Byron K. Lee, MD, Nitish Badhwar, MBBS, Jeffrey E. Olgin, MD
A 48-year-old man with no significant past medical history presented with coughing and shortness of breath and was diagnosed with a non-ST elevation myocardial infarction (MI). Cardiac catheterization found 3-vessel coronary artery disease. Echo showed an ejection fraction (EF) of 40% and a left ventricular apical thrombus. He underwent coronary artery bypass surgery and surgical removal of the apical thrombus. Postoperatively, atrial fibrillation (AF) was seen intermittently. He was discharged in sinus rhythm and in stable condition. An ambulatory ECG monitor was placed during an outpatient visit to assess AF frequency. Three months after his MI, while at the hospital cardiac rehabilitation unit, he had sudden loss of consciousness. He was found to be in ventricular fibrillation (VF). He was externally cardioverted, intubated, and brought to the cardiac care unit (CCU). The ambulatory ECG monitor caught the initiation of VF (Figure 60-1) and the external cardioversion (Figure 60-2).
FIGURE 60-1 Ambulatory ECG while patient was at the hospital cardiac rehabilitation unit for therapy shows the sudden onset of ventricular fibrillation.
FIGURE 60-2 Ambulatory ECG shows successful external cardioversion to a slower and more stable rhythm.
• Patients who have had a recent MI are at high risk for sudden cardiac death, particularly if their EF is low.1
• The potential cardiac causes of sudden death following MI include:
Tachyarrhymias (ie, ventricular tachycardia [VT] and VF)
Bradyarrhythmias (ie, complete heart block)
• Tachyarrhymias and bradyarrhythmias could be secondary to recurrent ischemia.
• Typically, VF or polymorphic VT is due to recurrent ischemia or cardiac rupture while monomorphic VT is due to a reentrant circuit from the MI scar.
• In the absence of evidence for cardiac rupture, the management of post-MI patients with syncope or life-threatening arrhythmias typically begins with ruling out recurrent ischemia, especially when the presenting rhythm is VF or polymorphic VT.
PATHOPHYSIOLOGY AND MANAGEMENT
• The patient had two more episodes of VF requiring external cardioversion in the CCU.
• Troponin was found to be positive.
• Emergent cardiac catheterization found a stenosis at the anastomosis of the LIMA to the LAD, which was opened by PTCA. The vessel was considered too small and tortuous for stent delivery.
• Echo following VF arrest showed an EF of 30% and no thrombus.
• An implantable cardioverter defibrillator (ICD) was later implanted.
FEATURES OF VENTRICULAR ARRHYTHMIAS OCCURRING EARLY AFTER ACUTE MYOCARDIAL INFARCTION
• The VALIANT study, which studied 14 609 patients for a median duration of 24.7 months after MI, demonstrated that 19% of all cardiac arrests occurred in the first 30 days after the infarct and that 83% of the patients who died suddenly in the first 30 days did so after hospital discharge. Patients with an EF ≤30% had a significantly higher incidence of early cardiac arrest, with a rate of 2.3% in the first month, followed by an additional 1.1% in the second month.2
• The EPHESUS study also investigated patients with low EF after MI and found that patients with an EF ≤40% had 5% mortality in the first 2 months, with more than half of the deaths sudden and likely due to arrhythmia.3
• Two randomized trials of ICDs implanted early in the post-MI period (<40 days) in patients with low EF showed no reduction in overall mortality.4,5
• Based on these two studies, the AHA/ACC/ESC Practice Guidelines for the Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Death recommends ICD implantation for the primary prevention of sudden death in patients with ischemic cardiomyopathy and EF of 30% to 40% only after waiting at least 40 days after MI and 90 days if revascularized.6
• Waiting 40 to 90 days before ICD implant means patients are unprotected from sudden death immediately post-MI.
• Some clinicians employ a wearable defibrillator vest in this waiting period to protect patients from ventricular tachyarrythmias. The most recent guidelines for management of post-MI patients state that the wearable defibrillator vest is investigational in this population. Currently there is no proof that this approach decreases sudden death and does no harm, although a randomized clinical trial (VEST trial) is currently underway.7
1. Moss AJ, Hall WJ, Cannom DS, et al. Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia. Multicenter Automatic Defibrillator Implantation Trial Investigators. N Engl J Med. 1996;335(26):1933-1940.
2. 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.
3. Pitt B, et al. Eplerenone, a selective aldosterone blocker, in patients with left ventricular dysfunction after myocardial infarction. N Engl J Med. 2003;348(14):1309-1321.
4. Hohnloser SH, 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, et al. Defibrillator implantation early after myocardial infarction. N Engl J Med. 2009;361(15):1427-1436.
6. Zipes DP, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (writing committee to develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation. 2006;114(10):e385-484.
7. O’Gara PT, et al. 2013 ACCF/AHA guidelines for the management of ST-elevation myocardial infarction: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines. Circulation. 2013;127(4):e362-425.