AJCC
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

American Journal of Critical Care. 2008;17: 443-452
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Respond to This Article
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in AJCC
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Right arrow Take the CE Test
Citing Articles
Right arrow Citing Articles via HighWire
Google Scholar
Right arrow Articles by Chapa, D. W.
Right arrow Articles by Bardy, G. H.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chapa, D. W.
Right arrow Articles by Bardy, G. H.

CE Article

Reducing Mortality With Device Therapy in Heart Failure Patients Without Ventricular Arrhythmias

By Deborah W. Chapa, PhD, ARNP-BC, Hyeon-Joo Lee, RN, MS, ANP-C, Chi-Wen Kao, RN, PhD, Erika Friedmann, PhD, Sue A. Thomas, RN, PhD, Jill Anderson, RN, BSN and Gust H. Bardy, MD. Deborah W. Chapa is an assistant professor at Florida Gulf Coast University, Fort Myers, Florida. Hyeon-Joo Lee is a doctoral student, Erika Friedmann is a professor, and Sue A. Thomas is assistant dean of the PhD program and a professor at the University of Maryland School of Nursing, Baltimore, Maryland. Chi-Wen Kao is an assistant professor, School of Nursing, National Defense Medical Center, Taipei, Taiwan. Jill Anderson is director of clinical affairs and Gust H. Bardy is president of the Seattle Institute for Cardiovascular Research, Seattle, Washington.

Corresponding author: Sue A. Thomas, RN, PhD, University of Maryland School of Nursing, 655 W. Lombard St, Baltimore, MD 21201 (e-mail: Thomas{at}son.umaryland.edu).


   Abstract
Top
 Abstract
Devices
 Population Characteristics
 Study Design
 Results
 Nursing Implications
 Conclusion
 References
 
Use of device therapy to prevent sudden cardiac death in patients with heart failure is expanding on the basis of evidence from recent clinical trials. Three multicenter prospective clinical trials—Sudden Cardiac Death in Heart Failure (SCD-HeFT); Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION); and Cardiac Resynchronization-Heart Failure (CARE-HF)—were conducted to determine the effectiveness of devices in reducing mortality in patients with heart failure who did not have a history of ventricular arrhythmias. The 3 trials varied in the devices used, the population of patients included, and the study designs. In SCD-HeFT, implantable cardioverter defibrillators were more effective than pharmacological therapy in preventing mortality among patients with mild to moderate heart failure. In COMPANION, cardiac resynchronization therapy alone and cardiac resynchronization therapy plus an implantable cardioverter defibrillator were more effective than optimal drug treatment in reducing morbidity and all-cause mortality in patients with moderate to severe heart failure. In CARE-HF, cardiac resynchronization therapy alone was more effective than optimal drug treatment in reducing all-cause mortality in patients with moderate to severe heart failure. No direct comparison of the devices used has been done. These 3 clinical trials provide clear evidence that device therapy is beneficial for some patients with heart failure, even patients who do not have a history of ventricular arrhythmia.

Notice to CE enrollees:
A closed-book, multiple-choice examination following this article tests your understanding of the following objectives:
  1. Describe the pathophysiology of heart failure leading to sudden cardiac death.
  2. Recognize different devices used to treat patients with heart failure.
  3. Understand how pacemaker/ICD devices can decrease the overall mortality of patients with heart failure.
To read this article and take the CE test online, visit www.ajcconline.org and click "CE Articles in This Issue." No CE test fee for AACN members.

As mortality from myocardial infarction has decreased because of improved treatment, the number of persons living with heart failure has increased. Heart failure is the only major cardiovascular disorder that is increasing in incidence and prevalence; roughly 5 million people in the United States have this disorder.1 Heart failure is a major cause of sudden cardiac death (SCD).2 More than half of the deaths due to heart failure are from SCD; the remainder are due to progressive heart failure.3–5 The most important preexisting condition and the best predictor of SCD is left ventricular dysfunction, the underlying cause of heart failure.6,7 Ventricular tachycardia reentry circuits occur when the left ventricle is enlarged because of ischemia, scarring, or muscle stretching. These myocardial changes in patients with heart failure promote conduction delays and lead to ventricular arrhythmias.


Heart failure is the only major cardiovascular disorder that is increasing in incidence and prevalence.

