２２例中扩张型心肌病８例、肥厚型心肌病２例、冠心病７例、ＱＴ延长综合症１例，４例未发现器质性心脏病。所有患者均经临床证实有室性心动过速或（和）心室颤动（ＶＴ／ＶＦ）发作。ＩＣＤ具有多项治疗及信息储存记忆功能（即第三代）。随访时通过体外程控仪调出ＩＣＤ储存的资料进行分析。平均随访７．１（１～２３）个月，１１例患者（５０．０％）ＶＴ／ＶＦ发作１１８次，其中５４次为非持续性ＶＴ，均自行终止；接受ＩＣＤ治疗的６４次为ＶＴ／ＶＦ发作，４５次为ＶＴ，２２次由ＩＣＤ的抗心动过速起搏（ＡＴＰ）终止、１６次由低能量（２～１５Ｊ）转复终止、２次发作为窦性心动过速（误判为ＶＴ），其余５次ＶＴ在ＡＴＰ治疗过程中加速转为ＶＦ，由高能量除颤终止。ＩＣＤ诊断的ＶＦ发作共有１９次，发生于４例患者，有１例患者接受除颤１６次，４次系为频率超过ＶＦ感知频率的ＶＴ。１９次发作均被ＩＣＤ有效除颤终止。２例扩张型心肌病患者，１例术后３个月死于心功能衰竭，另１例术后２个月反复发作ＶＦ，多次接受ＩＣＤ除颤治疗，最后死于心功能衰竭。结果表明常规进行?     

Clinical Experience with the Combination of an Antitachycardia Pacemaker (Orthocor II) and the Implantable Cardioverter-Defibrillator in Drug-Refractory Ventricular Tachycardia

Four men with remote myocardial infarction, left ventricular dysfunction, aborted episodes of sudden death, and recurrent ventricular tachycardia (VT) slowed but not controlled by drugs (mean five trials) were treated with an automatic antitachycardia pacemaker (ATP) (Orthocor II) and an implantable cardioverter-defibrillator (ICD). Cardiac electrophysiological evaluation had disclosed that the VT could be reliably terminated with decremental extrastimuli. Two defibrillation patches and two epimyocardial sensing electrodes were used. The ATP was implanted separately using a bipolar endocardial electrode. During follow-up three patients died. One from hepatitis B at two months, and two from sudden cardiac death at 10 and 13 months. One of these deaths was related to ICD battery depletion, the other to a high defibrillation threshold. One patient is alive after 41 months. During the first year postimplant, 359 episodes of VT occurred and there were 105 ICD discharges. The rate and duration of VT episodes terminated by the ICD were 208 ± 7 bpm and 22 ± 9 seconds; and of VT episodes terminated by the ATP were 158 ± 15 bpm and 6 ± 1.8 seconds, respectively. Deleterious device-to-device interactions could be avoided. All patients required full antiarrhythmic drug therapy. Conclusions: (1) In highly selected patients, drug-resistant VT can be terminated by antitachycardia pacing unperceived by the patient; (2) An ICD must provide reliable back-up defibrillation capability for rapid or accelerated VT or ventricular fibrillation; (3) this initial experience demonstrates the feasibility of utilizing the Orthocor II ATP in combination with an ICD as therapy for refractory clinically recurrent VT.     

Therapeutic electrical procedures in recurring, drug refractory tachycardias. I. Antitachycardiac implantable pacemaker systems

