Hughes Md, Paul
NHIC DME DraftLCDFeedback; Hoover Jr MD, Robert D (Bob) 795
Subject:
I am submitting a response to the DME MAC medical directors on external defibrillators. I have one conflict of interest to disclose: I have consulted with Zoll Medical on several occasions over the last year (per current definitions: “modest” or <$10,000 total). However, I am responding to this LCD as a cardiologist in academic practice. I have not been approached by Zoll to post commentary nor has the company played any role in the development of this document.
I have used the LifeVest in the clinical setting. I should also note that I have published a series of papers that deal with the overuse of implantable cardioverter defibrillators (Hauptman PJ, Swindle J, Burroughs T. Underutilization of beta blockers in patients undergoing implantable cardioverter defibrillator and cardiac resynchronization procedures. Circulation: Cardiovascular Quality and Outcomes 2010;3:204-11 and Swindle J, Burroughs TE, Schnitzler MA, Hauptman PJ. Short term mortality and costs associated with cardiac device implantation in patients hospitalized with heart failure. Am Heart J 2008;156:322-8. NIHMS169504). The external wearable defibrillator provides, in my opinion, a safe and cost effective option for patients who may improve ventricular function and not require ICD placement. Although there are other reasons for use of this technology (e.g. explant of ICD to treat infection), the majority of use in my practice occurs in patients who have the potential to experience an improvement in their LVEFs (new diagnosis of cardiomyopathy or in the early post infarction / post revascularization periods) with use of optimal medical therapy.
Finally Dr. Hoover and I were co authors on a paper published in the American Heart Journal in 2006.
Professor of Medicine and Director of Heart Failure
Address: Division of Cardiology, DT-15, Saint Louis University Hospital, 3635 Vista Avenue, Saint Louis MO 63110. Office 314 268 5293
Commentary on Draft Policy for revised coverage criteria for automatic external defibrillator LCDs for wearable (K0606) and non-wearable (E0617) defibrillators.
The proposed changes fail to recognize the sudden death risk that exists for patients in the early period following acute myocardial infarction and following a new diagnosis of non-ischemic dilated cardiomyopathy.
While it is recognized and accepted that left ventricular function can improve over time following an ischemic insult and after initial diagnosis of cardiomyopathy, in part upon the initiation of optimal medical therapy (usually defined by the use of beta adrenergic antagonists, angiotensin converting enzyme inhibitors / angiotensin receptor antagonists and aldosterone antagonists), the risk of sudden death remains finite. Since current coverage rules do not allow the use of an implantable cardioverter defibrillator during the 40-day period post myocardial infarction and at least 90 days following diagnosis of non-ischemic cardiomyopathy, patients may be relatively unprotected during these limited periods of time. The use of non wearable external defibrillators is unlikely to provide safety given the failure of the HAT trial [1]; rather a wearable external defibrillator is a reasonable and necessary component of care in patients with recent myocardial infarction or revascularization or new diagnosis of cardiomyopathy.
Ultimately, the use of the wearable external defibrillator may decrease overall use of ICDs as patients eventually fall outside the criteria for implant (based on improvement in left ventricular ejection fraction).
Post MI Setting
• Kaplan Meier survival curves from the EPHESUS and VALIANT trials clearly demonstrate that risk of death following myocardial infarction has an initial (early) sharp slope and a second lesser slope after a period of approximately 3 months [2,3]
• In EPHESUS, the risk of sudden death ranged from 3.7 to 6.9% over a mean of 16 months (data on use of ICDs were not provided) [4]
• Current prognostic models do not specifically address sudden death risk during the 40-day period following myocardial infarction
A.d.i-ii: Invasive electrophysiologic studies are no longer obtained on a routine basis to determine the risk of sudden cardiac death nor are they considered standard of care.
A.e.ii: Risk of sudden death in the early period following revascularization is significant [5] probably because improvement in left ventricular ejection fraction may be gradual.
