The initial clinical experience with an implantable cardioverter defibrillator/antitachycardia pacemaker

Comparison of cycle lengths between induced and spontaneous sustained ventricular tachycardia during concordant antiarrhythmic therapy associated with healed myocardial infarction

We propose that in clinical practice, whenever possible, the VT detection interval should be selected by adding >60 ms to the induced maximal VT cycle length in order to ensure a high sensitivity for the detection of future spontaneous VT episodes.

The impact of the implantable cardioverter defibrillator on quality-of-life

The implantable cardioverter defibrillator (ICD) is an established treatment for patients with life-threatening ventricular arrhythmias. While it clearly reduces the incidence of death from recurrent arrhythmia, little is known about the impact on patients' quality-of-life. In this prospective study, quality-of-life was assessed by questionnaire before and after ICD implantation. The "Sickness Impact Profile" (SIP), which evaluates physical, psychosocial, and other activities, as well as functions of daily life, was used. Employment and rehospitalization rates were also examined. Twenty-one of 23 consecutive patients, aged 58 +/- 11 years, undergoing ICD implantation at Royal Perth Hospital were studied. During the 14 +/- 8 month follow-up, 4 patients died. Functional capacity was unchanged in all but one of the survivors in whom it improved from New York Heart Association Class III to II. Four of 8 survivors employed before implant have since retired. Six patients required rehospitalization on 13 occasions, problems related to arrhythmias or the ICD. Overall SIP scores preimplant (11.2 +/- 9.3; P < 0.05) were significantly worse at 6-month follow-up (21.7 +/- 18.2), but returned to preimplant levels by 12-month follow-up (8.8 +/- 10.8; NS). This was primarily due to transient problems in the areas of emotional behavior, alertness, and social interaction. SIP psychosocial dimension scores: preimplant: 7.2 +/- 9.0; 6-month: 17.8 +/- 18.1 (P < 0.05); and 12-month: 8.6 +/- 10.3 (NS). Early retirement and hospitalizations due to arrhythmias may still be expected even after implantation of an ICD; however, quality-of-life appears only to temporarily decline.

Implantation of an automatic defibrillator using a new nonthoracotomy approach

Most current nonthoracotomy systems for defibrillator implantation use monophasic devices. To determine the safety and efficacy of a new nonthoracotomy lead configuration when used in conjunction with a device that used biphasic waveforms, 38 consecutive patients were taken to the operating room for implantation of a Cadence tiered therapy defibrillator system. The lead system consisted of a transvenous coil electrode positioned at the right atrial-superior vena caval junction, a bipolar endocardial right ventricular lead, and a large patch placed subcutaneously near the cardiac apex. Of the 38 nonthoracotomy defibrillator implantations attempted, 36 (95%) were completed with adequate defibrillation thresholds. The mean defibrillation threshold in these 36 patients was < or = 563 +/- 10 V (< or = 20 +/- 1 J). There was no perioperative mortality. Complications included coil lead migration (5), sensing lead migration (1), infection (3), pneumothorax (2), arterial embolism (1), and folding of the subcutaneous patch with an increase in defibrillation threshold (1). No patient died during a median follow-up period of 22 weeks. Fourteen patients (39%) had spontaneous sustained ventricular tachyarrhythmias, which were all successfully terminated by the implanted device. Shocks for nonsustained arrhythmias were aborted in eight patients (22%). Spurious discharges for sinus tachycardia or atrial fibrillation occurred in six patients (17%) and were readily diagnosed by examination of the stored electrograms. Thus, implantation of a biphasic tiered therapy defibrillator system using this nonthoracotomy approach is feasible in the majority of patients. The major complication associated with this procedure is lead dislodgment.(ABSTRACT TRUNCATED AT 250 WORDS)

Potential hazards of fixed gain sensing and arrhythmia reconfirmation for implantable cardioverter defibrillators

Appropriate sensing of ventricular tachycardia (VT) and ventricular fibrillation (VF) is of paramount importance for safety of patients with implanted cardioverter defibrillators (ICDs). Recently, the GuardianR ATP 4210, a new third generation ICD that uses programmable but fixed sensing during sinus rhythm and doubles its sensitivity settings when VF is detected, to a maximum programmable sensitivity of 1 mV, has been tested in phase I and II clinical trials. A reconfirmation algorithm of this ICD confirms the presence of VT or VF prior to therapy. This case report describes undersensing of VF in a patient with the GuardianR ATP 4210 at the maximum programmed sensitivity of 1 mV. Inappropriate episodes of asystole and prolonged bradycardias were also observed in this patient due to shortcomings in the reconfirmation algorithm design. Reoperation was required, with positioning of a new endocardial sensing lead to correct the undersensing of VF. This, however, did not correct asystolic pauses following antitachycardia pacing or spontaneous tachycardia termination prior to therapy. This case report highlights the hazards of fixed gain sensing for implantable ICDs and a potential limitation of a specific tachyarrhythmia reconfirmation algorithm used in this device.

Clinical experience with antitachycardia pacing and improved detection algorithms in a new implantable cardioverter-defibrillator

OBJECTIVES

This study was conducted to assess the effectiveness of antitachycardia pacing modes and detection algorithms in patients with a new third-generation implantable cardioverter-defibrillator.

