You do not need to wait for a BP before giving GTN, unless the patient is dancing the macarena around the department. In which case, they probably don't need the GTN either. Why would the patient be hypotensive anyway? In the setting of chest pain, potentially the patient is in caridogenic shock, that is, the heart is failing to pump adequately because of ischaemia. This may be exacerbated by pain, which produces tachycardia, which worsens ischaemia. Why? Well, as I'm sure you already know Tom, the coronary circulation fills in diastole, and a tachycardia will shorten this interval. If the patient is hypotensive because of cariogenic shock, then GTN will reduce pre- and afterload, perhaps allowing the patient's heart to pump more efficiently, as Starling's law dictates. But you knew that didn't you Tom? As regards to ECG changes in chest pain, how many first ECGs are normal in acute MI? Do you know THAT one Tom? * If my family member has chest pain, please don't fanny about spending 20mins on scene doing ECGs, BPs or attempting a diagnosis. Please take them immediately to the big building marked 'hospital' with people inside who are trained to diagnose. *Up to 30% of people with acute myocardial infarction have a normal ECG. A single normal ECG means JACK ALL in the setting of chest pain