What class of antiarrhythmic drugs blocks potassium channels prolonging phase 3 of the action potential and slowing the rate and conduction of the heart?
I.
IV.
III.
II.
The Correct Answer is C
Choice A rationale
Class I antiarrhythmic drugs block sodium channels, affecting phase 0 of the action potential, not phase 3.
Choice B rationale
Class IV antiarrhythmic drugs block calcium channels, which affects phase 2 of the action potential and slows heart rate and conduction.
Choice C rationale
Class III antiarrhythmic drugs block potassium channels, prolonging phase 3 of the action potential. This results in a prolonged repolarization period, reducing the risk of arrhythmia.
Choice D rationale
Class II antiarrhythmic drugs are beta-blockers that primarily affect phase 4 of the action potential, reducing heart rate and conduction, but they do not block potassium channels.
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Related Questions
Correct Answer is D
Explanation
Choice A rationale
Ergotamine does not increase hypoperfusion. It is used to constrict blood vessels to reduce blood flow.
Choice B rationale
Ergotamine does not decrease hypoperfusion. It is used to constrict blood vessels to reduce blood flow.
Choice C rationale
Ergotamine does not increase hyperperfusion. It is used to constrict blood vessels to reduce blood flow.
Choice D rationale
Ergotamine decreases hyperperfusion by constricting blood vessels in the basilar artery vascular bed, reducing the blood flow to relieve migraine headaches. .
Correct Answer is D
Explanation
Choice A rationale
Vitamin E is an antioxidant and is not indicated to counteract the effects of warfarin. It does not have a role in reversing anticoagulation or managing bleeding. High doses of Vitamin E can actually interfere with clotting and potentially exacerbate bleeding.
Choice B rationale
Protamine Sulfate is an antidote for heparin, not warfarin. It works by neutralizing the effects of heparin, which is an anticoagulant that acts quickly to prevent clot formation. Warfarin works differently and requires a different antidote for its anticoagulant effect.
Choice C rationale
Calcium Gluconate is not an antidote for warfarin. It is typically used in cases of hypocalcemia and can stabilize cardiac membranes in hyperkalemia but has no effect on reversing warfarin-induced anticoagulation or bleeding.
Choice D rationale
Vitamin K is the correct antidote for warfarin. It counteracts the anticoagulant effects by promoting the synthesis of clotting factors that warfarin inhibits. Administering Vitamin K is standard practice in reversing the effects of warfarin and managing bleeding complications.
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