Final answer:
Abruptly stopping metoprolol, a beta blocker, may cause myocardial ischaemia as the heart rate and blood pressure can rebound, which increases the heart's oxygen demand.
Step-by-step explanation:
Ceasing metoprolol preoperatively can lead to a risk of myocardial ischaemia. Metoprolol is a beta blocker that works by binding to the beta-1 receptor, which can help in the treatment of hypertension by effectively slowing the heart rate (HR). If the medication is abruptly stopped without medical advice, especially in patients with heart disease, there may be a heightened risk of ischemic events due to a rebound increase in HR and blood pressure, leading to increased oxygen demand by the heart muscle which can't be met, particularly in the setting of pre-existing coronary artery disease.
Bradycardia can also be a side effect of beta blocker medications like metoprolol, particularly when they are overprescribed. However, ceasing them would typically lead to an increased HR, not a decrease.
External causes for bradycardia include over-prescription of beta blocker drugs that reduce HR, but if stopped abruptly, the body's response may swing in the opposite direction, causing potential cardiac complications such as myocardial ischaemia.