 

Pacemakers have been the standard treatment for heart block since 1958. The technology for pacemakers has evolved from simple pacing devices to biventricular or cardiac resynchronization devices. These new devices that coordinate the contraction of the ventricles and improve cardiac output are used in a select group of patients with heart failure.8 In the late 1960s, the implantable cardioverter defibrillator (ICD) was developed to treat patients at risk for SCD. The first successful implantation in a human occurred in 1980. Since then, ICD technology has continued to evolve. Use of device therapy to prevent SCD and to correct dyssynchrony in patients with heart failure is expanding on the basis of evidence from recent clinical trials. Left ventricular dyssynchrony results from intraventricular conduction abnormalities evidenced by a wide QRS on electrocardiograms. The most common intraventricular conduction delay is left bundle branch block, which occurs in as many as 25% of patients with moderate to severe heart failure.9

Three multicenter prospective clinical trials—Sudden Cardiac Death in Heart Failure (SCD-HeFT)10; Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION)11; and Cardiac Resynchronization-Heart Failure (CARE-HF)12—addressed the prophylactic effectiveness of devices in decreasing mortality in patients with heart failure without ventricular arrhythmias.

These 3 trials all provide evidence of device effectiveness but do not conclusively indicate which device is superior in preventing mortality in patients with heart failure.

The 3 trials varied in the devices used, study designs, and patients’ level of disease severity. All 3 trials showed decreased mortality with devices in patients with heart failure without electrical disturbances. These trials were the first demonstrations of the effectiveness of devices for patients without previous ventricular arrhythmias. In this article, we review and clarify the results of these 3 trials. We review the similarities and differences in the studies and discuss the nursing implications of the findings.


   Devices
Top
 Abstract
 Devices
Population Characteristics
 Study Design
 Results
 Nursing Implications
 Conclusion
 References
 
The first major difference in these studies is the devices that were used. Understanding these 3 trials requires an understanding of the devices and the therapeutic goals. A single-chambered ICD was used in SCD-HeFT. With this device, a single lead is inserted into the right ventricle (Figure 1Go). The tip of the lead has a total of 4 electrodes: 2 small ones to monitor heart rate and rhythm and 2 large ones to deliver high-energy shocks when ventricular tachycardia or ventricular fibrillation occurs. ICDs have pacing capabilities as well as shocking capabilities.13


Figure 1
View larger version (96K):
[in this window]
[in a new window]

  		Figure 1 Lead placement for single-chamber implantable cardioverter defibrillator. Large arrow indicates lead placed in right ventricle; double arrows represent interactions of the 2 monitoring electrodes and the 2 shocking electrodes.
Reprinted with permission of Medtronic, Inc, Minneapolis, Minnesota.

 
The single-chamber ICDs used in SCD-HeFT were programmed to prevent untoward effects of pacing in patients with heart failure who had not had previous life-threatening arrhythmias. Right ventricular pacing may produce iatrogenic left bundle branch block with resulting electrical and mechanical changes that may exacerbate heart failure. In SCD-HeFT, ICDs were programmed to pace only if the intrinsic rate was less than 34/min. The goal of single-lead ICD therapy was to shock the heart if it went into ventricular tachycardia and to prevent SCD.

CRT devices were used in both COMPANION and CARE-HF. A CRT device is a special type of pacemaker that uses 3 leads: 1 in the right atrium, 1 in the right ventricle, and 1 in the left lateral ventricular epicardium (Figure 2Go). The leads coordinate the pacing of the left ventricle with the pacing of the right ventricle and compensate for disease-induced delays in cardiac electrical activation. The CRT pacer is a pacing-only, nonshock device. The goal of CRT is to reduce cardiac dyssynchrony and thereby improve left ventricular systolic function and decrease patients’ signs and symptoms.11


Figure 2
View larger version (38K):
[in this window]
[in a new window]

  		Figure 2 Lead placement for a biventricular pacing system.
Reprinted with permission of Boston Scientific Corporation, Natick, Massachusetts.

 
CRT-Ds were used in the COMPANION study. A CRT-D device combines a CRT pacer and a dual-chamber ICD. A CRT-D is a pacing and shock-providing device. A dual-chambered ICD (2-lead system) has an additional lead in the right atrial endocardium (Figure 3Go). The functions of this lead are detection of atrial tachycardia and atrial fibrillation, anti-tachycardia pacing, and cardioversion. The functions of the lead in the right ventricle are detection of ventricular tachycardia and ventricular fibrillation, antitachycardia pacing, cardioversion, and defibrillation. Both leads can detect and provide pacing for bradycardia.


