经静脉心律转复除颤器的临床应用

目的　评价经静脉心律转复除颤器 (ICD)对恶性室性心律失常的治疗作用。方法　 6例药物难治性反复发作的室性心动过速 (VT)及 /或心室颤动 (VF)患者接受经静脉ICD治疗 ,并随访 12±7 0月 (1～ 2 1月 )。其中冠心病 2例 ,扩张型心肌病 1例 ,原发性室颤 3例。结果　 6例成功地置入经静脉ICD ,脉冲发生器埋于左上胸皮下 5例 ,胸大肌与胸小肌之间 1例。 3例经ICD储存资料证实共发生VT45 1次 ,均被ICD有效终止。 3例患者共有 6次VT经电击复律成功。 2例分别因窦性心动过速和心房颤动而误放电 ,其中 1例因口服胺碘酮致VT频率减慢至VT探查窗口以下而未被ICD察觉 ,经程控调整有关设置后得以纠正。结论　经静脉ICD是一种植入方法简单、能有效终止恶性室性心律失常和减少心律失常性死亡的重要手段。定期随访和针对患者改变的心律失常状况的再程控 ,是防止误放电和保证ICD有效工作的重要措施     

Dual Chamber Implantable Cardioverter Defibrillator Benefits and Limitations

Dual chamber ICD capable of providing dual chamber pacing (DDD) and ventricular arrhythmia therapy is now available. We report our experience of clinical performance of dual chamber ICDs amongst Chinese population.Methods: 9 patients (6 men and 3 women) received dual chamber ICDs, mean age 50 ± 18.8 years. The indications were ventricular fibrillation (VF) [5], hemodynamic intolerant ventricular tachycardia (VT) [3] and unexplained syncope plus positive induction of VF [1]. The underlying cardiac pathology were congenital LQT syndrome(1), hypertrophic cardiomyopathy [2], coronary artery disease [2], rheumatic valvular disease [1], Brugada syndrome [1], arrhythmogenic right ventricular dysplasia [1] and idiopathic VF [1]. Four patients have documented paroxysmal atrial fibrillation (AF). All patients have defibrillation thresholds (DFT) determined with a binary search protocol starting at 12 joules (J) at implantation.Results: A total of 34 episodes of VF were induced at implantation with mean DFT 13.8 ± 7 J. The average shocking impedance was 40 ± 3.6 . The mean acute P wave measured 3.3 ± 1.3 mV and R wave measured 13.2 ± 3.2 mV. Atrial and ventricular thresholds, at pulse width 0.5 ms, averaged 0.8 ± 0.4 V and 0.4 ± 0.2 V. During follow-up period, 16 episodes of VF were documented and were successfully treated with the first programmed shock. In the patient with LQT syndrome, DDD was initiated to prevent pause-dependant VF. Three episodes of inappropriate therapy (15.8%) were delivered. One patient experienced 2 shocks after exercise. Stored electrograms showed sinus tachycardia with first degree heart block which was misdiagnosed as VT with retrograde 1:1 conduction. Another inappropriate therapy occurred with AF with fast ventricular response within the VF zone and VT therapy inhibitor was disabled.Conclusion: Dual chamber ICD allows combined benefits of DDD and VT/VF therapy. Storage of both atrial and ventricular electrograms provide more information in elucidation of nature of dysarrhythmias. Inappropriate shocks, though reduced, are still possible and the rigid algorithms of SVT discrimination from VT will need further published.     

Recording of Pacing Stimulus Artifacts by Endovascular Defibrillation Lead Systems: Comparison of True and Integrated Bipolar Circuits

