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PubMed2003

Preventing sudden death and the use of prophylactic implanted defibrillators.

Implanted defibrillators have become mainstream therapy for the prevention of sudden cardiac death from ventricular tachyarrhythmias. A decade of studies has confirmed the superiority of ICDs over antiarrhythmic drug therapy in prolonging the life of patients with a prior history of sustained VT or VF. More recent studies have compared ICD therapy to drugs or no antiarrhythmic therapy as 'primary prophylaxis' in patients considered at high risk for sudden death or with prior MIs. In selected patients, ICDs lead to important relative and absolute reductions in mortality in patients with no prior history of sustained VT or VF. Clinicians need to carefully consider these studies in their management of patients with CAD and severe LV dysfunction.

Journal Article↗

PubMed2005

Particulate air pollution and nonfatal cardiac events. Part II. Association of air pollution with confirmed arrhythmias recorded by implanted defibrillators.

Implanted cardioverter defibrillators (ICDs) monitor patients for episodes of cardiac arrhythmias and can initiate a therapeutic intervention to restore normal heart rhythm. These devices also record dates, times, and electrograms of these episodes. We examined the effects of air pollution on the incidence of arrhythmias in 195 cardiac patients with ICD devices in the Boston metropolitan area between July 1995 and July 2002. Gaseous air pollutant and meteorologic data were measured on essentially all days, fine particle mass on 80% of the days, and black carbon (BC) on 61% of the days. Date and time of detected arrhythmias, intracardiac electrograms, and therapeutic interventions were downloaded during the patients' regular follow-up visits every 3 months on average. A cardiac electrophysiologist reviewed electrograms recorded before, during, and after the arrhythmias and categorized them into ventricular and supraventricular events. Risk of arrhythmias associated with air pollution was estimated using logistic regression with adjustments for season, temperature, relative humidity, day of the week, and patient. We found increased relative risks of ventricular arrhythmias (VAs) associated with an increase in 2-day mean concentrations for all air pollutants considered, although these associations were not statistically significant. The relative risks of supraventricular arrhythmias (SVAs) increased in association with 2-day mean concentrations for all air pollutants, and this association was significant only for sulfur dioxide (SO2) at 4 ppb (odds ratio [OR] = 1.33; 95% confidence interval [CI] = 1.04, 1.70). The positive associations of VAs and SVAs with particulate matter less than 2.5microm in aerodynamic diameter (PM2.5; also referred to as fine particles), carbon monoxide (CO), nitrogen dioxide (NO2), BC, and SO2 suggest a link with motor vehicle pollutants. We explored patient characteristics that may have identified subjects susceptible to the effects of air pollution. The association of air pollution with SVAs was blunted by regularly prescribed beta-blockers. We found stronger associations of air pollution with VAs for episodes within 3 days of a previous arrhythmia, suggesting that VAs were triggered by air pollution episodes in combination with other factors that raised the patient's underlying risk. Although ICDs are specifically designed to monitor and treat only VAs, these results suggest that air pollution may trigger both VAs and SVAs.

Adult↗

PubMed1999

Impact of the Multicenter Automatic Defibrillator Implantation Trial on implantable cardioverter defibrillator indication trends.

Since publication of the Multicenter Automatic Defibrillator Implantation Trial (MADIT) in 1996, indications for implantation of implantable cardioverter defibrillators (ICDs) have expanded. Initial criticisms of the study have been addressed, including the need to await the conclusion of several additional ICD clinical trials. These other trials have generally shown an improved survival with ICD therapy when compared with antiarrhythmic agents. As a result, ICD implantation volumes have increased worldwide. However, ICD usage has regional variation with 120 implants per million population in the United States, 45 per million in Germany, but only 7 and 8 per million in France and the United Kingdom, respectively. Although many factors affect implant decisions, reimbursement issues are particularly important. Other factors may explain the slower growth in Europe when compared with the United States including greater skepticism regarding MADIT, less industry-sponsored marketing, and lack of unified cardiology society support for the MADIT recommendations. Nevertheless, it is anticipated that > 50,000 ICDs have been implanted worldwide in 1998, with a growing percentage in the countries of Europe.

