Reduction in defibrillator shocks with an implantable device combining antitachycardia pacing and shock therapy

Implantable defibrillators reduce the risk of sudden death in patients with malignant ventricular arrhythmias, but significant restriction in quality of life can occur as a result of frequent device activation. To determine if a device that provides both antitachycardia pacing and shock therapy can safely reduce the frequency of shocks after implantation, 46 consecutive patients undergoing initial implantation of a defibrillator were studied. In all patients, the implanted device provided antitachycardia pacing and shock therapy. Detected tachycardia characteristics and the results of therapy were stored in the device's memory. There were 42 men and 4 women, aged 26 to 71 years (mean 58.7 +/- 13.5). Left ventricular ejection fraction ranged from 13% to 67% (mean 32.2 +/- 13.4%) and 31 patients had experienced one or more episodes of cardiac arrest. Induced arrhythmias included sustained monomorphic ventricular tachycardia in 38 patients, nonsustained polymorphic ventricular tachycardia in 2 and ventricular fibrillation in 4. Over a total follow-up period of 255 patient-months (range 1 to 13, mean 6.1), 25 patients experienced spontaneous arrhythmic events. In 22 patients, 909 episodes of tachycardia were treated by antitachycardia pacing, which was successful on 840 occasions (92.4%). Acceleration of ventricular tachycardia by pacing therapy was estimated to have occurred 39 times. Syncope occurred once during pacing-induced acceleration of ventricular tachycardia. Forty-four episodes of tachycardia in seven patients were treated directly by shocks because of short tachycardia cycle length; 88% of all detected tachycardias were treated without the need for shocks. Four patients died from cardiorespiratory failure and one patient died suddenly without any detected tachyarrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)     

植入型心律转复除颤器抗心动过速起搏治疗室性心动过速疗效评价

目的恶性室性心律失常（室性心动过速,心室颤动）是心脏性猝死的主要直接原因.而大部分患者先发生室性心动过速（室速）,继而蜕变为心室颤动（室颤）.研究表明,抗心动过速起搏（ATP）可有效终止室速.本文观察了172例植人植入型心律转复除颤器（ICD）的患者应用ATP终止室速的效果.方法172例植入ICD的患者,男性137例,女性35例,平均年龄52.8岁.103例患者术前有阿-斯综合征发作史,其中75例有电击除颤史.137例术前记录到室速或室颤心电图.植入ICD患者定期随访,随访时应用体外程控仪调出ICD储存记录,分析ICD治疗中ATP治疗室速的效果.结果在平均随访37个月中,ICD共记录室速l 789阵.其中,316阵为短阵室速,在ICD治疗前自行终止;1 473阵室速接受了ICD有效治疗.其中ATP治疗成功981阵（成功率66.6%）,余492阵室速由低能量转复终止.在981阵ATP治疗成功的事件中,ICD第一次发放ATP成功终止室速513阵（成功率52.3%）.结论ICD抗室速起搏功能可有效终止大多数室速,对于植入ICD前有明确室速史的患者,ICD治疗应尽量先采用ATP治疗,以减少ICD放电,延长ICD使用寿命及避免电击时的痛苦,即所谓的＂无痛性ICD治疗＂.     

Fracture of the subcutaneous patch electrode in a patient with an implanted cardioverter-defibrillator.

There are more than 20 years of experience with implantation of defibrillator devices in humans and the procedure is an important therapeutic option for patients at high risk of life-threatening ventricular arrhythmias. The incidence of new defibrillator implantation has gradually increased, being used even in children, (1) although pediatric use is associated with several complications, especially with epicardial systems,(2) including fracture of the subcutaneous patch,(3-5) mainly because of growth.(3) We present a case of subcutaneous patch electrode fracture in the left axillary pectoral region of a patient who needed the patch for effective defibrillation, and we discuss the methods of treatment.     

Efficacy of patient activated antitachycardia pacing therapy using the Medtronic AT500 pacemaker.

A 28-year-old female with corrected anomalous pulmonary venous drainage presented with multiple atrial arrhythmias many years later. Ablation techniques eliminated most of the arrhythmias except atrial tachycardia with 1:1 AV conduction. A dual-chamber pacemaker with antiatrial tachycardia features was implanted and was shown to be effective in arrhythmia control when the standard algorithm was overridden by an external patient activation device.     

