ECG
Eval for ACS only in:
Patient with ECG changes suggestive of ischemia, hypotension, angina
A fib is rarely only manifestation of ACS, although RVR and hypotension can provoke demand ischemia
Acute lab studies for all patients:
CBC
Chem-10
Coagulation studies (for patients requiring anticoagulation)
Additional labs (consider based on clinical scenario):
TSH & free T4 (Afib increased in sublinical hyperthyroidism)
BNP
D-dimer
Troponin
Magnesium level
Digoxin level (if appropriate)
Imaging
CXR (if concern for heart failure or infection)
Chest/Abdominal CT (if concern for sepsis)
Patient with ECG changes suggestive of ischemia, hypotension, angina
A fib is rarely only manifestation of ACS, although RVR and hypotension can provoke demand ischemia
CBC
Chem-10
Coagulation studies (for patients requiring anticoagulation)
TSH & free T4 (Afib increased in sublinical hyperthyroidism)
BNP
D-dimer
Troponin
Magnesium level
Digoxin level (if appropriate)
CXR (if concern for heart failure or infection)
Chest/Abdominal CT (if concern for sepsis)
3 patterns on ECG:
Irregularly, irregular R waves
QRS rate 140-160/min
May look like flutter waves
Unlike a-flutter, the fibrillatory waves are irregular
Unlike a-flutter, the fibrillatory waves are irregular
Due to complete AV block with escape rhythm
Ischemic changes?
Rate > 250? (think preexcitation)
Atrial fibrillation 
Regular
Atrial flutter
AV Node Independent
Torsades de pointes
Sinus tachycardia
Atrial tachycardia
Atrial tachycardia 