What is the major cardiovascular danger of anti-arrhythmic drugs (especially class III agents)?
Anti-arrythmic drugs (especially class III agents) can significantly prolong repolarization (QT) and therefore can result in Torsade de Pointe as a form of Proarrhythmia.
What is the only anti-arrythmic that has been shown to improve mortality in the post infarct patient?
What is the preferred therapy for high risk arrhythmia patients (low EF <35% or sustained VT/VF)?
Implantable Cardioverter Defibrillator
What are class I anti-arrhythmic drug agents?
Class I => are Na channel blockers
- Class Ia => moderate Na channel blocker (prolongs conduction and repolarization) and increases effective refractory period
- Class Ib => weak Na channel blocker and decreases effective refractory period
- Class Ic => strong Na channel blocker and maintains effective refractory period
What are some examples of Class Ia anti-arrhythmic drugs?
What are some examples of Class Ib anti-arrhythmic drugs?
What are some examples of Class Ic anti-arrhythmic drugs?
What are class II anti-arrhythmic drug agents?
Class II => Beta Blockers
How do class III anti-arrhythmic drug agents act?
Class III => K channel blockers that delay depolarization
Why is Ibutilide a pseudo class III anti-arrhythmic drug?
Ibutilide causes a slow inward Na current that also delays depolarization
What are examples of class III anti-arrhythmic drug agents?
Sotalol, Dofetilide, Amiodarone, Dronedarone
How do class IV anti-arrhythmic drug agents act?
Act primarily on slow response cells (SA & AV node), which are dependent on Ca2+ influx for Phase 0 of the action potential.
What are 3 examples of class IV anti-arrhythmic drug agents?
How does adenosine work to prevent arrhythmia?
- Blocks A1 receptor
- Prolongs AV conduction by causing cell hyperpolarization and reduces catacholamine stimulation
What drugs are used to treat SVT?
Calcium Channel Blockers
What steps are taken if the routine SVT drugs do not work?
- IV: Ibutilide, Quinidine, Procainamide, Amiodarone
- PO: Quinidine, Procainamide, Amiodarone, Disopyramide, Flecainide, Propafenone, Sotalol, Dofetilide, Dronedarone
- DC cardioversion
- Ablation => now generally replaced traditional anti-arrhythmic therapy
When does ablation NOT work better than "traditional" anti-arrhythmic therapy?
Which drugs improve survival chances after MI?
Beta blocker (Class II) => propanolol
*Amiodarone (Class III) appears to increase the probability of survival but actually increases cumulative risk => pro-arrhythmia
Which drug classes can cause Torsades from Early Afterdepolarization (EAD)?
Class III (K+ blockers)
Class Ia (Na + blockers)
How do class Ic anti-arrhythmic drugs cause incessant monomorphic VT?
REMEMBER => Type 1C (Na+ blockers) delay conduction
-Slowing of conduction in limb 1 allows limb 2 to recover by the time the retrograde wavefront arrives at 2; thus facilitating reentry
What drugs should be used in acute VT?
IV Lidocaine or Amiodarone till definitive therapy can be instituted
Which drugs should be used in sustained VT?
*However, ICDs are superior
What is the most effective treatment strategy for reducing mortality in a patient with a low ejection fraction, and sustained ventricular tachycardia or cardiac arrest?