Correct Answer: A

Rationale: Hypertrophic cardiomyopathy is the correct answer. It is a condition characterized by the abnormal thickening of the heart muscle without an obvious cause, which impairs the heart's ability to effectively pump blood. Dilated cardiomyopathy (choice B) involves the enlargement and weakening of the heart chambers, not thickening. Restrictive cardiomyopathy (choice C) refers to the stiffening of the heart muscle, limiting its ability to fill properly. Myocarditis (choice D) is inflammation of the heart muscle usually caused by a viral infection, not thickening.

Correct Answer: A

Rationale: The PR interval measures the time it takes for the electrical impulse to travel from the atria to the ventricles. It is crucial in diagnosing heart rhythm disorders, as abnormalities in this interval can indicate conduction abnormalities between the atria and ventricles. Choices B, C, and D are incorrect. The QRS complex represents ventricular depolarization, the QT interval represents the duration of ventricular repolarization, and the ST segment represents the time between ventricular depolarization and repolarization.

Correct Answer: A

Rationale: Pneumothorax is the correct answer for this question. Pneumothorax is the collapse of a lung caused by the presence of air in the pleural space between the lung and chest wall. This condition can lead to chest pain, shortness of breath, and may require emergency treatment such as chest tube insertion to remove the air. Pleural effusion is the accumulation of fluid in the pleural space, not air. Atelectasis is the collapse or closure of a lung resulting in reduced or absent gas exchange. Pulmonary fibrosis is a condition characterized by scarring and thickening of lung tissue, not related to air leaking into the pleural space.

Correct Answer: A

Rationale: The correct answer is A, Myocarditis. Myocarditis is an inflammation of the heart muscle, typically caused by a viral infection. It can impair the heart's ability to pump blood efficiently, potentially leading to other complications. Endocarditis (choice B) is an inflammation of the inner lining of the heart chambers and valves. Pericarditis (choice C) is inflammation of the pericardium, the outer lining of the heart. Cardiomyopathy (choice D) is a disease of the heart muscle that affects the heart's ability to pump blood.

Correct Answer: A

Rationale: The correct answer is A, Coronary artery bypass graft (CABG). This surgical procedure involves grafting a blood vessel to bypass a blocked coronary artery, improving blood flow to the heart muscle. Choice B, Valve replacement, is a procedure to replace a damaged heart valve and is not directly related to bypassing blocked arteries. Choice C, Stent placement, involves inserting a mesh tube to keep blocked arteries open and is different from grafting a blood vessel. Choice D, Angioplasty, is a procedure to widen narrowed or blocked arteries, typically using a balloon catheter, and does not involve grafting a blood vessel.