Figure 3
View larger version (83K):
[in this window]
[in a new window]

  		Figure 3 Lead placement for a cardiac resynchronization therapy pacer plus an implantable cardioverter defibrillator.
Reprinted with permission of Medtronic, Inc, Minneapolis, Minnesota.

 
With a CRT-D inserted, antitachycardial intervention will slow the heart rate, a situation that can lead to a ventricular arrhythmia and result in an appropriate shock from the device. The ability of a CRT-D to provide a shock in this situation contrasts with that of a CRT pacer, which has no capacity to terminate ventricular arrhythmias that occur when the heart rate is reduced. The goals of treatment with CRT-Ds are to decrease left ventricular dyssynchrony, improve left ventricular systolic function, provide atrial and ventricular pacing, and decrease the risk of SCD due to ventricular tachyarrhythmia.


   Population Characteristics
Top
 Abstract
 Devices
 Population Characteristics
Study Design
 Results
 Nursing Implications
 Conclusion
 References
 
The 3 trials had similar patient recruitment criteria for left ventricular ejection fractions (LVEF <35%) but varied in criteria for patients’ perceptions of the severity of their heart failure (New York Heart Association [NYHA] classification) and for the degree of cardiac dyssynchronization (as indicated by the QRS interval). Understanding differences and commonalities in the findings of the 3 trials requires understanding the severity of heart failure and degrees of cardiac dyssynchrony in the study participants. Table 1Go provides a summary of the inclusion criteria for each study.


View this table:
[in this window]
[in a new window]

  		Table 1 Criteria for inclusion and exclusion of patients in the 3 clinical trials

 
The NYHA functional classification system is used to evaluate patients’ reports of the signs and symptoms of their heart failure during everyday activities (Table 2Go). Most patients in SCD-HeFT had less severe heart failure (70% NYHA class II) than did the patients in the other 2 trials. Most patients in COMPANION and CARE-HF had signs and symptoms of more severe heart failure and included patients with NYHA class III (82%–94%) and class IV heart failure. None of the trials included patients with NYHA class I heart failure, only SCD-HeFT included patients with NYHA class II heart failure, and only a few patients in COMPANION and CARE-HF had NYHA class IV heart failure.


View this table:
[in this window]
[in a new window]

  		Table 2 Criteria for New York Heart Association classes of heart failurea

 

More than half of the deaths from heart failure are due to sudden cardiac death.

 

Cardiac electrical dyssynchrony is reflected by prolonged QRS duration. Limits for the QRS duration differed in the 3 trials. In SCD-HeFT, prolonged QRS duration was not an inclusion criterion because the trial was not a study of resynchronization of the ventricles. In SCD-HeFT, the QRS duration was normal in some patients and prolonged in others. Prolonged QRS duration was an inclusion criterion for both COMPANION and CARE-HF. However, participants in all 3 trials had prolonged QRS, with intervals of 120 milliseconds or longer. The median QRS intervals were almost identical in CARE-HF and COMPANION (160 milliseconds) and were much shorter in SCD-HeFT. In SCD-HeFT, the median QRS duration was 120 milliseconds or less in more than 60% of the participants. Approximately 30% of all patients with heart failure have prolonged QRS.15,16

An inclusion criterion for all 3 trials was an LVEF of 35% or less. LVEF is often used as an index of ventricular function. It is defined as the percentage of total ventricular volume ejected during each contraction [(stroke volume/end-diastolic volume) x 100]. Fractions greater than 55% are considered normal.13 Patients with systolic dysfunction causing heart failure have LVEFs less than 40%.


   Study Design
Top
 Abstract
 Devices
 Population Characteristics
 Study Design
Results
 Nursing Implications
 Conclusion
 References
 
All 3 studies were multicenter, randomized clinical trials. Randomization equalizes the characteristics of the patients across treatments within a trial. The effectiveness of the randomization is confirmed by comparison of the patients’ characteristics in each treatment arm. Equivalent samples were achieved in each treatment arm in all 3 trials. In all 3 trials, outcomes were analyzed according to intention to treat. Therefore, each patient was assigned to a treatment group at randomization, and the patient’s data remained in that group, even if the patient changed treatments or did not adhere to treatment. This design is intended to minimize the potential bias in data that could occur if uncomfortable treatments cause a large number of patients to drop out of the study.17

The SCD-HeFT was the only placebo-controlled trial. It was designed to test the hypotheses that amiodarone or a shock-only, single-lead ICD would decrease the risk of death due to any cause in patients with mild to moderate heart failure (NYHA class II and class III).

