PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Defibrillators, Implantable”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed1994

Safety and diagnostic yield of noninvasive ventricular stimulation performed via tiered therapy implantable defibrillators.

Extensive electrophysiological testing is critical for the effective utilization of sophisticated tachycardia detection and termination algorithms available in tiered therapy ICDs. To evaluate the safety and diagnostic yield of electrophysiological testing via noninvasive ventricular stimulation, we performed 294 electrophysiological studies in 154 patients (age 65 +/- 10; left ventricular ejection fraction 0.36 +/- 0.15) with tiered therapy ICDs. Stimulation was performed under methohexital anesthesia. A total of 918 sustained ventricular tachyarrhythmias were induced (3.1 +/- 2.5 per procedure): monomorphic VT, 550; ventricular flutter, 74; and VF, 246. The results of invasive and noninvasive programmed stimulation were compared for 79 patients who had both studies under similar treatment. Overall concordance was 83%, and did not differ significantly between patients who had the noninvasive stimulation via epicardial or endocardial pacing leads. VF could be induced in 206 of 257 studies (82%), and it was less likely to be induced in patients on amiodarone (74% vs 85%; P = 0.02), or beta blockers (55% vs 83%; P = 0.017). No patient presented a serious complication. Minor complications occurred during 39 studies: transient laryngospasm in 1, unintended delivery of an ICD shock to a conscious patient in 4; induction of sustained atrial fibrillation in 8; need for external rescue defibrillation shocks in 13; and delivery of inappropriate shocks for supraventricular rhythms in 14 studies. Noninvasive ventricular stimulation performed under methohexital anesthesia is safe. Its diagnostic yield compares favorably with that of conventional electrophysiological studies. VF can be induced in a majority of patients. There is good correlation between invasive and noninvasive programmed stimulation for induction of VT. Noninvasive ventricular stimulation may emerge as standard procedure for the initial programming and follow-up of ICDs.

Aged↗
PubMed1996

Dual level sensing significantly improves automatic threshold control for R wave sensing in implantable defibrillators. The Angeion Corporation.

ICDs must sense R waves over a range of amplitudes without sensing P or T waves. Automatic threshold control (ATC) is an accepted sensing method for that task. ATC sensing levels are from 25%-75% of the electrogram (EGM) peak, decreasing with an exponential decay. A high sensing level for a time after peak detection may better allow ATC to pass over a T wave, while a lower sensing level thereafter may better allow ATC to sense the next R wave. An ATC was designed with two sensing levels and time constants (tau), using a 58% level (tau = 1.75 s) for 325 ms after peak detection switching to 33% (tau = 1.1 s) thereafter, and was compared to a single level ATC (sensing level = 50%, tau = 1.4 s). The two ATC circuits were tested with 22 arrhythmia EGMs to determine sensitivity and specificity rates at +/-1-, 2-, 5-, 10-, and 20-mV amplitudes. It was confirmed that a dual level ATC significantly improves the sensitivity rate without degrading the high specificity rate of a standard sensing circuit.

Arrhythmias, Cardiac↗
PubMed1997

Standardized assessment of psychological well-being and quality-of-life in patients with implanted defibrillators.

The ICD has become a standard treatment for patients with malignant arrhythmias. Despite its benefits it may cause additional discomfort to the patients. Thus, quality-of-life needs to be assessed in these patients. Previous studies have used only small samples or unstandardized measures of quality-of-life that do not allow comparisons with other patient groups. The present study used standardized questionnaires for a cross-sectional assessment of psychological well-being and quality-of-life in ICD patients and to compare them to a similar group of coronary artery disease (CAD) patients without ICD. Overall, quality-of-life did not differ between both groups, ICD patients being less anxious than the CAD group. With increasing numbers of ICD shocks, however, the percentage of psychologically distressed ICD patients rose from 10% to > 50%. Psychologically distressed patients had significantly worse scores on most of the quality-of-life subscales, showed less treatment satisfaction, and more negative attitudes. It is concluded that ICD patients have an acceptable mean quality-of-life and low mean anxiety. However, a relevant subgroup of about 15%, especially patients with frequent shocks, experience psychological distress and reduced quality-of-life and should receive special care.

Adaptation, Psychological↗
PubMed1997

Dysfunction of implantable defibrillators caused by slot machines.

The electrogram storage is a feature offered by the last generation of defibrillators, which enables the physician to establish whether the sensed episode and the electrical therapy delivered by the device was appropriate. The incidence of electromagnetic interferences may be higher than initially suspected with the latest generation of defibrillators. Such interference was documented in 4 out of 100 patients over a 24-month period. The electrical interference occurred in all four of them, while they were playing with slot machines. In the RR interval history, irregular QRS sensing of variable frequency was documented in some episodes. The intervals were irregular and nonphysiological satisfying the rate cut-off criteria in an intermittent and nonsustained way. There may be high risk of electromagnetic interference between slot machines and defibrillators. Our experience calls for a warning to all defibrillator patients and, perhaps some regulatory intervention.

Adult↗
PubMed1999

Implantable defibrillators impedance measurement using pacing pulses versus shock delivery with intact and modified high voltage lead system.

At present the only method for measuring the high voltage system lead impedance in patients with an ICD is to deliver a low energy test shock. This is painful, requires sedation, and carries a risk of ventricular fibrillation induction. We sought to assess the shock lead and electrode function by calculating IMP using low voltage pacing pulses, and compared it to the measured impedance of a shock through the same lead. This was performed in both an intact and a modified lead system in order to mimic common clinical scenarios that alter lead system IMP (e.g., lead fracture). In an anesthesized canine model (n = 12) a standard (S) transvenous defibrillation lead (TDL), a modified (M) TDL (two-thirds of coil covered with heat-shrunk tubing), an active can (AC), and a M epicardial patch (EP) (two of four coils were disconnected) were used. Three configurations (C) were tested: C1:S/TDL-->AC, C2:M/TDL-->AC, and C3:M/TDL-->MEP. A measured IMP was obtained by an ICD using a 5-J shock as control. IMP was calculated using a 5-J shock, pacing pulses of 10-, 5-, 2-, and 1-V amplitude, as well as from a square wave drive train of low amplitude/high frequency signals (1 and 0.2 V, at 10 kHz) in all Cs. Ohm's law (V = IR) was utilized for measuring calculated IMP. As the surface area of the high voltage lead system decreased, the mean measured IMP (control) increased from C 1 to 3 (63 +/- 10, 95 +/- 4, and 127 +/- 20 omega, respectively). The correlation of calculated IMP from all Cs to measured impedance (control) remained high throughout the IMP range (range of correlation coefficient (r): 0.921-0.981). Calculated IMP using delivery of pacing pulses is highly correlated to IMP measured during shock delivery. This correlation remains high over a clinically significant range of high voltage lead system IMP changes. This study suggests that pacing pulses can be used to predict the IMP changes in the high voltage lead system which may occur clinically, reducing the need to deliver a shock for IMP measurement.

Animals↗