Arrhythmias

Question 1

By what mechanism does Dofetilide increase the risk of TdP in bradycardia?

Answer 1

Reverse-use dependence

Class IC drugs cause use dependence, greater drug affect at faster heart rates

Class III drugs cause reverse use dependence, increased drug affect at lower heart rates

Question 2

How should the dose of Coumadin be adjusted in patients being started on Amiodarone?

Answer 2

Decrease dose 25-33%

Question 3

What is the mechanism of action of Warfarin, Rivoroxaban, Edoxoban, Apixiban, and Dabigatran?

Answer 3

Warfarin: Vitamin K Antagonist

Rivoroxaban, Edoxaban, Apixiban: Factor Xa inhibitor

Dabigatran: Direct thrombin inhibitor

Question 4

What is the functional effect of LQTS1, LQTS2, LQTS3?

Answer 4

LQTS1: Loss of K

LQTS2: Loss of K

LQTS3: Gain of Na

Question 5

32 year old, 10 weeks pregnant, with symptomatic episodes of AVNRT, currently back in NSR. What is the drug/treatment of choice?

Answer 5

Digoxin or a BB (Metoprolol or Propanolol) are first line agents.

Question 6

Fleicanide and other 1c drugs can cause complete heart block in a patient with a pacemaker via which mechanism?

Answer 6

Increasing pacing thresholds

Question 7

3 types of tachycardia?

Answer 7

1. Automaticity
2. Re-entry
3. Triggered

Question 8

In Brugada Syndrome, why do you see coved ST segments in V1-V2?

Answer 8

Difference in gradients between the epicardium and endocardium creating a voltage mismatch. Typically RVOT is most involved, close to the septum, thus V1-V2.

Question 9

Name the most common class I anti-arrhythmic drugs (7 in total)

Answer 9

1A: Quinidine, procainamide, disopyramide

1B: Lidocaine, Mexiletine

1C: Fleicanide, Propafenone

Question 10

Name the most common class III anti-arrhythmic drugs (5 in total)

Answer 10

Sotalol, dofetilide, ibutilide, amiodarone, dronedarone

Question 11

What is the treatment of choice in patient who has pre-excited AFib with RVR but otherwise hemodynamically stable?

Answer 11

Ibutilide or Procainamide

Question 12

What are the reversal agents for Coumadin, Factor Xa inhibitors, and Pradaxa?

Answer 12

Coumadin - Vit K, FFP, PCC

Factor Xa inhibitor - Andexanet

Dabigatran - Idarucizumab

Question 13

30 yo F currently 7 months pregnant with episode of palpitations which has now resolved. WPW on EKG. She is on Metoprolol Tartrate 50mg bid. What is recommended?

Answer 13

Change BB to anti-arrhythmic (Fleicanide or Propafenone). BB, CCB not recommended in WPW as may increase use of accessory pathway or lead to AFib

Question 14

In what conditions can you see bidirectional VT?

Answer 14

Calcium overload conditions:

1. Digoxin toxicity
2. CPVT
3. Andersen-Tawil

Question 15

VT with LBBB morphology in V1-V3 and positive in inferior leads is likely originating from what location?

Answer 15

RVOT

Question 16

VT with RBBB morphology in V1-V3 with L axis/LAFB morphology is likely originating from where? Treatment?

Answer 16

Left posterior fascicle VT

Treatment: Verapamil