What is a key outcome of abruptly discontinuing receptor antagonists like beta-blockers?

Abruptly discontinuing receptor antagonists, such as beta-blockers, can lead to an exaggerated response, which often manifests as a rebound effect. This occurs because the body has become reliant on the medication to block certain receptors, such as beta-adrenergic receptors that regulate heart function and blood pressure. When the antagonist is suddenly removed, there can be an overactivity of these receptors due to their previous inhibition. This overactivity can result in increased heart rate, heightened blood pressure, and a potential resurgence of underlying cardiac symptoms such as angina or arrhythmias, making the "exaggerated response" a significant concern.

In contrast, the other options do not accurately represent the physiological consequences of stopping beta-blockers abruptly. Improved cardiac function and decreased blood pressure would generally be undesired outcomes of stopping these medications, as they typically stabilize heart activity and reduce blood pressure. Additionally, while increased heart rate may occur, it is a part of the exaggerated response rather than an independent outcome, hence not the most comprehensive choice.