Editor's Note: Commentary based on Kini V, Soufi MK, Deo R, et al. Appropriateness of primary prevention implantable cardioverter-defibrillators at the time of generator replacement: are indications still met? J Am Coll Cardiol 2014;63:2388-94.

Background

Implantable cardioverter-defibrillators (ICDs) for primary prevention have been shown to decrease mortality in patients with reduced left ventricular ejection fraction (LVEF).^1,2 However, little is known about changes in the clinical profile that may occur in the interval between initial ICD implantation and battery depletion requiring generator replacement. In particular, some patients may no longer meet guideline criteria for ICD therapy³ at the time of elective generator replacement if their LVEF improves, and they have not experienced any appropriate ICD therapies. The benefits of continued ICD therapy in this setting are uncertain. Furthermore, the generator replacement procedure carries potential risks and a significant health care cost.^4,5

The study covered in this review addresses some of these issues. The purpose of the study was to assess how often guideline-derived indications for ICD therapy are present when patients receiving the initial ICD for primary prevention undergo elective ICD generator replacement. The authors also compared rates of subsequent ICD therapy (following generator replacement) among patients who did or did not meet indications for an ICD. The authors also estimated the cost implications of replacing generators in all patients versus only those who continued to meet ICD indications.

Methods

The study involved retrospective chart reviews of patients undergoing routine, elective ICD replacement procedures at two large Veterans Affairs Medical Centers. Only patients who had their initial ICD implanted for primary prevention based on an LVEF <35% were included. Clinical, demographic, and device interrogation data were collected.

At the time of the generator replacement, ICD therapy was considered to be indicated for any patient whose LVEF was ≤35% based on assessment within one year prior to generator replacement, or if the patient had received appropriate therapy (shock or ATP) from their ICD after initial implantation, regardless of the LVEF. ICD therapy was considered not indicated in patients who demonstrated an improvement in their LVEF to ≥40% and had not received any appropriate therapies over the lifetime of the original device. ICD therapy was considered unclear in patients who had not received any appropriate therapies over the lifetime of the original device and had also not undergone reassessment of their LVEF in the year prior to generator replacement.

Rates of appropriate ICD therapies delivered after generator replacement were assessed, and Medicare payment rates were used to model the potential cost savings of not performing generator replacement for patients who no longer met ICD indications.

Results

The study cohort comprised 231 subjects. Mean time between initial implantation of ICD and generator replacement was 61 months. At the time of generator replacement, ICD therapy was considered indicated, not indicated, and unclear in 40%, 26%, and 34% of patients, respectively. The only statistically significant difference between the group for whom ICD therapy was considered indicated versus not indicated was a higher LVEF (25% vs. 49%; p <0.001). In a multivariable logistic regression analysis, baseline LVEF of 30-35% (compared to LVEF of <30%) was the only significant characteristic associated with a lower likelihood of meeting primary-prevention ICD criteria at the time of generator replacement (odds ratio 0.52, 95% CI 0.3-0.88; p = 0.01).

After the generator replacement procedure, follow-up data on patients was available for a mean of 3.5 ± 2.0 years. Patients without ICD indications subsequently received appropriate ICD therapies at a significantly lower rate than patients who did (2.8% vs. 10.7% annually, p <0.001). In patients who no longer met ICD indications, the number needed to treat with generator replacement to prevent one appropriate ICD therapy was 76. In the cost analysis, the study found that if ICD generator explants were performed instead of replacements in the patients without ICD indications, the cost savings would be $1.6 million.

Conclusions

Approximately 25% of patients who receive ICDs for primary prevention may no longer meet guideline-driven indications for continued ICD use at the time of elective generator replacement. These patients may subsequently receive fewer ICD therapies than those who continue to meet indications.

Commentary/Perspective

It is likely that patients with ICDs for primary prevention who no longer have a guideline-derived ICD indication at the time of generator replacement derive less benefit from continued ICD therapy compared to patients who do meet indications. Furthermore, any lifesaving benefit must be weighed against the potential for harm, in the form of unnecessary shocks, procedural complications, infection, device malfunction, and manufacturer recalls. However, better risk stratification for sudden cardiac death is needed for this group of patients in the form of large-scale studies and/or prospective randomized trials. Until then, LVEF reassessment and an informed discussion with the patient regarding the risks and uncertain benefits of generator replacement is reasonable. Ultimately, in the setting of uncertainty, deference to patient preference is usually a prudent approach.

References

1. Moss AJ, Zareba W, Hall WJ, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction (MADIT-II). N Engl J Med 2002;346:877-83.
2. Bardy GH, Lee KL, Mark DB, et al. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure (SCD-HeFT). N Engl J Med 2005;352:225-37.
3. Epstein AE, Dimarco JP, Ellenbogen KA, et al. ACC/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Revise the ACC/AHA/NASPE 2002 Guideline Update for Implantation of Cardiac Pacemakers and Antiarrhythmia Devices) developed in collaboration with the American Association for Thoracic Surgery and Society of Thoracic Surgeons. J Am Coll Cardiol 2008;51:e1-62.
4. Poole JE, Gleva MJ, Mela T, et al. Complication rates associated with pacemaker or implantable cardioverter-defibrillator generator replacements and upgrade procedures: results from the REPLACE registry. Circulation 2010;122:1553-61.
5. Kramer DB, Buxton AE, Zimetbaum PJ. Time for a change--a new approach to ICD replacement. N Engl J Med 2012;366:291-3.

Keywords: Adenosine Triphosphate, Cohort Studies, Cost Savings, Death, Sudden, Cardiac, Defibrillators, Implantable, Demography, Follow-Up Studies, Health Care Costs, Logistic Models, Medicare, Odds Ratio, Patient Preference, Primary Prevention, Probability, Prospective Studies, Retrospective Studies, Risk, Stroke Volume, Uncertainty, Veterans

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