1/23 This is part 2 of the “The Aorta is not just a pipe” #Tweetorial, focusing on abnormal aortic function and its consequences. Make sure to read part 1 before you read this one! 
2/23 Let’s see what happens when the aorta is unhealthy. I am not even
talking about aortic aneurysms or dissections (that would be another Tweetorial). I am talking about impairment of the aorta’s pressure buffering function due to aortic stiffness.
talking about aortic aneurysms or dissections (that would be another Tweetorial). I am talking about impairment of the aorta’s pressure buffering function due to aortic stiffness.
3/23 Just like any other elastic material, the elastin fibers in the aortic wall fatigue as we age. Long story short, with aging, there is elastin fiber fatigue and increased proteolytic activity in the wall, with elastin breakdown and deposition of collagen.
4/23 Opposite to elastin, collagen is a tensile fiber. This process stiffens the aortic wall. In addition, there is inflammation and smooth muscle proliferation, all of which contribute to aortic stiffening as well.
5/23 These processes occur in all of us as we age, but are accelerated in the presence of CV risk factors and inflammation. For these reasons, aortic stiffness is often spoken of as a surrogate of arterial age. “A man is as old as his arteries”, said Thomas Sydenham.
6/23 So what happens when the aorta becomes stiffer? A stiffer aorta is inefficient in buffering pressure. As the aorta’s characteristic impedance goes up, the same flow from the LV will lead to a higher systolic pressure. Pulsatile arterial load goes up.
7/23 The LV has to deal with this higher pulsatile load, making its job much harder (HFpEF, anyone?). In addition, with less efficient pressure buffering, the end-organs will now be subjected to higher pulsatile pressures, which is detrimental.
8/23 The kidney and 🧠 are particularly affected because their circulation is ‘wide open’ (⬆️ flow, ⬇️impedance),so pulsatility can penetrate these organs even easier and cause havoc. Think arteriosclerosis, microvascular dysfx , and eventually end-organ damage.
9/23 Also, the pressure wave travels forward and backward in a faster speed across a stiffer aortic wall (read: higher aortic pulse wave velocity).
10/23 We use the carotid-femoral pulse wave velocity as the gold-standard for non-invasive aortic stiffness assessmentà It is safe, cheap, and easy to measure – just do it!
11/23 Faster speed of pressure wave propagation ➡️ timing of wave reflections is off: reflected wave arrives at the root earlier, in systole, augmenting SBP rather than DBP. This further increases pulsatile load while removing the beneficial diastolic ‘boost’ to the coronaries.
12/23 Wait a minute, aortic stiffness makes systolic BP go up and diastolic BP go down, increasing pulse pressure? That’s isolated systolic hypertension (ISH), ya’ll! So prominent in the elderly, especially women, ISH is a disease of aortic stiffness.
13/23 And this is why ISH is such a pain to treat – antihypertensives are typically designed to lower systemic vascular resistance but have much less effect on aortic compliance, so they are very good at lowering MAP (which is normal to low in ISH) but poor at lowering PP.
14/23 As you can see, an impairment of the aorta’s pressure buffering function significantly impairs the efficiency of the entire cardiovascular system, increasing pulse pressure (ISH), LV workload (HFpEF, paradoxical low-flow, low-gradient aortic stenosis),
15/23 and pressure pulsatility delivered to the end-organs (arteriosclerosis, target-organ damage, microvascular damage, and dysfunction).
16/23 AND YOU THOUGHT THE AORTA WAS JUST A PIPE, HUH?
17/23 I am asked all the time how to reverse arterial stiffness. That’s tough (pun intended).
18 /23 Just like the old, stiff elastic band I have holding my ponytail right now (which will never go back to the stretchy elastic band I originally purchased), once the integrity of the elastin fibers in the aortic wall is compromised, it will be difficult to repair it.
19/23 Other components of arterial stiffness such as inflammation and smooth muscle proliferation may be more easily manipulated perhaps; and, as such, may contribute to some
aortic de-stiffening in conditions where these mechanisms are predominant.
aortic de-stiffening in conditions where these mechanisms are predominant.
20/23 But once elastic fibers are broken and collagen is deposited, there is not much way to turn back. So the best strategy is to try to delay aortic stiffening in the first place.
21/23 How can we do this? Habitual aerobic exercise, avoiding excessive sodium intake, maintaining optimal blood pressure, eating our fruits and veggies – all of these things have been
shown to help delay aortic stiffness.
shown to help delay aortic stiffness.
22/23 I have witnessed this first hand in my lab, where I have studied people in their 70s whose aortas were as healthy as a 35 year-old’s. Their secret? Habitual exercise. JUST DO IT.
23/23 Iwill conclude here by re-affirming that the aorta is not just a pipe, and some of us aorta fans will even say the aorta’s functions are so complex and essential it could be called an organ. 😉For all of you cardio-centric people out there: THINK AORTA! Thanks for reading!
And here's the link to part 1 of this series of #Tweetorials: @pabeda1
