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PubMed2004

Microvolt T-wave alternans distinguishes between patients likely and patients not likely to benefit from implanted cardiac defibrillator therapy: a solution to the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II conundrum.

BACKGROUND: In 2003, the Centers for Medicaid and Medicare Services recommended QRS duration as a means to identify MADIT II-like patients suitable for implanted cardiac defibrillator (ICD) therapy. We compared the ability of microvolt T-wave alternans and QRS duration to identify groups at high and low risk of dying among heart failure patients who met MADIT II criteria for ICD prophylaxis. METHODS AND RESULTS: Patients with MADIT II characteristics and sinus rhythm had a microvolt T-wave alternans exercise test and a 12-lead ECG. Our primary end point was 2-year all-cause mortality. Of 177 MADIT II-like patients, 32% had a QRS duration >120 ms, and 68% had an abnormal (positive or indeterminate) microvolt T-wave alternans test. During an average follow-up of 20+/-6 months, 20 patients died. We compared patients with an abnormal microvolt T-wave alternans test to those with a normal (negative) test, and patients with a QRS >120 ms with those with a QRS < or =120 ms; the hazard ratios for 2-year mortality were 4.8 (P=0.020) and 1.5 (P=0.367), respectively. The actuarial mortality rate was substantially lower among patients with a normal microvolt T-wave alternans test (3.8%; 95% confidence interval: 0, 9.0) than the mortality rate in patients with a narrow QRS (12.0%; 95% confidence interval: 5.6, 18.5). The corresponding false-negative rates are 3.5% and 10.2%, respectively. CONCLUSIONS: Among MADIT II-like patients, a microvolt T-wave alternans test is better than QRS duration at identifying a high-risk group and also better at identifying a low-risk group unlikely to benefit from ICD therapy.

Aged↗
PubMed1991

Late results of the left subcostal approach for automatic implantable cardioverter defibrillator implantation.

A left subcostal surgical approach was used to implant an automatic implantable cardioverter defibrillator (AICD) in 48 patients with a history of nonfatal cardiac arrest or documented ventricular tachycardia/fibrillation. Electrophysiologic studies before surgery yielded induction of monomorphic or polymorphic ventricular tachycardia in 40 patients, whereas 8 were noninducible. Mean (+/- standard deviation) age was 58 +/- 12 years. Mean ejection fraction was 33 +/- 16%. Thirty patients (63%) had documented coronary artery disease; 14 patients (29%) had previous coronary bypass surgery. The mean intraoperative defibrillation threshold was 13.8 +/- 6.6 J. In 6 patients, an adjunctive right minithoracotomy was used to position 1 patch over the right atrium and thus optimize the defibrillation threshold. Patients with prior exposure to amiodarone and previous coronary bypass surgery had higher defibrillation thresholds at implantation. Two perioperative deaths occurred. There were no infections. Long-term follow-up yielded a 1- and 5-year survival of 0.88 and 0.58, respectively, and a freedom from sudden cardiac death of 1.0 and 0.97, respectively. The nonthoracotomy, left subcostal surgical approach is safe and effective, provides adequate defibrillation thresholds in most patients, and yields long-term survival comparable to other implantation techniques.

Cardiac Pacing, Artificial↗
PubMed2002

Implantable cardioverter defibrillator implantation rates in the Olmsted County, Minnesota, population: 1989-1999.

Although the efficacy of implantable cardioverter defibrillators (ICDs) has been demonstrated in randomized clinical trials, implantation and survival rates have not been reported for a defined population. We performed a retrospective cohort analysis of Olmsted County, Minnesota residents (n = 70) who received their first ICD between 1 January 1989 and 31 December 1999. The ICD implantation rate increased from approximately 2.5/100,000 (95% confidence interval [CI], 0.9-4.1) in the first 4 years to 11.5/100,000 (95% CI, 6.7-16.2) in the last 2 years. Twenty-three patients (33%) received an appropriate ICD shock during the observation period. Based on these data, ICDs are estimated to reduce total mortality rates in this population by 0.3%. We conclude that, in patients drawn from a community setting with AHA/ACC class I indications for ICD implantation, implantation of ICDs appears to be highly efficacious in aborting potentially fatal events.

Death, Sudden, Cardiac↗
PubMed2003

Determinants of geographic variations in pacemakers and implantable cardioverter defibrillators implantation rates.

