🧵What Does the Left Atri...
Highlights
- 🧵What does the left atrial appendage do? Is it just a nidus for thrombus?
A brief review of proposed & proven functions of the LAA👇
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@drpaulfriedman @ChetRihal (View Tweet)
- #1 LAA plays a very important capacitance role.
Animal studies in 1990s showed:
- LAA is more compliant than LA
- LAA acts like a decompression chamber during systole
- The capacitance/reservoir role is key when LAP is elevated
- Eliminating LAA acutely ⬆️ LA pressure in dogs
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- Effect of LAAO on hemodynamics in humans is debatable
- OBS data ➡️ that LAAO ⬆️ LAP, ⬇️ LA transport function, ⬆️ HF
- However, in LAAOS III RCT there was no ⬆️ in HF admissions w LAAO
- Caveat: epicardial closure vs ednocadail plugging of LAA don’t produce similar effects
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- #2 LAA has a hemostatic function
Data from hemostasis I & II studies & PRAGUE-17 showed that
- Epicardial LAAO has considerable impact on neurohormonal parameters & BP. This effect was persistent during mid term f/u
- Endocardial LAAO has minimal or no hormonal or BP impact
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- #3 Arrhythmia roles of the LAA
- LAA is suggested to be an underrecognized source of AF initiation
- THE BELIEF trial showed that empirical isolation of the LAA ⬆️ freedom from AF without increasing complications
- A meta analysis by Friedman et al confirmed this concept
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- BUT: stroke risk w electrical isolation of LAA was a major concern
- However, Di Biase et al showed that this risk can be mitigated with appropriate OAC or LAAO
- LAA may not always be pro-AF. Melduni showed that routine LAAO during surgery was associated w ⬆️ post-op AF👇
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- #4 LAA as a source of stem cells
- In 2000-2010s. several groups showed that the LAA contains a large number of cardiac progenitor cells (CPCs) - reported to present up to 20% of LAA tissue in some studies!
- This fueled an interest in the role for LAA in regenerative medicine
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- First in human feasibility studies (Patching the myocardium w LAA CPCs during CABG) has been published
- A limited number of ‘efficacy’ studies in animals showed a potential role for LAA CPC in myocardial salvage after myocardial infarction
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- #5 Coronary protection
It has been suggested that the left and right atrial appendages overlay & protect the origin of the coronary arteries from the friction associated with the dynamic motion of the heart. However, this proposed function hasn’t been studied. (View Tweet)
- In Summary,
📌 The LAA has important roles hemodynamic, hemostatic & electrical functions. Our knowledge of those functions is limited.
📌 While we continue to learn about this unique structure, we should not discard it as a mere nidus for thrombus. (View Tweet)