Which one of the following is the most common congenital heart defect to cause an initial left-to-right shunt?

Correct Answer: C

Rationale: Ventricular septal defect (VSD) is the most common congenital heart defect causing an initial left-to-right shunt due to higher left ventricular pressure.

Correct Answer: C

Rationale: The human heart has four valves: tricuspid, pulmonary, mitral, and aortic.

Correct Answer: B

Rationale: Levels above this range increase the risk of toxicity.

Correct Answer: B

Rationale: Amiodarone can cause pulmonary toxicity, requiring immediate intervention.

Correct Answer: A

Rationale: Diltiazem can cause bradycardia and hypotension, requiring these parameters to be assessed before administration.