PubMed · 10459416
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W R Elliott. Defibrillator testing.. https://pubmed.ncbi.nlm.nih.gov/10459416/
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CONTEXT: Unanticipated pacemaker and implantable cardioverter-defibrillator (ICD) generator malfunctions sometimes warrant recall by the US Food and Drug Administration (FDA). Despite increasingly frequent device implantation, pacemaker and ICD recalls and safety alerts (advisories) remain poorly characterized. OBJECTIVES: To determine pacemaker and ICD generator advisory rates in the United States, to identify trends in these rates, and to examine their clinical and financial implications. DESIGN AND SETTING: Analysis of weekly FDA Enforcement Reports issued between January 1990 and December 2000 to identify all advisories involving pacemaker or ICD generators in the United States. Recalls and safety alerts involving lead malfunctions were not included. MAIN OUTCOME MEASURES: Number of pacemakers and ICD generators in the United States subject to FDA recall or safety alert in 1990-2000; annual pacemaker and ICD advisory rates in the United States in 1990-2000; and estimated cost of device advisories. RESULTS: During the study period, 52 advisories (median [25th and 75th percentiles], 4 [4 and 7] per year) involving 408 500 pacemakers and 114 645 ICDs (523 145 total devices) were issued. Hardware malfunctions (35 advisories affecting 280 641 devices) and computer errors (10 advisories affecting 216 533 devices) accounted for 95% of device recalls. Implantable cardioverter-defibrillators were recalled more frequently than pacemakers (mean [SD], 16.4 [1.6] vs 6.7 [0.8] advisories per 100 person-years; P<.001). Between 1995 and 2000, the annual advisory rate increased for both pacemakers (P for trend <.001) and ICDs (P for trend =.02). An estimated 1.3 million device checks and analyses and 36 187 device replacements resulted from the advisories and cost approximately $870 million. CONCLUSIONS: Pacemaker and ICD recalls and safety alerts occur frequently, affect many patients, and appear to be increasing in number and rate. With the growing number of device implants and expanding indications for device therapy, the number of patients affected by device advisories will likely continue to increase.
OBJECTIVES: The aim of this prospective study was to evaluate the role of programmed ventricular stimulation (PVS) after noninvasive risk stratification to identify a subgroup of acute myocardial infarction (AMI) survivors considered at risk for ventricular arrhythmias and whether these patients could benefit from internal cardioverter-defibrillators (ICDs). BACKGROUND: The predictive value of noninvasive and invasive risk stratifiers after AMI has been questioned. The question of whether the group of patients with inducible monomorphic ventricular tachycardia (VT) after AMI could profit from ICD implantation is unanswered. METHODS: A consecutive series of 1,436 AMI survivors was screened noninvasively by Holter monitoring, heart rate variability, ventricular late potentials, and ejection fraction. A subgroup of 248 patients (17.3%) were identified as high-risk patients and scheduled for PVS. Due to the study design, 54 patients >75 years were excluded; thus, 194 patients were eligible for PVS. Triple extrastimuli at two paced cycle lengths (600 ms and 400 ms) were applied. RESULTS: In a subgroup of 98 (51%) high-risk patients, PVS was performed; 21 patients had an abnormal response, and in 20 patients an ICD was implanted. During a mean follow-up of 607 days the arrhythmic event rate (sudden cardiac death, symptomatic VT, cardiac arrest) was 33% with a positive electrophysiological test versus 2.6% (p < 0.0001) with a negative electrophysiological test. A subgroup of 96 high-risk patients declined electrophysiological study. In this nonconsent group, cardiac mortality (combined sudden and nonsudden) was significantly higher (log-rank chi-square 9.38, p = 0.0022, relative risk 4.7, 1.6 to 13.9) compared to the group guided by electrophysiological testing and consecutive ICD implantation. CONCLUSIONS: After a two-step risk stratification, PVS is helpful in selecting a subgroup of AMI survivors without spontaneous ventricular arrhythmias who benefit from prophylactic ICD implantation.
Ventricular fibrillation, the major reason behind sudden cardiac death, is turbulent cardiac electrical activity in which rapid, irregular disturbances in the spatiotemporal electrical activation of the heart make it incapable of any concerted pumping action. Methods of controlling ventricular fibrillation include electrical defibrillation as well as injected medication. Electrical defibrillation, though widely used, involves subjecting the whole heart to massive, and often counterproductive, electrical shocks. We propose a defibrillation method that uses a very low-amplitude shock (of order mV) applied for a brief duration (of order 100 ms) and over a coarse mesh of lines on our model ventricle.