Thread by @SonuAbrahamMD

#MedTweetorial #Part2 on RV Failure based on @NEJM article by @RyanTedfordMD @Brian_Houston12 !

We will discuss RV-PA uncoupling today!

PV loops are a scary thing to many. Refer to this #Tweetorial by my friend @AHajduczok for a primer on PV loops.

#1 This image summarizes all the parts of the PV loop of the left ventricle .

Note the end-systolic pressure, end-diastolic volume and stroke volume specifically to understand the upcoming tweets.

Let’s begin with a poll

Do you understand what RV-PA uncoupling is?

#2 The right ventricular PV loops is slightly different from the LV.

⭐️ Lower end-systolic pressure /afterload
⭐️ Larger end-diastolic pressure
⭐️ Lower systolic pressure

#3 Let’s learn 2 terms :
1️⃣ End systolic elastance (Ees)
2️⃣ Effective pulmonary arterial elastance (Ea)

#4 Some basic physics and math before we move forward 😉

1️⃣ What is elastance ?

Elastance 🟰 Pressure/Volume

It’s the opposite of compliance.

2️⃣ How do you calculate the slope of a graph?

Refer to the image 👇🏽

#5
1️⃣ End systolic elastance

⭐️ Manipulate load ➡️ a family of PV loops can be created.

⭐️ The ratio of maximal pressure to volume at end systole for each loop is determined.

⭐️ The slope of a line connecting the end-systolic points represents the end-systolic elastance.

#6
2️⃣ Effective pulmonary arterial elastance (Ea) ( Some more physics ! )

🔺P 🟰 Flow X Resistance

Pes 🟰 SV X HR X Resistance

Pes/SV 🟰 HR X Resistance

Ea 🟰 Pes/SV 🟰 Measure of afterload on the RV

#7 What does coupling mean ?

✅ Coupling ➡️ the energy transfer between ventricular contractility and arterial afterload.

✅ Ventricular contractility 🟰End-systolic elastance (Ese)

✅ Arterial afterload 🟰net arterial stiffness 🟰 Effective pulm arterial elastance (Ea)

#8 Ese/Ea 🟰Coupling 📏

As long as the ventricle can adapt to the increasing afterload, coupling is maintained.

So when Ea ⬆️ , then Ese ⬆️ initially .

Later stages of pressure overload ➡️ RV gives up 😩 ➡️ Ese doesn’t proportionally increase to Ea ⬆️ ➡️ RV-PA uncoupling

#9

Normal Ese/Ea 🟰 1.5 - 2

RV-PA uncoupling 🟰 Ese/Ea < 0.6 to 0.8 ➡️ worse outcomes

#10 But PV loops are usually done only in research labs.

How can this be useful to a clinician ? 🤷🏼‍♀️

Are there echo correlates to Ese/Ea?

#11

TAPSE 🟰 Measure of RV contractility

PASP 🟰 Measure of RV afterload

TAPSE/PASP 🟰 moderately correlated with the reference standard of RV-PA coupling

TAPSE/PASP <0.31 mm/mm Hg can predict RV-arterial uncoupling (defined as Ees/Ea <0.805).

#12 For other exam findings, echo, RHC and MRI findings in RV failure , refer to table from the paper. 👇🏽@NEJM

#13

Do you understand the concept of RV-PA coupling ?

Hope you find this #MiniTweetorial useful . Await #Part3 on RV failure !

@NEJM @RyanTedfordMD @SaurabhSDani @SarjuGanatraMD @AndrewJSauer @AHajduczok @hvanspall @SantosGallegoMD @rachkataria @DavidMintz17 @SahoorKhan @SaheliNandiMD @AdrianaCMares

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