New Onset of Non-Ischemic Dilated Cardiomyopathy
• Current prognostic models do not specifically address sudden death risk during the 90 day period following new diagnosis of cardiomyopathy [6,7]
• It is crucial to delineate between new onset of cardiomyopathy and new diagnosis of cardiomyopathy. These terms are not synonymous. A patient who presents with new symptoms but a left bundle branch block pattern on electrocardiography and a large end-diastolic dimension (especially over 6.5cm) has a new diagnosis of an established cardiomyopathy. The risk of sudden death is likely higher than in a patient who presents with a narrow QRS and a left ventricle that is not significantly dilated, since the latter group has a higher likelihood of improvement in left ventricular ejection fraction. In addition, a new diagnosis of cardiomyopathy accompanied by a family history of sudden death represents an at-risk scenario that is often not recognized. However, the presence of a first or close family member with a history of sudden death increases risk in the patient with a new diagnosis of cardiomyopathy.
• A limited number of studies (or sub studies) have specifically addressed outcomes in patients with non-ischemic dilated cardiomyopathy. The Metoprolol in Dilated Cardiomyopathy and PRAISE-2 trials, while limited to patients with dilated cardiomyopathy, did not specifically address early risk of death following randomization and both required the diagnosis of established heart failure [8,9]. The ATLAS study investigators evaluated mode of death by diagnosis (ischemic vs. non-ischemic cardiomyopathy) but did not assess mode by time from diagnosis or initiation of therapy. Sudden death was noted as a cause of death in patients in the non ischemic group [10]. Finally, the IMAC study enrolled new onset cardiomyopathy [11] but did not evaluate mode of death (sudden vs. other).
• In the “ACC/AHA 2006 Guidelines for Management of Patients with Ventricular Arrhythmias and Prevention of Sudden Cardiac Death”, LifeVest is mentioned as a therapeutic option as follows: “The wearable automatic defibrillator has been approved in the United States by the FDA for cardiac patients with a transient high risk for VF such as those awaiting cardiac transplantation, those at very high risk after a recent MI or an invasive cardiac procedure, or those requiring temporary removal of an infected implanted defibrillator for antibiotic therapy” [12]. Although the timing of use of the wearable external defibrillator is not delineated in this particular guideline, the use itself is supported.
A.g: The majority of patients who are described with this criterion will be implanted with an ICD. The major concern is the first 3 months, when medical therapy is initiated and up titrated, and all reversible causes are identified. As currently proposed, very few patients will qualify for a wearable defibrillator at a time of maximal risk.
References
1. Bardy GH et al. Home use of automated external defibrillators for sudden cardiac arrest. N Engl J Med 2008;358:1793-1804
2. Pfeffer MA et al. Valsartan, captopril or both in myocardial infarction complicated by heart failure, left ventricular dysfunction or both (VALIANT). N Engl J Med 2003;349:1893-1906.
3. Pitt B et al. Eplerenone, a selective aldosterone blocker in patients with left ventricular dysfunction after myocardial infarction (EPHESUS). N Eng J Med 2003;348:1309-21.
4. Adamopoulos C et al Timing of eplerenone initiation and outcomes in patients with heart failure after myocardial infarction complicated by left ventricular systolic dysfunction: insights from the EPHESUS trial. Eur J Heart Fail 2009;11:1099-1105.
5. Kaul TK et al. Ventricular arrhythmia following successful myocardial revascularization: incidence, predictors and prevention. Eur J Cardio-Thor Surg 1998;.13:629-36.
6. Lee DS et al. Predicting mortality among patients hospitalized for heart failure. Derivation and validation of a clinical model. JAMA 2003;290:2581-2587
7. Levy W et al. The Seattle Heart Failure Model. Prediction of survival in heart failure. Circulation 2006; 113:1424-1433.
8. Waagstein F et al. Beneficial effects of metoprolol in idiopathic dilated cardiomyopathy. Metoprolol in Dilated Cardiomyopathy (MDC) Trial Study Group. Lancet 1993;342:1441-6.
9. Packer M et al. Effect of amlodipine on morbidity and mortality in severe chronic heart failure. (PRAISE-2). N Engl J Med 1996;335:1107-14.
10. Poole-Wilson PA et al. Mode of death in heart failure: findings from the ATLAS trial. Heart 2003;89: 42–48.
11. McNamara DM et al. Controlled trial of intravenous immune globulin in recent onset dilated cardiomyopathy (IMAC). Circulation 2001;103:2254-2259.
12. ACC/AHA/ESC 2006 Guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Circulation 2006;114:e385-e484
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