In 9 Patients with medicamentously therapy-refractory tachycardias (twice paroxysmal AV-node-reentry tachycardia, four times paroxysmal orthrodromic reentry tachycardia in the WPW-syndrome, once paroxysmal atrial reentry tachycardia, twice recurrent ventricular tachycardia) after adequate electrophysiological testings antitachycardiac pacemakers able to activate the patients were implanted. In these cases the implantable tachyblocker TUR-RFP-01 was used in 4 cases for the highly frequent volley atrial stimulation, in 2 cases for the more highly frequent volley ventricular stimulation. In 3 patients the interruption of the tachycardia was performed by ventricular underdrive stimulation by means of putting the magnet on a conventional R-wave-inhibited ventricular pacemaker. In all cases the recurrent tachycardias could reliably be terminated by the patients themselves by activation of the antitachycardiac systems (duration of the follow-up period 3-14 months, on an average 10.7 +/- 3.4 months); only in one case in the further course a change of the stimulation parameters was necessary which were carefully tested at the beginning. On account of the danger of the acceleration of the tachycardia and of the evocation of ventricular fibrillation, respectively, should, however, be performed highly frequent ventricular stimulations for the termination of ventricular tachycardias only in readiness for defibrillation.     

Transvenous cardioversion for the management of recurrent ventricular arrhythmias

The efficacy of transvenous cardioversion and defibrillation for treating life threatening spontaneous ventricular arrhythmias was assessed in a study of 17 patients in a cardiac care unit. Eleven had ventricular tachycardia, five had ventricular fibrillation, and one had both. Transvenous cardioversion successfully terminated tachyarrhythmias on 42 separate occasions in ten patients. Stable electrode positions could not be achieved in two patients, recurrent late displacement occurred in one, and four patients had no further arrhythmias requiring cardioversion once the lead was placed. The energy levels required for successful cardioversion ranged from 0.05 J to 25 J for ventricular tachycardia and from 1 J to 25 J for ventricular fibrillation. The nine successful shocks of 1 J or less did not require sedation or general anaesthesia. High energy (25 J) endocardial shocks were unsuccessful in terminating arrhythmias in two patients, one with ventricular tachycardia and the other with both ventricular tachycardia and fibrillation. Minor unwanted effects of endocardial shocks occurred in five patients. These were acceleration of ventricular tachycardia in two patients and complications of pacing via the special lead in three others: failure of sensing occurred in all three and one patient also had a transient rise in pacing threshold. A postmortem examination in one patient who had received three unsuccessful high energy shocks revealed localised endocardial necrosis at the site of the distal electrode. Transvenous cardioversion offers advantages over external cardioversion but at present practical difficulties limit its application to patients with recurrent ventricular arrhythmias that cannot readily be controlled by conventional methods.     

Electrophysiologic manifestations of ventricular tachyarrhythmias provoking appropriate defibrillator interventions in high-risk patients with hypertrophic cardiomyopathy

Introduction: Our objective was to determine features of ventricular tachyarrhythmias triggering appropriate implantable cardioverter-defibrillator (ICD) interventions in hypertrophic cardiomyopathy (HCM).
Methods and Results: The study cohort was 68 high-risk HCM patients who received ICDs for primary sudden cardiac death prevention from 1995 to 2003. All episodes of sustained ventricular tachyarrhythmias identified by stored intracardiac electrograms were analyzed. Nine patients had 51 episodes of sustained ventricular tachyarrhythmic events that required device therapy (mean follow-up, 3.4 ± 2.2 years; cumulative event rate, 3.2% per year): five had 47 episodes of monomorphic ventricular tachycardia (VT); four each had one episode of ventricular fibrillation (VF). Sinus tachycardia or atrial fibrillation was the initiating rhythm in five of nine patients and in 43 of 51 episodes of events. Of the 17 episodes of monomorphic VT detected in the VT zone, 16 (94%) were terminated by antitachycardia pacing. Thirty episodes of monomorphic VT were detected in the VF zone and were terminated by defibrillation.
Conclusion: Sustained monomorphic VT is common in a high-risk cohort with HCM. Sinus tachycardia is often the initiating rhythm, suggesting that high sympathetic drive may be proarrhythmic when a susceptible substrate is present. Antitachycardia pacing is highly effective in terminating VT in this patient population.     

Transvenous cardioversion for the management of recurrent ventricular arrhythmias.

