6/ Actually, with CSP lead only+RBB fusion, we got a QRS almost as good. Previous morphology slightly nicer I think but is this worth the complexity of a LOT-CRT cf. LBB-CRT? (Would be a no from me). Overall, I thought this was an interesting case worth sharing with #Epeeps.

5/ This was the final optimised result with both LBB and CS lead pacing, and after adjusting VV plus the AV delay (which Biotronik allows via the autoAdapt %). It does look very good, with a QRS of around 110ms. But what if I had only used a CSP lead (or CS lead)?

4/ Identified a good lateral branch which gave usable thresholds, and selected that. Confirmed electrical delays to that spot was good (140ms). So now had to decide between conventional CRT, LBB-CRT or LOT-CRT. I succumbed to choosing a LOT-CRT. Was this a smart choice?

3/ Some key moments shown here. Used a RBB knock test to induce temporary CHB to confirm there *was* LBBB. Started w/LBB lead. However, LVAT on right septum was massive 170ms, and although it dropped++ to 104ms on crossing to left, it was still long >> not happy to accept this.

2/ Thank you for all the viewpoints! I went ahead with the case with my thoughts summarised in this short clip here.

1/ I wonder what #Epeeps would do for a 62yo male patient with NICMP, LBBB QRSd >200ms, LVIDd 71mm, LVEF12%? Conventional CRT, LBB-CRT, LOT-CRT, too advanced for CRT? For CRT, any vendor preferences? @finnakerstrom @James_Elliott01 @enes_elvin @riley_guntrip @chris_monkhouse

8/ End with a nice ladder diagram of the intracardiacs which allow me to see the His. I think it might be possible to construct other ladder diagrams consistent with the EGMs but this is what I came up with.

7/ Slow pathway targeted for ablation. 6s of RF was enough to totally remove the two for one responses (TFORs). Post ablation everything normalised. I thought this was a rare but satisfying case. @finnakerstrom

6/ EP study showed helped confirm. There was no VA conduction. Antegrade conduction showed continuous double fire responses without tachycardia. Very hard to systematically do an EP study.

5/ So as @finnakerstrom suspected, we also thought this guy had DAVNNT - dual AV nodal non-reentrant tachy. Wildly different PR intervals, the QRS complexes identical to sinus but with one P to 2QRS is very suggestive. Here's a proposed ladder diagram of one of the ECGs. #EPeeps

4/ This was the Holter.

3/ This was the treadmill test.

2/ ... this running 12-lead ECG may be more useful to help make the diagnosis. #Epeeps

1/ Here's an interesting ECG. Young man referred for high resting heart rate and mild effort intolerance. This was the baseline 12-lead ECG. I will follow with his TMX and Holter subsequently, then finally EP study. What do you think the diagnosis is?

5/ For reference, here is another Ebstein case where the AP is located at the anatomic TA, as expected. By slowly pulling the #HDGrid from the V to the A side of the pathway, pathway potentials can often be identified, as in this case. #Epeeps

4/ ... A+V signals were present at [1]. S2 placed while grid is over [1] showed A signals were extremely early there with possible pathway potentials. RF#1 led to VA block in 1.4s. So, to me, a surprising case.

3/ My interpretation of the map was [1] represents the functional tricuspid annulus and [2] represents the anatomic tricuspid annulus. So [2] should be the location of the pathway. However ...

2/ Mapping using #EnsiteX #HDGrid and #OWM, we saw this. I was a little surprised. The most likely location of the accessory pathway? #Epeeps

1/ This 17 year old boy with Ebstein anomaly was referred to me prior to surgical correction of his tricuspid valve. He turned out to be interesting. EPS suggested a concealed posteroseptal pathway. #Epeeps

6/ RF at tricuspid annulus (*away* from site of earliest activation) immediately terminated tachy. Even after a single RF, no further tachy was inducible and no more evidence of pathway with subsequent EP study. Overall, I think this was an uncommon but interesting case.