Anti-Arryhthmics Flashcards
T or F. There is no parasympathetic (vagal) innervation in the heart past the AV node
T. only sympathetics
What are arrhythmias caused by in a general sense?
abnormal impulse generation (automaticity) or abnormal propagation (re-entry)
T or F. The SA node fires at a more rapid rate than the atrial conducting fibers, AV node or purkinje fibers
T.
What things could cause latent pacemakers to fire more rapidly?
-B1 stimulation-hypokalemia-fiber stretch-hypoxemia-acidosis-injury
Describe arrhythmias caused by abnormal triggered automaticity.
abnormal impulse generation following a normal action potential
What are some arryhthmias caused abnormal ‘triggered’ automaticity?
-early after depolarization (EAD) interrupts phase 3 repolarization -delayed after-depolarization (DAD)
Early after depolarization (EAD) interrupts phase 3 re-polarization causes what?
long QT related arrhythmias i.e. Tornado de pointes
What causes delayed after-depolarization?
result from calcium overload in digoxin toxicity and is exacerbated by catecholamines and hypokalemia
Treatment for delayed after-depolarization caused by digoxin overload?
Digibind
Torsades de pointes occurs in the setting of prolongation of phase __ and __ of the action potential (reflected as prolonged QT interval)
2 and 3 repolarization
What things can cause early after-depolarization (or delayed phase 3 re-polarization)?
-K+ channel blocking anti-arrhythmics (class III) -hypokalemia-low heart rate
What is re-entry?
occurs when an impulse repetitively activates the same area of the heart leading to sustained arrhythmias
What conditions are needed for re-entry to occur?
-an anatomic or physiologic obstacle (circuit)-unidirectional block-conduction time must exceed effective refractory period in the ‘slow’ circuit
What is re-entry typically caused by?
a premature impulse (automaticity) that gives off ‘daughter impulses’ resulting in rapid activation of the ventricle (or atrium)
T or F. Re-entrant arrhythmias are characteristically rapid and sustained
T. greater than 140 bpm
Where in the heart can re-entrant arrhythmias occur?
any location- atria, AV node, ventricle
A re-entrant arrhythmia in the atria could be what?
-a fib (disorganized) or -a flutter (organized)
A re-entrant arrhythmia in the AV node could be what?
paroxysmal supraventricular tachycardia (PSVT)
A re-entrant arrhythmia in the ventricles could be what?
-ventricular tachycardia (organized)-ventricular fibrillation (disorganized)
What is the preferred treatment for sustained ventricular tachycardia?
DC cardioversion followed by drug therapy to prevent recurrence of re-entry
What are some options that can used for drug therapy in sustained ventricular tachycardia?
A class I anti-arrhythmic (Na+ channel blocker) such as procainamide or lidocaineA class III (K+ channel blocker) such as sotolol or amiodarone
How would a class I anti-arrhythmic (sodium channel blocker) such as procainamide or lidocaine interrupt re-entry?
by slowing conduction through the circuit and by increasing effective refractory period also slow automaticity
How would a class III anti-arrhythmic (sodium channel blocker) such as procainamide or lidocaine interrupt re-entry?
by prolonging depolarization and increasing the effective refractory period (ERP) by extending phase 3phase 2 and 3 re-polarization is delayed, extending the action potential and potentially prolonging the QT interval resulting in increased risk of early after-depolarization (EAD) and Torsado de pointes
What are the class II anti-arrhythmics?
BBs- metoprolol and atenolol