Background: The occurrence ICD undersensing of ventricular fibrillation due to the presence of a pacing stimulus artifact (PSA) is in part related to the amplitude of the artifact recorded on the ICD rate sensing circuit. There is little comparative data regarding PSA amplitude recorded by commercial ICD rate-sensing circuits.Purpose: To compare PSA amplitude recorded by commercial endovascular defibrillation leads utilizing integrated or true bipolar sensing circuits.Methods: Nineteen large (60–120 kg) pigs were utilized. Two different commercial endovascular defibrillation leads were evaluated, each with its distal tip located at the right ventricular apex: (1) Medtronic Transvene; and (2) CPI Endotak. Three different rate-sensing circuits were evaluated: (1) Transvene true bipolar (tip-ring); (2) Transvene integrated bipolar (tip-coil); and (3) Endotak integrated bipolar (tip-coil). Using a separate pacing lead located at the left ventricular apex (n = 19 animals) or right ventricular outflow tract (n = 10 animals), pacing was performed at a pulse width of 0.5 milliseconds at outputs of 1.5, 5 and 10 volts. PSA amplitude was recorded at each output by each circuit.Results: During pacing from the left ventricular apex, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.6 ± 0.1 mV at 1.5 volts, 2.0 ± 0.5 mV at 5 volts, 3.7 ± 0.8 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.4 ± 0.3 mV at 1.5 volts, 3.8 ± 0.7 mV at 5 volts, 4.1 ± 0.8 mV at 10 volts) or the Endotak integrated circuit (1.8 ± 0.4 mV at 1.5 volts, 4.2 ± 1.0 mV at 5 volts, 6.3 ± 1.8 mV at 10 volts). During pacing from the right ventricular outflow tract, at each pacing output voltage the PSA amplitude recorded by the true bipolar circuit (0.7 ± 0.1 mV at 1.5 volts, 1.7 ± 0.4 mV at 5 volts, 4.0 ± 0.7 mV at 10 volts) was significantly smaller than recorded by the Transvene integrated circuit (1.1 ± 0.4 mV at 1.5 volts, 3.9 ± 1.2 mV at 5 volts, 7.5 ± 1.8 mV at 10 volts) or the Endotak integrated circuit (1.6 ± 0.7 mV at 1.5 volts, 4.3 ± 1.7 mV at 5 volts, 7.5 ± 2.6 mV at 10 volts). For both pacing sites, the PSA amplitude recorded by the two integrated circuits was not significantly different.Conclusions: For a given pacing output voltage, PSA amplitude recorded by commercial endovascular rate sensing/defibrillation leads is greater when the sensing circuit is integrated than when it is true bipolar. These data may be helpful in planning ICD implantation in patients with previously implanted permanent pacemakers.     

Recurrence of ventricular tachycardia degeneration by low-energy implantable cardioverter-defibrillator shocks: a case report

Despite their proven efficacy at reducing mortality in selected patients, implantable cardioverter-defibrillators have some proarrhythmic effects. In this report, we present a case of a patient with recurrent ventricular tachycardia degeneration to ventricular fibrillation by appropriate low-energy implantable cardioverter-defibrillator shocks.     

Coronary sinus electrode does not reduce atrial defibrillation thresholds

BACKGROUND: Atrial defibrillation can be achieved with a conventional dual-coil, active pectoral implantable cardioverter-defibrillator (ICD) lead system. Shocking vectors that incorporate an additional electrode in the CS have been used, but it is unclear if they improve atrial DFTs. OBJECTIVE: The objective of this prospective, randomized study was to determine if a coronary sinus (CS) electrode reduces atrial defibrillation thresholds (DFTs). METHODS: This was a prospective study of 36 patients undergoing initial ICD implant for standard indications. A defibrillation lead with superior vena cava (SVC) and right ventricular (RV) shocking coils was implanted in the RV. An active can emulator (Can) was placed in a pre-pectoral pocket. A lead with a 4 cm long shocking coil was placed in the CS. Atrial DFTs were determined in the following 3 shocking configurations in each patient, with the order of testing randomized: RV --> SVC + Can (Ventricular Triad), distal CS --> SVC + Can (Distal Atrial Triad), and proximal CS --> SVC + Can (Proximal Atrial Triad). RESULTS: The Proximal and Distal Atrial Triad configurations were both associated with significant reductions in peak current (p < 0.01), but this effect was offset by significant increases in shock impedance (p < 0.01), resulting in no net change in the peak voltage or DFT energy in comparison to the Ventricular Triad configuration (Ventricular Triad: 4.9 +/- 6.6 J, Proximal Atrial Triad: 3.3 +/- 4.1J, Distal Atrial Triad: 4.4 +/- 6.7 J, p > 0.2). CONCLUSION: Shocking vectors that incorporate a CS coil do not significantly improve atrial defibrillation efficacy. Since the Ventricular Triad shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.     

A memorable experience.

The electrocardiographic phenomenon of cardiac memory results from aberrant ventricular activation and causes transient ECG features that can mimic ischaemia. We present the case of a patient with ischaemic cardiomyopathy who exhibited evidence of T-wave memory in the setting of multiple episodes of non-sustained ventricular tachycardia that were triggered by an insect bite.     

Oversensing issues leading to device extraction: When subcutaneous implantable cardioverter-defibrillator reached a dead-end

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