Predictors of atrial antitachycardia pacing efficacy in patients affected by brady-tachy form of sick sinus syndrome and implanted with a DDDRP device

Predictors of ATP efficacy in brady/tachy patients. BACKGROUND: Recent options to treat atrial tachyarrhythmias (ATA) include implantable devices delivering antitachycardia pacing therapies (ATP). No prospective study selected patients with higher chances of episode termination by ATP or indicated the most effective ATP use. Our aim was to study ATP efficacy in patients with brady-tachy form of sinus node disease (SND), identifying clinical factors, ATA characteristics, and device features predicting ATP efficacy. METHODS AND RESULTS: Three hundred and sixteen patients (105 M, aged 71.1+/-8.8 years) received a DDDRP pacemaker and were prospectively followed. Median follow-up was 18 months: 37,125 ATA episodes occurred in 217 patients; ATP treated 5,536 of them. Overall, ATP efficacy was 50.0%. A multivariate analysis identified longer arrhythmia cycle lengths (OR=1.25; CI=1.07-1.47) and shorter delays to ATP delivery (OR=0.15; CI=0.10-0.22) as independent predictors of ATP efficacy for episodes preceded by >or=5 minutes of sinus rhythm. Additionally, ATP efficacy for all treated episodes was predicted by lower New York Heart Association (NYHA) class (OR=0.64; CI=0.42-0.98), episode classification as nonimmediate recurrence of ATA (non-IRAT) (OR=0.07; CI=0.02-0.33), absence of overlap in the device detection windows (OR=0.54; CI=0.32-0.91), and flecainide treatment (OR=2.22; CI=1.04-4.71). CONCLUSIONS: In patients paced for SND, multivariate analysis shows that ATP efficacy is associated to longer arrhythmia cycle lengths, shorter ATP delivery delays, NYHA class I, episode classification as non-IRAT, absence of overlap in the atrial arrhythmia device detection windows, and flecainide treatment.     

Syncopal monomorphic ventricular tachycardia with pleomorphism, sensitive to antitachycardia pacing in a patient with Brugada syndrome.

Polymorphic ventricular tachycardia and ventricular fibrillation are the most common arrhythmias in Brugada syndrome, causing syncope or sudden death. Sustained monomorphic ventricular tachycardias are rare in this context. We report the case of a 41-year-old man with repetitive syncopal episodes and an ajmaline-induced characteristic Brugada ECG pattern, in whom episodes of monomorphic ventricular tachycardia with pleomorphism and response to ventricular pacing were documented.     

High atrial antitachycardia pacing therapy efficacy is associated with a reduction in atrial tachyarrhythmia burden in a subset of patients with sinus node dysfunction and paroxysmal atrial fibrillation.

BACKGROUND: Atrial tachycardia (AT) and atrial flutter that occur in association with paroxysmal atrial fibrillation (AF) can be successfully terminated by antitachycardia pacing (ATP) therapy. We hypothesized that atrial ATP therapy reduces AT/AF burden in a subset of patients with symptomatic bradycardia and frequent paroxysmal AT/AF. OBJECTIVES: This study evaluated the effect of atrial ATP therapy on AT/AF burden in a pacemaker population with paroxysmal AF. METHODS: We compared AT/AF burden in 261 patients who received a Medtronic AT500 pacemaker for treatment of AT/AF in the setting of symptomatic bradycardia based on device-classified atrial ATP efficacy < 60% and > or = 60%. Patients with > or = 10 device-detected episodes of AT/AF before and after atrial ATP therapy initiation were identified from four clinical studies performed in 72 centers worldwide. RESULTS: The high efficacy group comprised 75 patients with atrial ATP efficacy > or = 60%. The low efficacy group comprised 186 patients with atrial ATP efficacy < 60%. AT/AF episode frequency was similar in both groups prior to ATP activation and decreased in the low efficacy group following ATP activation. Following atrial ATP initiation, total AT/AF burden increased slightly in the low ATP efficacy group (median 2.77 [25th-75th percentiles 0.84-5.86] hours/day vs 2.92 [0.59-8.12] hours/day, P = .01). In contrast, total AT/AF burden decreased significantly in the high efficacy group (median 2.46 [0.29-8.88] hours/day vs 0.68 [0.13-2.97] hours/day, P < .001). CONCLUSION: Up to 30% of patients with frequent episodes of paroxysmal AF and symptomatic bradycardia experience a reduction in AT/AF burden from atrial ATP therapy over time.     