Anti-Arrhythmia Agents↗

PubMed1998

The cost-effectiveness of automatic implantable cardiac defibrillators: results from MADIT. Multicenter Automatic Defibrillator Implantation Trial.

BACKGROUND: The recently reported Multicenter Automatic Defibrillator Implantation Trial (MADIT) showed improved survival in selected asymptomatic patients with coronary disease and nonsustained ventricular tachycardia. The economic consequences of defibrillator management in this patient population are unknown. METHODS AND RESULTS: Patients were followed up to quantify their use of healthcare services, including hospitalizations, physician visits, medications, laboratory tests, and procedures, during the trial. The costs of these services, including the costs of the defibrillator, were determined in patients randomized to defibrillator and nondefibrillator therapy. Incremental cost-effectiveness ratios were calculated by relating these costs to the increased survival associated with the use of the defibrillator. The average survival for the defibrillator group over a 4-year period was 3.66 years compared with 2.80 years for conventionally treated patients. Accumulated net costs were $97,560 for the defibrillator group compared with $75,980 for individuals treated with medications alone. The resulting incremental cost-effectiveness ratio of $27,000 per life-year saved compares favorably with other cardiac interventions. Sensitivity analyses showed that the incremental cost-effectiveness ratio would be reduced to approximately $23,000 per life-year saved if transvenous defibrillators were used instead of the older devices, which required thoracic surgery for implantation. CONCLUSIONS: An implanted cardiac defibrillator is cost-effective in selected individuals at high risk for ventricular arrhythmias.

Cost-Benefit Analysis↗

PubMed1999

The implantable cardioverter defibrillator and primary prevention of sudden death: the Multicenter Automatic Defibrillator Implantation Trial and the Coronary Artery Bypass Graft (CABG)-Patch Trial.

The Multicenter Automatic Defibrillator Implantation Trial (MADIT) and the Coronary Artery Bypass Graft (CABG)-Patch study were the first 2 randomized trials investigating the usefulness of the implanted cardioverter defibrillator (ICD) for primary prevention of sudden death. Patients enrolled in MADIT and CABG-Patch had never experienced a sustained ventricular tachycardia (VT) but were thought to be at high risk of sudden death. All patients had coronary artery disease and severely suppressed left ventricular ejection fraction. CABG-Patch patients received their ICD during CABG surgery. Most MADIT patients already had received CABG or percutaneous transluminal coronary angiography and had no indication for revascularization procedures at study entry. MADIT patients had nonsustained spontaneous VT and inducible, nonsuppressible VT; CABG-Patch patients had only an abnormal signal-averaged electrocardiogram as an indicator of their arrhythmic risk. CABG-Patch patients did not benefit from ICD implantation, presumably due to the influence of revascularization on ischemia and left ventricular function. In contrast, MADIT patients showed an improved survival by the ICD. MADIT patients had no need for revascularization and, presumably, their risk indicator for arrhythmic events was stronger than the one used in CABG-Patch. MADIT criteria have become a class I indication for ICD implantation and, in the absence of testing for suppressibility of induced VTs, a class IIb criterion for ICD implantation. Screening for MADIT patients is expensive, as only relatively few patients after myocardial infarction fulfill the criteria. Nevertheless, in comparison with amiodarone, treatment of MADIT patients with ICDs seems to be cost-effective, especially if ICDs are implanted transvenously and have the improved battery longevity of the current devices.

Aged↗

PubMedDate not supplied

Sequential pulse defibrillation for implantable defibrillators.