From September 1997 to July 2001, a total of 2521 patients with heart failure were randomized to treatment with amiodarone, placebo (double blinded), or shock-only single-lead ICD therapy. Patients at each clinical site were stratified according to ischemic versus nonischemic cause of heart failure and NYHA class to ensure equal proportions of cause of heart failure and NYHA class within each treatment group. All patients also received OPT. The primary end point of SCD-HeFT was all-cause mortality. Of the 3 trials, SCD-HeFT had the longest follow-up, from 24 to 72.6 months for survivors. Median duration of follow-up was 45.5 months. Analyses were performed according to the intention-to-treat principle. Differences in mortality were examined by comparing amiodarone with placebo and ICD with placebo.

The COMPANION investigators tested the hypothesis that prophylactic CRT with or without an ICD reduces mortality and morbidity of patients with moderate to severe heart failure (NYHA class III and class IV) and prolonged QRS duration. In COMPANION, from January 2000 to December 2002, a total of 1520 patients with heart failure were randomized to 3 treatment arms: OPT only (n = 308), CRT-D (n = 595), and CRT only (n = 617). Approximately double the number of control (OPT) patients were randomized to each of the treatment arms. All patients who received devices also received OPT. The primary end point was a composite of all-cause mortality and hospitalization for any cause. The secondary end point was all-cause mortality. All analyses were conducted according to the intention-to-treat principle. The median duration of follow-up for the primary end point was shorter in the OPT-only group (11.9 months) than in the CRT-D (15.7 months) and CRT-only (16.2 months) groups. The small number of patients in the usual-care group and the shorter follow-up in this group limit the ability to compare each treatment with usual care while maintaining the ability to compare the treatments with each other.

CARE-HF was designed to test the hypothesis that CRT decreases complications and mortality in patients with moderate to severe heart failure (NYHA class III and class IV) who have prolonged QRS duration. From January 2001 to March 2003, a total of 813 patients were randomized to OPT or OPT plus CRT. The primary end point was a composite of all-cause mortality and unplanned hospitalization for major cardiovascular events. Follow-up ranged from 18.0 to 44.7 months, with a mean of 29.4 months. Statistical analyses were conducted according to the intention-to-treat principle.

SCD-HeFT was the largest trial; it had a total of 2521 patients, more than 825 patients in each treatment group, and the longest duration of follow-up. In SCD-HeFT, the larger sample size allowed power for comparison of the placebo group with each treatment group. The primary sponsor of SCD-HeFT was the National Heart, Lung, and Blood Institute. COMPANION was sponsored by Guidant Corporation (now part of Boston Scientific Corp, Natick, Massachusetts). Medtronic, Inc (Minneapolis, Minnesota) sponsored the CARE-HF study. Industry-sponsored trials have smaller sample sizes and shorter follow-ups and emphasize comparisons between treatments rather than hypothesis testing.


Devices decrease mortality in patients with heart failure without electrical disturbances.

 

Despite the overrepresentation of women among patients with heart failure, only 23% to 33% of the patients in the trials were women. Mean LVEF in the treatment arms of the trials ranged from 20% to 25%.

In all 3 trials, all-cause mortality was determined for patients treated with devices. Survival analysis was used to compare the relative risk of all-cause mortality between OPT and devices. In SCD-HeFT, all-cause mortality was the primary end point, and analyses were adequately powered. Subgroup analyses as well as all-cause mortality comparisons in CARE-HF and COMPANION were secondary end points and lacked adequate power to accept null hypotheses. Thus, if no significant difference is found between the subgroups, we cannot conclude that no difference exists.


   Results
Top
 Abstract
 Devices
 Population Characteristics
 Study Design
 Results
Nursing Implications
 Conclusion
 References
 
The primary outcome variable of SCD-HeFT was all-cause mortality. ICD therapy reduced all-cause mortality by 23% compared with placebo. Amiodarone therapy did not reduce all-cause mortality compared with placebo. In patients with NYHA class II heart failure, ICDs resulted in a significant 46% reduction (P < .05) in all-cause mortality compared with placebo treatment. In patients with NYHA class III heart failure, ICDs did not result in reductions in all-cause mortality, but the results were inconclusive because of the small sample size.

Planned subgroup analyses in SCD-HeFT indicated that ICDs were significantly more effective than placebos for men and for patients who were less than 65 years old, had an LVEF less than 30%, had a QRS interval greater than 120 milliseconds, had ischemic heart failure, or were taking β-blockers. The effectiveness of ICD therapy vs placebo in SCD-HeFT could not be refuted or established in smaller groups, including women and patients who were more than 65 years old, had an LVEF between 30% and 35%, had a QRS duration less than 120 milliseconds, had nonischemic heart failure, or were not taking β-blockers.

