Thread by @sukritibanthiya

1/18 What if I told you that the Frank Starling mechanism which usually serves to ⬆️  the stroke volume with ⬆️ diastolic filling, can actually ⬇️ it in a certain condition?

Discover why this paradox occurs in this 🧵 on Brockenbrough-Braunwald-Morrow sign #CNshowmeasign

2/ But first, some🥼 clinical features that are useful in suggesting a Dx of HCM & differentiating it from fixed valvular obstruction.

3/ Now, your patient has Sx & dynamic murmurs suggestive of HCM.

Congratulations! You have revived the art of bedside diagnosis #medtwitter.. but you still find yourself in a pickle 🥒😂

Echo shows LVOT gradient is <50mmHg at rest and with maneuvers.

What do you do next?

4/ You’ve heard about the “4 P’s” or four preventions of hypertrophic cardiomyopathy management (cardionerds.com/hypertrophic-c…) thanks to wonderful teaching by @AmitGoyalMD & @CarineHamo

Now, let’s look at the 3 D’s of Brockenbrough-Braunwald-Morrow sign 👇

5/ 1.  Dynamic🚪outflow obstruction increases significantly

In fixed🪟outflow obstruction the obstruction only increases slightly

6/ 2. Decrease in arterial pressure

It is described as a ⬇️ in arterial systolic pressure and pulse pressure after a PVC, accompanied by an ⬆️ in peak LV systolic pressure

(Image credits: @CharlieJainMD)

7/ 3. Deliberately provoke the Spike and Dome to diagnose dynamic obstruction in patients without resting obstruction

8/ In 1964 a B-blocker Nethalide showed a ⬇️ in LVOT gradient initially produced by Isoproterenol.

This revolutionized the use of B-blocker as the initial 💊 of choice in HCM, especially in pts. with angina!

9/ More here on the fascinating history behind the accidental discovery of the sign from Dr. Braunwald himself! Don’t miss this! 🏃‍♀️🏃‍♂️

10/ Next, let’s try to understand the mechanism underlying this sign.

First stop, to the symphony 🎶 orchestra! There appears to be another “royal screw up” by the conductor as Dr. Braunwald would say!😀

11/ In summary, the 3 step process is HCM is as follows:

1. ⬆️ inotropic response & ⬇️ afterload post-PVC

2. ⬆️ obstruction of LVOT

3. ⬆️ in LV systolic pressure, ⬇️ in arterial systolic pressure & ⬇️ pulse pressure

12/ In AS, changes in arterial systolic and pulse pressure reflect the changes in LV systolic pressure since the obstruction is fixed🪟

Thus, post-PVC ⬆️ LV systolic pressure is accompanied by ⬆️ arterial systolic &  ⬆️ pulse pressure without significant ⬆️ in obstruction.

13/ The factors that ⬆️ inotropic response:

- Frank-Starling mechanism
Compensatory ⏸️ post PVC ⬆️ filling time during diastole → ⬆️ EDV → ❤️stretch → ⬆️ contractility

- Post extrasystolic potentiation
Extracellular Ca2+ ↪️ ❤️ myocytes → ⬆️ post-extrasystolic contraction

14/ Here’s a cool case report that describes “Echocardiographic Brockenbrough-Braunwald-Morrow sign” bit.ly/3HSqDU1

An ⬆️ LVOT gradient & SAM following a premature atrial contraction!

15/ Finally a tweetorial on Brockenbrough-Braunwald-Morrow sign would be incomplete without mention of this awesome review by @CardioNerds mentor @Dr_DanMD!

https://twitter.com/Dr_DanMD/status/1164547453950943232

16/ Resources:
bit.ly/3j9WDJ2
bit.ly/3FNkQwo
bit.ly/3HSqDU1

A big thank you to the editors & reviewers @CharlieJainMD & @TDonisan for their teaching & mentorship!

Grateful for @ Cardionerds mentors for the #Showmeasign series @AmitGoyalMD, @Dr_DanMD, @ThomasMDas, @PatrickZakka & @a_h_ghoneem for their continued support.

18/18 If you enjoyed this, check out this tweetorial on diagnosing hypertrophic cardiomyopathy on echo @TiffanyDong6 @TDonisan @CardioNerds 😊

https://twitter.com/sukritibanthiya/status/1585218578495975424