Final answer:
Nitrates and β-blockers prolong ejection time by slowing heart rate and reducing the force of heart contractions, as β-blockers antagonize adrenaline's stimulatory effects on the heart.
Step-by-step explanation:
When considering the effects of nitrates and β-blockers on ejection time, it's important to understand their mechanisms of action. β-blockers, such as propranolol and other negative inotropic agents, decrease heart rate (HR) and the strength of heart muscle contraction, while nitrates primarily work by dilating blood vessels, reducing the preload on the heart. The combination of these effects from both types of medication leads to a prolonged ejection time because the heart beats more slowly and with less force, increasing the duration of each cardiac cycle, including ventricular ejection.
Adrenaline, on the other hand, normally has a stimulatory effect on both heart rate and blood pressure. However, β-blockers act by antagonizing the effects of adrenaline by binding to G-protein-linked receptors. This accounts for their efficacy in treating conditions such as hypertension and angina pectoris. Their overuse, however, can lead to adverse effects like bradycardia or even heart stoppage.