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At least 1,117 records · Page 62Linked to original sources
PubMed1994

Pseudo-oversensing of the T wave by an implantable cardioverter defibrillator: a nonclinical problem.

Two patients are described who had pseudo-oversensing of T waves during follow-up testing of the Medtronic PCD. Each patient exhibited appropriate T wave sensing following closely coupled spontaneous QRS complexes to subthreshold stimuli without having T wave sensing following sensed or paced complexes. One patient also revealed T wave sensing following fusion beats. The occurrence of T wave sensing in these unique clinical situations was due to the auto-adjusting sensitivity threshold function used by the PCD. Recognition of this normal sensing function will prevent inappropriate reprogramming of the sensitivity or postpace refractory period, interventions that could potentially lead to ventricular tachyarrhythmia undersensing.

Adult↗
PubMed1994

Troubleshooting implantable cardioverter defibrillator system malfunctions: the role of impedance measurements.

High impedance measurements may be used to troubleshoot ICD system malfunction. In four different cases a defective system was identified or confirmed by an abnormal impedance: two secondary to lead fractures, one to an adapter faulty connection, and one to a loose set-screw connection. This led to further diagnostic procedures that ultimately localized the difficulty. Though the problems with ICD may be of diverse origins, routine use of impedance measurement for the troubleshooting of these systems may serve as an early sign of malfunction and would point the need for further investigation.

Aged↗
PubMed1996

Limitations of tachycardia confirmation and rate classification algorithms in a third-generation implantable cardioverter defibrillator.

Newer ICDs provide antitachycardia (ATP) and bradycardia pacing and cardioversion and defibrillation shocks based on sensed interval criteria. The objectives of this investigation were to determine the algorithm related errors in tachycardia confirmation and rate classification that occurred in patients with a third-generation, noncommitted, tiered ICD therapy. Forty-three consecutive patients with the Guardian ATP 4210 ICD, which uses an X out of Y sensed interval counting algorithm for tachycardia detection, confirmation, and classification were studied. Surface ECGs, intracardiac electrograms, stored data logs, and sense histories were reviewed to diagnose errors due to these algorithms that resulted in delivery of inappropriate therapy or inhibition of appropriate therapy. Sixty-eight classification or confirmation algorithm errors from 7,610 tachycardia detections (< 1%) were diagnosed in 23 (53%) of 43 patients. Three types of errors not related to device or sensing lead malfunction or programming mistakes were seen. In 26 episodes, the confirmation algorithm failed to detect late tachycardia reversion of nonsustained tachyarrhythmias, on the last or next to last sensed interval, and did not inhibit ATP (n = 17) or shocks (n = 9). In 28 episodes, inaccurate classification of tachycardia rate resulted in inappropriate ATP (n = 23) or shock (n = 5) therapy. In 14 episodes, the posttherapy reconformation algorithm produced inhibition of VVI pacing and prolonged asystole following shock therapy. These errors in tachycardia confirmation and rate classification were due to the inherent limitations of the X out of Y counting algorithm.

Adult↗
PubMed1996

Implantable cardioverter defibrillator detection during radiofrequency catheter ablation of ventricular tachycardia.

Right ventricular radiofrequency catheter ablation was performed in an ICD patient with frequent ventricular tachycardia without prior inactivation of the device. The registrations of intracardiac ECG and marker channel were excellent during energy delivery: the surface ECG was affected. The device did not show dysfunction during and after energy delivery.

Catheter Ablation↗
PubMed1997

Inadequacy of qualitative implantable cardioverter defibrillator electrogram analysis to distinguish supraventricular from ventricular tachycardia due to electrogram changes during normally conducted complexes.

Stored electrograms (EGMs) recorded from ICD leads are used to evaluate the appropriateness of ICD therapies. Stored EGMs different from sinus have been interpreted as ventricular in origin. We present a patient with an ICD for VT who received multiple shocks for a tachycardia with a stored EGM different than sinus, suggesting VT. An electrophysiological study demonstrated EGMs different than sinus during atrial pacing and induced supraventricular arrhythmias. This case points out the limitations of stored EGMs and suggests complete electrophysiological study with analysis of EGMs during induced arrhythmias should be performed prior to discharge.

Cardiac Pacing, Artificial↗
PubMed1997

Predictors of psychosocial adjustment in patients with implantable cardioverter defibrillators.

Predictors of psychological distress/adjustment were examined in 25 patients following placement of ICDs. Patients completed a demographic questionnaire and a standardized questionnaire of psychological symptoms (i.e., Symptom Checklist-90 Revised; SCL-90-R). The number of discharges categorized by the patient as inappropriate and appropriate were also ascertained. The number of ICD discharges categorized as inappropriate and diminished levels of physical activity (r = 0.53 and 0.63, P < 0.01, respectively) did significantly relate to overall psychological distress. In addition, after controlling for age and prior psychiatric and physical health status through a stepwise multiple regression analysis, the occurrence of ICD discharges categorized as inappropriate and diminished physical activity continued to significantly predict overall psychological distress (R2 = 0.41, P < 0.01). However, the number of ICD discharges categorized as appropriate did not significantly predict overall psychological distress. The results of this investigation suggest that further refinement of the ICD could reduce the risk of exposure to potential psychological distress, and an analysis of prior and anticipated patient physical activity levels should be a factor when calibrating minimum ICD discharge threshold levels.

Activities of Daily Living↗