Biomedical subjects

E Fain

Publications and source records attributed to E Fain.

8 recordsLinked to original sources

PubMed2000

The defibrillator in acute myocardial infarction trial (DINAMIT): study protocol.

BACKGROUND: The implantable cardioverter/defibrillator (ICD) has been shown to be superior to antiarrhythmic drug therapy for the secondary prevention of sudden cardiac death. Its role in the primary prevention of sudden death after myocardial infarction is unknown. Methods and Results The Defibrillator in Acute Myocardial Infarction Trial (DINAMIT) is a randomized, open-label, parallel-group comparison of ICD therapy versus no ICD therapy in selected survivors of acute myocardial infarction. It will test the hypothesis that reduction of sudden arrhythmogenic death by means of the ICD will result in reduction of overall mortality rates in patients at high risk after acute myocardial infarction. Accordingly, this international multicenter study aims to enroll patients shortly after their infarction (day 6 to day 40) who have reduced left ventricular function (left ventricular ejection fraction </=0. 35) and impairment of cardiac autonomic function shown by depressed heart rate variability (standard deviation of normal-to-normal R-R intervals </=70 ms) or elevated average 24-hour heart rate (mean 24-hour R-R interval </=750 ms, assessed by Holter monitoring). Patients will be followed for approximately 3 years on average with subsequent data analysis based on the intent-to-treat principle. Primary outcome is all-cause death. The trial is expected to be completed in 2003. CONCLUSIONS: DINAMIT is the first prospective study to evaluate the benefit of ICD therapy for the primary prevention of sudden cardiac death in patients at high risk after acute myocardial infarction.

Defibrillators, Implantable↗

PubMed2000

ICD waveform optimization: a randomized, prospective, pair-sampled multicenter study.

The theoretical tissue model-based estimates of phase 1 and phase 2 duration of biphasic waveforms are considerably shorter than the pulse widths currently used in ICDs with standard tilt. This study used a tissue resistance/capacitance (RC) model to identify optimal biphasic pulse widths. By paired step-down defibrillation threshold (DFT) testing, the efficacy of standard versus "tuned" biphasic waveforms was evaluated in 91 patients. Standard waveforms consisted of a phase 1 set to 65% tilt and phase 2 = phase 1. The tuned waveform was based on an RC model of membrane characteristics with a time constant of 3.5 ms. The optimal phase 1 truncation point is at the peak of membrane response. The optimal phase 2 duration ends with a membrane response near or just below 0. In paired analysis, no significant differences were found in DFT or impedance between standard and tuned waveforms. In patients with DFTs > 400 V, the tuned waveform lowered the DFT by an average of 38 V (P < 0.05). Multivariate analyses showed a significant inverse relationship between DFT and impedance (P < 0.001). As impedance increased, the tuned waveform was associated with DFTs comparable to the standard waveform with shorter pulse duration and lower delivered energy. No single tilt value allowing an easy calculation of delivered energy was related to ICD waveform efficacy. The use of ICDs with tuned optimal pulse durations offer a greater flexibility of choice for patients with high DFTs.

Aged↗

PubMed1999

Mission critical challenges: a data repository that addresses everyone's needs.

UNLABELLED: Ochsner Health Plan, New Orleans. PROBLEM: The health plan's information systems were inflexible and ineffective in meeting the needs of healthcare administrators, clinicians and others within the organization. SOLUTION: Ochsner officials reorganized the information systems by restructuring the computing architecture and building an enterprisewide relational database. RESULTS: Separate departments within the health plan now can share the same base of clinical and financial data online. KEYS TO SUCCESS: "The new server gave us the benefits of a centralized system combined with powerful back-end processing capabilities that enabled online analytical processing."

Chronology as Topic↗

PubMed1997

Transvenous defibrillation leads: is there an ideal position of the defibrillation anode?

A potential benefit of two-lead transvenous defibrillation systems is the ability to independently position the defibrillation electrodes, changing the vector field and possibly decreasing the DFT. Using the new two-lead transvenous TVL lead system, we studied whether DFT is influenced by SVC lead position and whether there is an optimal position. TVL leads and Cadence pulse generators were implanted in 24 patients. No intraoperative or perioperative complications were observed. In each patient, the DFTs were determined for three SVC electrode positions, which were tested in random order: the brachiocephalic vein, the mid-RA, and the RA-SVC junction. The mean DFTs in the three positions were not statistically different, nor was any single lead position consistently associated with lower DFTs. However, an optimal electrode position was identified in 83% of patients, and the DFT from the best lead position for each patient was significantly lower than for any one of the electrode positions (P < 0.01). The mean safety margin for the best SVC lead position was approximately 27 J. These results demonstrate the advantage of a two-lead system, as well as the importance of testing multiple SVC lead positions when the patient's condition permits. Both of these factors can decrease the DFT and maximize the defibrillation safety margin. This will become increasingly important as pulse generator capacitors become smaller (as part of the effort to decrease generator size) and the energy output of the generators consequently decreases.

Adult↗

PubMed1996

First experience with a new nonthoracotomy defibrillation lead system.

