The primary outcome is frequency of hypotension (SBP<100) on initial ED vital signs after treatment with nitroglycerin for suspected STEMI in the field. The onset of action of sublingual nitroglycerin is 2-5 minutes, with a duration of 60 minutes. Average transport times in LA County are approximately 15 minutes. Therefore, the primary outcome will be measured upon ED arrival, after completion of field care and prior to any ED intervention.