1. This will help determine if STEMI is present, which may change your destination, based upon your local destination protocols. (See also: TOTW Early 12 Lead EKGs are Critically Important).
2. A STEMI-positive 12-lead ECG would change the total number of nitroglycerin sprays administered (Max. 3 vs Max. 6 in suspected cardiac ischemia, non-STEMI).
3. If the 12-lead ECG identifies an Inferior STEMI, a 15-lead ECG (or modified 12-lead) is to be performed to rule in or out right ventricular infarct (specifically examining lead V4R). These patients are often preload-dependent and administration of nitroglycerin may cause significant hypotension. Therefore, administration of nitroglycerin is contraindicated in a patient with a 12-lead ECG compatible with Right Ventricular MI (ST elevation 1mm in V4R).