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PubMed1996

[Clinical usefulness of stored electrograms in implantable defibrillators].

BACKGROUND AND PURPOSE: The storage of intracavitary electrograms by the automatic implantable defibrillators is one of the latest advantages. The objective of this study was to determine the clinical utility and limitations of electrograms stored by the new generation of defibrillators. MATERIAL AND METHODS: We have implanted at our institution 43 generators with the facility of storing electrograms; 8 Ventak P2, 17 PRxII, and 1 PRxIII from CPI, 14 Jewel, from Medtronic and 3 Guardian ATP 4215, from Telectronics. All were implanted with an endocavitary system lead, an only one patient needed a subcutaneous patch. Mean age was 57 +/- 16 years, 36 were males and 7 women. The mean left ventricular ejection fraction was 44 +/- 23%. The mean follow up was 6 +/- 8 months (limits 1-20 months). RESULTS: We registered and analyzed a total of 268 episodes in 20 patients. Fourteen (82%) received what was considered appropriate therapy. Three patients (from 17 with any treatment delivered by the defibrillator) presented an inappropriate therapy. The parameters, "onset" and "stability", were differentiated in each arrhythmia, the "onset" is useful to differentiate sinus tachycardia, but not atrial fibrillation, from ventricular tachycardia. Programming a stability value between 30-40 mseg eliminates 88% of inappropriate therapies due to atrial fibrillation. In all patients, the identification of the event, facilitated by the stored electrograms, allowed us to resolve the problem. CONCLUSIONS: The programmable features "onset" and "stability" allowed us to eliminate a significant number of inappropriate therapies. The stored electrograms facilitate the identification of the events, leading to treatment by the generator, and were very useful in guiding the clinical management of the patient.

Adult↗
PubMed1996

[Limiting costs of implanted defibrillators].

The use of implanted defibrillators is increasing recently. In view of the costs of a gadget, which amount to DM 40,000 to 45,000, arises the questions which juridical requirement have to exist, that after the death of a patient it is possible to reuse a still functional defibrillator. The solution should be that the health insurance keeps the property, whereas the patient receives merely the defibrillator as loan.

Cost Savings↗
PubMed1996

[Medium-term clinical experience with automatic transvenous defibrillators implanted in the chest area without subcutaneous electrodes].

From March 1992 to April 1996 a pectoral biphasic transvenous implantable cardioverter defibrillator without subcutaneous leads was implanted in 35 patients with life threatening ventricular tachyarrhythmias. Mean age was 58 +/- 9 years; 23 patients had coronary artery disease, 10 non ischemic dilated cardiomyopathy and 2 arrhythmogenic right ventricular dysplasia. All were in NYHA functional class I and II and 4 in class III: mean ejection fraction was 35 +/- 12%. The mean duration of the implantation procedure was 85 +/- 35 min. The mean defibrillation threshold, measured in 23 active-CAN devices was 8.8 +/- 5 J. There were no operative complications except in one case of transient ischemic electromechanical dissociation. The mean hospital stay from the time of implant to predischarge evaluation was 6.2 +/- 2 days. The average follow-up period was 18.5 +/- 11 months. Two patients had non sudden and non arrhythmic cardiac death in the third and sixth month, respectively. In 19 patients 171 implantable cardioverter defibrillator interventions were reported: in 5 patients five inappropriate interventions were reported and in the remaining 14 were reported: 35 ventricular fibrillation and 131 ventricular tachycardia. The short duration of the procedure, brief hospitalization with very low perioperative morbidity, high efficacy and low mid-term complications give a new image to this therapeutic option.

Adult↗
PubMed1997

The impact of the implantable cardioverter defibrillator on quality of life.

The implantable cardioverter defibrillator may prolong survival and prevent sudden cardiac arrest in patients with ventricular arrhythmias. Whereas previous research focused on mortality, attention is now turning to the impact of the device on the recipient. We reviewed the literature on the effects of the implantable cardioverter defibrillator on recipients and their families; our aim was to consolidate our current understanding and guide further research in this area. We found a number of effects on which researchers agree. Primarily, recipients are happy to have the device and generally feel more confident. However, recipients experience many psychological reactions such as fear and anxiety that can be related to the unpredictable nature of the shocks. Recipients also are affected by intellectual changes. Both recipients and their families experience similar effects and use a range of coping mechanisms; the most effective is optimism. Only one nursing intervention has been investigated that directly addresses these effects. Areas that need more research are the effects of the implantable cardioverter defibrillator during childhood, adolescence, and pregnancy; the impact of vigilance on recipients and their families; costs; and nursing interventions. More consistent, standardized quality-of-life measures are needed so that comparisons can be made between samples.

