New ICD-technologies: first clinical experience with dual-chamber sensing for differentiation of supraventricular tachyarrhythmias

Appropriate Result from an Inappropriate ICD Shock

A case of inappropriate detection of an ungrounded external AC current by an implantable cardioverter defibrillator (ICD) is reported. The resultant ICD shock dislodged the patient from the electrical source, thus preventing injury or electrocution.

Simultaneous Atrial and Ventricular Anti-Tachycardia Pacing as a Novel Method of Rhythm Discrimination

OBJECTIVE

To evaluate a new discrimination algorithm for supraventricular (SVT) and ventricular (VT) tachycardias, based on the response to simultaneous (A+V) atrial (A) and ventricular (V) anti-tachycardia pacing (ATP).

METHODS

Patients undergoing electrophysiological testing or dual-chamber implantable cardioverter-defibrillator (ICD) implantation were enrolled (N = 32) and underwent A+V ATP through a Marquis ICD with investigational software. If persisting after ATP, the rhythm was classified as VT if the first electrical event was sensed on the V channel and as an SVT otherwise.

RESULTS

Arrhythmia sequences (N = 275; 53 VT; 222 SVT) were analyzed in 26 patients (age = 51 +/- 17 years, 13 men, LVEF = 0.49 +/- 0.14). In response to A+V ATP, 55% of SVT versus 41% of VT episodes were terminated (P = NS). Termination of VT but not of SVT was more likely with faster (50% at ATP/arrhythmia cycle length (CL) = 0.81 vs 8% at ATP/arrhythmia CL = 0.88, P = 0.02) but not with longer ATP bursts (P = NS). Of the 115 arrhythmias that persisted after A+V ATP, the algorithm correctly classified 24 of 24 VT (GEE-adjusted sensitivity = 100%) and 85 of 91 SVT (GEE-adjusted specificity = 93%). Proarrhythmia was noted after two A+V ATP, in the form of atrial fibrillation induction and VT acceleration.

CONCLUSIONS

We describe a new algorithm that can discriminate between SVT and VT with a high sensitivity and specificity. This form of ATP can terminate 55% of SVT sequences. The performance of this new algorithm merits further testing in a large population of dual-chamber ICD patients.

Chronic Experiences with a Single Lead Dual Chamber Implantable Cardioverter Defibrillator System

Monitoring of atrial rhythm in patients implanted with ICDs may improve accuracy in identifying supraventricular arrhythmias and, therefore, prevent inappropriate therapies. Since difficulties were found in dual chamber ICDs with separate leads, a new designed single lead dual chamber ICD system was tested. Twenty-five patients implanted with a Deikos A+ (single coil defibrillation lead with two atrial sensing rings combined with a dual chamber ICD with a high amplifying atrial channel) were tested. Atrial and ventricular signals were analyzed during sinus rhythm (SR) and sinus tachycardias (STs), atrial flutter and AF, and VT or VF. Follow-ups were performed after 1, 3, 6, 9, and 12 months after implantation. Analysis of EGM amplitudes of stored episodes revealed that atrial signals during atrial flutter (2.1 +/- 0.51 mV) were comparable to those of ST (2.2 +/- 0.5 mV). Atrial amplitudes during AF were significantly lower (0.81 +/- 0.5 mV, P<0.01). During VF atrial "sinus" signals (2 +/- 0.8 mV) were stable. Ventricular parameters did not differ from a standard ICD lead; defibrillation threshold was 11.4 +/- 4.5 J (16 patients). During intraoperative and prehospital discharge measurements, 97.1% of SR-P waves and 99.2% of atrial flutter waves were detected correctly. In AF 91.11% of atrial signals were detected. Analysis of 505 stored episodes showed that 96.8% of ST and 100% of atrial flutter and 100% of AF episodes have been classified correctly and no underdetection of VT/VF was found. The first experiences with the new VDD-ICD system show an increase of the specificity to detect ventricular tachycardias to a level comparable to dual chamber ICDs with two leads. The reliability of this system has to be proven in a prospective randomized study.

High incidence of device-related and lead-related complications in the dual-chamber implantable cardioverter defibrillator compared with the single-chamber version

Recently, the routine use of dual-chamber implantable cardioverter defibrillators (DC-ICD) has been advocated over the single-chamber version (SC-ICD), but there are few reports of the frequency of complications between the 2 types of ICDs. Between July 1997 and April 1999, 178 consecutive patients underwent implantation of either a transvenous SC-ICDs (n=104) or a DC-ICDs (n=74). Twelve (16%) of the 74 patients with a DC-ICD had a total of 16 major complications compared with 6 (6%) of the 104 patients with a SC-ICD (p=0.01). The 16 DC-ICD complications included atrial lead dislodgment (4), ventricular lead malfunction (4), and pocket infection/hematoma (3), and the 6 SC-ICD complications included ventricular lead dislodgment (2) and pocket hematoma (3). Patients with a DC-ICD had less left ventricular function (29% vs 35%, p=0.035) and a higher prevalence of non-ischemic cardiomyopathies (48% vs 28%, p=0.0076). In conclusion, the DC-ICD may have a higher frequency of device- and lead-related major complications.

