To follow-up on the digoxin toxicity POD from aggggggges ago, here's a sampling of some pathognomonic EKG changes in the setting of drug toxicity (this is NOT all-encompassing-- there's a lot more out there!)
1) Older woman with HTN comes in w/ dizziness.
2) Young disheveled guy, somnolent.
3) Old guy on blood thinner w/ HTN, new renal failure and weakness.
4) Old Asian man with cardiac and renal problems comes in vomiting (1st EKG from PMD's office, 2nd from MMC)
5) Old lady with vomiting syncopizes (First EKG progresses to second
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Answers:
1) Long PR interval = AV nodal delay
= 1st degree Heart Block (may progress to complete heart block)
- Beta-blockade
- Calcium-channel blockade
- Digoxin
- Opioids, clonidine
2) Interventricular slowed conduction w/ long QRS, right axis deviation w/ R/S ration >0.7 in aVR
= Na-channel blockade
- TCA toxicity
- Anticholinergics
- Na-channel blockers like the "ides'
- Propanolol
- Anesthetics like bupivicaine
- Carbamazepine
3) Atrial tachycardia w/ AV block and PVCs (can also have PACs)
- digoxin! (classical finding)
4) Ventricular dysrhythmia w/ beat-to-beat alteration of QRS orientation
= Bidirectional Ventricular Tachycardia (may also have multiple ectopic beats mixed in)
- digoxin! (pathognomonic finding)***
- also a few herb toxidromes (aconite)
5) Long QT = prolongation of repolarization = risk of Torsades
- Non-toxicological risks: female, >60yo, genetics, structural heart dz/LV dysfunction
- Sympathicomimetics and:
- Use the QT normogram (based on absolute QT) to predict risk of Torsades! (drugs that cause bradycardia are MORE likely to cause Torsades)
*** Just to summarize, the most common EKG presentations of digoxin toxicity are:
1) PACs/PVCs
2) Atrial tachycardia w/ AV block (classic)
3) Bidirectional VT (answer on tests)