Adaptation, Psychological↗
PubMed1997

[Treatment with the implantable cardioverter defibrillator (ICD)].

Interventional techniques in clinical cardiology became important in rhythmology, because it is evident that antiarrhythmic drug therapy has several limitations, and side effects. The implantable cardioverter defibrillator is a very reliable tool in the therapy of ventricular fibrillation and ventricular tachycardia. Conversion of these arrhythmias is associated with the prevention of subsequent sudden cardiac death in patients who received implantation after cardiac arrest, not associated with myocardial infarction or metabolic disturbances. The exact place of the defibrillator in the treatment of ventricular tachycardia remains unsettled, as amiodarone, sotalol and catheter ablation are acceptable treatment modalities for some patients. Furthermore, associated antiarrhythmic drug therapy remains necessary in a large group of patients after implantation. The morbidity and mortality of the recently developed non-thoracotomy devices is low. The potential value of implantable defibrillators in the prevention of cardiac arrest in high-risk patients remains to be studied.

Anti-Arrhythmia Agents↗
PubMed1997

[The implantable cardioverter-defibrillator: the Portuguese experience].

OBJECTIVE: The aim of this study was to review the Portuguese experience with implantable cardioverter-defibrillator therapy (ICD), in order to evaluate the increase in the number of ICD implanted, the main indications for this kind of therapy, the technical evolution of the procedure and the results of the follow-up of these patients during the last five years. PATIENT SELECTION: The study group consists of 58 patients, 53 male and 5 female, mean age 54 +/- 14 years with ICD implanted in our country since 1992. The ICDs were implanted in 4 Hospitals, namely, Santa Cruz Hospital with 36 patients, Santa Maria Hospital with 11, Santa Marta Hospital with 8 and Coimbra University Hospital with 3 patients. Twenty six patients were resuscitated from cardiac arrest and the other 32 had ventricular tachycardia (VT) not tolerated haemodynamically and refractory to therapy. The diagnosis was coronary artery disease in 31 patients, dilated cardiomyopathy in 8, valvular disease in 4, congenital cardiopathy in 3, right ventricular dysplasia in 2, congenital long QT syndrome in 1, hypertrophic cardiomyopathy in one. Seven patients had idiopathic ventricular fibrillation without structural heart disease and one patient had isolated right ventricular dilatation. METHODS: All patients underwent electrophysiological study before ICD implantation. In 2 patients epicardial leads were used and in the remaining 56 patients a transvenous approach was used. The device was implanted in an abdominal position in 36 patients and in a pectoral position in 22. Defibrillation and pacing thresholds were measured during the implantation procedure and whenever necessary. Patients were followed up on an outpatient basis with evaluation of the number of arrhythmic episodes, therapy efficacy with reprogramming of the device when required. RESULTS: The number of implantations has increased, from 4 devices implanted in 1992, to 32 in 1996. The implantation was successful and without mortality or complications in all patients. Defibrillation threshold was 16 +/- 3 J, with an electrode impedance of 48 +/- 9 Ohms. During a mean follow-up time of 18 +/- 15 months (1 to 56) 5 patients died, one of sudden death and 4 of non cardiac deaths, 15 patients were re-admitted to hospital and in 8 patients the device was replaced due to exhaustion. In this period, 37 patients (64%) had arrhythmic episodes detected by the device, 32 patients (55%) had shocks and 9 (16%) were treated with anti-tachycardia pacing. Inappropriate shocks were observed in 10 patients (17%). The ICD were reprogrammed in 11 patients. CONCLUSIONS: Portuguese experience with IC implantation is increasing and has shown to be a safe procedure with no operative mortality or morbidity. The incidence of appropriate shocks was high with a good efficacy in sudden death reduction.

Adult↗
PubMed1997

Defibrillation threshold and electrode configurations: an experimental study testing three configurations in twelve pigs.