Despite the established therapeutic efficacy of pacemakers (PMs) and implantable cardioverter defibrillators (ICDs), marked geographic and national variations in their implant rates have been documented. Tabulation of implant rates and identification of variation patterns are of only modest significance as many factors influence geographic variations. This study examined statistical data regarding implant rates and analyzed the determinants behind these variations. The results showed: (1) the implantation rate of PMs and ICDs depends heavily on national economic status and demographics. (2) Economic factors are an important determinant of implant rates, though high rates were observed in countries with modest economic resources and highly educated physicians and populations. (3) Evaluation of PM and ICD implant rates per million of an overall population, unless based on demography, can lead to significant inaccuracy when comparing different regions and countries. Adjustment of implant rates consistent with demographic parameters is required. (4) Evaluation of the implant rate as appropriate, greater or less than expected in a given country can be achieved by calculation of a "reference" implant rate, and then by its comparison with the actual implant rate. Questions remaining after this analysis are: (1) How do variations in PM and ICD implant rate relate to quality of life, morbidity, and survival? (2) Will overall patient outcomes benefit from a greater implant rate, and is a higher implant rate cost-effective? (3) Should each country attempt to reach a "reference" implant rate, independent of its approach to medicine and level of economic development? These questions can only be answered by prospective randomized trials that allow the development of recommendations based on national needs and resources.

Age Factors↗
PubMed1998

When an AED meets an ICD... Automated external defibrillator. Implantable cardioverter defibrillator.

The chances of prehospital care providers being confronted with a patient with an implantable cardioverter defibrillator (ICD) are increasing and so care providers must receive proper training. Based on observations made during the resuscitation of a patient with an ICD using an automated external defibrillator (AED) some technical features and possible interactions of ICDs and AEDs are highlighted. Furthermore, we discuss the key points of basic knowledge, safety, and treatment protocols for cardiac arrest and other situations required for practical training in the ICD for prehospital care providers.

Adult↗
PubMed1999

Failure of left-sided implantable cardioverter defibrillator implantation due to absence of left brachiocephalic vein.

Implantation of an implantable cardioverter defibrillator by the transvenous approach was impossible from the left side in a patient with on absence of the left brachiocephalic vein; the left subclavian vein was connected by a large left superior intercostal vein to the accessory hemiazygos vein that joined the azygos vein; then the blood flowed into the superior vena cava. Implantation was successfully attempted using the right-sided venous access.

Aged↗
PubMed1991

Implantable cardioverter defibrillator implanted by nonthoracotomy approach: initial clinical experience with the redesigned transvenous lead system.

Standard implantation procedure for the implantable cardioverter defibrillator (ICD) has traditionally required a thoracotomy approach. A newly revised nonthoracotomy defibrillator lead system that uses a single transvenous tripolar endocardial lead alone or in combination with a subcutaneous/submuscular patch lead was introduced into clinical trials in September, 1990. Fourteen patients requiring a cardioverter defibrillator for recurrent sustained ventricular tachycardia (eight patients) or aborted sudden cardiac death (six patients) were evaluated for implantation of this lead system. Primary successful lead system implantation was obtained in nine patients. The remaining five patients had unacceptably high defibrillation thresholds (DFTs) for implantation. One of the nine initially successful implants demonstrated unacceptable DFTs and cross-talk inhibition from a permanent pacemaker necessitating removal of the nonthoracotomy lead system and replacement with a conventional lead system via thoracotomy. All remaining primary implanted patients experienced successful conversion of induced ventricular fibrillation prior to hospital discharge. Continued follow-up and greater experience to confirm the durability and efficacy of the nonthoracotomy AICD lead system are needed.

Aged↗
PubMed1996

The additional hospital costs generated in the management of complications of pacemaker and defibrillator implantations.

The rapid approach of capitated reimbursement mandates that providers examine their practice patterns associated with all surgical procedures. Documentation of (1) the complications associated with these procedures and (2) the additional hospital costs associated with the management of these complications is critical for comprehensive fiscal accountability. This study analyzed (1) the feasibility of obtaining accurate hospital cost data specific for complications and (2) the outcome in terms of fully loaded hospital costs generated in the management of the most common surgical complications associated with pacemaker and nonthoracotomy implantable defibrillator therapies. Between July 1989 and September 1994, a total of 1031 pacemaker and 105 implantable defibrillator procedures were performed by a cardiac surgeon in a tertiary-level teaching hospital setting. The additional fully loaded hospital costs were determined by (1) correlating clinical data from the complete medical record with complete hospital charge data for the admission(s) related to the complication, (2) carving out complication-related charges based on the clinical data, (3) converting complication-related charges to fully loaded costs based on conversion factors in effect at the time of service, and (4) correlating cost with hospital net reimbursement and payor source. The feasibility study determined that accurate and reliable cost data specific to complications can be obtained, although the process was cumbersome and difficult. The outcomes study determined that mean fully loaded complication costs were $4345 +/- $1540 for pacemaker lead revision and $4879 +/- $3167 for implantable defibrillator lead dislodgement, $24,459 +/- $14,585 for pacemaker infection, and $13,736 +/- $12,505 for defibrillator generator system malfunction. The one infected defibrillator cost $57,213 to treat. Costs exceeded reimbursement for almost all Medicare patients with complications in this study, suggesting that similar shortfalls would occur under a capitation scheme. This information is critical to a complete understanding of the financial impact of interventional procedures in a capitated reimbursement environment.

