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M H Schoenfeld

Publications and source records attributed to M H Schoenfeld.

At least 19 recordsLinked to original sources
PubMed2001

Inability to communicate with ICDs: an underreported failure mode.

The inability to perform telemetry on an ICD may have many potential causes. We report three recently identified cases where such a finding was indicative of unexpected device failure. Two of these cases involved identical failure mechanisms resulting from arcing of current within the high voltage hybrid. This placed the device into a high current state that caused rapid and complete battery depletion. There were no company alerts issued regarding this systematic problem. A multicenter arrhythmia device/lead database would be extremely useful in providing timely and unbiased information concerning device problems.

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PubMed2001

Unexpected ICD pulse generator failure due to electronic circuit damage caused by electrical overstress.

Because it is a lifesaving device, the unexpected failure of an ICD can be catastrophic. We report ICD electronic circuit failure due to electrical overstress damage (EOS) to the high voltage hybird circuit and other electronic components in a series of ICD pulse generator models. Data were obtained from the Multicenter Registry of Pacemaker and ICD Pacemaker and Lead Failures, and from the manufactures' adverse event reports, that were in the FDA's Manufacturer and User Facility Device Experience (MAUDE) database. Of 16 nonbattery Guidant/CPI ICD pulse generator failures reported to the registry, 6 (38%) have been confirmed by the manufacturer to be EOS related, and Guidant/CPI has reported 273 such failures to the FDA as of 12/29/00. The signs of failure included loss of telemetry and inability to deliver therapy, and some patients have experienced serious adverse events. Hybrid circuit damage may have occurred during capacitor charging or reform, and the majority appears to have happened during normal ICD function. While the incidence of this problem is unknown, a management strategy should be adopted that includes routine follow-up every 3 months and device evaluation after a shock or exposure to external defibrillation or electrosurgical devices. This study suggests that additional data are needed to determine the incidence of this problem, and that our present methods for monitoring the performance of ICD's following market release are inadequate.

Defibrillators, Implantable↗
PubMed1999

Optic neuropathy following amiodarone therapy.

Ocular changes during treatment with amiodarone are almost universal but are rarely serious. In this article we describe three patients from a single electrophysiology practice in whom optic neuropathy developed during treatment with amiodarone. All three patients were more than 65 years of age. The doses of amiodarone ranged from 100 to 400 mg/day, and the time intervals between the initiation of the amiodarone therapy and the appearance of first symptoms of optic neuropathy were 5 to 19 months. Two patients had bilateral involvement, and one had only unilateral involvement. Whether this result was due solely to amiodarone therapy, to the underlying poor health of these patients, or to the combination of these two factors is uncertain. These findings prompt us to recommend that all patients who receive amiodarone undergo complete ophthalmologic examinations, including careful evaluation of the ocular fundus regularly during such therapy. No randomized study had been undertaken to determine the true incidence of complications associated with this medication.

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PubMed1999

Twiddler's syndrome with transvenous defibrillators in the pectoral region.

Advances in technology have enabled the implantation of defibrillators in the pectoral region. Complications encountered with pacemakers may also be observed with defibrillators. We describe two cases of twiddler's syndrome in patients with defibrillators implanted subcutaneously in the left pectoral region.

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PubMed1998

Inappropriate shocks delivered by an ICD as a result of sensed potentials from a transcutaneous electronic nerve stimulation unit.

Although the potential for transcutaneous electronic nerve stimulation (TENS) units to interfere with appropriate function of cardiac pacemakers is well documented, an adverse interaction between a TENS unit and an ICD has never been reported. We describe a patient in whom a TENS unit created an electrical artifact that was interpreted by a transvenous ICD as ventricular fibrillation, leading to the delivery of inappropriate therapy. TENS units should be used with caution in patients with ICDs.

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PubMed1996

Exploration of the precision of classifying sudden cardiac death. Implications for the interpretation of clinical trials.

BACKGROUND: As cardiovascular clinical trials improve in sophistication and therapies target specific cardiac mechanisms of death, a more objective and precise system to identify specific cause of death is needed. Ideally, sudden cardiac death would describe patients dying of ventricular tachycardia and ventricular fibrillation. In this context, we explored the precision of current sudden death classification and implications for clinical trials. METHODS AND RESULTS: Deaths were analyzed in 834 patients who received an automatic implantable cardioverter-defibrillator (ICD). Three arrhythmia experts used a standard prospective classification system to classify deaths into accepted categories: sudden cardiac, nonsudden cardiac, and noncardiac. New aspects to this study included analysis of autopsy results and ICD interrogation for arrhythmias at the time of death. All of the patients receiving the ICD previously had documented sustained ventricular tachycardia/fibrillation or cardiac arrest. Of the 109 subsequent deaths in the 834-patient database, 17 (16%) were classified as sudden cardiac. Compared with the nonsudden cardiac and noncardiac categories, sudden cardiac death was more often identified in outpatients (59% versus 10%) and witnessed less often (41% versus 86%; both P < .001). The autopsy information contradicted and changed the clinical perception of a "sudden cardiac death" in 7 cases (myocardial infarction [n = 1], pulmonary embolism [n = 2], cerebral infarction [n = 1], ruptured thoracic [n = 1], and abdominal aortic aneurysms [n = 2]). Interpretable ICD interrogation was available in 53% of the deaths (47% unavailable: buried, programmed off, or other technical reasons). When evaluated, only 7 of 17 "sudden deaths" were associated with ICD discharges near the time of death. CONCLUSIONS: Even in a group of patients with an ICD, deaths classified as sudden cardiac frequently were not associated with ventricular tachycardia or ventricular fibrillation and were often noncardiac. It is possible to create a wide range of sudden cardiac death rates (more than fourfold) using the identical clinical database despite objective, prespecified criteria. Autopsy results frequently reveal noncardiac causes of clinical events simulating sudden cardiac death. ICD interrogation revealed that ICD discharges were often related to terminal arrhythmias incidental to the primary pathophysiological process leading to death.

Cause of Death↗
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.

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PubMed1993

Usefulness of electrophysiologic studies for new-onset sustained ventricular tachyarrhythmias shortly after coronary artery bypass grafting.

We retrospectively studied a group of 17 patients who developed life-threatening ventricular tachyarrhythmias shortly after coronary artery bypass grafting. The initial clinical event was sustained monomorphic ventricular tachycardia (VT) in 15 and ventricular fibrillation (VF) in 2, occurring at an average of 3.6 days postoperatively. All patients underwent electrophysiologic testing, with sustained monomorphic tachyarrhythmias inducible in 7. Three early deaths occurred after this initial evaluation. Among the 9 survivors with nonsustained, nonclinical or noninducible VT, 4 received no antiarrhythmic therapy and remained free of recurrence, whereas of the 5 that received drugs, implantable defibrillators, or both, 2 had spontaneous recurrence. For the surviving subgroup with inducible monomorphic VT, serial drug testing culminated in maintenance therapy with class IA agents or amiodarone, whereas defibrillators were also implanted in 3 patients. Overall, recurrence of life-threatening tachyarrhythmias beyond the immediate postoperative period was seen in 40% of patients with monomorphic clinical tachycardias and inducible sustained monomorphic VT. Ventricular tachyarrhythmias appearing shortly after cardiac surgery demonstrate significant chronicity and resistance to antiarrhythmic drug therapy, while statistically significant predictors of inducibility or their recurrence remain undefined.

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