Atrial fibrillation acute myocardial infarction


 * Associate Editor(s)-In-Chief: ; Varun Kumar, M.B.B.S.; Lakshmi Gopalakrishnan, M.B.B.S.

Overview
Acute MI patients with the AF have been shown to have an increased incidence of in-hospital mortality and worst prognosis. The incidence of stroke is also higher in patients with MI and AF than those without AF.

Epidemiology & Demographics

 * There are varied estimates about incidence and prevalence of atrial fibrillation (AF, Afib) in patients with coronary artery disease(CAD).


 * Coronary Artery Surgery Study (CASS) reported that AF was found to be present in 0.6% patients with CAD.


 * A community-wide study reported an overall incidence of Afib complicating myocardial infarction (MI) to be 16%.
 * Majority of atrial arrhythmias in the setting of MI usually occurs within first 72hrs.

Pathophysiology
Atrial fibrillation in the setting of acute myocardial infarction is due to:
 * 1) Atrial dysfunction secondary to atrial ischemia/infarction as a consequence of
 * 2) *Proximal left circumflex artery occlusion prior to atrial branch.
 * 3) *Poor blood flow down the atrioventricular branch of the right coronary artery which affect the functioning of AV and SA node.
 * 4) Increased left atrial pressure as a consequence of left ventricular dysfunction.
 * 5) Sympathetic stimulation.
 * 6) Iatrogenic factors.

Clinical trial data

 * Coronary Artery Surgery Study (CASS) involving 18,343 patients with CAD reported that AF was found to be present in 116 (0.6%) patients.


 * GUSTO-I trial involving 40,891 patients reported 2.5% patients had Afib at the time of admission and 7.9% patients had Afib at the time of randomization who frequently had triple vessel disease. The study concluded atrial fibrillation to be an independent predictor of stroke and 30-day mortality in the setting of acute MI.


 * GUSTO-III trial involving 13,858 patients reported patients with AF had a greater 30-day and 1-year mortality.


 * GISSI-3 trial and the TRACE trial concluded AF after MI was a independent worst prognostic indicator for both short-term and long-term mortality.


 * PURSUIT trail demonstrated increased 30-day and 6-month mortality in patients who developed AF in the setting of Unstable angina/NSTEMI.


 * Meta-Analysis involving 278 854 patients from 1970 – 2010 reported that the presence of a new onset AF after MI was associated with increased mortality even after adjusting several important risk factors for AF. Mortality odds ratio associated with AF was 1.46 while that of new onset AF was 1.37 and prior AF was 1.28 suggesting that AF is no longer a nonsevere event during MI.

Treatment
The management of new onset AF after MI is important, because majority of the patients with hemodynamic compromise during Afib is a result of rapid ventricular rate which increases myocardial oxygen demand, thereby exacerbating ongoing ischemia and possibly decreasing cardiac output.

If hemodynamically unstable:

 * Direct-current cardioversion (biphasic shock of 100 J or monophasic shock of 200 J)


 * If non-responsive to cardioversion or Afib recurs, IV-amiodarone is indicated to control rate and maintain sinus rhythm. Dofetilide is also another effective drug to maintain sinus rhythm in patients with new onset AF after MI.


 * Hemodynamic compromise in AF is mostly due to rapid ventricular rate, for which IV-beta blocker or IV-verapamil is recommended as amiodarone and digoxin only gradually slow the atrioventricular conduction.

If hemodynamically stable:

 * Rate control with IV-beta blocker (unless contra-indicated) and anticoagulation is indicated.


 * Cardioversion is indicated in patients without a history of AF prior to MI.


 * Long-term antiarrhythmic therapy is indicated only in cases of recurrent AF associated with heart failure or severe left ventricular systolic dysfunction.

Anticoagulation for new onset sustained Afib after MI

 * If the new onset AF is of known duration, AF can be cardioverted within 24hours without the need for anticoagulation after cardioversion.


 * If the AF is of unknown duration, Transesophageal echocardiography (TEE) is recommended before cardioversion (depending on the patients hemodynamic status) and anticoagulation with heparin followed by warfarin or dabigatran after cardioversion.


 * Anticoagulation is usually not recommended for patients with a single episode of AF after MI, however patients with recurrent or chronic AF should receive oral anticoagulation based on the CHADS2 Score assessment.

Prevention
Early statin therapy is indicated in ischemic heart disease, after cardiac bypass surgery, and to reduce AF recurrences. However it is not recommended to prevent AF in patients with MI.

==ACCF/AHA/HRS 2011 Guidelines- Postoperative AF (DO NOT EDIT) == {{cquote|

Class I
1. Direct-current cardioversion is recommended for patients with severe hemodynamic compromise or intractable ischemia, or when adequate rate control cannot be achieved with pharmacological agents in patients with acute MI and AF. (Level of Evidence: C)

2. Intravenous administration of amiodarone is recommended to slow a rapid ventricular response to AF and improve LV function in patients with acute MI. (Level of Evidence: C)

3. Intravenous beta blockers and non dihydropyridine calcium channel antagonists are recommended to slow a rapid ventricular response to AF in patients with acute MI who do not display clinical LV dysfunction, bronchospasm, or AV block. (Level of Evidence: C)

4. For patients with AF and acute MI, administration of unfractionated heparin by either continuous intravenous infusion or intermittent subcutaneous injection is recommended in a dose sufficient to prolong the activated partial thromboplastin time to 1.5 to 2.0 times the control value, unless contraindications to anticoagulation exist. (Level of Evidence: C)

Class IIa
1. Intravenous administration of digitalis is reasonable to slow a rapid ventricular response and improve LV function in patients with acute MI and AF associated with severe LV dysfunction and heart failure. (Level of Evidence: C)

Class III
1. The administration of class IC antiarrhythmic drugs is not recommended in patients with AF in the setting of acute MI. (Level of Evidence: C)}}

Vote on and Suggest Revisions to the Current Guidelines

 * The AF Living Guidelines: Vote on current recommendations and suggest revisions to the guidelines

Guideline Resources

 * ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation


 * 2011 ACCF/AHA/HRS Focused Updates Incorporated Into the ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation


 * ACC/AHA/Physician Consortium 2008 clinical performance measures for adults with nonvalvular atrial fibrillation or atrial flutter