Adult↗
PubMed1997

Comparison of outcome of implantable cardioverter defibrillator implantation in patients with severe versus moderately severe left ventricular dysfunction secondary to atherosclerotic coronary artery disease.

This study was undertaken to assess the feasibility and clinical outcome of implantable cardioverter-defibrillators (ICDs) among patients with coronary artery disease and left ventricular ejection fraction (LVEF) of <20%. The morbidity, mortality, and the long-term survival of 117 patients with LVEF of <20% (group 1) were compared with 321 patients with LVEF of 20% to 40% (group 2). Mortality in the first 30 days after ICD implantation was 0% for group 1 and 0.6% in group 2. Actuarial survival (all cause) at the end of 2, 4, and 5 years were 83%, 70%, and 62%, respectively, in group 1 and 90%, 80%, and 71% in group 2 (p = 0.05). Fifty-five patients (47%) in group 1 and 126 patients (39%) in group 2 received appropriate shocks during follow up. Among the patients in group 1, the overall survival at 2 years after an appropriate shock from an ICD was 92% for patients <60 years of age, 77% for patients ages 60 to 69, and 53% for patients >70 years old. Although the overall survival of patients in group 1 was slightly lower compared with those in group 2, in a multivariate analysis, the EF was not an independent predictor of poor survival. The ICD can be implanted with acceptable operative morbidity and mortality in selected patients with LVEF of <20%.

Aged↗
PubMed1998

Immediate reproducibility of upper limit of vulnerability measurements in patients undergoing transvenous implantable cardioverter defibrillator implantation.

INTRODUCTION: Measurement of the upper limit of vulnerability (ULV) with monophasic T wave shocks has been proposed as a patient-specific measurement of defibrillation efficacy that results in fewer episodes of ventricular fibrillation (VF) than measurement of a defibrillation efficacy curve. METHODS AND RESULTS: We sought to determine the magnitude of variance in ULV in 63 consecutive patients undergoing implantation of an implantable cardioverter defibrillator (ICD). We measured ULV as the strength at or above which VF is not induced when a stimulus is delivered at 310 msec after an 8-beat ventricular pacing drive at 400 msec. Defibrillation threshold (DFT) was measured in patients with an active can device using a biphasic waveform and the binary search method beginning at 12 J. Sixty-three patients were studied; they had a mean age of 62 +/- 12 years and a mean ejection fraction of 35% +/- 15%. Three quarters of patients had an ischemic cardiomyopathy. Each patient underwent 4.5 +/- 0.8 measurements of ULV. Monophasic ULV correlated poorly with biphasic DFT (R between 0.19 and 0.28, P = 0.04 to 0.17). There was no change in ULV between second to third, third to fourth, and first to last measurement in 22% to 41% of patients. The reliability coefficient was 0.87. A ULV > or = 20 J was found in eight patients. The only predictor of high ULV was a high DFT. CONCLUSION: Monophasic ULVs do not closely predict biphasic active can DFTs using a standard protocol. High DFTs were predicted by high ULVs. There was little variation in the acute measurement of ULV between trials. These findings have important implications for using ULV measurements to determine changes in DFTs after interventions. The methodology of determining ULV is critical to its use for predicting DFTs and programming ICDs.

Defibrillators, Implantable↗
PubMed1992

Time to first pulse after automatic implantable cardioverter defibrillator implantation.

Should automatic implantable cardioverter defibrillator (AICD) power sources be explanted and discontinued if they have not pulsed during the first generator life? We have followed 59 patients an average of 23 months (range, 3 days to 8.4 years) after AICD implantation. The indication for AICD implantation was based on clinical dysrhythmia, history of sudden death, and findings at electrophysiologic study. Thirty-eight of 59 patients (64%) had experienced sudden death and 52/58 (90%) were inducible at electrophysiologic study. Excluding 5 inappropriate pulsing episodes, 31 of 59 patients (53%) had 235 pulses (range, 1 to 36; median, 2 pulses). The time to first pulse after implantation ranged from 1 day to 3.5 years with a median time of 2 months. In 6 patients, the first pulsing occurred later than 1 year after AICD implantation. Fifteen generators demonstrating impending power source failure have been replaced in 11 patients. Power source depletion occurred at an average of 24.1 months (range, 8 to 40 months). In 3 patients, the first pulsing occurred after generator depletion and replacement. By univariate analysis, none of 13 variables (sex, age, cardiac disease process, functional class, previous myocardial infarction, sudden death history, ejection fraction, type of dysrhythmia, inducibility with electrophysiologic testing, number of extra stimuli required for induction, left ventricular aneurysm resection, endocardial resection, or concomitant operation) was found to be a predictor of pulsing (p greater than 0.05). We conclude that the majority of patients with pulses after AICD implantation will have them during the first 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Automatic implantable cardioverter defibrillator implantation after previous open heart surgery: subcostal incision and small left anterior thoracotomy.

