Angina & Antiarrhythmic Flashcards
Types of angina
Stable; Unstable; Prinzmetal’s
Drug classes for angina treatment
Organic Nitrates B-Blockers Ca+ Channel Blockers
MoA for Organic Nitrates
Decrease coronary vasoconstriction, increase perfusion by relaxing coronary arteries. Also relax veins, decrease preload and cardiac O2
MoA for B-Blockers (in Angina Tx)
Decrease O2 demands of myocardium by decreasing rate and force of contraction
MoA for CCB
Protect cardiac tissue by inhibiting influx of calcium into cardiac and smooth muscle.
Classes of anti-arrhythmics
Class I – Na Channel Blockers; Class II – Beta –Adrenergic Blockers; Class III – K Channel Blockers; Class IV – Ca Channel Blockers; Miscellaneous
MoA of Class I - Na Channel Blockers
bind to and block voltage-sensitive Na channels; Decreased rate of entry of Na slows rate of rise of Phase 0 of the action potential
MoA of Class II - β-Adrenergic Blockers
Diminish Phase 4 depolarization > depresses automaticity > prolongs AV conduction > decreases heart rate and contractility
MoA of Class III - K Channel Blockers
By increasing the ERP, these drugs are very useful in suppressing tachyarrhythmias caused by reentry mechanisms.
MoA of Class IV - CCB
Bind to L-type Ca channels located on the vascular smooth muscle, cardiac myocytes, & cardiac nodal tissue
MoA of Miscellaneous (Digoxin)
Refractory period shortened in atrial & ventricular cells.
AND
Refractory period prolonged in the AV node
Use of Class I - Na Channel Blockers
- Atrial fibrillation
- Atrial flutter
- Supraventricular & ventricular tachyarrhythmias
Use of Class II - β-Adrenergic Blockers
- Atrial Arrhythmias 2. Supraventricular tachycardias
Use of Class III - K Channel Blockers
- Atrial arrhythmias 2. Ventricular tachycardia
Use of Class IV - CCBs
- Atrial arrhythmias (A. fib & A. flutter)
- Supraventricular tachycardias
Use of Miscellaneous (Digoxin)
Control the ventricular response rate in a.fib or flutter
Adverse effects for Class I - Na Channel Blockers
- May cause paradoxical increase in ventricular rate 2. Black Box Warning – Now recommended to reserve these drugs for life threatening arrhythmias
Adverse Effects of Class III - K Channel Blockers
- Precipitation of arrhythmias 2. Similar toxicity to Class IA drugs 3. Caution with other drugs that may cause QT interval prolongation
Degree of sodium channel blockade in Class I antiarrhythmics
IC > IA > IB (Not directly related to ERP)
Explain how Class I antiarrhythmics effect ERP
Effects on ERP are not directly related to Na channel blockade, but are related to drug actions on K channels (involved in phase 3 repolarization of action potentials)
Effect of Class I antiarrhythmics on the slope of phase 0
IC > IA > IB - IC drugs having the greatest and IB drugs having the smallest effect on phase 0 (IA drugs are intermediate in their effect on phase 0)
ERP
Effective refractory period - Time required after a conducted impulse is propagated through an area before another impulse can be propagated through the same area
