Color Atlas and Synopsis of Electrophysiology, 1st Ed.

61. PREVENTION OF SUDDEN DEATH: CHRONIC ISCHEMIC CARDIOMYOPATHY

Khaled Awad, MD, and Andrew E. Epstein, MD, FAHA, FACC, FHRS

CASE PRESENTATION

A 56-year-old man collapsed in a park while attending an art show. Cardiopulmonary resuscitation (CPR) was performed by a bystander until the arrival of emergency medical services (EMS). The initial recordings showed ventricular fibrillation (Figure 61-1). Three direct current shocks were delivered, and amiodarone was given as an IV bolus (300 mg). On arrival at the emergency department, an electrocardiogram showed atrial fibrillation, probable inferior myocardial infarction (MI), and ventricular ectopy (Figure 61-2A). The presence of acute inferior MI became clear on a second electrocardiogram (Figure 61-2B). The patient was unresponsive, intubated, and CPR continued. He continued to have recurrent ventricular tachycardia and fibrillation treated with over 10 external shocks and repeat IV amiodarone. His past medical history was notable for cigarette use. On physical examination he remained unresponsive, had decorticate posturing, and his pupils were fixed and dilated. At emergent cardiac catheterization, an occluded right coronary artery was opened and stented (Figure 61-3). The following day he awoke with no memory defects. The left ventricular ejection fraction (LVEF) was 42%. On the day of discharge, the monitor tracing shown in Figure 61-4 was recorded. What should the next step be? Is an implantable cardioverter defibrillator (ICD) appropriate?

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FIGURE 61-1 Presenting rhythm strip.

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FIGURE 61-3 Angiograms of occluded and revascularized right coronary artery. (A) The initial angiogram of the right coronary artery, which is occluded. (B) The vessel after successful percutaneous intervention.

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FIGURE 61-4 Monitor tracing while awaiting hospital discharge. Thirty-five beats of monomorphic ventricular tachycardia are shown. The irregularity and acceleration suggests an automatic mechanism from injured myocardium.

DISCUSSION

The patient under discussion suffered a cardiac arrest in the setting of acute MI. This does not represent a guideline-driven indication for implantation of an ICD.1 The ventricular tachycardia recorded on the day of planned discharge, more than 48 hours after the infarction was nonsustained, accelerating, and likely automatic given the clinical circumstances. This suggests a changing substrate but not necessarily a fixed substrate with scar at risk for later ventricular tachycardia.

In the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II), patients with chronic ischemic heart disease, prior MI, LVEF ≤30%, and no requirement for ventricular arrhythmias or electrophysiologic study were randomized to receive either optimal medical therapy (OMT) or OMT with an ICD.2 The study showed a clear benefit from ICD implantation (Figure 61-5). Exclusions to enrollment in MADIT-II included MI within 1 month or revascularization within 3 months of the index MI.

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FIGURE 61-5 MADIT-II results. Kaplan-Meier survival probabilities of survival in patients treated with an ICD and conventional medical therapy. There was a benefit from ICD therapy (P = 0.007). Reproduced with permission from Moss AJ, Zareba W, Hall WJ, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002;Mar21;346(12):877-883.

The device-based therapy guidelines state that primary prevention ICD therapy is indicated in patients with an LVEF of ≤35% due to prior MI who are at least 40 days post-MI and in NYHA functional class II or III.1 Furthermore, since revascularization was performed, implicit in the guidelines is that a 3-month waiting period is indicated for this indication since recommendations were based on MADIT-II, which excluded patients from randomization within that time frame. In addition, the national coverage determination precludes reimbursement by Medicare for devices implanted within these waiting periods.3Notably, since the arrest occurred in the setting of acute MI, it does not represent an indication for secondary prevention ICD implantation either.

Additional evidence supporting the inadvisability of implanting an ICD within the first month following MI derives from the Defibrillator in Acute Myocardial Infarction Trial (DINAMIT)4 and the Immediate Risk Stratification Improves Survival (IRIS) study.5 In DINAMIT, patients with a LVEF ≤35% and abnormal autonomic function (decreased heart rate variability or heart rate >80 bpm on monitoring) were randomized between 6 and 40 days post-MI to OMT with or without an ICD. Survival in both groups was identical (Figure 61-6A). Notably, arrhythmic death was less in the ICD group compared to control, but exactly counterbalanced by nonarrhythmic death in the ICD group.4 In IRIS, patients with an LVEF ≤40% and a heart rate >90 bpm or nonsustained ventricular tachycardia were randomized 5 to 31 days post-MI on OMT to receive an ICD or not. Identical to DINAMIT, the IRIS study showed no survival benefit with ICD therapy, and similarly the reduction in SCD by the ICD was completely offset by a parallel increase in nonsudden death, thereby replicating the DINAMIT results (Figure 61-6B).5