A technique is described that reduces defibrillation threshold for automatic implantable defibrillators, permits either reducing the size of the pulse generator or increasing the effectiveness of the pulse generator, and provides an increased safety factor. Defibrillation threshold was compared in 12 anesthetized dogs with mean (+/- SD) body weight of 21.6 +/- 3.4 kg for two defibrillating modalities: 1) single pulse technique with current flowing from electrodes in the right ventricle to electrodes either in the superior vena cava or on the left ventricular epicardium, and 2) sequential pulse technique. The sequential pulse technique tested uses two pulses and three or four electrodes. Current of the first 5-ms pulse flows from the superior vena caval electrode to an electrode in the right ventricle, and after a 1-ms interval, current of the second pulse flows from electrodes on the left ventricular epicardium to the right ventricular electrode. Ventricular defibrillation threshold was reduced by 56% to 6.3 +/- 1.03 joules (mean +/- SEM) (P less than 0.01). Because defibrillation threshold is less for sequential pulse defibrillation than for conventional techniques, sequential pulse defibrillators can be smaller and more effective than previously available devices.

Animals↗

PubMed2004

[Subpectoral implantable cardioverter defibrillator implantation in a 20 kg-weighted child].

An 11-year-old boy (weight 20 kg, height 124 cm), who was survived from ventricular fibrillation due to hypertrophic cardiomyopathy, admitted to our institution for implantable cardioveter defibrillator (ICD) implantation. We implanted a transvenous single coil lead and a device (Medtronic model 6943, GEM II VR 7229 Cx) in the subpectoral pocket. We selected this system because of less restriction on normal cardiac function, low operative morbidity, and expectation of long-term defibrillation threshold stability. Subpectoral implantation is cosmetically acceptable comparing with abdominal area. Lead insertion by cut-down technique is feasible and recommended to avoid lead-related complications. ICDs are infrequently used in pediatric patients and prospective study with long-term follow-up will be required to ascertain the prognosis for young survivors from sudden cardiac death.

Body Weight↗

PubMed1997

Reproducibility of ventricular fibrillation characteristics in patients undergoing implantable cardioverter defibrillator implantation.

INTRODUCTION: The purpose of this study was to evaluate the immediate reproducibility of local electrogram characteristics recorded during repeated episodes of induced ventricular fibrillation (VF) in patients undergoing implantable cardioverter defibrillator (ICD) implantation. METHODS AND RESULTS: Power spectral analysis (using a fast Fourier transform algorithm) of electrograms recorded during 3 seconds of VF were analyzed in 24 patients undergoing ICD implantation using a Medtronic Transvene lead. Patients had 2 to 7 episodes of VF that were induced during defibrillation threshold testing. VF was induced by burst pacing (n = 20) or T wave shock (n = 4). Simultaneous electrograms during VF were recorded from a Medtronic Transvene lead with the following configurations: (1) a narrow spaced (12 mm) dedicated bipole used clinically for sensing; (2) a unipolar electrogram from the right ventricular coil; and (3) a widely spaced (18.3 mm) integrated bipole using the distal tip and the coil. Intraclass correlation coefficients (ICCs) were determined to examine the reproducibility of these VF characteristics among VF episodes in each patient. Recordings from both bipolar configurations had ICCs from 0.40 to 0.55, whereas unipolar recordings ICCs were below 0.40. Reproducibility was similar for dedicated and integrated recordings. CONCLUSIONS: Frequency characteristics of repeated episodes of VF induced in the same subjects show fair-to-good but not excellent reproducibility. Bipolar recordings were far more reproducible than unipolar recordings, but both bipolar configurations had similar reproducibility. These findings have implications for both the pathophysiology of induced VF and the design of VF detection algorithms.

Adult↗

PubMed1997

Admission to an intensive care unit after transvenous implantable cardioverter defibrillator implantation: analysis of risk factors.