In COMPANION, CRT-D significantly reduced all-cause mortality by 36% compared with OPT. CRT alone reduced all-cause mortality by 24%; this reduction was not significant. Because all-cause mortality alone was the secondary end point and the number of deaths was small, the apparent lack of effectiveness of CRT alone is not conclusive. The primary end point in COMPANION, a composite of all-cause mortality and hospitalization because of heart failure, was reduced significantly by 19% in the CRT-only group and 20% in the CRT-D group compared with the OPT-only group.

In the COMPANION trial, subgroup analyses were conducted to compare all-cause mortality of patients with CRT-D and patients with OPT only. In patients with NYHA class III heart failure, compared with OPT, CRT-D resulted in a significant 46% reduction in all-cause mortality. In patients with NYHA class IV heart failure, no reductions in all-cause mortality were found with CRT-D, but the results were inconclusive because of the small sample size. CRT-D was significantly more effective than OPT for men and for patients who were less than 65 years old, had an LVEF less than 20%, had a QRS interval greater than 147 milliseconds, or had nonischemic cardiomyopathy. The effectiveness of CRT-D compared with OPT in COMPANION could not be established in smaller groups including women and patients who were more than 65 years old, had an LVEF between 20% and 35%, had a QRS duration between 120 and 147 milliseconds, and had ischemic cardiomyopathy. Similar comparisons were not presented for the CRT-only patients.

In CARE-HF, CRT significantly reduced all-cause mortality by 36% compared with OPT. CRT significantly reduced all-cause mortality and unplanned hospitalization for major cardiovascular events by 37% and all-cause mortality and any hospitalization with worsening heart failure by 46%. Subgroup analyses were not done in CARE-HF. CRT reduced the intra-ventricular mechanical delay, the end-systolic volume index, and the area of the mitral regurgitant jet and increased LVEF (P values <.01) compared with OPT.

SCD-HeFT and COMPANION provided conclusive evidence that devices were effective at reducing all-cause mortality in patients with low LVEF and no ventricular arrhythmias. In SCD-HeFT, compared with placebo, ICD significantly decreased mortality in patients with an LVEF of 35% or less. In COMPANION, compared with OPT, CRT-D significantly decreased mortality in patients with an LVEF of 20% or less and a prolonged QRS duration. In all 3 trials, devices were effective at reducing all-cause mortality in patients with a QRS duration of 120 milliseconds. SCD-HeFT was the only trial in which an antiarrhythmic medication was compared with a placebo. The results showed conclusively that amiodarone is not effective at reducing all-cause mortality in patients with heart failure.18

None of the 3 trials included evaluation of device therapy for patients with NYHA class I heart failure. Currently, the effectiveness of ICD and CRT-D in out-patients with NYHA class I and class II heart failure is being addressed in the Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy study.19 The results of SCD-HeFT showed that ICDs were effective in decreasing all-cause mortality in patients with NYHA class II heart failure. The results of COMPANION and CARE-HF indicated that CRT and CRT-D are effective at decreasing all-cause mortality in patients with NYHA class III heart failure. The effectiveness of devices for decreasing all-cause mortality in patients with NYHA class IV heart failure was not evaluated adequately in any of the 3 trials.

The primary end points in COMPANION and CARE-HF were combined all-cause mortality and hospitalization. With the short duration of follow-up and low mortality rate in these trials, power was not sufficient to examine all-cause mortality alone.

The combination of differences in the 3 trials and the lack of direct comparisons between ICD, CRT alone, and CRT-D make it impossible to determine the appropriate device for patients with heart failure without ventricular arrhythmias. In CARE-HF, CRT alone was more effective than OPT. In COMPANION, CRT-D was more effective than OPT; CRT alone was examined, but the findings were inconclusive. SCD-HeFT was the only trial in which devices were used in patients without ventricular arrhythmias and with a QRS less than 120 milliseconds. ICDs were effective in this group, but CRT alone or CRT-D was not investigated. Thus, the most appropriate device for 70% of the patients with heart failure without prolonged QRS has yet to be determined.


