Inappropriate ICD Therapy: Does Device Configuration Make a Difference

Predictors and Proarrhythmic Consequences of Inappropriate Implantable Cardioverter-Defibrillator Therapy

BACKGROUND

Despite the benefits of implantable cardioverter-defibrillator (ICD) therapy, inappropriate shocks can lead to multiple adverse effects. The aim of this study was to clarify the predictors of inappropriate ICD shocks and their proarrhythmic consequences.

METHODS AND RESULTS

We retrospectively studied 316 consecutive patients who underwent ICD implantation from December 2000 to December 2011. Of them, 70 (22%) experienced inappropriate ICD shocks without proarrhythmia requiring some intervention; 2 patients (0.6%) had proarrhythmic inappropriate ICD therapy by antitachycardia pacing (ATP), thereby calculated to be 0.18% of patients per year. However, they did not have syncope from this inappropriate ATP. Multivariate analysis identified younger age (≤56 years: hazard ratio [HR] 1.68, 95% confidence interval [CI] 1.02-2.77, P=0.043), paroxysmal atrial fibrillation (HR 3.00, 95% CI 1.64-5.31, P=0.0002), stroke (HR 2.23, 95% CI 1.11-4.47, P=0.024), and no diuretic use (HR 1.72, 95% CI 1.03-2.93, P=0.039) as independent predictors of the occurrence of inappropriate ICD shocks.

CONCLUSIONS

Young age, paroxysmal atrial fibrillation, stroke, and no use of diuretics were independently associated with inappropriate ICD shocks. Proarrhythmic inappropriate ICD therapy was observed with an annual incidence of 0.18% by ATP.

Optimal Programming of ICDs for Prevention of Appropriate and Inappropriate Shocks

Expansion of indications for implantable cardioverter-defibrillators (ICDs) has led to a significant increase in the number of patients receiving ICDs and the number of lives saved because of ICD therapy. However, appropriate or inappropriate shocks are frequent and may result in a significant decrease in quality of life in patients with ICDs. Atrial fibrillation with rapid ventricular response, sinus tachycardia, atrial tachycardia or atrial flutter with rapid conduction, and other supraventricular tachycardias are the most common arrhythmias causing inappropriate therapy. Other causes include oversensing of diaphragmatic potentials or myopotentials, T-wave oversensing, double or triple counting of intracardiac signals, lead fractures or header connection problems, lead chatter or noise, and electromagnetic interference. Strategies to reduce inappropriate therapy using device programming rely on the ability to distinguish supraventricular and atrial arrhythmias from ventricular tachycardia. Avoiding therapy for nonsustained ventricular arrhythmias and increasing the role of antitachycardia pacing to terminate ventricular tachycardia are key approaches to reducing shocks for ventricular arrhythmias. Optimal programming holds great promise for decreasing the overall incidence of shock therapy and increasing ICD acceptance.

Inappropriate Implantable Cardioverter-Defibrillator Therapy

Although improvements in implantable cardioverter-defibrillator (ICD) therapy have taken place, many challenges do remain. Inappropriate delivery of therapy is a big problem that impacts the quality of life of ICD recipients. Although there is now a clear understanding that atrial arrhythmias are the main cause of inappropriate ICD therapies, physicians have not been very successful in preventing them. Additionally, although many tachycardia detection discriminators have been shown to be helpful, it is not clear that there is a particular combination that is ideal for all patients. Until such an algorithm is developed (which may not be possible), a detailed knowledge and use of all available programming options, guided by special characteristics of each unique patient, are the only foreseeable solutions. Finally, one must face the prospect that this problem cannot be vanquished, but only ameliorated.

A new approach for ICD rhythm classification based on support vector machines

Inappropriate shocks due to misclassification of supraventricular and ventricular arrhythmias remain a major problem in the care of patients with Implantable Cardioverter Defibrillators (ICDs). The purpose of this study was to investigate the ability of a new covariance-based support vector machine classifier, to distinguish ventricular tachycardia from other rhythms such as supraventricular tachycardia. The proposed algorithm is applicable on both single and dual chamber ICDs and has a low computational demand. The results demonstrate that suggested algorithm has considerable promise and merits further investigation.

[Sandwiched between the single- and triple-chamber ICD: do we still need the dual-chamber ICD?]

Since it has been shown that adverse events are more frequent with dual-compared to single-chamber ICDs in patients with heart failure, and since the importance of prevention of unnecessary right ventricular pacing and the success of biventricular pacing have been demonstrated in numerous studies, the need for dual-chamber ICD systems has to be reassessed. The development of these systems was accompanied by expectations of improved hemodynamics in patients with bradycardia, a reduced incidence of atrial fibrillation, inappropriate therapies, and bradycardia-associated ventricular tachyarrhythmias. Single-chamber ICDs should be used restrictively and with great caution in patients with (sinus-) bradycardia and heart failure, since a relevant proportion of these patients is at risk of hemodynamic deterioration. Even if the proportion of patients with proven pacemaker syndrome is so small that it does not reach the level of statistical significance in large studies, a small percentage of patients with hemodynamic deterioration due to VVI pacing is still clinically (and economically) intolerable. Since the development of bradycardia or symptomatic chronotropic incompetence (e.g., due to amiodarone) is difficult to predict, it seems reasonable to use the indication for dualchamber systems liberally. However, the systematic prevention of unnecessary right ventricular pacing is crucial if dual-chamber ICDs are used. If advanced tachycardia discrimination algorithms and careful, individual programming are used, dual-chamber ICDs are superior in the prevention of inappropriate therapies. Additionally, dualchannel electrograms allow a more reliable interpretation of stored tachycardia episodes. In summary, dual-chamber systems represent a valuable improvement of ICD therapy but require thorough programming to convey their advantage.