In order to avoid the risk of major bleeding with redo sternotomy, an alternative surgical approach for the implantation of an automatic implantable cardioverter defibrillation (AICD) is presented. A subcostal incision in combination with a small left anterior thoracotomy was used in three patients. The procedure was easy to perform, considerably shorter than a redo sternotomy and well tolerated by the patient. We recommend this approach for AICD implantation in cases with previous heart operation.

Coronary Artery Bypass↗
PubMed2003

Implications of national guidance for implantable cardioverter defibrillation implantation in the United Kingdom.

To determine the number of patients fulfilling recently issued national guidelines on the use of ICDs in patients with arrhythmias, the authors undertook two observational audits of clinical records. The first audit included patients investigated and treated at a tertiary referral cardiothoracic center during a 1-month period, and the second included patients admitted to the three coronary care units serving a circumscribed district population during a second month. Patient records were audited against the recommendations for ICD implantation made by the National Institute for Clinical Excellence to determine if the patient fulfilled the criteria for ICD implantation. The audit was repeated with the same patient records against the MADIT 2 selection criteria. The audit identified underprovision of ICD therapy in the United Kingdom for a variety of reasons. It also demonstrated that the number of patients fulfilling selection criteria defined by the national guidelines for ICD implantation is far in excess of the numbers predicted. The annual incidence of patients fulfilling national criteria is about 150/million, with an additional "prevalence" of at least 41/million. Applying the less restrictive MADIT II criteria to select patients for ICDs as a primary prevention increased the numbers to 504/million ("new incidence") and 311/million ("prevalence") per year, in excess of the predictions by a factor of between 10 and 25.

Defibrillators, Implantable↗
PubMed2004

Pacemaker and implantable cardioverter defibrillator implantation without reversal of warfarin therapy.

The study evaluated all patients undergoing permanent pacemaker and ICD implantation over a 4-year period to determine if anticoagulated patients required normalization of coagulation factors in the periprocedural period. The study included 1,025 (597 men, 428 women, age 24-100 years, mean 72 years) consecutive patients who underwent device implantation using mostly a percutaneous subclavian approach. The procedures were performed without reversal of anticoagulation in 470 patients with INRs >or= 1.5 at the time of the procedure (mean INR 2.6 +/- 1.0, range 1.5-7.5). The complication rate in the anticoagulated group was similar to those in patients with a normal INR. Routine normalization of coagulation factors prior to pacemaker/ICD placement may not be necessary.

Adult↗
PubMed2000

Therapeutic decision tree for patients with sustained ventricular tachyarrhythmias or aborted cardiac arrest: a critical review of the Antiarrhythmics Versus Implantable Defibrillator trial and the Canadian Implantable Defibrillator Study.

Antiarrhythmic drugs, mainly amiodarone and sotalol, radiofrequency catheter ablation, and the implantable cardioverter defibrillator (ICD) are the 3 therapeutic options in patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Idiopathic VT, incessant VT, frequently recurring, hemodynamically stable VT, and VT based on bundle branch reentry, are candidates for radiofrequency catheter ablation. Patients with high-risk ventricular tachyarrhythmias should receive ICDs as initial therapy. Two studies, the Antiarrhythmics Versus Implantable Defibrillator trial (AVID) and the Canadian Implantable Defibrillator Study (CIDS) have tried to approach the problem of these high-risk ventricular tachyarrhythmias. Although at 3 years, the ICD in AVID demonstrated a significant relative risk reduction over amiodarone of 31.5%, CIDS could not duplicate this finding. At 3 years, the relative risk reduction conferred by the ICD over amiodarone in CIDS was only 13.7%. A careful analysis of both studies suggests that CIDS was insufficiently powered to demonstrate statistically significant benefits similar to those shown by AVID, and furthermore, seemed to include an undetermined number of low-risk VT patients. The problem in the CIDS trial in this regard was the recruitment of patients in whom the inclusion criteria were met by the arrhythmias induced during the electrophysiology stimulation study, but which did not exist in real life. In addition CIDS included 14% of patients with (1) undocumented syncope and inducible monomorphic sustained VT; or (2) long runs of spontaneous nonsustained VT. Under these circumstances, the therapeutic implications of AVID remain unchallenged.

Anti-Arrhythmia Agents↗