Amiodarone therapy in patients implanted with cardioverter-defibrillator for life-threatening ventricular arrhythmias.

BACKGROUND: Whether amiodarone can improve the patient's clinical outcome by reducing implantable cardioverter-defibrillator (ICD) therapy deliveries for ventricular tachycardia or fibrillation (VT/VF) has not been clearly evaluated. METHODS AND RESULTS: A total of 507 patients with VT/VF due to organic heart disease who had ICDs implanted were enrolled in this study. The patients were divided into 3 groups: Amiodarone (n=247), Class I anti-arrhythmic drug (n=103) and Control (n=157) groups, and the total cause mortality and arrhythmic event free survival rates were evaluated between the groups. The mean follow-up period was 38+/-27 months. The left ventricular ejection fraction was significantly decreased in the Amiodarone group (Amiodarone: 37+/-15%; Class I: 39+/-16%; Control: 44+/-17%). The mortality and arrhythmic events were significantly higher in the Class I group than the Amiodarone group (p<0.05), but there was no significant difference between the Amiodarone and Control groups (arrhythmic event free rate at 5 years: Amiodarone: 53%; Class I: 35%; Control: 48%; 5 year survival: 86%, 74% and 77%, respectively). Side effects from amiodarone were found in 12% of the patients, but no fatal events were observed. CONCLUSIONS: The present study could not demonstrate the benefit of amiodarone in ICD patients, probably due to a significant clinical bias exerted in selecting this drug.     

Unusual cause for an increase of the sensing integrity counter in a patient with inappropriate implantable cardioverter-defibrillator therapy.

We describe the case of a patient who presented with multiple implantable cardioverter-defibrillator (ICD) shock discharges 12 months after device implantation. Upon device interrogation, intermittent oversensing of electrical noise and potential ICD lead failure were suggested by a significant increase in the sensing integrity counter (SIC), a cumulative count of very short ventricular sensed intervals. Analysis of stored episodes, however, revealed that inappropriate ICD therapy had been caused by intermittent T-wave oversensing (TWO), and that the increase of the SIC resulted from the coincidence of TWO and premature ventricular complexes (PVCs). T-wave oversensing resolved and the SIC did not increase any more during follow-up after adjustment of ventricular sensitivity. The coincidence of TWO and PVCs should therefore be considered as an uncommon cause for short ventricular sensed intervals in ICD patients presenting with a suspect increase in the SIC.     

植入型心律转复除颤器抗心动过速起搏治疗的临床应用

植入型心律转复除颤器(implantable cardioverter defibrillator,ICD)抗心动过速起搏(antitachycardia pacing,ATP)治疗是指ICD通过ATP终止快速性心律失常的治疗方法,主要是终止室性心动过速(ventricular tachycardia,VT).     

Oversensing during ventricular pacing in patients with a third-generation implantable cardioverter-defibrillator

Objectives. The purpose of this study was to identify the causes of oversensing during ventricular pacing in patients with a thirdgeneration implantable cardioverter-defibrillator.Background. Third-generation implantable cardioverterdefibrillators have the capability for bradycardia pacing as well as antitachycardia pacing and defibrillation. With the Ventritex Cadence Tiered Therapy Defibrillator System, the pulse generator sensitivity is increased during bradycardia pacing to prevent undersensing of an arrhythmia with small amplitude signals.Methods. Records from 85 consecutive patients who underwent implantation of a Cadence device for treatment of ventricular tachyarrhythmias were reviewed.Results. Four patients required continuous pacing for bradyarrhythmias. In three of these patients, ventricular pacing was accomplished using the bradycardia pacing feature of the Cadence device. All three experienced spurious device discharges or had aborted shocks for oversensing. Analysis of real-time and stored electrograms revealed intermittent high frequency, large amplitude noise in two patients and oversensing of maximally gained R and T waves in the remaining patient. No evidence of lead fracture was found in any patient. The problem was solved by implantation of a separate permanent pacemaker in two patients and was partially solved by reprogramming of the device in the remaining patient.Conclusions. Although the Cadence implantable cardioverterdefibrillator has the capability for ventricular pacing in patients with bradyarrhythmias, certain features of its automatic gain control circuit limit its utility in this instance. Oversensing occurs commonly, leading to device discharges or aborted shocks. Implantation of a separate permanent pacemaker may be required in patients who have a Cadence device for tachyarrhythmia control and who also need pacing for bradycardia.