Bolus intravenous nitroglycerin for ST-segment depression not associated with increased myocardial oxygen demand.

Ischaemic ST-segment changes may occur in patients with coronary artery disease when myocardial oxygen consumption is increased as a result of hypertension, tachycardia or increased contractility. Ischaemia can also occur as the result of decreased coronary perfusion pressure caused by hypotension or coronary artery spasm. We report ST-segment depression in the absence of hypertension, tachycardia or hypotension. The response to bolus intravenous nitroglycerin suggested coronary artery spasm as the cause.