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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
Increased jugular venous pressure is more commonly associated with right-sided heart failure, where blood backs up into the venous system.
Choice B rationale
Liver enlargement is also indicative of right-sided heart failure due to congestion of the liver blood vessels.
Choice C rationale
Increased pulse rate can occur in both left and right-sided heart failure but is not a specific indicator of worsening left-sided failure.
Choice D rationale
Increased crackles in lung fields indicate fluid accumulation in the lungs, a sign of worsening left-sided heart failure. Left-sided heart failure leads to pulmonary congestion due to inadequate pumping of blood from the left ventricle.
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. .
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