Thread by @realdocdan

🧵 1/7 Ever wondered why the Osborn wave looks the way it does? Stay with me during my newest #tweetorial. A thread 🧵1/7
#cardiotwitter #EPeeps #CardioEd #MedTwitter @TRassafMD @YoungDgk @DGK_org @YoungDZHK @AaronGoodman33 @Steph_Achenbach @fuzzymittens @AvrahamCooperMD

2/7 History
First described in 1953 by Osborn (camel-hump sign) upon #hypothermia in dogs. Upon systemic analysis similar #ECG patterns have been described in
➡️ hypercalcemia
➡️ brain injury
➡️ SAB
➡️ vasospastic angina / ischemia

3/7 Emslie-Smith et al showed that Osborn waves manifested more in epicardial than endocardial leads. Others finally showed that 4-aminopyridine sensitive transient outward current (Ito) is responsible and predominantly located in epicardium. ⬇️ heart rate led to ⬆️ Ito current

4/7 above mentioned triggers of Osborn waves open K-ATP channels, generating outward current during action potential notch. Due to channel distribution this happens more in epicardium than endocardium ➡️ transmural voltage gradient ➡️ resulting in typical ECG morphology. #EPeeps

5/7Why are Osborn waves assoc w/ v-fib?
Due to overactivation of transient outward current (Ito), potential at phase 1 of ventricular action potential (notch) is more negative, inhibiting inward calcium current. This can lead to loss of dome/plateau (2), triggering v-fib. #EPeeps

6/7 Clinical significance of Osborn wave
Observing the Osborn wave in patients - even without hypothermia - can be a red flag and precursor of ventricular arrhythmias and is positively correlated with increased in-hospital mortality.

7/7 Sources:
ncbi.nlm.nih.gov/pmc/articles/P…

doi.org/10.1161/01.cir…

doi.org/10.1093%2Feuro…

link.springer.com/article/10.100…