OBJECTIVE: The choice between epicardial or subcutaneous patches remains unclear and depends essentially on the team's habits. This study tested how much an additional patch can decrease defibrillation threshold (DFT), and compared a Subcutaneous Array and an epicardial patch. Today most implantable automatic defibrillators have a transvenous endocardial configuration alone but when the DFT remains high an additional patch is necessary. EXPERIMENTAL DESIGN: Three different configurations were tested with biphasic shocks in 12 pigs: Endovenous lead (Endo), Endovenous lead + subcutaneous patch (Endo + SQ) and Endovenous lead + epicardial patch (Endo + Epi). For each animal DFTs were determined in a balanced random order for the 3 configurations. Ventricular fibrillation was induced by pacing (30 Hz, 8 V, for 5 seconds). DFT was accurately measured with the up/down procedure until 3 reversal of defibrillation success or failure occurred. DFTs (mean +/- SD) were extracted and compared using paired t test and analysis of variance. RESULTS: DFTs were 14.6 +/- 11.0 J for Endo and significantly decreased (p < 0.01) when an additional SQ (9.4 +/- 7.2 J) or epicardial patch (8.9 +/- 6.5 J) was added to endovenous lead, without significant difference between Endo + SC and Endo + Epi configurations. CONCLUSIONS: Regarding this important decrease of DFT (respectively -35% for Endo + SC and -39% for Endo + Epi), additional patches should be more often recommended in patients with low safety margin of DFT. In those cases subcutaneous patches should be preferred instead of epicardial patches. Moreover, an additional reason to recommend this attitude could be the possible generator batteries saving.

Animals↗
PubMed1998

[Sub-pectoral implantation of defibrillators: intraoperative data and long-term outcome].

UNLABELLED: The present study examined the perioperative mortality and morbidity and lead-related complications in patients who had a defibrillator with a transvenous lead system and subpectoral implantation of the generator. Fifty-four out of 57 consecutive patients (95%) received a transvenous lead system. One patient had an acceptable defibrillation threshold with an additional subcutaneous patch whereas no sufficient defibrillation threshold was found in another 2 patients. Two patients died due to congestive heart failure after implantation. Perioperative complications were observed in 4 patients (7%) including pericardial effusion, pocket hematoma, injury of the plexus brachialis and a pneumothorax. None of these complications required surgical intervention. Fifty-five patients were discharged from the hospital. During 27 +/- 10 months none of these patients died. Lead-related complications were observed in 3 patients (5.5%) including microdislocation in two and a outer conductor fracture in one of the lead. CONCLUSION: Technical advancement such as a non-thoracotomy lead system and smaller devices have made the onc-incision approach and subpectoral implantation of the ICD generator clinical routine. Nevertheless complications related to the lead system can occur. Therefore frequent controls of patients with ICD are necessary.

Adult↗
PubMed1992

The automatic implantable cardioverter-defibrillator. Long-term clinical experience and outcome at a hospital without an open-heart surgery program.

From November 1982 through April 1989, 111 patients with refractory sustained ventricular tachycardia/fibrillation had the automatic cardioverter-defibrillator implanted at our institution, the first community hospital involved in implantation of such a device. We have reviewed our long-term clinical experience to assess the feasibility, learning curve, and efficacy of device implantation in a facility with cardiac electrophysiology expertise but without open-heart surgery facilities. All patients were considered inoperable or at high risk for other concomitant surgery. Eighty-six patients (77%) underwent uneventful implantation. Nine patients (8%) died prior to hospital discharge. Operative mortality declined from 10.9% to 5.4% during the first half (55 patients; November 1982 through September 1986) and second half (56 patients; October 1986 through April 1989) of the experience. Other postoperative complications occurred in 16 patients (14%), 12 of whom experienced complications during the first half of the experience. At 22 +/- 20 (mean +/- SD) months' follow-up, 78 (76%) of 102 patients discharged were alive, and 24 patients (24%) had died. Fifty patients (49%) had experienced at least one automatic cardioverter-defibrillator discharge associated with hypotensive symptoms. The actuarial incidence of sudden death at 1, 2, and 3 years was 1.2%, 5.5%, and 6.2%, respectively. We concluded that the automatic implantable cardioverter-defibrillator is an effective therapy for refractory ventricular tachycardia/fibrillation and that device implantation at community hospitals with an experienced cardiac electrophysiology team is both feasible and practical.

Adult↗
PubMed1989

Implantable cardioverter-defibrillators (ICDs) 1989: how close are we to the ideal device?

Major technical advances over the last few years have led to significant improvements in implantable cardioverter-defibrillators. Tachycardias can be detected using a number of criteria which include rate, rate of onset, duration, and stability of tachycardia. A number of target tachyarrhythmias can be distinguished in the same patient and differentiated from sinus or other benign tachycardias. Different tachycardias can then be treated with different electrical therapies. Therapies now incorporated in the latest generation of implantable devices include comprehensive antitachycardia pacing techniques, low-energy cardioversion and high-energy cardioversion-defibrillation. Bradycardia support pacing is also incorporated. Improvements in the electrodes used for sensing tachycardia and delivering therapy have resulted in the first implants of devices without the need for thoracotomy. Improvements in capacitor technology have resulted in a gradual reduction in the size of devices in spite of their increasing sophistication. Further research is needed to evaluate different shock charges and waveforms. Tachycardia prevention by implanted devices is also a field of much current research. Thus, though not yet "ideal," the latest generation of implantable cardioverter-defibrillators represents an important therapeutic option in the treatment of ventricular tachyarrhythmias.