The efficacy of transvenous cardioversion and defibrillation for treating life threatening spontaneous ventricular arrhythmias was assessed in a study of 17 patients in a cardiac care unit. Eleven had ventricular tachycardia, five had ventricular fibrillation, and one had both. Transvenous cardioversion successfully terminated tachyarrhythmias on 42 separate occasions in ten patients. Stable electrode positions could not be achieved in two patients, recurrent late displacement occurred in one, and four patients had no further arrhythmias requiring cardioversion once the lead was placed. The energy levels required for successful cardioversion ranged from 0.05 J to 25 J for ventricular tachycardia and from 1 J to 25 J for ventricular fibrillation. The nine successful shocks of 1 J or less did not require sedation or general anaesthesia. High energy (25 J) endocardial shocks were unsuccessful in terminating arrhythmias in two patients, one with ventricular tachycardia and the other with both ventricular tachycardia and fibrillation. Minor unwanted effects of endocardial shocks occurred in five patients. These were acceleration of ventricular tachycardia in two patients and complications of pacing via the special lead in three others: failure of sensing occurred in all three and one patient also had a transient rise in pacing threshold. A postmortem examination in one patient who had received three unsuccessful high energy shocks revealed localised endocardial necrosis at the site of the distal electrode. Transvenous cardioversion offers advantages over external cardioversion but at present practical difficulties limit its application to patients with recurrent ventricular arrhythmias that cannot readily be controlled by conventional methods.     

Automatic implantable cardioverter-defibrillator (AICD) and antitachycardia pacemaker (Tachylog 651) in the treatment of ventricular tachyarrhythmias

For the electrotherapy of refractory ventricular tachycardia the automatic implantable cardioverter-defibrillator (AICD) and antitachycardia pacemaker are available. The long-term use of antitachycardia pacing is still limited by the potential risk of acceleration to ventricular fibrillation. To combine the advantages of antitachycardia pacing with back-up defibrillation, we evaluated the use of an antitachycardia pacemaker with the automatic defibrillator. The AICD was implanted in 13 patients with a mean age of 62 years (from 46 to 75 years); six of them with recurrent ventricular tachycardia (170 +/- 16 per minute) which could reliably be terminated by overdrive pacing, received also an antitachycardia pacemaker (Tachylog 651). The underlying cardiac disease was coronary heart disease in 11 patients and cardiomyopathy in 2 cases. All patients had survived 1 to 6 cardiac arrests and had not responded to 6 +/- 1.5 antiarrhythmic drugs. For antitachycardia pacing we used burst stimulation with 4 to 6 stimuli and coupling intervals from 260 to 300 ms. During the follow-up period of 12 +/- 2 months, 83% of 744 tachycardias could be terminated by burst stimulation, according to the diagnostic data of the pulse generator. If the pacemaker failed to terminate or in case of acceleration (three patients), the automatic countershock of the AICD (5-42 per patient) restored sinus rhythm. In seven patients with high rate tachycardia, 2 to 69 AICD discharges occurred. No patient died suddenly, but three died due to underlying disease and one because of a pneumonia postoperatively. Future antitachycardia devices should be flexible with regard to detection and termination modes, combining antitachycardia pacing with back-up defibrillation.     

Worldwide clinical experience with a new dual-chamber implantable cardioverter defibrillator system

