Evaluation of morphology discrimination for ventricular tachycardia diagnosis in implantable cardioverter-defibrillators

Electrogram morphology discriminators in implantable cardioverter defibrillators: A comparative evaluation

BACKGROUND

Morphology algorithms are currently recommended as a standalone discriminator in single-chamber implantable cardioverter defibrillators (ICDs). However, these proprietary algorithms differ in both design and nominal programming.

OBJECTIVE

To compare three different algorithms with nominal versus advanced programming in their ability to discriminate between ventricular (VT) and supraventricular tachycardia (SVT).

METHODS

In nine European centers, VT and SVTs were collected from Abbott, Boston Scientific, and Medtronic dual- and triple-chamber ICDs via their respective remote monitoring portals. Percentage morphology matches were recorded for selected episodes which were classified as VT or SVT by means of atrioventricular comparison. The sensitivity and related specificity of each manufacturer discriminator was determined at various values of template match percentage from receiving operating characteristics (ROC) curve analysis.

RESULTS

A total of 534 episodes were retained for the analysis. In ROC analyses, Abbott Far Field MD (area under the curve [AUC]: 0.91; P < .001) and Boston Scientific RhythmID (AUC: 0.95; P < .001) show higher AUC than Medtronic Wavelet (AUC: 0.81; P < .001) when tested for their ability to discriminate VT from SVT. At nominal % match threshold all devices provided high sensitivity in VT identification, (91%, 100%, and 90%, respectively, for Abbott, Boston Scientific, and Medtronic) but contrasted specificities in SVT discrimination (85%, 41%, and 62%, respectively). Abbott and Medtronic's nominal thresholds were similar to the optimal thresholds. Optimization of the % match threshold improved the Boston Scientific specificity to 79% without compromising the sensitivity.

CONCLUSION

Proprietary morphology discriminators show important differences in their ability to discriminate SVT. How much this impact the overall discrimination process remains to be investigated.

Inappropriate implantable cardioverter defibrillator shocks due to atrial far-field on the tip-to-ring channel for lead dislodgement

We reported a case of inappropriate implantable cardioverter defibrillator shocks, due to atrial far-field on the tip-to-ring channel of the fast electrical activity during atrial fibrillation, caused by lead dislocation in the right ventricle outflow tract. During these episodes the can-to-right ventricle coil signal correctly recorded the ventricular activity. The shock storm stopped when an antitachycardia pacing restored sinus rhythm.

Preventing Implantable Cardioverter Defibrillator Shocks Improves Survival

Implanted cardioverter defibrillators (ICDs) reduce sudden cardiac death and all-cause mortality in patients at an elevated risk of ventricular arrhythmia (VA). Patients with ICDs who receive shocks for VA have an increased mortality primarily due to worsening heart failure. Although VA and ICD shocks are a marker of progression of the underlying cardiomyopathy and disease process, there is evidence suggesting that ICD shocks are directly harmful to the myocardium and may contribute to the increase in mortality. Thus, although ICD shocks are a lifesaving therapy, they are also harmful and should be avoided whenever possible.

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.

Tools and strategies for the reduction of inappropriate implantable cardioverter defibrillator shocks

Implantable cardioverter defibrillators (ICDs) have been shown to provide a survival benefit in patients at high risk of sudden cardiac death. A major problem associated with ICD therapy is the occurrence of inappropriate shocks which impair patients' quality of life and may also be arrhythmogenic. Despite recent technological advances, the incidence of inappropriate shocks remains high, thus posing a challenge that we have to meet. In the present review we summarise the available tools and the strategies that can be followed in order to reduce inappropriate ICD shocks.