Cardiovascular pharmacology III Flashcards
what are the effects of class IV antiarryhtmics?
- calcium channel blockers - primary effects on nodal phase 0
- depressed SA nodal automaticity, AV conduction, decreased ventricular contractility
what are the cardiovascular sites of action for the calcium channel blockers?
- vascular smooth muscle cells
- cardiac myocytes
- SA and AV nodal cells
how do the calcium channel blockers work?
interfere with entry of calcium into cells through voltage dependent L and T type calcium channels
what are the two classes of calcium channel blockers?
- dihydropyridine (DHP)
2. non-dihydropyridine (NDHP)
what is the DHP class drug? where are its effects?
- nifedipine
2. vasculature - vasodilation and reflex tachycardia
what are the NDHP class drugs? where are their effects?
- verapamil and diltiazem
2. heart - tx for arrhythmias
what are the major cardiovascular actions of the calcium channel blockers?
- vasodilation (arteries more than veins)
- negative chronotropic and dromotropic (NDHP ONLY)
- negative inotropic
what are the main clinical applications for calcium channel blockers?
- systemic hypertension
- angina pectoris
- SVT
- post-infarct protection
what is the mechanism of action of verapamil?
- blocks slow inward calcium channels
- decrease AV conduction - increase PR interval
- cardiac depression
- ineffective on ventricular arrhythmia
what ECG changes occur during calcium channel blocker use?
increased PR interval (decreased AV conduction)
what are the clinical applications for verapamil?
- SVT - want to decrease spontaneous activity
2. rate control in Af
what are the adverse effects of verapamil?
- exacerbate CHF
2. constipation
what are the contraindications for verapamil?
- WPW syndrome with Af
2. ventricular tachycardia
what is the mechanism of action of adenosine?
- activates a1 receptor in SA and AV nodes
- SA node hyperpolarization and decreased firing rate - INCREASE MAXIMUM DIASTOLIC POTENTIAL
- shortening of AP duration of atrial cells
- depression of AV conduction velocity
- activates a2 receptors in vasculature - vasodilation
what are the clinical applications of adenosine?
acute conversion of paroxysmal SVT caused by reentry involving accessory bypass pathways
