Cardio III Flashcards
What are the class IV types of drugs? MAO?
Verapamil
Diltiazem
Ca channel antagonists that affects nodal phase 0 depolarization
What are the major effects of class IV drugs?
Depressed SA nodal automaticity and AV nodal conduction
Decreased ventricular contractility
The metabolism of quinidine is inhibited by what other drug interaction? Induced by?
Inhibited by cimetidine
Stimulated by phenytoin, phenobarbital, rifampicin
What type of drug is phenytoin?
Class Ib antiarrhythmic
What type of drug is Mexiletin?
Class Ib antiarrhythmic
What type of drug is tocainide?
Class Ib antiarrhythmic
Why is it that blockage of Ca channels by class IV agents results in slowed pacemaker?
Because nodal tissues is regulated by Ca influx
How do class IV agents cause arrhythmias?
Cause an AV block if suppress long enough
What is the effect of Class IV agents on LV funx?
Lower
What is the effect of class IV drugs on HR?
Decrease
What are the two types of channels that class IV drugs block?
L and T type Ca channels
Can CCBs bind to all pores of Ca channels? Why is this important?
No, so it doesn’t stop HR all together
What are the three places that CCBs affect?
- vascular smooth muscle
- Cardiac myocytes
- SA and AV nodal cells
What is the overall effect of CCBs?
Diminish the degree to which the Ca channel pores open in response to voltage depolarization
What are the two main classes of CCBs?
Dihydropyridine (DHP)
Non-dihydropyridine (NDHP)
What is the main DHP?
Nifedipine
What are the two non DHP drugs?
Verapamil
Diltiazem
What are the tissues that the DHP drugs mainly affect? What is the effect here?
Vasculature–vasodilation and reflex tachycardia
Are DHPs used an antiarrhythmics?
No
What tissue do NDHPs affect?
Heart–used an antiarrhythmic
What drugs are phenylalkylamines?
Verapamil and derivatives
What drugs are benzothiazepines?
Diltiazem and derivatives
What is the effect of CCbs on chronicity and dromoticity?
Negative for NDHP agents only
What are the inotropic effects of CCBs?
Negative, but this may be offset by reflex tachycardia that DHPs produce
Drugs that have a -dipine suffix are what type of drugs?
DHPs
What is the ratio of vasodilation to negative inotropy for DHPs? NDHPs?
DHPs = 10:1 NDHPs = 1:1
What are the effects of CCBs on smooth muscle? Skeletal?
Little to none
What are the main clinical applications of CCBs? (4) Which are only for NDHPs?
Systemic HTN
Angina
SVT (NDHPs only)
Infarct protection (NDHPs only)
What is the MOA of verapamil?
CCB
Decreases SA automaticity
Decrease AV conduction
Cardiac depression
How does verapamil increase the PR interval?
Decreases AV conduction
Verapamil has no effect on ventricular Na conduction. What is the significance of this?
Ineffective on ventricular arrhythmia
What are the clinical applications of verapamil?
SVT
Rate control a-fib
How does verapamil rate control a-fib?
Slows the rate of conduction from the AV node
What are the adverse effects of verapamil?
constipation
Exacerbate CHF
What are the two contraindications of verapamil?
WPW w/afib
Ventricular tachycardia
How can verapamil cause constipation?
Decrease smooth muscle contraction
How can verapamil exacerbate CHF?
Decrease HR when heart is overloaded
Why don’t you want to give verapamil if there is an issue with the sinus node?
Decreases conduction
Why does WPW contraindicate verapamil?
Will force all signals down the fast pathway, causing ventricular tachycardia
What is the MOA of adenosine as an antiarrhythmic?
Activates A1 receptor on SA and AV node, to increase K channel sensitivity
What is the effect of adenosine on the SA node?
SA node hyperpolarization and decrease firing
What is the effect of adenosine on the AP duration of the atrial cells?
Shortens
What is the effect of adenosine on the av velocity?
Depresses
What is the effect of adenosine on the vasculature (MOA)?
Activates A receptor, causing an increase in NO production,and K hyperpolarization
What is the effect of adenosine on the pulmonary stretch receptors?
Stimulates
What are the clinical applications of Adenosine?
ACute conversion of paroxysmal SVT caused by a bypass pathway
How do you administer adenosine? What is its half life?
IV bolus via central line
10-15 seconds
What are the adverse effects of adenosine?
Hypotension
Heart block
Dyspnea
How does atropine work to stop bradycardia?
Blocks M2 receptors on the heart (and all M receptors elsewhere)
How does isoproterenol work to treat bradycardia?
B1 agonist causes an increase in HR
What is the last resort for treating chronic bradycardia?
Pacemaker
What is the indication for vagal stimulation through carotid sinus massage, or the valsalva maneuver?
Sinus tachycardia, PSVT
What is the normal QRS complex length?
120 ms