Cardiac Pacing, Artificial↗
PubMed1992

A critical appraisal of indications for the implantable cardioverter defibrillator (ICD).

The implantable cardioverter defibrillator (ICD) is a remarkably effective therapy for reducing sudden cardiac death in patients with malignant ventricular arrhythmias. The indications for implantation of the ICD were approved in 1985 by the United States Food and Drug Administration; it could be implanted in patients who have experienced cardiac arrest or in those with recurrent ventricular arrhythmias which are not suppressed by anti-arrhythmic drugs in the electrophysiology laboratory. These established indications have not changed in the last seven years. In the near future, the release of third-generation ICDs (with antitachycardia pacing) will likely further expand indications for the device. Many patients with stable ventricular tachycardia who have not had syncope or cardiac arrest will receive a third-generation defibrillator. Also, three clinical trials now in progress--CABG-PATCH, Multicenter Automatic Defibrillator Implantation Trial (MADIT) and Multicenter Unsustained Tachycardia Trial (MUSTT)--are studying "pre-event" patients with low ejection fraction and electrical instability; some of the patients in each trial are being prospectively randomized to the ICD. Within the next five years we will have a better understanding of the role of ICD therapy in such patients. Until these studies are completed, it is important that the indications for the ICD not be expanded.

Arrhythmias, Cardiac↗
PubMedDate not supplied

The role of catecholamines on intercellular coupling, myocardial cell synchronization and self ventricular defibrillation.

Ventricular fibrillation (VF) is one of the most life threatening events. Although in humans VF is generally sustained (SVF) requiring artificial defibrillation, in various mammals and in some cases in humans VF terminates by itself, reverting spontaneously into sinus rhythm. Since VF is one of the main causes of sudden death, one of the important clinical problems today is if and how we can transform the fatal SVF into a self limited transient one (TVF). From electrophysiological studies carried out on anaesthetized open chest animals, we have found that TVF requires a high degree of intercellular coupling and synchronization. Cardiac myocytes are electrically coupled with adjacent cells. The intercellular coupling is a focus of low electrical resistance which allows rapid transmission of electrical impulses between cells. Any decrease in intercellular coupling decreases the ability of the heart for self defibrillation. The cell-to-cell coupling decreases with age, ischemia, VF and variations in physiological conditions probably due to an increase in intercellular resistance (Ri), widening in the internexal gaps, decrease in electrotonic space constant (lambda) etc. All of these factors are known to be affected by intracellular concentration of free Ca++ ([Ca++]). On the basis of studies carried out on various mammals at different ages, we hypothesized that the ability of the heart to defibrillate depends on the cardiac catecholamine level [CA], during VF. This hypothesis is supported by the facts, known from the literature, that increase in [CA] decreases intracellular free Ca++ concentration, decreases Ri and increases lambda.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The effect of calcium concentration on spontaneous ventricular defibrillation and VF threshold.

In order to investigate the influence of the effective refractory period on spontaneous ventricular defibrillation, isolated rat hearts were perfused with Krebs-Henseleit solution containing 0.5, 2.7 and 5.1 mM calcium. After measuring the fibrillation threshold at spontaneous rate (SR), ventricular fibrillation (VF) was induced during basic ventricular pacing of 110% SR, or the highest rate permitting 1:1 electromechanical coupling. The VF threshold was significantly reduced from 13.6 +/- 3.5 to 7.9 +/- 5.3 and 5.1 +/- 3.4 mA at 0.5, 2.7 and 5.1 mM Ca++ concentrations, respectively. The incidence of spontaneous recovery from VF, induced during basic pacing, was 100%, 83% and 50% at calcium concentrations of 0.5, 2.7 and 5.1 mM, respectively, (p less than 0.01 for the incidences at 0.5 mM versus 5.1 mM Ca++). The incidence of spontaneous defibrillation decreased when the hearts were driven rapidly, with spontaneous recovery rates of 92%, 58% and 0% (p less than 0.0001] for corresponding increases in Ca++ concentration. Induced ventricular fibrillation of fine morphology was frequently observed at 5.1 mM Ca++. It appears that progressive impairment of spontaneous defibrillation is caused by an increase in calcium concentration, this effect being more pronounced at high ventricular rates. Variations in the effective refractory period, caused by alterations in extracellular calcium concentration and differences in intracellular Ca++ accumulation, may account for the above results.

