Correct Answer: A

Rationale: Bradycardia is the correct answer. It is a condition characterized by a slow heart rate, which reduces the amount of blood pumped to the body. This can lead to symptoms like fatigue and dizziness. Choice B, Tachycardia, is the opposite condition where the heart beats too fast. Choices C and D, Atrial fibrillation and Ventricular fibrillation, refer to irregular and potentially life-threatening rapid heart rhythms involving the atria and ventricles respectively, not a slow heart rate.

Correct Answer: A

Rationale: Heart block is the correct answer because it specifically refers to a condition where the heart's electrical impulses are delayed or blocked, resulting in a slower or irregular heartbeat. Tachycardia (choice B) is a condition characterized by a fast heart rate, Bradycardia (choice C) is a slow heart rate, and Arrhythmia (choice D) is a general term used to describe any abnormal heart rhythm, which may or may not involve delays or blocks in electrical impulses.

Correct Answer: A

Rationale: Mitral regurgitation is the condition where the heart's mitral valve does not close properly, allowing blood to leak backward into the left atrium. This can result in symptoms like shortness of breath and fatigue. Choices B, C, and D are incorrect because aortic stenosis, tricuspid regurgitation, and pulmonary hypertension involve different heart valves or conditions, not the mitral valve specifically.

Correct Answer: B

Rationale: In cases of myocardial infarction leading to shock, dopamine is the drug of choice. Dopamine helps increase blood pressure and improve blood flow to vital organs, making it beneficial in managing shock. Atropine is mainly used for symptomatic bradycardia, not for shock. Digoxin is a cardiac glycoside used in heart failure and atrial fibrillation, not for managing shock. Adenosine is typically used for diagnosing and treating supraventricular tachycardias, not for shock associated with myocardial infarction.

Correct Answer: A

Rationale: When administering furosemide (Lasix), it is crucial to monitor potassium levels closely. Furosemide is a loop diuretic that can lead to potassium loss, potentially causing hypokalemia. Monitoring potassium levels helps prevent adverse effects associated with low potassium, such as cardiac arrhythmias. While monitoring sodium, calcium, and chloride levels may also be important in certain situations, potassium is the most critical to monitor when administering furosemide.