   Nursing Implications
Top
 Abstract
 Devices
 Population Characteristics
 Study Design
 Results
 Nursing Implications
Conclusion
 References
 
More than 1 million patients with heart failure are now eligible to receive device therapy. The American College of Cardiology and the American Heart Association recommend the insertion of ICDs and CRT pacers, depending on the patient’s stage of heart failure (Table 3Go). To receive device therapy, a patient must be in optimally stable condition with pharmacological treatment and have a life expectancy of more than 1 year.20 These recommendations reflect changes in Medicare and Medicaid services as a result of SCD-HeFT.10,21


View this table:
[in this window]
[in a new window]

  		Table 3 Device therapy recommendations according to the 4 stages used to categorize heart failure from least (stage A) to most (stage D) severe

 
Device Complications
Complications associated with device therapy were reported in all 3 trials. In SCD-HeFT, complications from ICDs occurred in 5% of the patients at implantation and in 9% later during the trial. These complications were listed as events that required surgical correction, hospitalization, or new and otherwise unanticipated drug therapy. In COMPANION, complications related to implantation occurred in 10% of patients in the CRT group and in 8% of patients in the CRT-D group. These complications were coronary venous dissection, coronary venous perforation, and coronary venous tamponade. In CARE-HF, events related to implantation of the CRT pacer included problems with lead placement (24 patients), coronary sinus dissection (10 patients), pocket erosion (8 patients), pneumothorax (6 patients), and device-related infection (3 patients).


Complications of device implantation increase as the complexity of devices increases.

 

As shown in the 3 clinical trials and other studies, the complication rate of device implantation increases as the complexity of devices increases. After inappropriate shocks, which occurred in 12% of 440 consecutive patients receiving ICD therapy, were excluded, complications occurred in 22% of 356 patients who received single-chamber ICDs, 27% of 51 patients who received dual-chamber ICDs, and 35% of 43 patients who received CRT-Ds.22,23

After device insertion, complications can be associated with the leads or with the device generator. Lead complications include lead dislodgement, loose setscrew, lead fracture, lead insulation defect, and fluid within the ICD connector.22,24,25 Complications or problems related to the device generator include malfunction during testing, premature battery depletion, erosion of pulse generator, and manufacturer recall.22 Chronic health problems such as chronic nerve damage, diaphragmatic stimulation, fluid accumulation/seroma, infection of the pocket/system, keloid formation, venous thromboembolism, and endocarditis also may occur after the device has been in place for some time.13

The list of possible complications is extensive, but each type of complication occurs infrequently. The most common complications or problems are lead-related complications and inappropriate shocks, each of which occur in 12% of recipients; procedure-related complications, which occur in 10%; generator-related complications, which occur in 6%; and manufacturer recall, which occurs in 4%.22

Patient and Family Education
Education of patients, health professionals, and the public will help protect patients with devices from untoward complications due to exposure to electromagnetic interference. Unshielded electric and magnetic signals can inhibit or trigger the devices. Pacemakers, including CRT pacers, will pace at fixed frequencies when their electronic safety circuits are activated. Pacemakers also may wrongly interpret electric currents induced by magnetic signals and may not pace as a result. Similar problems occur with ICDs.26

Antitheft detectors used in stores and libraries produce electromagnetic interference fields that also may affect the operation of devices. Quickly passing through the antitheft systems does not cause a threat because the interference ends immediately. Patients should not expose themselves to detection systems for more than a minute. Digital cellular phones use electromagnetic fields and should be more than 6 inches away from the devices at all times.27 Specific written instructions from the manufacturers of the devices should be provided to all patients who have devices.

Hospitals present the greatest risk to patients with implantable devices. The electromagnetic sources with the greatest potential to interfere with devices are magnetic resonance imaging equipment and electrosurgical devices.28 Electrolytes, drugs, and metabolic disturbances could alter the pacing threshold, a situation that could cause a failure to pace. Other medical treatments such as lithotripsy, radiation therapy, cardiopulmonary resuscitation, and external defibrillation also could interfere with an implantable device.28


   Conclusion
Top
 Abstract
 Devices
 Population Characteristics
 Study Design
 Results
 Nursing Implications
 Conclusion
References
 
One million patients with heart failure are now eligible to receive device therapy. These 3 clinical trials show that ICDs, CRT pacers, and CRT-Ds are effective in reducing mortality in patients who have heart failure without ventricular arrhythmias. CRT-Ds are more complicated to implant and more expensive than ICDs or CRT pacers. The increasing use of CRT-Ds has serious clinical and financial implications. No direct comparison of the 3 devices has been done. At this time, it is not possible to definitively ascertain which device is the most cost-effective, appropriate intervention for patients with heart failure without ventricular arrhythmias. Cost-effectiveness of these devices is calculated on the basis of estimated survival. These predictions are not valid beyond the 5-year follow-up demonstrated in SCD-HeFT.29 Continued research to determine the cost-effectiveness of these devices, especially the more expensive CRT-Ds, is important.