A retrospective review was undertaken of 90 patients admitted to the cardiothoracic intensive care unit and who comprised 47% of all transvenous implantable cardioverter defibrillator operations performed between March 1991 and August 1995. The review aimed to evaluate the necessity for routine postoperative intensive care unit (ICU) admission after implantable cardioverter defibrillator operation. Pre-, intra- and postoperative data were analysed. Eight of 90 patients (9%) subsequently required care unique to the ICU. None of the variables examined, including the Acute Physiology Score (APACHE II system), was helpful in identifying patients who required unique ICU services. Patients undergoing transvenous implantable cardioverter defibrillator surgery are identified as a low risk group requiring in over 90% of cases monitoring services rather than active therapy in an ICU. As no reliable predictors seem to exist to identify the necessity for postoperative ICU admission, cardioverter defibrillator implantations should only be performed in hospitals where adequate facilities are readily available.

APACHE↗

PubMed1993

Can amiodarone pulmonary toxicity be predicted in patients undergoing implantable cardioverter defibrillator implantation?

Implantable cardioverter defibrillator (ICD) implantation is rapidly becoming accepted as primary therapy for malignant ventricular arrhythmias. Many patients undergoing ICD implantation are on concomitant antiarrhythmic drugs to decrease shock frequency, slow tachycardia rate, and suppress supraventricular arrhythmias. Amiodarone is a potent antiarrhythmic agent that is also frequently used in the treatment of patients with refractory ventricular arrhythmias. Ten to forty percent of patients undergoing ICD implantation will also be taking amiodarone. It has been reported to cause pulmonary toxicity in about 5% of patients per year. Acute amiodarone toxicity presenting as adult respiratory distress syndrome has been reported much less frequently. Although perioperative morbidity due to amiodarone has been described, the risk, predictability, and consequences of acute pulmonary toxicity from amiodarone in patients undergoing ICD implantation have not been previously described. We reviewed the records of 99 consecutive patients undergoing ICD implantation at our institution from October 1987 to April 1992. Thirty-nine patients were taking 480 +/- 230 mg of amiodarone (median 400 mg, lower 20th percentile 400 mg, upper 80th percentile 800 mg) for 291 +/- 554 days prior to ICD implantation. Ten patients taking amiodarone developed acute pulmonary toxicity clinically manifesting as diffuse pulmonary infiltrates on chest radiography and adult respiratory distress syndrome with hypoxia (arterial pO2 < 60 mmHg) without evidence of pneumonia or elevated pulmonary capillary wedge pressure (PCW < or = 15 mmHg). Of the 60 patients not taking amiodarone none developed adult respiratory distress syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed2001

Effects of implantable cardioverter defibrillator implantation and shock application on biochemical markers of myocardial damage.

BACKGROUND: Implantable cardioverter defibrillator (ICD) implantation is a common approach in patients at high risk of sudden cardiac death. To check for normal function, it is necessary to test the ICD. For this purpose, repetitive induction and termination of ventricular fibrillation by direct current shocks is required. This may lead to minor myocardial damage. Cardiac troponin T (cTnT) and I (cTnI) are specific markers for the detection of myocardial injury. Because these proteins usually are undetectable in healthy individuals, they are excellent markers for detecting minimal myocardial damage. The objective of this study was to evaluate the effect of defibrillation of induced ventricular fibrillation on markers of myocardial damage. METHODS: This study included 14 patients who underwent ICD implantation and intraoperative testing. We measured cTnT, cTnI, creatine kinase MB (CK-MB) mass, CK activity, and myoglobin before and at definite times after intraoperative shock application. RESULTS: Depending on the effectiveness of shocks and the energy applied, the cardiac-specific markers cTnT and cTnI, as well as CK-MB mass, showed a significant increase compared with the baseline value before testing and peaked for the most part 4 h after shock application. In contrast, the increases in CK activity and myoglobin were predominantly detectable in patients who received additional external shocks. CONCLUSIONS: ICD implantation and testing leads to a short release of cardiac markers into the circulation. This release seems to be of cytoplasmic origin and depends on the number and effectiveness of the shocks applied.

