ACE inhibitors correct heart failure by:

Correct Answer: D

Rationale: The correct answer is D: Reducing afterload. ACE inhibitors reduce afterload by inhibiting the conversion of angiotensin I to angiotensin II, leading to vasodilation and decreased peripheral resistance. This results in reduced workload on the heart, improved cardiac output, and overall improvement in heart failure symptoms. Option A is incorrect as ACE inhibitors do not increase preload. Option B is incorrect as ACE inhibitors cause vasodilation, not vasoconstriction. Option C is incorrect as ACE inhibitors actually reduce afterload, rather than increasing it.

Correct Answer: B

Rationale: The correct answer is B: They decrease the velocity of electrical activity on the AV node. Calcium channel blockers specifically target calcium channels in the heart muscle, which slows down the influx of calcium ions responsible for electrical conduction in the heart. By reducing the velocity of electrical activity on the AV node, calcium channel blockers help to decrease heart rate and improve myocardial oxygen supply. Incorrect choices: A: They increase the preload on the heart - This is incorrect because calcium channel blockers do not directly affect preload, which is the volume of blood in the heart at the end of diastole. C: They block the sodium channels in the heart muscle - This is incorrect because calcium channel blockers do not target sodium channels; they specifically inhibit calcium channels. D: They cause vasoconstriction of coronary arteries - This is incorrect because calcium channel blockers actually have a vasodilatory effect on coronary arteries, which can help improve blood flow to the heart muscle.

Correct Answer: D

Rationale: The correct answer is D: Adenosine. Adenosine is the drug of choice for treating paroxysmal supraventricular tachycardia (PSVT) due to its ability to rapidly terminate the arrhythmia by blocking the AV node temporarily. It works by slowing down the conduction of electrical impulses in the heart. Flecainide (A) and Lidocaine (B) are antiarrhythmic drugs used for ventricular arrhythmias, not PSVT. Metoprolol (C) is a beta-blocker that can be used for long-term management of PSVT but is not the first-line choice for acute treatment.

Correct Answer: C

Rationale: The correct answer is C: It relaxes vascular smooth muscle. Nitroprusside is a vasodilator that works by directly relaxing the smooth muscle in blood vessels, leading to vasodilation and subsequently lowering blood pressure. This mechanism of action is essential in treating hypertension. Incorrect choices: A: It blocks conversion of angiotensin I to angiotensin II - This is not the mechanism of action of nitroprusside. Angiotensin-converting enzyme (ACE) inhibitors work by inhibiting this conversion. B: It blocks the calcium channels in the blood vessels - This is the mechanism of action of calcium channel blockers, not nitroprusside. D: It blocks the sodium channels in the heart - This is not the mechanism of action of nitroprusside. Sodium channel blockers are used in antiarrhythmic medications.

Correct Answer: A

Rationale: The correct answer is A: Thrombocytosis. Warfarin is an anticoagulant that works by inhibiting clotting factors. Thrombocytosis, an elevated platelet count, increases the risk of clot formation, so giving warfarin can further increase the risk of bleeding. Mild thrombocytopenia (low platelet count) is a contraindication but not as severe as thrombocytosis. Lumbar puncture and history of eye surgery are not direct contraindications to warfarin use.