Currently, a marked risk exists that clinicians in their quest to improve survival will extend the prophylactic use of these devices to both lower-risk (NYHA class I) and highest-risk (NYHA class IV) patients with heart failure, for whom the efficacy of the devices is unproven and the cost-benefit ratio is not established.30 These 3 clinical trials provide clear evidence that devices are beneficial for some patients with heart failure; additional trials are needed to clarify which devices are effective for specific groups of patients with heart failure, including older patients, women, and minorities.


   ACKNOWLEDGMENTS
 
This research was performed at the University of Maryland School of Nursing.

FINANCIAL DISCLOSURES
None reported.

eLetters
Now that you’ve read the article, create or contribute to an online discussion about this topic using eLetters. Just visit www.ajcconline.org and click "Respond to This Article" in either the full-text or PDF view of the article.

SEE ALSO
To learn more about interventional cardiology, visit http://ccn.aacnjournals.org and read the article by Lauck and colleagues, "A New Option for the Treatment of Aortic Stenosis: Percutaneous Aortic Valve Replacement" (Critical Care Nurse, June 2008).


   REFERENCES
Top
 Abstract
 Devices
 Population Characteristics
 Study Design
 Results
 Nursing Implications
 Conclusion
 References
 

  1. American Heart Association. Heart Disease and Stroke Statistics—2006 Update. Dallas, TX: American Heart Association; 2006.
  2. MERIT-HF study group. Effect of metoprolol CR/XL in chronic heart failure: Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF). Lancet. 1999; 353(9169):2001–2007.[Medline]
  3. Cohn JN. Prognosis in congestive heart failure. J Card Fail. 1996;2(4 suppl):S225–S229.[Medline]
  4. Cowburn PJ, Cleland JG, Coats AJ, Komajda M. Risk stratification in chronic heart failure. Eur Heart J. 1998;19(5):696–710.[Free Full Text]
  5. Smith WM. Epidemiology of congestive heart failure. Am J Cardiol. 1985;55(2):3A–8A.[Medline]
  6. Myerburg RJ, Kessler KM, Castellanos A. Sudden cardiac death: structure, function, and time-dependence of risk. Circulation. 1992;85(1 suppl):I2–I10.[Medline]
  7. Myerburg RJ, Interian A Jr, Mitrani RM, Kessler KM, Castellanos A. Frequency of sudden cardiac death and profiles of risk. Am J Cardiol. 1997;80(5B):10F–19F.[Medline]
  8. Bubien RS, Ching EA, Kay GN. Cardiac defibrillation and resynchronization therapies: principles, therapies, and management implications. AACN Clin Issues. 2004;15:340–361.[Medline]
  9. Doval HC, Nul DR, Grancelli HO, Perrone SV, Bortman GR, Curiel R. Randomised trial of low-dose amiodarone in severe congestive heart failure. Grupo de Estudio de la Sobrevida en la Insuficiencia Cardiaca en Argentina (GESICA). Lancet. 1994;344(8921):493–498.[Medline]
  10. Bardy GH, Lee KL, Mark DB, et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure [published correction appears in N Engl J Med. 2005;352(20):2146]. N Engl J Med. 2005;352(3):225–237.[Abstract/Free Full Text]
  11. Bristow MR, Saxon LA, Boehmer J, et al. Cardiac-resynchronization therapy with or without an implantable defibrillator in advanced chronic heart failure. N Engl J Med. 2004;350(21):2140–2150.[Abstract/Free Full Text]
  12. Cleland JG, Daubert JC, Erdmann E, et al; Cardiac Resynchronization-Heart Failure (CARE-HF) Study Investigators. The effect of cardiac resynchronization on morbidity and mortality in heart failure. N Engl J Med. 2005;352(15):1539–1549.[Abstract/Free Full Text]
  13. Woods SL, Sivarajan Froelicher E, Underhill Motzer S, Bridges EJ, eds. Cardiac Nursing. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005.
  14. Heart Failure Society of America. The stages of heart failure: NYHA classification. http://www.abouthf.org/questions_stages.htm. September 26, 2006. Accessed June 16, 2008.
  15. Freudenberger R, Sikora JA, Fisher M, Wilson A, Gold M. Electrocardiogram and clinical characteristics of patients referred for cardiac transplantation: implications for pacing in heart failure. Clin Cardiol. 2004;27:151–153.[Medline]
