Class IV antidysrhythmics or calcium channel blockers have what action on the cardiovascular system?
Increase blood vessel spasm.
Decrease flow of calcium ions thus decreasing heart rate and contractions.
Decrease refractory period.
Increase heart rate.
The Correct Answer is B
Class IV antidysrhythmics or calcium channel blockers decrease the flow of calcium ions into cardiac and vascular smooth muscle cells, thus decreasing heart rate and contractions. By reducing the calcium influx, they also decrease the slope of phase 0 and 4 and prolong phase 2 of the cardiac action potential. This results in vasodilation, reduced myocardial oxygen demand, and decreased conduction through the AV node.
Choice A is wrong because calcium channel blockers do not increase blood vessel spasm, but rather cause vasodilation.
Choice C is wrong because calcium channel blockers do not decrease refractory period, but rather prolong it by extending phase 2 of the cardiac action potential.
Choice D is wrong because calcium channel blockers do not increase heart rate, but rather decrease it by slowing down the pacemaker activity and AV nodal conduction.
Normal ranges for heart rate are 60 to 100 beats per minute, and for blood pressure are 120/80 mmHg or lower.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Class IV antidysrhythmics or calcium channel blockers have the action ofdecreasing the flow of calcium ionsinto the cardiac and vascular smooth muscle cells, thusdecreasing heart rate and contractions.
This leads to vasodilation and myocardial depression, which can help control arrhythmias, hypertension and angina.
Choice A is wrong because calcium channel blockers do not increase blood vessel spasm, but rather relax them by inhibiting the calcium influx that causes contraction.
Choice C is wrong because calcium channel blockers do not promote platelet aggregation, but rather inhibit it by interfering with the calcium-dependent binding of fibrinogen to platelets.
Choice D is wrong because calcium channel blockers do not enhance sympathetic nervous system activity, but rather counteract it by reducing the cardiac output and peripheral resistance.
Some normal ranges for reference are:
• Heart rate: 60-100 beats per minute
• Blood pressure: 120/80 mmHg
• Calcium: 8.5-10.5 mg/dL
Correct Answer is D
Explanation
This is because digoxin can cause bradycardia (slow heart rate) as a side effect, which can be dangerous and require dose adjustment or discontinuation of the medication.Digoxin helps make the heart beat stronger and with a more regular rhythm by inhibiting sodium-potassium ATPase in cardiac cells.It is used to treat heart failure and atrial fibrillation.
Choice A is wrong because increasing sodium intake can worsen fluid retention and exacerbate heart failure symptoms.Patients with heart failure should follow a low-sodium diet to reduce the workload on the heart.
Choice B is wrong because checking pulse rate for 30 seconds and multiplying result by 2 is not accurate enough to monitor the effects of digoxin.
Patients taking digoxin should check their pulse rate for one full minute before taking each dose and record it daily.If the pulse rate is too fast or too slow, they should contact their provider.
Choice C is wrong because taking digoxin with food may reduce its absorption and effectiveness.Digoxin should be taken on an empty stomach, at least one hour before or two hours after a meal.If nausea occurs, it may be a sign of digoxin toxicity and should be reported to the provider.
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