METHODS

Twenty-three of 42 consecutive patients had coronary artery disease, 14 had dilated cardiomyopathy, 2 had prior valve replacement and 3 had arrhythmogenic right ventricular dysplasia. The mean ejection fraction was 41 +/- 14%; there were 31 men (74%) and 11 women, with a mean age of 53 years. On the basis of preoperative and postoperative electrophysiologic studies, in 28 patients antitachycardia pacing was postoperatively programmed randomly as "burst" (66%) or autodecremental "ramp" (34%) stimulation with a first coupling interval of 81% of tachycardia cycle length and up to 8 sequences with 3 to 10 stimuli.

RESULTS

During a follow-up interval of 6.3 +/- 2.2 months, 15 patients were treated by antitachycardia pacing for a median of 6 (range 1 to 59) hemodynamically stable ventricular tachycardias (175 +/- 12 beats/min). In 5 patients, 22 ventricular tachycardias (9%) were not terminated by antitachycardia pacing but by cardioversion. Seven (3%) of these episodes accelerated (> 50 ms) during antitachycardia pacing. Syncope did not occur during these episodes. In seven patients initial antitachycardia pacing in cases of supraventricular tachycardias delayed charging and redetection prevented inappropriate discharges. Additional detection algorithms were programmed only after inappropriate therapy. The sudden "onset" and "sustained rate duration" criteria were programmed in three patients and the cycle length "stability" criteria in six patients, respectively. After activation of these detection algorithms only two of the seven patients had further inappropriate device discharges.

CONCLUSIONS

Thus, antitachycardia pacing by this implantable cardioverter-defibrillator effectively and appropriately terminated 91% of hemodynamically stable ventricular tachycardias. Inappropriate device discharges were prevented in some patients by antitachycardia pacing and additional detection algorithms.

Experience of cardioverter-defibrillators inserted without thoracotomy: evaluation of transvenously inserted intracardiac leads alone or with a subcutaneous axillary patch

OBJECTIVES

To compare the efficacy of a purely transvenous cardioverter-defibrillator (ICD) system with that of a system with a supplementary subcutaneous patch. To evaluate clinical follow up of these lead arrangements that do not require thoracotomy.

DESIGN

A simplified defibrillation protocol to test two different lead arrangements during implantation, with routine clinical follow up after implantation.

SETTING

Tertiary referral centre for treatment of arrhythmia.

PATIENTS

22 consecutive patients selected for implantation of an ICD because of life-threatening ventricular arrhythmias (ventricular fibrillation or sustained ventricular tachycardia) of whom 20 entered the test protocol.

INTERVENTION

Implantation of an ICD with transvenously inserted intracardiac leads and a subcutaneous patch and assessment of effective defibrillation followed by testing of the purely transvenous approach.

MAIN OUTCOME MEASURES

Reproducible conversion of ventricular fibrillation to sinus rhythm at a certain energy level, providing a safety margin of at least 10 J for both lead arrangements. Confirmation of efficacy during clinical follow up (mean 6 months).

RESULTS

A transvenous lead system combined with a subcutaneous axillary patch was implanted in 20/22 patients and it provided adequate and acceptable energy levels. In 10/20 tested patients a purely transvenous lead configuration provided an acceptable safety margin as well. Nine patients had clinical recurrences: all these arrhythmias were successfully converted.

CONCLUSION

A transvenous lead system was sufficient in 50% of the patients at the time of implantation. Data on long-term clinical follow up of this arrangement are not available. The approach without thoracotomy with a subcutaneous patch is feasible and effective in most patients selected for ICD treatment.

Radiofrequency catheter ablation of the AV node to improve the function of an antitachycardia implantable defibrillator

A case of coexisting atrial fibrillation and ventricular tachycardia in a patient with an implantable cardioverter defibrillator is described. Despite careful reprogramming, the device was not always able to distinguish between the two arrhythmias and continued to deliver inappropriate antitachycardia therapy including DC shocks. Attempts to pharmacologically control the atrial fibrillation were unsuccessful so radiofrequency ablation of the atrioventricular node was performed. Following successful ablation, there have been no further false detections no episodes of further ventricular tachycardia.

Use of telemetry functions in the assessment of implanted antitachycardia device efficacy

Twenty patients (aged 50 +/- 21 years and mean left ventricular ejection fraction 37 +/- 17%) with recurrent ventricular arrhythmias were treated with an investigational, implantable combined antitachycardia-pacing cardioverter defibrillator. The device's telemetry capabilities include both stored (1-second snapshots) and real-time display of endocardial and device-circuit signals. The device can store these before, during and after up to 50 tachycardia and antitachycardia pacing episodes. All stored events are indexed to a 24-hour internal clock. During 10.1 +/- 5.1 months of follow-up, the device was used in 11 of 20 patients. In the entire group, antitachycardia pacing was activated on 44 +/- 14 occasions per patient (total 874) and shock delivery occurred on 8 +/- 14 occasions per patient (total 156). Reconstruction by stored telemetry of all device-therapy episodes was possible. Twenty-six percent of all shocks delivered were not appropriate and were due to atrial arrhythmias in 2 patients and dysfunction of the sensing lead in 3. The absence of a relation between symptoms and appropriate shock delivery was documented in 1 patient. Antitachycardia pace acceleration occurred in 5.3% of cases; 7% of attempts at pacing were unsuccessful and needed shock therapy. It is concluded that the enhanced telemetry available in newer antitachycardia devices enables more accurate assessment of device use and enhances diagnosis of inappropriate therapy delivery.