Clinical Evaluation of Automatic Tachycardia Diagnosis by an Implanted Device

Reliable discrimination between sinus tachycardia (ST) and pathologic tachycardia has been a major problem for automatic implantable antitachycardia devices. In patients whose sinus response to activity is as rapid or faster than their pathologic tachycardia (rate crossover), these unsophisticated devices deliver the programmed tachycardia response to either the pathologic or sinus tachycardia. Over a one-year period, 50 Intermedics Intertach Model 262–12 antitachycardia pulse generators were implanted to evaluate the specificity of a new group of tachycardia recognition algorithms. Patients were subjected to exercise testing and noninvasive programmed stimulation to demonstrate the efficacy of this new approach. The five recognition algorithms tested were various combinations of the following criteria: high rate HR), sudden onset (SO), rate stability (RS), and sustained high rate (SHR). False positive rates (tachycardia response inappropriately triggered by ST) were as follows: HR (93%); HR + SO (3%); HR + RS (63%); HR + (RS or SHR) (87%); HR + HS + SO (8%). Pair-wise significance testing between HR only and HR + SO (p < 0.001), HR + RS (p = 0.01) and HR + SO + RS (p < 0.001), demonstrated a significant reduction in the rate of false positives through the use of the sudden onset and rate stability criteria in concert with the standard high rate criterion.     

起搏器高度依赖性患者起搏器置换方法与疗效探讨

目的 :探讨起搏器高度依赖性患者起搏器置换方法与疗效。　方法 :对 8例起搏器高度依赖性患者 ,在起搏器与电极的接口松解前 ,应用在体起搏器间断接触法 ,使自身逸搏心律得已恢复 ,然后再行松解接口以及必要的起搏参数测试。　结果 :起搏器离体次数为 3～ 7(5± 2 )次 ,最长逸搏间期为 3.38～ 6 .2 0 (4.5 1± 1.11)s,自身逸搏心率为 30～ 4 3(38± 5 )次 /min ,均顺利完成起搏器置换。　结论 :在体起搏器间断接触法切实可行 ,能够明显提高起搏器高度依赖性患者起搏器置换的安全性     

Left Ventricular Transvenous Electrode Dislodgement After Mustard Repair for Transposition of the Great Arteries

An 11-year-old girl who underwent Mustard's operation for complete transposition of the great arteries in infancy, developed Mobitz type II second-degree AV block 81/2 years later. A transvenous, active fixation left ventricular lead was inserted and connected to a rate responsive pacemaker. Two years later the lead dislodged due to the child's growth. A new active fixation electrode was positioned in the left ventricle below the pulmonary valve, leaving an electrode loop in the ventricle. Such an approach may prevent lead dislodgement due to growth after intraatrial repair for transposition of the great arteries, but regular radiological or echocardiographic follow-up of lead position is recommended in these patients.     

Automatic Implantable Cardioverter Defibrillator/Permanent Pacemaker Interaction: Loss of Pacemaker Capture Following AICD Discharge

A 78-year-old man treated with amiodarone for recurrent ventricular tachycardia, had sequential placement of a bipolar VVI pacemaker and an automatic implantable cardioverter defibrillator (AICD). During defibrillation threshold testing, there was failure to capture of the pacer in the post-shock period. The time of failure to capture appeared energy-related: the greater the energy delivered, the longer the failure to capture. Careful attention will be necessary in constructing combined AICD/pacemaker units.     

Understanding capture detection.

Automatic capture detection systems are currently available in several cardiac pacing devices. All current systems use low-polarization electrodes and no beat to beat detection system is available for all types of electrodes. In addition the success ratio for currently available systems is not always 100%. Failure to detect capture reliably is often related to the behaviour of the electrode-tissue interface under different circumstances. Pacemaker electrodes can be considered electrochemical cells with complicated characteristics depending on time, temperature and electrical charge. This electrochemical cell is disturbed when a charge is transferred across the electrode-tissue interface during pacing. Several measures can be taken in order to minimise this disturbance or pace polarization artefact (PPA) including the use of high active surface area electrodes and application of tri-phasic pacing pulses. Another factor influencing detection of evoked potentials is the input circuit of the pacemaker affecting the PPA and the evoked response. Positive PPAs can be falsely interpreted as evoked potentials due to the undershoot of the second order filters applied in modern cardiac pacemakers. This paper explains the behaviour of the interface between the electrode and the cardiac tissue in combination with the pacemaker output circuits and input amplifiers under different circumstances.     

54例严重缓慢心律失常病人的起搏器治疗

1978年～1987年用永久起搏器治疗54例严重缓慢心律失常的病人,共进行103次手术。随访8年多,发现7例死亡,其中6例死亡原因与起搏器治疗无关,1例死于与起搏器并发感染密切相关。本文就严重缓慢心律失常的类型、病因、安装永久起搏器的指征、手术并发症等加以讨论。     

微处理器控制的植入式心脏起搏器专用电路研制

介绍了一种基于微处理器的植入式心脏起搏器专用电路设计。该设计采用的技术路线和国外现有技术方案不同，它采用通用微处理器设计，降低了投资风险，缩短了开发周期．特别适合于我国这样的发展中国家。