INTRODUCTION: Management of atrial tachyarrhythmias represents a significant challenge in patients with implantable cardioverter defibrillators (ICDs). Drug therapy of these arrhythmias is limited by moderate efficacy, ventricular proarrhythmia, and drug-device interactions. This study tested the safety and efficacy of a new dual-chamber ICD to detect and treat atrial as well as ventricular tachyarrhythmias. METHODS AND RESULTS: A dual-chamber ICD (Medtronic 7250 Jewel AF) was implanted in 293 of 303 patients at 49 centers in Europe, Canada, and North America. Specific data were collected at implant and during a mean follow-up period of 7.9+/-4.7 months. There were no clinically evident failures to detect and treat ventricular arrhythmias. In patients with at least one of the dual-chamber detection criteria activated, 1,056 of 1,192 episodes of ventricular tachycardia or fibrillation detected were judged to be appropriate (89% positive predictive accuracy). Therapy efficacy was 100% in the ventricular fibrillation zone and 98% in the ventricular tachycardia zone. Positive predictive accuracy for detection of atrial episodes was 95% (1,052/1,107). For episodes classified as atrial tachycardia by the device, the efficacy of atrial antitachycardia pacing and high-frequency (50-Hz) burst pacing was 55% and 17%, respectively. High-frequency burst pacing terminated 16.8% of episodes classified as atrial fibrillation, and atrial defibrillation had an estimated efficacy of 76%. The actuarial estimates of 6-month complication-free survival and total survival were 88% and 94%, respectively. CONCLUSION: This novel dual-chamber ICD is capable of safely and effectively discriminating atrial from ventricular tachyarrhythmias and of treating atrial tachyarrhythmias without compromising detection and treatment of ventricular tachyarrhythmias.     

Comparative efficacy of transvenous cardioversion and pacing in patients with sustained ventricular tachycardia: a prospective, randomized, crossover study

We performed a prospective, randomized crossover study to evaluate the comparative efficacy of transvenous cardioversion and rapid ventricular pacing for termination of induced ventricular tachycardia in patients with spontaneous ventricular tachycardia and organic heart disease. Sixty-two episodes of ventricular tachycardia were induced in 15 patients, mean age 60 +/- 10 years, during electrophysiologic studies. All patients underwent a preselected electrical therapy protocol in a randomized crossover sequence. Transvenous cardioversion was performed by an incremental protocol of three sequential shocks (0.5, 1.1, and 2.7 J). Six asynchronous sequential bursts of rapid ventricular pacing (10 and 15 paced stimuli at 90%, 75%, and 65% of ventricular tachycardia cycle length) were used. Mean cycle length of ventricular tachycardia for the study population was 391 +/- 85 msec. The morphology of the tachycardia was left bundle branch block in 27, right bundle branch block in 32, and indeterminate in three. Characteristics of ventricular tachycardia terminated by the two techniques were comparable. Rate of success for termination of tachycardia with the two methods was also comparable (transvenous cardioversion 83%, rapid ventricular pacing 80%; p greater than .1) and these responses were concordant in 78%. The modes of termination of ventricular tachycardia were similar. The incidence of acceleration of ventricular tachycardia per episode with these preselected protocols was also comparable (transvenous cardioversion 11%, rapid ventricular pacing 6%; p greater than .2). Transient supraventricular tachyarrhythmias were more frequent after transvenous cardioversion (23%) than after rapid ventricular pacing (3%). Significant patient discomfort occurred only after transvenous cardioversion (incidence of 57%).(ABSTRACT TRUNCATED AT 250 WORDS)     

置入型心律转复除颤器52例术中除颤阈值的测定及术后随访

目的 探讨置入型心律转复除颤器(ICD)置入术中除颤阈值(DFT)的测定方法并观察术后随访结果.方法 52例置入ICD患者,其中单腔ICD 25例(48.08%),双腔ICD 23例(44.23%),三腔ICD 4例(7.69%).置入术中用测定除颤安全范围(DSM)方法进行DFT测定,并对患者进行定期随访.结果 52例ICD置入术中,测得DFT为(13.27±2.95)J,DSM为(17.40±2.89)J,手术中无严重并发症发生.52例中,38例出现恶性室性心律失常,其中469次为非持续性(可自行终止)室性心动过速(VT),持续性VT发作265次;经抗心动过速起搏治疗1阵转复成功245次(92.45%),2阵转复成功13次(4.91%),抗心动过速起搏治疗转复未成功经电转复7次(2.64%),均经低能量电转复成功.心室颤动(VF)发作141次均成功识别,其中14次在释放治疗前VF自行终止.127次VF经电除颤治疗,经电除颤治疗1次成功116次(91.34%),除颤能量为(12.84±3.18)J,2次成功11次(8.66%),除颤能量为(16.36±2.34)J.结论 应用DSM测定进行ICD置入术中DFT测定安全可行.     

