a

What Does Your Stress Test Really Mean? - The Princeton Longevity Center

welcome to the Princeton longevity

Center video series on preventing heart

attacks I'm dr. David fine Medical

Director at Princeton longevity and in

this video we're going to discuss stress

tests what they mean and how they are

used

stress test is primarily intended to be

a tool to look for severe blockage in an

artery that's a very useful test when

somebody has chest pain or other

symptoms that may be indicative of

severe coronary artery disease but as

we'll see it's a very very limited test

when it comes to looking for the

presence of early plaque that may not be

severe enough to yet cause symptoms but

can still be putting you at very high

risk for heart attacks the wave stress

test works very simple we increase your

heart rate in order to increase the

demand for oxygen and blood flow in the

heart muscle by monitoring your EKG or

performing other tests we can look to

see if there's an area of the heart

muscle that cannot increase blood flow

sufficiently that has something we call

a limited functional flow Reserve

functional flow reserve is simply a

measure of how much you can increase the

blood flow through that coronary artery

if you have a severe enough blockage

present then you can't increase the flow

enough to meet the demand in general it

turns out that the point at which the

functional flow reserve begins to be

impaired is not until you have roughly

about a 70% narrowing in an artery any

or any narrowing less than that is

likely to be too minor

to actually impair the maximum amount of

blood flow that you can get and it isn't

really until you hit about 70% that the

amount of blood flow that you can

increase through that artery really

begins to taper off the problem with

that is as you develop coronary artery

disease over the years you gradually may

be narrowing down an artery to becomes

more and more blocked doing a stress

test regardless of what type it is

whether it's simply just a treadmill

test whether we do a stress echo a

nuclear stress test we're not going to

pick up anything until you have at least

about a 70% blockage at that point you

have advanced coronary disease and this

is really a late diagnosis of the

disease the reason why because most

heart attacks

are going to happen in arteries that are

less than 50% blocked so a positive

stress test is a indicator of a severe

blockage this is a useful test for

determining whether or not you have

disease that is bad enough to cause you

symptoms such as chest pain walking up

two flights of stairs but it is not

sensitive enough to pick up blockages

that may not yet have reached that level

but are still certainly more than enough

to put you at risk for a heart attack by

the time you have a positive stress test

then you have severe disease you've

probably been at very high risk for a

number of years and really at this point

because you have a significant blockage

the only real treatment decision we can

make on the basis of a stress test is is

that bad enough to put in a stent or

does it require bypass surgery but this

is not really an effective test for

picking up early plaque that is not yet

symptomatic because we can't pick up non

obstructive disease disease that is not

yet causing a 70% blockage and most

heart attacks occur in arteries that are

less than 50% blocked this is simply a

poor predictor of heart attack risk and

in fact the way that most heart attacks

actually happen is that as you develop

plaque over the years within the wall of

the artery you have a soft Center filled

with cholesterol and other materials

that is separated from the blood flow by

a thin layer of tissue and if that

tissue rupture is what we call plaque

rupture that causes the formation of a

blood clot within the artery and it's

actually the cloth that will block off

the artery not the plaque it's only a

very late event that the plaque becomes

severe enough that it blocks off the

artery but by that point you've already

been at high risk for quite a number of

years so how do we pick up the presence

of coronary disease earlier and treat

you before you get to be at high risk

really the only way is to look directly

at the coronary arteries with a scan

here I'll show you some examples of what

a typical heart scan can show us here we

have a cross sectional view through the

heart with the breastbone in the front

and we're starting above the heart here

and here is the aorta with one of the

coronary arteries coming out of it

this is a nice normal-looking artery in

this patient these white spots represent

the presence of calcium deposits within

the plaque in the arteries wherever we

see calcification we have coronary

artery disease there this patient has

mild a moderate disease here we see a

patient with much more extensive disease

this patient is likely at very high risk

for a heart attack

that's very severe disease but also

would very likely still pass a stress

test and this disease would go

undetected unless we actually use the

scan to look directly at the arteries