Final answer:
A contraindication to nitrate administration in a patient with possible STEMI and ongoing chest discomfort is the use of phosphodiesterase inhibitors within the previous 24 hours, due to the risk of a severe drop in blood pressure.
Step-by-step explanation:
A patient with possible STEMI (ST-elevation myocardial infarction) experiencing ongoing chest discomfort may be considered for nitroglycerine administration. However, there are specific contraindications to the administration of nitrates. One such contraindication is the use of phosphodiesterase inhibitors within the previous 24 hours. Phosphodiesterase inhibitors are medications commonly used to treat erectile dysfunction, such as sildenafil (Viagra), and they can lead to a significant and dangerous drop in blood pressure when combined with nitrates.
Other listed options, such as a heart rate (HR) less than 90/min, anterior wall myocardial infarction, and systolic blood pressure greater than 180mmHg, are not standard contraindications for nitrate administration in the acute setting.