The potential for inappropriate ventricular tachycardia confirmation using the Intracardiac Electrogram (EGM) Width Criterion

The "Intracardiac Electrogram (EGM) Width Criterion," the first digital signal processing feature used in an implantable cardioverter defibrillator (ICD), is a detection enhancement algorithm that intends to improve ventricular tachycardia (VT) defection specificity by rejecting inappropriately detected supraventricular tachyarrhythmias. The algorithm may be activated after setting the optimal EGM source, slew, and width thresholds based on EGM width testing during sinus rhythm. This study evaluates the accuracy of the EGM width measurements during exercise testing. Twenty-one patients with Medtronic Micro Jewel II Model 7223 ICDs underwent treadmill exercise testing. EGM width resting was repeatedly performed during exercise and recovery to detect potential inappropriate measurements. In seven (33%) patients the EGM Width Criterion inappropriately confirmed VT detection. Eleven patients had inappropriately wide EGM width measurements, but did not satisfy the EGM Width Criterion. The causes of wide EGM width measurements were an actual increase in EGM width and/or inappropriate detection of the baseline irregularities as EGM onset or offset points. Based on our observations, we recommend to test the EGM Width Criterion during exercise testing for optimal ICD programming.