1/🧵
Why does Wenckebach AV nodal block (aka Mobitz type 1) present with progressive prolongation of the PR interval and eventually a non-conducted P wave?
3/ The pattern Wenckebach observed corresponds exactly w/ the progressive PR prolongation, followed by a non-conducted P wave, that characterizes what we call “Wenckebach” heart block.
💥 Amazingly, he observed this BEFORE the AV node was discovered.
13/ Wenckebach cycle length, and P:QRS ratios, are determined by when depolarizations shift into the Absolute Refractory Period.
Earlier shifts lead to shorter cycles and a lower ratio, eg 4:3.
Later shifts lead to longer cycles and a higher ratio, eg 5:4.
14/ 🫀 The Wenckebach pattern arises when ⬇️AV node conduction ➡️depolarization during the Relative Refractory Period
🫀 This progressively ⬆️ PR intervals w/ each beat
🫀 Eventually depolarization occurs during the Absolute Refractory Period and results in a non-conducted p-wave
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2️⃣ I ❤️ the way he zooms in on individual stories and then zooms out. One chapter he’s in a ramshackle hut in rural Haiti, the next he’s building Haiti’s first neurology residency or meditating on the sociocultural basis for global health inequities
3️⃣ Through the stories he tells he actually manages to teach a decent bit of neurology (whether intentional or not)
3/ This question had major implications for the nascent field of anesthesiology.
Some practitioners began to use curare alone during surgery, without sedation, believing that curare adequately sedated patients in addition to paralyzing them.