The clinical efficacy and safety of a new nonthoracotomy defibrillation lead system (TVL lead system, Ventritex, inc., Sunnyvale, Calif.) was studied in patients with ventricular tachycardia or fibrillation. Implantation of the TVL lead system and a Cadence pulse generator (Ventritex, Inc.) was attempted in 27 patients. A subcutaneous patch lead was added if required to achieve adequate defibrillation energy. Patients were monitored for an average of 6 +/- 4 months (range 1 week to 14 months). Implantation was successful in 26 patients (96%). Twenty-three of those patients (88%) were implanted in a lead-alone configuration; the remaining three (12%) required a subcutaneous patch lead. The mean defibrillation threshold was 401 +/- 120 V (12 +/- 7 J) at implantation, 467 +/- 134 V (15 +/- 8 J) at predischarge testing, and 452 +/- 151 V (14 +/- 9 J) at 4-month follow-up. The mean defibrillation threshold at 4 months was not significantly different from that at implant. No deaths, sensing anomalies, infections, lead fractures, or lead dislodgments occurred. One patient required addition of a subcutaneous patch 4 months after device implantation because of an elevated defibrillation threshold. Eight patients (31%) experienced 545 spontaneous arrhythmic episodes, and all episodes were successfully terminated by the device. In conclusion, the TVL lead system combined with Cadence tiered-therapy defibrillator has a high success rate and low complication rate, and it can be recommended for treatment of patients with life-threatening ventricular tachyarrhythmias.

Adult↗

PubMed1996

Improved nonthoracotomy defibrillation based on ventricular fibrillation waveform characteristics.

The heart has been shown to be more susceptible to defibrillation at a higher absolute ventricular fibrillation voltage (AVFV) measured on the surface ECG. This study evaluated in a closed-chest canine model (n = 7) the clinical applicability of using a real-time VF waveform analysis system using an electrogram defined between the generator can and an RV endocardial electrode. Under fluoroscopic guidance, superior vena cava and RV spring coil catheter electrodes were inserted through the external jugular vein. A subcutaneous patch was placed on the left chest. A two-parameter tracking algorithm was used to dynamically identify the high AVFV area, and a biphasic shock was triggered synchronously at the next peak. The performance of this new peak shock method (PSM) was compared to the conventional method of shocking at a fixed time in 175 paired trials. Five shocks per voltage and five voltages per animal were randomized between the two methods to permit the generation of sigmoidal dose response curves for the estimation of 50% (E50), 75% (E75), and 100% (E100) success energies. Induction of VF and discharge voltage were kept constant while energy delivered, impedance (R), and AVFV at the point of shock were measured. Energy (8.63 +/- 0.40 vs 8.64 +/- 0.40 J), R (48.60 +/- 0.30 vs 48.59 +/- 0.30 omega), and current (7.50 +/- 0.18 vs 7.51 +/- 0.16 A) were not significantly different between trials for either the conventional or the PSM. The time from the onset of VF until the defibrillation shock was 7.98 +/- 1.44 seconds. Higher overall successes (46.3% vs 33.1%; P < 0.01) and lower E50, E75, and E100 were observed for the PSM. Finally, the significantly higher AVFV (9.12 +/- 0.32 vs 4.73 +/- 0.34 mV; P < 0.0001) with the peak method suggests that the high VF voltage could be detected as it occurred in real-time. The improved defibrillation success supports the use of this method for nonthoracotomy defibrillation.

Animals↗

PubMedDate not supplied

Surface coverage effects on defibrillation impedance for transvenous electrodes.

Transvenous defibrillation electrodes are constructed by wrapping conductive elements around an insulating base. However, these conductive elements do not cover the entire area of the base. The effects of varying the surface area coverage on the defibrillation impedance (DZ) are unknown. To understand the effects, four transvenous right ventricular test leads were specially fabricated. A ring design was used with 3 mm diameter cylinders equally spaced along a 5 cm length, ending 11 mm from the pacing tip. Three leads consisted of 4, 8, and 15 rings each of length approximately 2.4 mm so that the coverages were 20%, 40%, and 70%, respectively. The fourth lead used 8 rings of length approximately 1.2 mm each and had a coverage of 20%. DZ for each lead was obtained using three methods: (i) computer simulation; (ii) in vitro measurement in a tank; and (iii) in vivo measurement in nine dogs during defibrillation testing. The DZs from either of the first two methods correlated very well (r = 0.98) with the mean DZs from the third method, indicating that in vivo DZs can be predicted from computer and in vitro models. The study shows that: (i) at the same ring length, DZ decreases as coverage (number of rings) increases; (ii) at the same coverage, DZ decreases as ring length decreases; and (iii) in vivo, a statistically significant difference was observed in DZ between the leads with 20% coverage and the leads with higher coverages. No statistically significant difference was observed between leads with coverages > 40%.

Animals↗

PubMedDate not supplied

Today's or tomorrow's computer systems?

The computer technology of behavioral healthcare information systems must meet at least twelve requirements to effectively support clinical and management operations. Existing, antiquated "legacy" computer systems often fail to meet these requirements, due to high cost, slow turnaround, inconsistent data definitions, duplication, inflexibility and the lack of data integrity. There are five major transitions that an organization's information system undergoes to realize the full potential of new technology: from monolithic to parallel architectures; from procedural to object-oriented programming; from structural to relational databases; from legacy to "leap-frog" systems; and from fragmented systems to multimedia.

Budgets↗