What’s Going On In Your Heart?

Dear readers,

This is Samarth, your Editor. I am writing today’s piece to explain two lesser-known diagnostic tests for heart disease.

The genesis lies in this provocative article: ‘Don’t Die of Heart Disease’. I strongly recommend you read it. Jared Hecht writes:

“Over the past several months I’ve spoken with several of the world’s leading cardiologists and lipidologists to better understand the key elements of heart disease prevention… I’ve found that the steps/protocol for avoiding death by heart disease are very simple.”

Among the recommendations listed, he makes a case for two diagnostic tests: measuring ‘ApoB’ and getting your ‘calcium score’.

What are these two metrics? And how does that link to heart disease?

That led me to a chain of exploration, which is the article for today.

I got my ApoB test last week and have booked my appointment for a calcium score test next week. So the understanding here is something I actually acted on, and because I learnt this while figuring this out, I thought I should write about it.

I must add the mandatory caveat that I am—obviously—NOT a doctor. This article is coming from a dilemma many of us face: modern medicine often feels reactive rather than preventive. It shows its magic when things get worse rather than creating conditions to reduce the chance of getting there.

So comes the urge to take charge—to educate ourselves, to understand what we might not be hearing, and what we can do for ourselves and our loved ones before a crisis hits. At that point, we want to understand disease a bit better.

This is an attempt to get there for heart disease with a clear action: how these tests can help. But of course, please consult your physician if this is relevant to you.

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I. The Mechanics

Our heart has one main job: it must continuously beat to keep us alive. Each beat sends oxygen-rich blood throughout our body.

To do this job well, the heart needs at least three things to work perfectly:

1) Its own blood supply through what are called coronary arteries.

2) A reliable electrical system to trigger each beat.

3) Strong heart muscle to pump effectively.

One of these things breaks when there is a heart disease.

1) Blood supply is blocked: Imagine your heart muscles are working as they are supposed to. They are pumping blood to the rest of the body. But suddenly, one of its own supply lines—a coronary artery that feeds oxygen to the heart muscle itself—gets blocked. The part of the heart muscle fed by that specific artery starts starving for oxygen and that specific muscle begins to die.

This is a heart attack.

You’re not dead—but part of your heart muscle is damaged or dying. They are often sudden and that’s why it’s called an attack.

2) The heart’s electrical system fails: Think what would happen if the heart’s electrical system which is supposed to trigger each beat fails. No electrical signals means the heart will simply stop beating—just no pumping. Which means no blood flow to the brain or other organs.

This is a cardiac arrest.

Without immediate treatment, it can be fatal. Within minutes, lack of oxygen to the brain leads to unconsciousness, and eventually, it can lead to death.

3) The heart becomes too weak to pump: Sometimes the heart doesn’t stop suddenly or get blocked—it just gets weaker over time. Imagine a pump that’s been overworked for years. The heart muscle stretches and becomes flabby, losing its ability to pump blood effectively.

This is heart failure.

Your heart is still beating, but it can’t pump enough blood to meet your body’s needs

This develops gradually, usually because the heart has been damaged or strained over time.

For example, routinely high blood pressure forces the heart to work too hard for years. Or a previous heart attack can leave behind scarred heart muscle that can’t pump as effectively. Or some other conditions that directly weaken or stiffen the heart muscle.

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II. The Common Enemy

These heart problems might seem quite different—a sudden blockage causing a heart attack, an electrical failure leading to cardiac arrest, or the gradual weakening in heart failure. But they’re often connected by a single underlying process: the buildup of fatty deposits in your arteries.

These deposits, called plaque, form when fatty particles stick to damaged spots in artery walls. (Doctors call this process atherosclerosis.)

They matter because they can either block blood flow (leading to heart attacks), or narrow arteries so much that your heart slowly wears out from working too hard (leading to heart failure).

What makes it particularly dangerous is how silently plaque develops: it usually shows no symptoms until something serious happens. This is why the first time many people know they have a heart problem is when they have an attack. By the time they feel chest pain or shortness of breath, significant damage may have already occurred.

This is where modern medicine offers hope: we have ways to look inside our arteries and detect plaque buildup before it causes problems.

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III. The Two Tests

Since plaque forms from fatty substances in our blood, doctors have traditionally relied on cholesterol tests to assess heart disease risk. These tests measure HDL (often called “good” cholesterol) and LDL (often called “bad” cholesterol because these are the particles that can form plaque) in your blood.

The idea was simple: knowing how much cholesterol is floating in your blood should tell us your risk of developing plaque and heart disease.

But now we have more precise ways to detect potential problems. I learned about two key measurements from the article I linked that can help us catch this process early:

1) ApoB testing: When doctors check your cholesterol, they typically measure how much fat is floating in your blood. But what matters more is how this fat is transported.

Every particle that can stick to your artery walls and form plaque carries exactly one ApoB protein. That’s why measuring ApoB gives us an exact count of potentially dangerous particles.

Think of it this way: traditional cholesterol tests tell you how much fat is in your blood, but ApoB tells you how many particles are carrying it—and it’s these particles that actually cause plaque.

This matters because you could have “normal” cholesterol levels but have it carried by many small particles (high ApoB), putting you at higher risk for heart disease. Each standard deviation increase in ApoB levels raises your heart attack risk by 38%. That’s why many experts now consider ApoB a better predictor of heart disease than standard cholesterol tests.

For more, see this comprehensive 2021 scientific review which examines multiple studies on the predictive value of ApoB and offers important caveats on its lack of widespread clinical adoption.

2) Coronary artery calcium (CAC) score: While ApoB shows your current risk, a calcium score shows the damage that’s already happened. It’s a special type of CT scan that looks for hardened (calcified) plaque in your arteries. When plaque first forms, it’s soft and can be particularly dangerous because it can break loose and cause sudden blockages. Over time, this plaque hardens and becomes calcified. Measuring this calcium gives us a good picture of how much plaque has built up in your arteries over the years.

Together, these tests tell a complete story: ApoB shows your risk of forming new plaque, while your calcium score reveals plaque that’s already there. This combination can help catch problems early—when you can still prevent serious heart problems, rather than waiting until you have symptoms.

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This is my understanding of the diagnostics. In his article, Jared has a bit more on treatment. (I haven’t done a deep-dive on it yet. You may want to check that out.)

Some of the fundamentals of how our heart works I learnt from Bill Bryson’s excellent book ‘The Body: A Guide for Occupants’.

And I want to end this with one of his ideas that really shaped the way I think about efforts to take charge of our health:

“All forms of heart failure can be cruelly sneaky. For about a quarter of victims, the first (and, more unfortunately, last) time they know they have a heart problem is when they suffer a fatal heart attack. No less appallingly, more than half of all first heart attacks (fatal or otherwise) occur in people who are fit and healthy and have no known obvious risks. They don’t smoke or drink to excess, are not seriously overweight, and do not have chronically high blood pressure or even bad cholesterol readings, but they get a heart attack anyway. Living a virtuous life doesn’t guarantee that you will escape heart problems; it just improves your chances.”

Knowing it early— through precise diagnosis—can perhaps improve our chances a little bit more.