Thread by @RawanAAmir

1/🏥It's your first night alone in the CCU
😵‍💫You admit a patient with syncope due to complete heart block
🕡HR is 30 bpm with a wide ventricular escape rhythm
You wonder if it's time for your first #TVP, but
🔆is it indicated?
🔆& how are you going to set it up for success?

2/ Learning Objectives:
🔆Recognize indications for pacing
🔆How to manage TVP/adjust settings

3/ But first let’s start with a huge thank you to @AmitGoyalMG @A_h_ghoneem and @RichardAFerraro for their never-ending guidance and help making this happen! 👏🏼

@CardioNerds 🫀

4/ The author has no conflicts of interest.  
There is no commercial support for this content.

5/ Let's first take a vote 🗳️

I feel comfortable identifying patients who may require a TVP and troubleshooting common TVP problems

6/ What are the most common indications for TVP? 🤔

🔆Bradyarrhythmia à symptoms😵‍💫or hemodynamic compromise 🏥(eg. sinus bradycardia, 2nd or 3rd degree AV block)
🔆Overdrive pacing (eg. VT, TdP)
🔆Digoxin toxicity💊
🔆PPM Failure

ncbi.nlm.nih.gov/pmc/articles/P…

7/ So let’s get to know our TVP settings better🤓

For our case, our TVP mode will be VVI
V=Ventricle sensed
V=Ventricle paced
I=pacing Inhibited if native beat is sensed

Vs the other common mode of VOO
V=Ventricle paced
O=not sensed
O=no inhibition of pacing

8/ Although there are different types of generators, they all have the same 3 variables that you can control:

🕑Rate
⚡️Output
⚠️Sensitivity

Let’s start with Rate🕑meaning the number of impulses generated by your TVP/minute

9/ Next, let’s look at the Output ⚡️which is the current🔌produced by the generator during every beat (measured in milliAmpers, mA)

The⬆️the mA, the⬆️the output

(obvious right? wait until you see what's coming next though😉)

10/ Finally, let’s talk about Sensitivity ⚠️which is the minimum current 🔌needed to detect native cardiac activity and inhibit pacing 🫀(measured in millivolts, mV)

🚨Don’t be fooled!

The⬇️the mV, the ⬇️ current is needed to be detected by the TVP so the⬆️the sensitivity!

11/ To make sure we really understand the concept of sensitivity ⚠️

Let’s look at our favorite sensitivity analogy where you’re the pacer trying to see the QRS complex from behind a fence 👇🏻

Fence = mV

12/ 🚨So let’s go back to the CCU!

Your patient now has a TVP, rate is set at 60 bpm, output 10, sensitivity 8, but you see this on tele 👇🏻

So,
What is the problem?🤔
What are potential causes? 📋
How can you troubleshoot it? 🔧

13/ 🚨Prob = undersensing ⚠️

Pacer doesn’t detect intracardiac signal🫀(native QRS) ➡️asynchronous pacing

Possible causes➡️low sensitivity (fence too high), electrolyte abnormality, lead failure

14/ ✅ How to correct?

⬆️sensitivity by ⬇️mV, this allows pacer to detect more cardiac signals🫀

Review reversible causes such as electrolytes🩸

Check hardware (lead placement)🛠️

15/ You ⬆️sensitivity from 8 mV to 7 mV ➡️you are no longer seeing asynchronous pacing (no inappropriate pacing spikes after native QRS)

You cut down mV to roughly half (7 mV ➡️4 mV) and perfecto!👌🏼

Your patient is being paced at a rate of 60 bpm and feels great!👏🏼

16/ Congratulations! First curveball dodged!

But now, your patient’s tele shows this 👇🏻

So, let’s try this again

What is the problem?🤔
What are potential causes? 📋
How can you troubleshoot it? 🔧

17/ 🚨Prob = capture 🥅 failure

An impulse is generated by pacer but it does not cause myocardial depolarization🫀
(pacing spikes not followed by QRS complexes)

Possible causes➡️lead dislodgment, low output

18/ ✅ How to correct?

Increase output⚡️by increasing mA

Check lead positioning

19/You ⬆️ output from 10 mA to 12 mA ➡️ each pacing spike is now followed by a QRS complex (capture achieved! 👏🏼)

You double your output to 24 mA, and the patient feels great! 🥳

But why do you need such a high output? 🤔

Check your lead position, it probably moved!

20/ Amazing job so far! But wait, you now look at tele and you see this 👇🏻
Your patient is in complete heart block again! And there are no pacing spikes at all! 💔
So, one last time folks 🦾
What is the problem?🤔
What are potential causes? 📋
How can you troubleshoot it? 🔧

21/ it could be one of two problems:

DDx 1: Oversensing ⚠️

Pacer senses signals it shouldn’t (eg. T waves or P waves) thinking they are QRS complexes ➡️ inappropriate inhibition of pacing

Possible causes➡️ high sensitivity (fence too low), lead failure

22/ 🚨DDx 2: output⚡️failure

Native HR < set rate🕑, but still no pacing
(no pacing spikes when there should be pacing spikes)

Possible causes ➡️lead failure, generator failure, battery failure, oversensing

23/ So how can you trouble shoot? 🔧

⬇️ sensitivity by ⬆️ mV (bring the fence up), will overcome both DDx!

Check hardware (as below) 🛠️

24/ General check list 📜to go through when troubleshooting🧑🏻‍🔧

-generator on? 🔛
-Battery low? 🪫
-Wires attached well?
-Leads connected?🔌
-Could the TVP wire have been displaced?

25/ So lets ask again now 👀

I feel comfortable identifying patients who may require a TVP and troubleshooting common TVP problems🦸🏾‍♀️

26/ I learned something in this Tweetorial that may change my clinical practice🤓

27/ Congratulations on making it to the end of this thread and for keeping your patient alive in the CCU! 🥳

Thank you so much for listening and hope you learned something new from this little tweetorial 📚

#Cardiotwitter #TVP