The Valsartan in Acute Myocardial Infarction Trial (VALIANT) has been cited as evidence that the risk of sudden arrhythmic death in the first month post-MI, especially in patients with left ventricular dysfunction and an LVEF ≤30%, is such that ICD implantation early post-MI is advisable. In the study, 19% of all sudden deaths or cardiac arrest occurred in the first month, at a rate of 1.4% per month, and 83% of sudden deaths in the first month occurred after hospital discharge.6 Despite these risks, in a subanalysis of patients who had died suddenly in VALIANT and who had autopsies, only 54 of 105 deaths could be attributed to an arrhythmic origin.7 For the other 51 patients, causes for these nonarrhythmic but apparently sudden deaths included MI (31 patients), cardiac rupture (13), heart failure (4), stroke (1), pulmonary embolus (1), and overdose (1). Overall, autopsy results lead to reassignment of cause of death in 17% of the patients most commonly because of fatal MIs or ruptures that were not recognized in patients who died suddenly.7 Although sudden death due to recurrent MI or rupture was highest in the first month in VALIANT, it later declined.7 However, arrhythmic death increased over time from 20% in the first month to 75% later in the study. Thus, the actual rate of early sudden death was overestimated in VALIANT.

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FIGURE 61-2 ECGs on presentation after CPR. (A) The initial ECG. (B) The subsequent ECG.

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FIGURE 61-6 DINAMIT and IRIS Results. (A) Kaplan-Meier estimates of death due to any cause by study group in DINAMIT. (Reproduced with permission from Hohnloser SH, Kuck KH, Dorian P, et al. Prophylactic use of an implantable cardioverter-defibrillator after acute myocardial infarction. N Engl J Med. 2004;Dec 9;351(24):2481-2488.) (B) IRIS (Reproduced with permission from Steinbeck G, Andresen D, Seidl K, et al. Defibrillator implantation early after myocardial infarction. N Engl J Med. 2009;Oct 8;361(15):1427-1436.) In neither study was there a benefit from the addition of an ICD to optimal medical therapy. Furthermore, in both studies the decrease in sudden arrhythmic death provided by an ICD was exactly balanced by an increase in nonarrhythmic causes, virtually all cardiac.

The patient under discussion underwent emergent cardiac catheterization. Recent data show that resuscitated victims of SCA with or without known cardiac causes should undergo emergency angiography and percutaneous intervention if indicated.8 If comatose they should also undergo therapeutic hypothermia. Kern reviewed the literature regarding outcomes of coronary angiography after resuscitation from cardiac arrest and showed that 60% may survive to hospital discharge with 86% having a favorable neurologic outcome.8

Finally, based on the above information, while the infarct is healing a life vest may be useful in situations as described in this case scenario in addition to OMT with β-blockade, an ACE inhibitor, and statin therapy.8-10 In follow-up, the presented patient’s LVEF increased to over 55% in one month, and no arrhythmia events were recorded by the life vest. An ICD was not implanted.

REFERENCES

1. 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(21):e1-62.

2. Moss AJ, Zareba W, Hall WJ, et al. Prophylactic implantation of a defibrillator in patients with myocardial infarction and reduced ejection fraction. N Engl J Med. 2002;346(12):877-883.

3. National Coverage Determination (NCD) for Implantable Automatic Defibrillators. 2005; http://www.cms.gov/medicare-coverage-database/details/ncd-details.aspx?NCDId=110&ncdver=3&bc=AAAAgAAAAAAAAA%3d%3d&. Accessed 10/21/2014.

4. Hohnloser SH, Kuck KH, Dorian P, et al. Prophylactic use of an implantable cardioverter-defibrillator after acute myocardial infarction. N Engl J Med. 2004;351(24):2481-2488.

5. Steinbeck G, Andresen D, Seidl K, et al. Defibrillator implantation early after myocardial infarction. N Engl J Med. 2009;361(15):1427-1436.

6. Solomon SD, Zelenkofske S, McMurray JJ, et al. Sudden death in patients with myocardial infarction and left ventricular dysfunction, heart failure, or both. N Engl J Med. 2005;352(25):2581-2588.

7. Pouleur AC, Barkoudah E, Uno H, et al. Pathogenesis of sudden unexpected death in a clinical trial of patients with myocardial infarction and left ventricular dysfunction, heart failure, or both. Circulation. 2010;122(6):597-602.

8. Kern KB. Optimal treatment of patients surviving out-of-hospital cardiac arrest. JACC Cardiovasc Interv. 2012;5(6):597-605.

9. Chung MK, Szymkiewicz SJ, Shao M, et al. Aggregate national experience with the wearable cardioverter-defibrillator: event rates, compliance, and survival. J Am Coll Cardiol. 2010;56(3):194-203.

10. Epstein AE, Abraham WT, Bianco N, et al. Wearable cardioverter-defibrillator use in patients perceived to be at high risk early post-myocardial infarction. J Am Coll Cardiol. 2013;62(21):2000-2007.