Correct Answer: A

Rationale: The correct answer is A: Coronary artery bypass graft (CABG). CABG involves grafting a blood vessel to bypass a blocked coronary artery, enhancing blood flow to the heart muscle. This procedure helps reduce the risk of heart attack by restoring proper blood circulation to the heart. Choice B, valve replacement, is a different surgical procedure that involves replacing damaged or dysfunctional heart valves. Choice C, angioplasty, is a minimally invasive procedure that uses a balloon to open narrowed or blocked blood vessels. Choice D, endarterectomy, is the surgical removal of plaque from the lining of an artery to improve blood flow.

Correct Answer: A

Rationale: Refractoriness is the correct term to describe the inability of cardiac cells to respond to a new stimulus while they are still in contraction from a previous stimulus. This period is essential for the heart to complete its contraction and relaxation phases without interference. Excitability refers to the ability of cells to respond to stimuli, not the inability to respond. Contractility is the force of cardiac muscle contraction, and automaticity is the ability of cardiac cells to generate electrical impulses spontaneously, which are not relevant to the described scenario.

Correct Answer: A

Rationale: Cardiac arrest is the correct answer. It is a sudden, unexpected loss of heart function, breathing, and consciousness, typically resulting in death if not treated immediately. Myocardial infarction (choice B) refers to a heart attack caused by a blockage in the coronary arteries. Heart failure (choice C) is a chronic condition where the heart is unable to pump blood efficiently. Atrial fibrillation (choice D) is an irregular and often rapid heart rate that can lead to complications but is not the same as cardiac arrest.

Correct Answer: A

Rationale: Heart failure is the correct answer. It is a condition where the heart is unable to pump blood effectively, resulting in fluid accumulation and swelling in the body. Cardiomyopathy is a disease of the heart muscle that affects its ability to pump blood but is not the specific condition described in the question. Angina is chest pain or discomfort caused by reduced blood flow to the heart, not directly related to fluid buildup and swelling. Myocarditis is inflammation of the heart muscle and does not necessarily involve the inability to pump blood effectively.

Correct Answer: A

Rationale: Anaphylaxis is the correct answer. It is a severe, potentially life-threatening allergic reaction that can lead to difficulty breathing, low blood pressure, and loss of consciousness. An asthma attack is a separate condition characterized by narrowed airways and difficulty breathing, but it is not necessarily related to an allergic reaction like anaphylaxis. Bronchospasm refers to the sudden constriction of muscles in the bronchi, leading to breathing difficulties, and is not specific to allergic reactions. Hypersensitivity is a general term for an exaggerated immune response to a substance, which may or may not manifest as severe allergic reactions like anaphylaxis.