Thread by @LukerJakob

#tweetorial: basic SVT Dx for those new to EP. Differentiate atypical AVNRT from AVRT. By no means complete, meant as an introduction #EPeeps #SVT @YoungDgk

1⃣ Go by a standard every time. Include programmed A and V pacing, to catch if the patient has dual AVN properties.

2⃣ why specifically aAVNRT vs AVRT? Because typical AVNRT is easy, it looks like this.

3⃣ A septal VA > 70ms is the harder differential diagnosis because it can be 3 things.

@DrBradleyKnight

4⃣ don't miss out on valuable observations BEFORE you even see the tachy. Include programmed ventricular pacing in your standard approach to SVT, so you catch non-decremental conduction (also in reference to 1⃣).

5⃣ Before I get to the pacing maneuvers: a lot can be learned from just looking at the tachy. Like CS activation. Bracketing can be seen during tachy or RV pacing.

6⃣ If there's a new BBB during tachy, make sure to
take a good look if anything happens to the cycle length.

7⃣ first maneuver (belongs in every SVT Dx): Ventricular Overdrive Pacing. A-V response like in this case could still be aVNRT or AVRT, so we have to measure some things.

8⃣ and then do some math or caliper acrobatics and check the table for your diagnosis.

@DrGregMichaud

9⃣ what if the tachy terminates during V-pacing? We can still learn from it: check the transition zone.

🔟if you can dissociate the ventricle during V-pacing and the tachy continues, you can exclude AVRT.

@SoufianAlMaha

1⃣2⃣ next maneuver: VPD scanning aka preceding. I like this one because it is so evidently logical.

Only works well when the RVA catheter is close to the circuit, so for left lateral APs this may fail. ..but you caught that one with the CS activation anyway.

That's all, hope it makes for a good introduction into SVT Dx. Now you're warmed up for the absolute must-read 2 part SVT compendium by @Yorgo_V
👉bit.ly/3d4GAXp

👉and check out @narrowQRS 's videos

modified figures from @atrialappendage 🙏