We're going to talk here in these series of slides about a very important cause of heart disease.
This is going to be one of the major things that ends up causing morbidity and mortality
for roughly a third to 40% of the population globally.
So if you are sitting next to two friends, look to the right, look to the left.
One of you will probably exit this world via ischemic heart disease.
Kind of a scary thought. Alright, with that happy entry, let's get started.
Fundamentally, in ischemic heart disease or IHD,
it's a balancing of how much blood supply the heart gets
versus how much it needs in order to maintain itself, to maintain viability.
And usually, under most circumstances, we have an excess supply.
So blood supply is shown here.
Perfusion usually exceeds any of our myocardial oxygen and nutritional demands.
That is until other diseases supervene.
If it gets to the point where things are pretty close to being equal,
then a little bit of extra activity can tip us over
so that the demands of the myocytes exceed the perfusion. And that will be stable angina.
Meaning, we'll get a little sense of heart chest pain and we'll talk about the mechanism shortly.
But if we stop doing whatever it is we're doing, the scales come back to even.
Now, however, if the scales tip completely the other way
where demands far exceed the nutritional supply, the perfusion.
Then, we're talking about out and out, ischemia and infarction.
Okay. That's a big picture, but that's really all ischemic heart disease is about.
It's a big problem. I've already said, a third of us are going to die as a result of this.
It's the leading cause of death worldwide.
Although cancer is catching up, ischemic heart disease
is still the most common way that the grim reaper takes us off the planet.
So about 9 million deaths each year are attributable to this.
In the United States alone, 700,000 Americans,
almost three quarter of a million Americans will experience a myocardial infarction each year.
That's what an MI is, a myocardial infarction. So they will have a heart attack.
And the lifetime risk of coronary artery disease.
That's not necessarily to say a heart attack
but the lifetime risk of developing coronary artery disease
which is the major cause of ischemic heart disease is about 50% for men lifetime.
So half of us, me, maybe, are going to have some coronary artery disease.
And in women, the risk over a lifetime is 40%, so it's substantial.
As I've already mentioned previously, more than 90% of ischemic heart disease
is caused by obstructive atherosclerotic vascular disease.
And we'll talk about this briefly but there is a whole separate talk elsewhere
that you can listen to my dulcet tones explain how atherosclerosis develops in greater detail.
We'll cover it briefly but it's the major cause.
And then there are 10% of causes of ischemic heart disease that are other causes,
which we will talk about very briefly.
Those other causes of ischemic heart disease include increased demand.
So remember the scales?
I may have actually, not bad atherosclerotic disease of a coronary artery,
but I may increase demand so much by increasing heart rate
or increasing blood pressure that I exceed the capacity,
even though there's normal coronaries to do their job.
You can also have diminished blood volume.
So if you have inadequate blood supply because you've exsanguinated
that's going to be a cause of ischemic heart disease.
You may not have serious coronary artery disease
but you don't have enough blood to flow through those vessels.
You can have diminished oxygenation.
So, remember, it's not just providing nutrition to the myocardium.
It's providing oxygen because you have to generate ATP.
So if the lungs are compromised, if we're not getting adequate oxygenation
due to pneumonia or congestive heart failure,
that's going to be a cause of ischemic heart disease
and if you don't have enough red blood cells or their oxygen-carrying capacity is diminished,
say, because of carbon monoxide poisoning.
That's also going to be a cause of ischemic heart disease. So that's 10%. Let's cover the other 90%.