Adult↗

PubMed1989

Right mini-thoracotomy: an adjunct to left subcostal automatic implantable cardioverter defibrillator implantation.

High defibrillation thresholds are encountered in some patients during implantation of the automatic implantable cardioverter defibrillator (AICD). In a consecutive series of 52 patients with AICD implants, 46 had allepicardial implants by left subcostal thoracotomy, and 8 of these patients had thresholds greater than 30 J. Placement of an apicolateral large left ventricular patch and an extrapericardial large right atrial patch electrode through a limited right thoracotomy produced substantial reduction in their thresholds. Especially in patients who have had previous intrapericardial operations, this technique provides a simple solution to the problem of high thresholds.

Electric Countershock↗

PubMed2005

Implantable cardioverter defibrillator implantation in children in The Netherlands.

UNLABELLED: To evaluate the indications, underlying cardiac disorders, efficacy and complications involved with implantable cardioverter-defibrillators (ICDs) in paediatric patients in The Netherlands, the records of all patients aged 18 years or younger who underwent ICD placement were reviewed retrospectively. Between January 1995 and September 2002, 23 patients (11 males, 12 females; median age 12 years, range 6 months to 16 years) underwent ICD implantation. The ICD was implanted for aborted sudden cardiac death ( n = 14), syncope ( n = 5) or for primary prevention of sudden cardiac death ( n = 4). Underlying cardiac disorders were electrical diseases ( n = 16), hypertrophic or dilated cardiomyopathy ( n = 4) and congenital cardiac malformations ( n = 3). Five patients had an epicardially placed ICD, while 18 underwent a transvenous approach. The generator was placed in an abdominal position in eight patients, whereas it was placed in the subpectoral region in 15. There was no early mortality. Median hospital stay was 5 days (range 2-30 days). Median follow-up time was 29 months (range 1 month to 7 years). Seven patients experienced an inappropriate shock after a median period of 7 months; five patients an appropriate shock after a median period of 3 months. The reasons for inappropriate shock were supraventricular tachycardia ( n = 1), sinus tachycardia ( n = 4) or T-wave sensing (n = 2). One patient with malignant long QT syndrome died of intractable arrhythmias and irreversible cardiomyopathy. Generator replacement was necessary in four patients after 28, 44, 51 and 54 months respectively. CONCLUSION: Implantable cardioverter-defibrillator implantation in paediatric patients is a safe procedure with a good medium-term outcome. The most serious problem is the occurrence of a significant number of inappropriate shocks.

Adolescent↗

PubMed2004

Anesthetic management of cardiac tamponade after dual-chamber implantable cardioverter defibrillator implantation in a patient with dilated cardiomyopathy.

We report a case of cardiac tamponade in a patient with dilated cardiomyopathy after undergoing dual-chamber implantable cardioverter-defibrillator (ICD) implantation. General anesthesia was required for subxiphoid pericardiotomy. Although the occurrence rate of adverse events with ICDs has been reported to be high, the acute onset of significant cardiac tamponade is uncommon as a short-term complication of ICD implantation. We describe our anesthetic management of cardiac tamponade in the ICD patient with dilated cardiomyopathy.

Adult↗

PubMed2002

Effects of implantable cardioverter defibrillator implantation and shock application on serum endothelin-1 and big-endothelin levels.

