arrhythmia Flashcards
When is the relative refractory period?
Late phase 3 and early phase 4
SA node resting rate
AV node resting rate
bundle branch escape rate
SA: 60-100
AV: 40-60
BB: 20-40
Arrhythmias caused by early after depolarizations
Torsade des Pointe
Tachycardia
Reentry arrhythmias
AVNRT AVRT WPW syndrome Atrial flutter Atrial fib Ventricular tach Ventricular fib
Class I anti-tach agents
MOA
Na+ channel blockers, thus reducing Vmax of depolarization
Ia: all heart rates (Quinidine, Procainamide)
Ib: little effect on slow rates, effect increased on faster rates, does not decrease Action Potential duration (lidocaine)
Ic: all heart rates, minimal effect on AP duration (flecainide)
Class II anti-tach agents
B-blockers decrease SA node automaticity increase AV node refractoriness decrease AV node conduction velocity (propranolol, metoprolol)
Class III anti-tach agents
Potassium channel blockers
Prolong AP duration
(amiodarone)
Class IV anti-tach agents
Calcium channel blockers
decreases conduction velocity
increases refractoriness
(verapamil)
Class I indications
Ia: less used
Ib: v tach
Ic: v tach or supra-ventricular tach
Class II indications
Metoprolol (selective)
for hypertension/coronary artery disease associated tach
Class III indication
Amiodarone: coronary artery disease and heart failure patients
Class IV indications
superaventricular tach
Anti-bradycardia agents
Isoprenaline
Epinephrine
Atropine
Aminophylline
Which anti-tach drugs can cause arrhythmias?
Ia and Ic: can cause VT or VF
III
II, IV can cause bradycardia
Best treatment for sick sinus syndrome?
Pacemaker since drug treatment is not responsive
Treatment for atrial flutter
Treatment of underlying Restore rhythm: cardioversion,cardioablasion, class Ia or Ic or III
Control ventricular rate: CCB, Bblocker, anti-coag
Atrial fib has danger of developing
Stroke, thus prevention of embolism is #1 goal of treatment
Digitalis toxicity most likely cause this type of arrhythmia
Nonparoxysmal AV junctional tach
PVST (paroxysmal supra ventricular tach) due to what cause
REENTRY
90% due to AVNRT
10% from AVRT
Therapy for paroxysmal tach
for nodal RT, increase vagal tone by carotid sinus massage or valsalva maneuver.
Or verapamil, adenosine
Wolf Parkinson White
MOA
Anterograde conduction over accessory pathway that bypasses the AV node, may lead to ventricular tach
WPW treatment
cardioaversion
DO NOT USE DIGOXIN OR CCB because these cause VT
use drugs that prolong refractory period
Ia,Ic,III,IV
What drugs should be avoided in ventricular premature contractions (PVC)
Ic agents because they can cause arrhythmias
Events that cause Torsades de Pointes
hypokalemia
prolongation of AP duration
early after depolarizations
slow conduction that contributes to reeentry
Treatment of VT
cardioversion (for unstable VT of when drugs have no effect)
B-blockers (II)
Lidocain (Ib)
amiodarone(III)
Pattern for second degree AV block (type I)
location of block
aka Mobitz type I aka Wenckebach
it’s a gradual elongation of PR interval until a a beat is dropped
location is the AV node (commonly)
secondary degree AV block type II pattern
location
aka Mobitz II
constant PR intervals preceding a dropped beat
His bundle is most common site
Routine lab tests for hypertension
Blood glucose Serum K and Ca (hyperparathyroid) Creatinine in urine (test GFR) Lipoprotein EKG
Microalbuminuria tests for what?
Diabetic nephropathy