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↗
PubMed2000

[Recurrent ventricular fibrillation after defibrillation in a patient with pacemaker].

HISTORY: A 62-year-old patient was admitted for an operation of a hernia of the right groin in the surgical department. He had a dual chamber pacemaker because of a binodal disease. Pre-operatively the patient was reanimated because of ventricular fibrillation in dilated cardiomyopathy and was defibrillated 12 times, unexpectedly often. DIAGNOSIS: The reason of the repeated ventricular fibrillation was a spike-on-T-phenomenon due to loss of the sensing function of the pacemaker (entrance bloc). TREATMENT: Therefore, the pacemaker was explanted, and the ventricular fibrillation came to an end. The patient recovered. CONCLUSIONS: The repeated defibrillations with the electrodes over the basis and the apex of the heart damaged the pacemaker. The following fibrillation episodes were founded on a spike-on-T-phenomenon. In order to prevent such damage of pacemakers, pacemaker patients should be defibrillated and cardioverted in anterior-posterior position of the electrodes.

Cardiomyopathy, Dilated↗
PubMed1998

[Electroconvulsive therapy and defibrillation in the paper. An analysis of the media].

In our study on Psychiatry, Mass Media and Public Opinion we made a content analysis of newspaper reports on ECT and electric defibrillation. We traced only few special articles on the subject in the 1994 and 1995 CD-Rom versions of the "Der Spiegel", The "Frankfurter Allgemeine Zeitung" (FAZ), the "Neue Zürcher Zeitung" (NZZ) and the "Berliner Tageszeitung" (taz), although the word "Elektroschock" was employed 118 times. Even in high standard newspapers the style of language becomes special when they deal with ECT. The articles are strongly biased and lack informations. In contrast to Defibrillation ECT is not generally accepted. Referring to ECT horror pictures of past psychiatry are cited. The language used is biased and discriminative. Referring to Defibrillation technical details are described and the language is neutral. The social representation of ECT is completely negative.

Electric Countershock↗
PubMed1979

Elevation of ventricular defibrillation threshold in dogs by antiarrhythmic drugs.

Effects of antiarrhythmic drugs upon the threshold delivered energy (TDE) and threshold peak current (TPC) for electrical ventricular defibrillation by damped sinusoidal shocks were investigated in 25 pentobarbital-anesthetized dogs. TDE and TPC were increased by the three antiarrhytmic drugs tested. Bolus injections produced a transient rise and continuous infusions produced a steady rise in difibrillation threshold. The maximal percent elevations in mean defibrillation threshold during the 60 minutes after intravenous drug treatment in groups of n = 5 dogs were: (formula: see text). Accordingly, individuals receiving antiarrhythmic drugs who nonetheless fibrillate may require greater electric shock strength for defibrillation.

Animals↗
PubMed1979

Electrocardiographic and serum enzymic alterations associated with cardiac alterations induced in dogs by single transthoracic damped sinusoidal defibrillator shocks of various strengths.

The safety margin between the strength of shock needed to defibrillate the ventricle and shocks which produce cardiac damage has not previously been reported. This study quantitates the shock intensity required to produce ECG alterations, serum alpha-1LDH and MB CPK isoenzyme elevation and myocardial damage using single transchest damped sinusoidal defibrillator shocks. Shocks of 1 to 20 amperes per Kg. of body weight were applied. Fifty-six dog weighing 2.4 to 15 kilograms were shocked with defibrillator pulses via 10 centimeter diameter electrodes applied to the thorax. Electrocardiograms were taken to be analyzed for arrhythmias, S-T segment changes, and T wave changes. Serum enzyme levels were determined in 25 dogs. Macroscopic and histopathologic studies were conducted on the hearts. Transchest single damped sine wave shocks did not produce microscopically detectable cardiac damage until at least a threefold current overdose was applied. No macroscopic morphologic alterations were observed until at least a sixfold current overdose was applied and no deaths occurred until a twelvefold or greater current overdose was delivered. Incidence and severity of ECG changes, increase in serum enzyme activity, incidence and severity of cardiac damage, and incidence of mortality all correlated positively with shock strength. However, these four adverse effects did not correlate well with each other. Transient ECG changes were very frequent following shock application regardless of the morphologic damage produced, and hence the transient changes have little value as indicators or predictors of damage. Persistent ECG changes were predictive of morphologic changes but were not sensitive enough to detect damage in mildly injured hearts. Likewise, elevated serum cardiac isoenzyme activity was a reliable but insensitive indicator of damage.

Animals↗