Antiarrhythmics I and II Flashcards Preview

Pharmacology Unit 4 > Antiarrhythmics I and II > Flashcards

Flashcards in Antiarrhythmics I and II Deck (70)
Loading flashcards...

Describe the conduction thru the heart

SA node -> Atrium -> AV node -> Bundle of His -> Bundle branches of Purkinje fibers -> Ventricle


Describe the four phases of the typical myocardial action potential and the ions primarily responsible for each phase (not SA or AV nodes)


  • Phase 0: Na+ influx
  • Phase 1: K+ efflux
  • Phase 2: Ca2+/Na+ influx
  • Phase 3: K+ efflux
  • Phase 4: High conductace of K+ predominates


What channel is responsible for the slow upstroke in the SA and AV node? What ion is responsible for the AP once the SA/AV nodes reach threshold?

The funny current (If); Calcium


What are 2 general mechanisms of arrhythmias?


  • Disturbance of Impulse Formation - Inappropriate automaticity (Rhythm initiated in place other than the SA node)
  • Disturbance of Impulse Conduction


What are the two general classes of arrhythmias? (Give me some subtypes too!)


  1. Bradyarrhythmia - Sinus bradycardia, sinus arrest, heart block (I, II, III)
  2. Tachyarrhythmia - Supraventricular Tach, Ventricular Tach


What bradyarrhythmias are cause by a problem with impulse initiation? Impulse conduction?


  • Impulse Initiation - Sinus arrest, sinus bradycardia, sinoatrial exit block
  • Impulse conduction - Heart block



Sinus Arrest


Diagnosis? Why?

First Degree Heart Block; PR interval > .2 s



Second Degree Heart Block (Mobitz I aka WENCKBACH)


Diagnosis? Treatment?

Second Degree Heart Block, Mobitz II; Pacemaker


Diagnosis? Treatment?

Third Degree Heart Block; Pacemaker


What are the three general classes of tachyarrhythmia? Which is most common? Least common?


  1. Impulse Initiation (Increased automaticity)
  2. Triggered Automaticity - Early and Delayed Afterdepolarizations (Least Common)
  3. Impulse Conduction: Reentry (Most Common)


What are three tachyarrhythmias that fall under increased automaticity? Causes?


  1. Atrial tach - Impulse from atrial tissue other than SA
  2.  Junctional tach - abnormal impulse from AV junction
  3. Ventricular tach - Abnormal impulse coming from ventricle


What is multifocal tachycardia?

Three or more P-waves of variable morphology with rate > 100 bpm. Multiple foci fire at the same time


What is ventricular arrhythmia?

3 or more consecutive ventricular beats at > 100 bpm, usually wide and regular


  1. When in the action potential do EADs occur?
  2. What condition is thought to arise from EADs?
  3. When in the AP do DADs occur?
  4. What is an example of DAD?
  5. What type of tachyarrhythmi are EADs and DADs examples of?

  1. Phase 3
  2. Long QT Syndrome
  3. Phase 4
  4. Digoxin toxicities
  5. Triggered Automaticity


What is the top arrow pointing to? The bottom arrow?

  • Top arrow: Early After Depolarization
  • Bottom Arrow: Delayed After Depolarization


What are the three components necessary to have a reentry arrhythmia?


  1. Parallel fast and slow conduction pathway
  2. Unidirectional block
  3. Final common pathway


Describe the mechanism of reentry arrhythmia


  1. An extrasystole may occur when the fast pathway is still refractory, sending a signal down the slow pathway
  2. The slow signal reaches the His and may find the fast pathway and return to the atria
  3. The signal is propagated up the fast path to the slow pathway where steps 1-3 can happen over and over and over and over and over....


A patient has an EKG tracing showing the following. What is the arrow pointing to? What is the diagnosis? What is the mechanism?

  1. DELTA Wave
  2. Wolff-Parkinson-White
  3. An abnormal accessory conduction pathway betwixt the atria and ventricles conducts signal faster than the AV node and can result in tachyarrhythmias


Shown below are schematics of the AV node an aberrant connection betwixt the atrium and the ventricle. The arrow indicates the direction of the signal flow. What is the diagnosis for 1? 2?


  1. Orthodromic Atrioventricular Reentrant Tachycardia
  2. Antidromic Atrioventricular Reentrant Tachycardia


Diagnosis? Rhythm?

Atrial fibrillation; Irregularly Irregular


How do you treat a bradyarrhythmia?

Withhold inciting agents and use a pacemaker if needed.


What are 3 broad strategies used to treat tachyarrhythmias?

Ablation therapy, antiarrhythmic agents, and implantable defibrillators.


How does ablation work?

Radio frequency is used to permanently disable culprit tissue (areas of reentry or accessory pathways).


Which of the great vessels may be isolated from the heart in attempt to fix atrial fibrilation?

The pulmonary veins (isolated from the left atrium).


What is another name for membrane active agents?



What are the pros and cons of ablation?

Pro: if the mechanism of arrhythmia is identified and targeted appropriately, ablation is likely to be successful in curing the arrhythmia. Con: ablation is invasive with procedural risks (ex. create a heart block).


What are the pros and cons of antiarrhythmic use?

Pro: It is non-invasive and can be stopped at any time. Con: these drugs are not specific in vivo and carry substantial pro-arrhythmic risks as well as other side effects.


Describe the ideal antiarrhythmic.

- Has specific activities against arrhythmia mechanism. - Specifically targets the site of arrhythmia. - Clear mechanism of action in vivo. - Safe (not pro-arrhythmic). - Effective (terminates and prevents recurrence). - No negative inotropic effect. - Does not interfere with other drugs. - No end organ toxicity.