The incidence of ventricular tachyarrhythmias in the early post-operative period following implantable cardioverter-defibrillator (ICD) implantation is relatively high compared with that in control periods. Since endothelin-1 (ET-1) has been proven to be an endogenous arrhythmogenic substance, we investigated the changes in serum ET-1 and big-ET levels in patients undergoing ICD implantation. Serum concentrations of ET-1 and big-ET were measured in 14 patients with various heart diseases before the operation, as well as 1 min and 1 h after the last shock therapy. Big-ET levels and the sum of ET-1 and big-ET levels were unchanged immediately after the operation, but had increased significantly by 1 h after implantation (before, 1.57+/-0.61 pmol/l; 1 min, 1.86+/-0.87 pmol/l; 1 h, 4.29+/-1.65 pmol/l for big-ET; before, 3.44+/-1.07 pmol/l; 1 min, 3.79+/-1.29 pmol/l; 1 h, 6.36+/-2.03 pmol/l for big-ET+ET-1). There was a significant correlation between left ventricular ejection fraction and big-ET level measured 1 h after the last shock delivery (r=-0.542, P<0.05). We conclude that the increased big-ET level observed 1 h after the last induction and shock therapy of ventricular fibrillation might have a pathophysiological role in the increased incidence of post-operative spontaneous ventricular arrhythmias.

Aged↗

PubMed1991

Retrospective analysis of patients undergoing one- or two-stage strategies for myocardial revascularization and implantable cardioverter defibrillator implantation.

Internal defibrillation leads were placed at time of coronary revascularization in 79 patients. In 34, an implantable cardioverter defibrillator (ICD) was placed simultaneously (group I). A two-stage strategy (selective implantation of the ICD in patients with postoperative spontaneous or inducible ventricular tachycardia [VT]) was followed in 45 patients (group II). Group I patients had failed more antiarrhythmic drug trials (2.9 +/- 1.6 vs 1.5 +/- 1.6; P = 0.02), including amiodarone (62% vs 20%; P less than 0.001). There were four operative deaths in each group. Postoperatively, VT was present in 27 group II patients (60%), 25 of whom received an ICD (two refused device implantation). Patients with postoperative VT had a lower left ventricular ejection fraction than those without VT (33 +/- 9 vs 47 +/- 16; P = 0.01). Actuarial survival at 1, 2, and 3 years was 88 +/- 6, 88 +/- 7, and 88 +/- 10 in group I; and 83 +/- 6, 76 +/- 7, and 76 +/- 11 in group II (NS). No patient without an ICD (based on the postoperative electrophysiological study [EPS]) died suddenly. Five patients (6%) had ICD system infection. Sudden death was largely prevented by either strategy, but relatively high rates of operative mortality and ICD system infection were observed. Prospective studies should identify patients more likely to benefit from one or another strategy.

Aged↗

PubMed1994

Clinical predictors of successful implantable cardioverter defibrillator implantation.

Successful implantation of an implantable cardioverter defibrillation system is critically dependent on demonstration that the lead system to be implanted can defibrillate reliably. Defibrillation efficacy in turn is dependent on several sets of factors that include: (1) defibrillation technique and the lead system being tested; (2) defibrillation testing protocol and criteria for implantation; and (3) clinical variables that may be intrinsic to the patient or extrinsic factors to which the patient is being exposed. Existing clinical data are limited but suggest that poor left ventricular function is the clinical variable most consistently associated with poor defibrillation efficacy and a failure to meet implant criteria of the epicardial lead systems. Antiarrhythmic drugs may elevate the defibrillation threshold, but evidence that this has important clinical ramifications on implantation success rates is very limited and incomplete.

Anti-Arrhythmia Agents↗

PubMed2000

Prophylactic implantable cardioverter defibrillator trials: MUSTT, MADIT, and beyond. Multicenter Unsustained Tachycardia Trial. Multicenter Automatic Defibrillator Implantation Trial.

MUSTT and MADIT have clearly shown the survival benefit of an implantable cardioverter defibrillator (ICD) in patients with previous myocardial infarction, left ventricular ejection fraction < or = 0.40, and nonsustained ventricular tachycardia (VT), and who have had sustained VT induced at electrophysiology study. Progress in primary prevention of sudden cardiac death (SCD) depends on a concerted effort by clinicians to identify and appropriately treat MUSTT/MADIT-type patients; further research to more precisely define patient subgroups at risk for SCD and the willingness of industry to develop a lower priced ICD for prophylactic use are needed.

Clinical Trials as Topic↗