Cardiac Cycle

Which of the following events occurs during the isovolumetric contraction phase of the left ventricle?

A 58-year-old man with hypertension and a history of myocardial infarction presents with acute decompensated heart failure. Echocardiography shows reduced ejection fraction (EF 28%). He is currently on lisinopril and metoprolol. Which drug should be added as the next-line agent to reduce mortality in systolic heart failure?

A 65-year-old woman with atrial fibrillation (AF) and a rapid ventricular response (HR 120 bpm) presents to the emergency department. She is haemodynamically stable. Which drug is the first-line choice for acute rate control in this patient?

A 38-year-old woman with a history of rheumatic heart disease presents with new-onset atrial fibrillation and haemodynamic instability. Clinical examination reveals a loud first heart sound and an opening snap. Which investigation is most appropriate to assess the degree of mitral stenosis and guide urgent management?