Methods of minimizing inappropriate implantable cardioverter-defibrillator shocks

As more and more patients receive complex implantable cardioverter-defibrillators (ICDs), profound knowledge about the incidence of inappropriate device therapy, the reasons it happens, and the possibilities for prevention is crucial. In this article, the most important prevention algorithms incorporated in current ICD models and their advantages and handicaps are discussed in detail, which should help to guide the device selection for a particular patient. Also, emphasis is put on adjunctive drug therapy and interventional treatment strategies, which are crucial in managing patients with inappropriate ICD shocks.

Implantable dual-chamber cardioverter-defibrillator-pacemaker

The fifth generation of implantable cardioverter-defibrillators offer enhanced modes of detection of atrial and ventricular arrhythmias, antitachycardia pacing and shocks, multiprogrammability, intracardiac electrogram storage, and all functions of antibradycardia dual-chamber pacing including rate responsiveness and mode switching. There is no consensus on the indications for dual-chamber pacemaker defibrillator systems. This review focuses on the four major options of newer devices that might benefit patients: 1) permanent dual-chamber pacing in ischemic coronary disease patients, 2) detection and management of atrial fibrillation or other atrial tachyarrhythmias, 3) some newer indications for pacing, and 4) the suppression of inappropriate interventions. On the basis of published data, newer indications for the dual-chamber systems, advantages and limitations, and future perspectives are discussed.

Evaluation of antiarrhythmic drug efficacy in patients with an ICD: unlimited potential or replete with complexity and problems?

There are a number of novel ways in which implantable cardioverter defibrillator (ICD) endpoints can be used in clinical trials to evaluate antiarrhythmic drugs. The advances in ICD technology (storage, retrieval, and accurate interpretation of ICD electrograms) expand the potential to include the use of an ICD endpoint as a clinical surrogate for sudden death. The ICD also provides the necessary safety net to test new drugs. The frequent need for antiarrhythmic drugs in patients already fitted with an ICD (e.g., for atrial fibrillation) necessitates knowledge of the drugs' effect on defibrillator threshold. There are interpretative problems and challenges associated with all types of ICD trials. A particular difficult issue is the degree to which the results of data on antiarrhythmic drug efficacy and safety acquired in the context of an ICD endpoint trial might be extrapolated to patient populations in which the device is not used. These and other challenging issues are discussed, with the goal of enhancing the design and interpretation of clinical trials featuring ICD endpoints.

Managing atrial tachyarrhythmias in patients with implantable cardioverter defibrillators

The implantable cardioverter defibrillator (ICD) is accepted as the therapy of choice in preventing sudden cardiac death. Multiple studies, such as Antiarrhythmics Versus Implantable Defibrillators (AVID), the Canadian Implantable Defibrillator Study (CIDS), the Cardiac Arrest Study Hamburg (CASH), and the Multicenter Automatic Defibrillator Implantation Trial (MADIT), have shown a substantial benefit in survival rates for patients treated with ICDs compared with antiarrhythmic drug treatment. The detection of spontaneous ventricular tachycardias (VT) is based primarily on the programmed heart rate for intervention of the device. Supraventricular tachycardias (SVTs) cause unnecessary therapy delivery in about 10-20% of patients with ICDs. ICD therapy needs to be improved to become more specific for VT detection, by implementing algorithms that discriminate between VTs and SVTs. The enhanced detection criteria in currently available ICD devices are able to decrease the rate of unnecessary therapy to < 5% of patients. Atrial tachyarrhythmias can be managed with programmable features of the device, antiarrhythmic drug treatment, and in rare cases, ablation procedures. Dual-chamber ICDs, requiring an additional atrial lead, are indicated in specific situations of slow VT and concurrent, continuous SVTs at very similar heart rates. Using all these options, SVTs can be managed to achieve an acceptably low incidence of unnecessary therapy delivery in < 5% of ICD patients.

Reliability of coated wire defibrillation leads

A higher rate of complications and need for reoperation has been identified with epicardial and endocardial defibrillator systems. Improved reliability may be achieved with alternate designs that use coated wire and coated coil conductors. Six-year reliability in the 98% range is reported for one bipolar design, the Sulzer Intermedics Intervene lead.