infections we're all familiar with.

It often affects young people, has very few symptoms, and goes largely undiagnosed…until

the autopsy stage.

If this already has your heart racing, you'll want to stay put.

Myocarditis, is kind of a hard word to pronounce.

It stands for myo, which means muscle, card means the heart, and itis means inflammation.

My name is DeLisa Fairweather.

I'm a PhD researcher from Mayo Clinic in Jacksonville, Florida.

I've studied myocarditis for about 25 years.

It's not like a heart attack where you get pain symptoms or something that alerts you

that you have a problem.

With myocarditis, you often don't get any symptoms at all related to your heart.

Unlike atherosclerosis, which is commonly linked to heart attacks, and involves your

vessels and arteries, myocarditis is an inflammation of the heart muscle itself.

It's often caused by viral infections.

And in the United States, the most common type is called Coxsackie virus.

Or, by its more common name, hand, foot, and mouth disease. You may have even experienced this

as a child.

It usually goes through the daycares, it causes little sores in the mouth, on the fingers, and feet.

That's the first time you catch the virus.

You actually then catch it every year of your life, so it's a very common virus.

You don't get the sores after the first time.

Myocarditis can also be caused by other types of viruses such as influenza, hepatitis B

and C, and HIV.

Coxsackie is something that your body's immune system usually takes care of.

But what happens when it gets to your heart?

So one of the mysteries that there's been about myocarditis, is why do viruses that normally

infect the gut, like enteroviruses, or the flu, which normally infects the lung, why

would they go to the heart?

And we found out in recent years, the reason they do that, is because they want to hijack an

organelle that's called mitochondria.

Mitochondria are the energy-producing organelles—you might even say, the powerhouses—in our cells.

They make what's called ATP or the energy that fuels our bodies.

Alongside the brain, the heart and kidneys together represent the body's highest demand

for energy.

If a cell is a car, you have to have an engine that

makes the car run and produces the energy to make the car run.

The heart has a lot of them, so rather than just having one engine like our car, a typical

heart cell will have 10,000 engines or mitochondria, because it needs so much energy to pump.

Typically, viruses travel through the bloodstream and infect the mitochondria,

essentially hijacking the powerhouse's normal role to instead replicate the virus.

But then, our body's immune system targets that activity and tries to stop this from happening.

You can think of the virus really as an enemy.

And the immune system is like the fort and it's trying to protect the heart from disease or

the intruder.

Mast cells or M-A-S-T, those are our allergy cells.

They're the watchmen on the wall that are trying to prevent the virus from getting in.

Those are the cells that we usually think of as protecting us or causing allergies,

but they also do many other things and they're very important at starting an immune response.

When they detect it, then they set out an alarm; they send for the large army and the

large army are called macrophages.

Those are a type of immune cell that is really good at destroying the virus and helping to

get rid of the virus.

And in most cases, this is a good thing.

The macrophages will come in and get rid of the infection, and we never know the difference.

But certain activities can put you at a greater risk for sudden death due to this inflammation

in the heart.

You may have heard of reports where someone was swimming, or they were running a race

or a marathon, or playing soccer on the field and suddenly they collapsed, or maybe even

they dropped dead.

Often at autopsy, that turns out to have been myocarditis and just was not realized.

That's because exercise or strenuous action can actually exacerbate this condition.

We need the mitochondria to give us more fuel when we exercise.

Those mitochondria will actually split.

When we exercise, we

need more energy, and it's like the engine splits into two engines to provide us even

more energy.

But when that happens, it allows the virus to accelerate its replication, in turn causing

even more inflammation and increasing your risk of acute heart failure.

So if there are no symptoms and it's so tricky to diagnose, how do we know when to seek medical

attention?

The one thing that we have heard from patients where they really have survived, is that

they had a gut feeling that something was wrong.

So one thing we always tell people is to really trust your gut, and if you feel like something

is wrong, just keep going to the doctor and make sure that you get it looked into.

So, if you've recently had flu-like symptoms or just haven't been feeling well… maybe

lay off the power squats.

And as for the future of diagnosis and treatment...

The good news is that we are developing new imaging methods to detect myocarditis.

It's going to make it easier for doctors to be able to work out that you have myocarditis

And we're also working on new methods to be able to prevent myocarditis, to reduce the inflammation,

and reduce whether you're going to progress from myocarditis to dilated cardiomyopathy.

The healthcare profession in general is getting really good at saving people's lives when

they're having sudden heart failure.

So if you get into a hospital and you are having problems, then it is really very high chance

that your life is going to be saved.