G'day Team,

Those who read my posts regularly will be familiar with my habit of setting out to write about 'x' and half an hour later deciding I first need to explain 'a' and 'b' in order to really give people the basics needed to understand why a discussion about 'x' is so important... so leading up to a discussion about detecting heart attacks... let's talk about what a heart attack is!

This will be a very basic introduction... medically trained fellows please don't crucify me, details will be covered in future updates (including further classes of MI).

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Image Source - Pixabay

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The Heart

Luckily, I've already made a post about the basics of the anatomy of the heart and while I never got around to doing an advanced post, this is enough information for what we'll be chatting about today!

The most important thing to pay attention to are the coronary arteries, a network of vessels which supply blood to the heart itself. These are the arteries that are often responsible for heart attacks.

Atherosclerosis

The term atherosclerosis may sound a little complex, but its name pretty much gives it away. 'Athero' is a common medical prefix for 'vessel', and 'sclerosis' for 'harden' and that's quite literally what atherosclerosis is... hardening of our vessels. Now we won't go into the exact process here, but to put it simply, it involves the movement of lipids from our blood into our vessel walls leading to a build-up which can calcify.

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Image Source - wiki CC BY-SA 3.0

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Atherosclerosis is a big problem because our body relies on the flexibility of our vessels to help blood flow freely and easily through our body. As our vessels harden they lose compliance and resist the flow of blood, in order to compensate our heart works harder and our blood pressure goes up! Increased blood pressure just accelerates the rate of atherosclerosis and the whole process feeds-back on itself.

But the issues don't end there... in fact, bad atherosclerosis can lead to significant build-ups in our vessels that are so thick they hinder or completely block the flow of blood. This is called an occlusive thrombus and, depending on where it is, can completely stop blood flow to a particular part of our body.

Alternatively, many thick atherosclerotic lesions are capped with a hard calcified cap. This calcified cap may break, leading to a rapid thickening of the lesions as the contents underneath spills out and blocks the vessel. This will either lead to a blockage of blood flow at this site or a breaking off of material which can lodge further along in other arteries. When this occlusive lesion travels and blocks a vessel further down from where it originated, it's called an embolism.

Heart Attacks

So this is where we are going to talk about 'Heart Attacks'... and it's going to be a really quick chat. Because, unfortunately, the medical profession doesn't really use the term 'Heart Attack'... that would be too simple and, honestly, it just isn't specific enough for what we want to know!

What most people are talking about when they say 'Hear Attack' is actually what we call a 'Myocardial Infarction' (MI)... so let's talk about MI!

Myocardial Infarction

Myocardial Infarction is another big term which boils down to have a really simple meaning! Our entire body relies on a good supply of oxygen in order to work, and when we can't supply tissue with oxygen they become starved, or ischaemic. Ischaemic tissue doesn't work properly, it lets off inflammatory signals and over time it begins to break down. Once the tissue has broken down enough to be 'beyond repair' (essentially dead) then we say it's 'infarcted'. 'Myocardium' is the term we use for heart muscle.

So myocardial infarction is the death of heart muscle, due to a reduction in oxygen supply.

But how does this happen?

Well, remember how we mentioned atherosclerotic lesions occasionally burst, spilling out their contents and rapidly thickening and occluding the vessels they are in. Well, this can occur in the arteries that supply blood to the heart (the coronary arteries) and when it does the ensuing lack of blood supply can result in a myocardial infarction. This is the most common mechanism for sudden myocardial infarctions, though it should be noted it's not the only one. Something we'll discuss more in Part II.

Consiquences

As the heart becomes increasingly starves of oxygen the muscle dies, which can lead to a number of problems. The dead muscle stops contracting properly, which may result in a failure of the heart to get blood to the brain, resulting in a person passing out. The dead tissue may cause problems with conduction of electrical signals too, which can lead to fatal arrhythmias or abnormal heart-beats. It's even possible for the dead heart tissue to 'blow-out' leading to a bleed out of the heart wall, which often results in sudden death.

Even if the initial attack is survived, there are long-term consequences of heart attacks too. The dead heart muscle may never recover and in it's weakened state the heart may never be able to pump blood properly again. This leads to a condition called heart failure.

Dead muscle tissue may continue to reak-havoc with electrical conduction through the heart and lead to arrhythmias, or the tissue that holds valves together may die resulting in valvular prolapse which can also cause heart failure.

The ultimate take-home is that the heart is a pump, with an important job and heart attacks can lead to a permanent reduction in the heart's capacity to do its job. While not everyone is so unlucky, it's possible that this reduction is so severe that even short-term recovery is not possible and these patients have few options left... but we'll discuss more on the specifics later

Thanks

Thanks for reading team, as usual I hope everyone learned something useful! Keep posted and please vote, re-steem or comment :)

Thanks

-tfc

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Resources
Medscape - paywalled
UpToDate

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