  16. Kearney MT, Zaman A, Eckberg DL, et al. Cardiac size, autonomic function, and 5-year follow-up of chronic heart failure patients with severe prolongation of ventricular activation. J Card Fail. 2003;9:93–99.[Medline]
  17. Friedman LM, Furberg CD, DeMets DL. Fundamentals of Clinical Trials. 3rd ed. New York, NY: Springer; 2006.
  18. Anderson J, Bardy GH. Key clinical insights from the Sudden Cardiac Death in Heart Failure Trial. J Cardiovasc Nurs. 2006; 21(6):463–468.[Medline]
  19. Moss AJ, Brown M, Cannon DS, et al. Multicenter Automatic Defibrillator Implantation Trial-Cardiac Resynchronization Therapy (MADIT-CRT): design and clinical protocol. Ann Noninvasive Electrocardiol. 2005;10(4 suppl):34–43.[Medline]
  20. Hunt SA, Abraham WT, Chin MH, et al. ACC/AHA 2005 Guideline Update for the Diagnosis and Management of Chronic Heart Failure in the Adult: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure): developed in collaboration with the American College of Chest Physicians and the International Society for Heart and Lung Transplantation: endorsed by the Heart Rhythm Society. Circulation. 2005;112(12):e154–e235.[Medline]
  21. Centers for Medicare and Medicaid Services. Medicare expands coverage of implantable defibrillators to save lives and develop evidence to maximize benefits [press release]. http://www.cms.hhs.gov/apps/media/press/release.asp?Counter=1331. Published January 27, 2005. Updated May 14, 2007. Accessed May 26, 2008.
  22. Alter P, Waldhans S, Plachta E, Moosdorf R, Grimm W. Complications of implantable cardioverter defibrillator therapy in 440 consecutive patients. Pacing Clin Electrophysiol. 2005;28(9):926–932.[Medline]
  23. Reynolds MR, Cohen DJ, Kugelmass AD, et al. The frequency and incremental cost of major complications among Medicare beneficiaries receiving implantable cardioverter-defibrillators. J Am Coll Cardiol. 2006;47(12):2493–2497.[Abstract/Free Full Text]
  24. Gradaus R, Breithardt G, Bocker D. ICD leads: design and chronic dysfunctions. Pacing Clin Electrophysiol. 2003;26: 649–657.[Medline]
  25. Niu HX, Hua W, Wang FZ, Zhang S, Chen KP, Chen X. Complications of cardiac resynchronization therapy in patients with congestive heart failure. Chin Med J (Engl). 2006; 119(6):449–453.[Medline]
  26. Sweesy MW, Holland JL, Smith KW. Electromagnetic interference in cardiac rhythm management devices. AACN Clin Issues. 2004;15:391–403.[Medline]
  27. US Food and Drug Administration, Center for Devices and Radiological Health. Electromagnetic compatibility-cellular phone interference: update on cellular phone interference with cardiac pacemakers. http://www.fda.gov/cdrh/emc/pace.html. Published November 1, 1995. Updated September 10, 1997. Accessed May 26, 2008.
  28. Stone KR, McPherson CA. Assessment and management of patients with pacemakers and implantable cardioverter defibrillators. Crit Care Med. 2004;32(4 suppl):S155–S169.[Medline]
  29. Mark DB, Nelson CL, Anstrom KJ, et al. Cost-effectiveness of defibrillator therapy or amiodarone in chronic stable heart failure: results from the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT). Circulation. 2006;114(2):135–142.[Medline]
  30. Goldberger Z, Lampert R. Implantable cardioverter-defibrillators: expanding indications and technologies. JAMA. 2006;295:809–818.[Abstract/Free Full Text]

Related articles in AJCC:

Clinical Pearls
Mary Jo Grap
AJCC 2008 17: 406. [Full Text]  



This article has been cited by other articles:


Home page
 Am J Crit CareHome page
L. Bell
Care of Patients With an Implanted Cardiac Device
Am. J. Crit. Care., September 1, 2008; 17(5): 454 - 454.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Respond to This Article
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in AJCC
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Right arrow Take the CE Test
Citing Articles
Right arrow Citing Articles via HighWire
Google Scholar
Right arrow Articles by Chapa, D. W.
Right arrow Articles by Bardy, G. H.
PubMed
Right arrow PubMed Citation
Right arrow Articles by Chapa, D. W.
Right arrow Articles by Bardy, G. H.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS