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Arrhythmias
Drugs used to treat arrhythmias
| Term | Definition |
|---|---|
| cardiac arrhythmias | any abnormality of the normal electrical activity of the myocardium. caused by ischemia, electrolyte deficiencies, genetic mutations, and drugs. Leading cause of sudden cardiac death. |
| Atrial fibrilation | most common type of arrhythmia. doubles mortality and increases risk of stroke (blood pools in ventricles and can form clots which when they dislodge can cause a stroke. |
| arrhythmia symptoms | may be assymptomatic, dizziness, acute syncope (passing out), decreased cardiac output, angina, heart failure |
| P wave | Atrial contraction |
| T wave | Ventricular repolarization |
| QRS complex | Ventricular contraction. If prolonged (>0.12 sec) this is abnormal |
| PR interval | conduction time from atria to ventricles. >0.2 sec = conduction defect (usually within the AV node) |
| ST segment | time between ventricular depolarization and repolarization. Should be flat. Elevation is evidence of MI (STETMI.) Depression is evidence of ventricular hypertrophy, hypokalemia, and tachycardia |
| QT interval | time of ventricular depolarization + repolarization. Often used to diagnose arrhythmia. >0.44 sec = abnormality |
| Automatic arrhythmias | abnormal impulse generation. SA node or non-node tissue spontaneously generates action potentials. Sinus and Junctional tachycardia. relatively uncommon |
| Reentrant arrhythmias | abnormal impulse conduction. Reentry of a previously initiated impulse due to damaged tissue causing abnormal contraction. More common than automatic. |
| DAD | Delayed After Depolarization. An automatic arrhythmia where there is a sharp increase in phase 4 resulting in an inappropriate action potential. associated with digitalis toxicity, catecholamines, and MI. |
| EAD | Early After Depolarization. An automatic arrhythmia where phase 3 is elongated and never depolarizes to threshold before another action potential takes place. exacerbated by slow heart rates (QT related arrhythmias) |
| Supraventricular tachyarrhythmias | atrial arrhythmia characterized by atrial fibrillation (lots of P waves). 15% of all strokes are associated with these arrhythmias. |
| Ventricular tachycardia (VTach) | ventricular arrhythmia characterized by QT prolongation. Most common drug induced arrhythmia (Ia and III AAD's) |
| Bradyarrhythmias | characterized by delayed conduction through the AV node. CCB's are notorious for causing this. |
| Class I AAD's | sodium channel blockers |
| Class II AAD's | Beta blockers |
| Class III AAD's | potassium channel blockers |
| Class IV AAD's | calcium channel blockers |
| Class Ia | Prolong action potential duration and have intermediate dissociation kinetics (Phase 0 takes more time to reach a maximum) |
| Class Ib | shorten the action potential duration and have rapid dissociation kinetics (no affect on phase 0) |
| Class Ic | no affect on action potential duration and have slow dissociation kinetics (phase 0 takes the longest to reach a maximum) |
| Procainamide (Pronestyl) | Class Ia AAD. Strong sodium blocker, moderate potassium blocker. Used to treat atrial and ventricular arrhythmias. ADR: strong proarrhythmic, HF, hypotension, naseau/ vomitting. short 1/2 life (requires frequent dosing.) causes lupus like condition |
| Lidocaine (Xylocaine) | Class Ib AAD. Strong sodium blocker. Used for ventricular arrhythmias. Least cardiotoxic of Class I's. ADR: tremor (anesthesia) |
| Flecainide (Trambocor) | Class Ic AAD. Strong sodium blocker. Used for atrial arrhythmias. ADR: strong proarrhythmic, HF |
| Carvedilol (Coreg), Propanolol (Inderal), Esmolol (Brevibloc), Metoprolol (Lopressor) | Class II AAD. Beta blockers. Esmolol = short 1/2 life (IV for acute situations.) Decrease autometicity and conduction velocity of the SA node. Used for atrial arrhythmias. ADR: fatigue, poor glycemic control. CI: AV node block, bradycardia, asthma |
| Amiodarone (Cordarone) | Class III AAD. Primarily blocks potassium channels, also blocks sodium, calcium, beta, and alpha receptors. Currently, most commonly prescribed AAD. Many side effects. CI: heart block or bradycardia. broad spectrum |
| Dofetilide (Tikosyn) | Class III AAD. highly selective potassium blocker. Mostly used in atrial arrhythmias. ADR: proarrhythmic. CI: renal impairment & QT prolongation. |
| Sotalol (Betapace) | Class III AAD. Potassium and strong beta blocker. broad spectrum. ADR: proarrhythmic, reduced contractility, bradycardia, tachycardia & angina if sudden withdrawal, bronchospasms |
| Verapamil (Calan), Diltiazem (Cardizem) | Class IV AAD. CCB's. Used in atrial arrhythmias. ADR: bradycardia, hypotension, headache, peripheral edema, fatigue, heart block. CI: ventricular tachycardia. Concurrent use with beta blockers can cause heart block. |
| Adenosine | AAD which increases postassium conductance to hyperpolarize cardiac membranes, slowing the conduction velocity of the AV node. Used in atrial arrhythmias. ADR: flushing, bronchoconstriction. |
| Magnesium sulfate | AAD with unknown MOA. perhaps blocks calcium channels. Indicated for Torsades and digoxin induced arrhythmias. |
Created by:
lhammeren