经静脉置入埋藏式心律转复除颤器的临床随访

对 1 0例经静脉置入埋藏式心律转复除颤器 (ICD)的恶性室性心律失常患者进行随访 ,观察ICD的治疗效果。男 6例、女 4例 ,年龄 5 6.9± 1 3.3( 30～ 70 )岁。基础心脏病为冠心病 6例、心肌病 3例、先天性长QT综合征 1例。所有患者均经临床证实有室性心动过速或 /和心室颤动。ICD具有多项治疗及信息储存记忆功能。随访时通过体外程控仪调出ICD储存的资料进行分析。结果 :随访 2 9.3± 2 0 .4( 8～ 64)个月 ,7例患者分别接受了抗心动过速起搏、电转复及电除颤治疗。 2例患者因窦性心动过速、阵发性心房颤动 ,ICD给予误治疗。 1例患者术后 3年发生电极断裂。结论 :常规进行随访和设定合适的诊断和治疗参数 ,对保证ICD及时有效的治疗至关重要。     

Low energy conversion of atrial fibrillation in the sheep.

OBJECTIVES. In this study, the feasibility, efficacy and safety of low energy internal atrial cardioversion were investigated in a sheep model. The relation between the level of energy used for atrial defibrillation and the probability of successful cardioversion was examined. BACKGROUND. Atrial fibrillation is a common clinical arrhythmia that frequently recurs after termination with high energy external cardioversion. In some patients with drug-refractory and poorly tolerated atrial fibrillation, an automatic implantable cardioverter may prove useful by providing rapid restoration of sinus rhythm. METHODS. In 16 pentobarbital-anesthetized sheep, a right atrial spring electrode was implanted percutaneously and a left thoracic cutaneous patch electrode was placed on the thorax. Sustained atrial fibrillation was induced by rapid atrial pacing and terminated by biphasic cathodal shocks synchronized to the R wave of the surface electrocardiogram (ECG). RESULTS. During 768 defibrillation attempts in 16 sheep, the percent of successful cardioversion attempts increased in a dose-response manner, reaching a plateau at the average energy level of 5 J. With greater than or equal to 1.5 and greater than or equal to 2.5 J energy levels, cardioversion was achieved, respectively, in greater than 50% and greater than 80% of attempts. Ventricular fibrillation occurred in 18 (2.4%) of 768 cardioversion attempts; in all 18 cases, the shock was poorly synchronized with the ECG R wave. CONCLUSIONS. Low energy cardioversion of atrial fibrillation to sinus rhythm is feasible with use of a right atrial spring/cutaneous patch electrode configuration. The percent of successful cardioversion attempts depends on the level of energy output, and there is a risk of ventricular fibrillation if cardioversion is poorly synchronized with ventricular depolarization.     

Successful treatment by overdrive pacing of recurrent quinidine syncope due to ventricular tachycardia

A 54 year old patient who experienced recurrent ventricular tachycardia subsequent to quinidine administration for conversion of atrial fibrillation is described. Over a 10 hour period, 25 sustained episodes of ventricular tachycardia occurred for which electrical cardioversion was required in addition to numerous self-terminating paroxysms. Medical therapy with lidocaine, procainamide and propranolol was unsuccessful in controlling the arrhythmia. However, placement of a transvenous right ventricular pacemaker with overdrive pacing at a rate of 110 beats/min abrupty terminated all further ventricular ectopic activity during the period of quinidine elimination. Temporary overdrive pacing may be the treatment of choice for refractory, recurrent, ventricular tachycardia associated with quinidine therapy.