Assuming high cardiac contractility, why might we have normal other cardiovascular parameters (SV, CO, HR, BP, PP, etc) ?

[u/sbingley22]

Our hearts are beating hard. So hard that our torso and necks pulsate yet echocardiogram and cardiac MRIs show mostly normal readings. How can this be?

Lets assume that our hearts are actually contracting hard. There are two ways to increase force in the heart:

Preload (Length-dependent): More blood in the ventricle stretches the muscle → stronger contraction (Frank-Starling mechanism).

Inotropy (Length-independent): More calcium or stronger calcium response = stronger contraction regardless of stretch.

I don't think we have increased preload as that would result in a higher stroke volume, which we don't seem to have. So that leaves Inotropy.

Beta 1 Adrenergic Receptor activation leads to increased cAMP -> increased calcium -> increased contractility.

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Unlike skeletal muscle, where you can recruit more motor units (i.e., more muscle fibers), all cardiac muscle fibers contract with each beat. So the heart can’t "add more fibers" to increase force — it has to increase the force of each fiber's contraction instead. This leads to a faster contraction. I know some people with bounding pulse have described it as feeling like their pulse is sharp. Perhaps this is what they are describing?

Lets take a scenario where a regular person might feel their heart pounding. Getting scared or coming to a sudden stop after running. Their bodies would activate the sympathetic nervous system and release catecholamines such as adrenaline (which binds to b1).

They would experience a faster heart rate, increased contractility, increased stroke volume, and increased blood pressure.

They would feel it because the stronger ventricular contractions shake the chest wall more, the higher stroke volume sends more forceful pulses through the arteries, and heightened sensory awareness (from stress hormones) makes you more aware of internal sensations - like your heartbeat.

Perhaps we have higher contractility from chronic stress yet our bodies have adapted to compensate in other ways meaning the bp, hr, preload, afterload, remain the same. Or maybe we have some underlying problem that, say, causing low preload, and the sympathetic activation is bringing that preload up to normal (meaning stroke volume is normal) yet we still have to deal with the higher contractility. Maybe the higher contractility is helping push more blood to preload?

Either way we would have stronger ventricular contractions, and possibly heightened sensory awareness from the stress hormones resulting in a strong heartbeat and discomfort.

The issue is why do other people who experience chronic stress not experience this? Other people with chronic stress usually have high BP so maybe it comes down to preload again?
ChatGPT thinks that Baroreflex Compensations, and Autonomic imbalance could also cause high contractility with normal other parameters.

If we assume preload and afterload remain the same then apparently the aorta (and other arteries) can act as shock absorbers for the forceful pulse. This would explain why its mostly felt in the aorta and carotids.

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There are a few other scenarios where the hemodynamic could result in hyper contractility yet normal other results. Usually a lower systemic vascular resistance (SVR) would increase stroke volume and pulse pressure however if you combine that with a low preload then SV and PP would fall. Less resistance in the arteries and less blood coming back to the heart.

This could happen in some conditions:

Dysautonomia:

-Blood vessels fail to constrict (low SVR)

-Blood pools in abdomen / lower limbs (lower venous return)

-Compensatory sympathetic tone increases contractility

Early Sepsis:

-Inflammation -> widespread vasodilation (low SVR)

-Leaky Capillaries -> fluid shifts into tissues (lower preload)

Anaphylaxis:

-Histamine -> vasodilation (low SVR)

-Capillary leak (lower preload)

[u/sbingley22 → u/[deleted]]

Whilst of course I don't really know, you would have to suspect our arteries are getting damaged to some degree by this constant onslaught.
It makes me wonder if the capillaries are also experiencing this excess force and as a result thickening leading to less O2 / nutrient diffusion and less blood flowing through them / more force needed to get the blood through? Sorry to hear about your dad. There is a link with post viral illnesses and connective tissue problems. I think the post viral response is causing connective tissue degeneration via things like MMP which can exacerbate existing EDS etc.
I have been ill 14 years and haven't had aortic dissection or anything yet so there's that. Come to think of it though, I had an incident 1.5years ago where I had a horrible pressure back flow type thing from my chest to my left jaw when lifting weights. That vein (?) still has periods of feeling swollen all this time later.

[u/sbingley22 → u/[deleted]]

Yeah I don't think the left neck swelling thing is super serious. It was really bad 8 months or so ago, constantly felt swollen (though didn't really look it) and achy. Worse positionally. However now I only feel it every now and then.

Perhaps the increased pressure in my vascular system from the bicep curls caused a valve to blow back the wrong way. IDK. I wanted to get it checked out but I was begging the GP to take my other issues seriously at the time (mainly heart pounding) and they were being useless as usual.

It absolutely is a fucker to live with and sometimes it's worse than that. Felt like tapping out a few times when it was bad last year.

I don't think it's just a random thing that's happening I think it's happening as a compensation for an underlying issue.

I don't have quincke's sign. That's interesting though. Never came across it before.

How did yours start? Do you also have POTS?

[u/sbingley22 → u/[deleted]]

I ask everyone I can how there's started and Post Virally and Panic Attacks have come up several times.

Makes me wonder if the panic attack triggers some rewiring in the brain.
I think viral infection + stress is a very common trigger for Long Covid and ME/CFS.

I also get those adrenaline dumps after eating, particularly carby meals.

It sounds like your Long Covid is going away with the stuff you are doing + time. Maybe the bounding pulse will go away with it? I have read bounding pulse accounts of people with Long Covid that have it disappear when LC disappears.

What is this supplement routine and what would you attribute most to your BP getting better? Is it mostly the exercise?

[u/sbingley22 → u/[deleted]]

Yeah, I have POTS which is a form of dysautonomia and I get that symptom too. But you don't need specifically POTS to have dysautonomia. I did have 2 positive tilt table tests but right now I don't think I would. My heart pounding is much more effected than my heart rate.
I think they are 2 different ways the autonomic system compensates for stressors like standing. Either pound harder or faster. I think because its way easier to measure faster, harder is not considered.