S-115
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Improved supraventricular and
ventricular tachycardia discrimination using electrogram morphology in an implantable
cardioverter defibrillator
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Mae-Mae Shieh, Lisa Clem, Lisa
Malden, April Pixley, Eric Fain.
St. Jude Medical, Sunnyvale, Usa
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Abstract
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Background. Inappropriate therapies
due to supraventricular tachycardias remain a problem for patients with implantable
cardioverter defibrillators. A new discriminator utilizing characteristics of the
electrogram morphology to differentiate supraventricular tachycardia from ventricular
tachycardia has been implemented in the Ventritex Contour MD/Angstrom MD implantable
defibrillators. This morphology discrimination algorithm compares a series of ventricular
complexes during the rhythm under evaluation to a patient specific template, and if the
complexes are similar to the template, the rhythm is diagnosed as supraventricular
tachycardia. The performance of the morphology algorithm when customizing the morphology
threshold parameter to individual patients was evaluated.
Methods. Stored electrograms of spontaneous ventricular tachycardia
and/or supraventricular tachycardia episodes from 138 patients were input into Ventritex
Contour MD/Angstrom MD device circuitry. A small subset of electrograms was
retrospectively analyzed to determine the best morphology match threshold for each
patient. These patient specific morphology match thresholds were prospectively applied to
subsequent electrograms for the same patient, and performance was quantified by
calculating sensitivity (i.e., appropriate ventricular tachycardia diagnosis) and
specificity (i.e., appropriate inhibition of ventricular tachycardia therapy) values. The
performance at different morphology match threshold settings was also evaluated by adding
a safety margin of 5, 10, 15, 20, 25, and 30% to the patient specific morphology match
threshold.
Results. A safety margin of 20% resulted in a 98% sensitivity and 94%
specificity.
Conclusions. The Ventritex Contour MD/Angstrom MD morphology
algorithm greatly improves the discrimination of supraventricular tachycardia from
ventricular tachycardia. This data set demonstrated a 94% reduction of inappropriate
detections due to supraventricular tachycardia while maintaining 98% ventricular
tachycardia diagnosis when patient specific parameter settings are selected after
evaluation of previous episodes.
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Key Words
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Implantable cardioverter defibrillator -
therapy
ICD inappropriate incidences, detection criteria, supraventricular tachycardia, morphology
discrimination algorithm, OA
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