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Coronary Calcium Scans Can Save Your Loved One's Life


When the coroner told me my 69-year-old father had collapsed on the street from coronary plaque rupture, I couldn't believe my ears. Despite paramedics' quick action, he passed from a blocked artery in the ambulance with no hand to hold.

Throughout his life, my dad fought against numerous illnesses: severely herniated discs, continuous major depressive disorder, a range of motor impairments and neurodegeneration from Parkinson's disease. So to think a cholesterol plaque caused his demise was absurd.

Once the initial shock of the news subsided, my left rational brain kicked in. My family and I could not wrap our heads around the information vacuum surrounding my dad's heart health in the lead-up to his death.

My dad's laboratory tests were constantly under the microscope since his Parkinson's diagnosis for possible related complications—including cardiovascular diseases such as coronary artery disease (CAD).

He frequently underwent different diagnostics tests routinely used by cardiologists, including the electrocardiogram (ECG), the echocardiogram, the (exercise) stress test and the angiogram.

His blood tests controlled for inflammatory biomarkers of arterial stiffness like C-reactive protein (CRP) or cytokines like interleukins (ILs) with no red flags.

So how did his doctors miss a diagnosis of atherosclerosis?

They probably thought he was in perfect cardiovascular shape, yet he had the arteries of an 85-year-old man even though he was in his late 60s.

My dad was amongst this subset of the population who fell through the cracks of a proper CAD diagnosis because of an absence of more overt bad markers or signs for his age group.


Challenging Traditional Cardiac Risk Assessment

There is a lot of debate around the root causes of heart disease, but not so much on diagnostic tools at our disposal to prevent it. Still, the stakes are higher than ever to ensure we refine the diagnosis of major adverse cardiac events (MACEs).

In the UK alone, cardiovascular disease causes more than a quarter of all deaths, with around 168,000 casualties yearly, according to the British Heart Foundation (BHF)'s latest August 2022 figures. These include 48,000 people under the age of 75, like my dad.

Atherosclerotic plaque ruptures cause many heart attacks, so focusing on diagnosing damage to the main arteries is even more critical.

While the efficacy of standard heart disease tests has been proved, they do not directly measure the extent of the disease. But rather related-risk factors, like inadequate blood flow or low oxygenation (hypoxia), that can eventually lead to heart failure.

Unfortunately, an angiography only measures blood flow and won't necessarily identify fatal plaque, for example.

The ECG has its place in Accident and Emergencies (A&E) or intensive care units, as it mainly reveals evidence of a previous heart attack or one in progress.

The echocardiogram can highlight parts of the heart wall that move weakly but does not indicate the origin of the damage, whether through CAD or various other conditions.

As for the stress test, fitness isn't sometimes representative of heart health.

So while all these tests provide insights, they have a weak predictive value. Patients at greater risk for cardiovascular disease, such as those with associated conditions, need the best non-invasive method that accurately determines cardiac risk.

The good news is that this test exists, but only some know about it. This test, called coronary artery calcium scanning (CAC), can precisely identify and monitor arterial damage predisposing to heart disease.

A CAC scan, also known as a calcium-score screening heart test, sees calcium deposits in the arteries, which directly correlate with CAD burden.

During advanced atherosclerosis, the artery lining is coated with layers of immune cells (macrophages), lipids, calcium and fibrous connective tissue—restricting blood flow downstream.

During advanced atherosclerosis, the artery lining is coated with layers of immune cells (macrophages), lipids, calcium and fibrous connective tissue—restricting blood flow downstream.

What Is Coronary Calcium?

Inflammation is a cardiovascular risk factor leading to atherosclerosis, where the body's arterial network shores up the worst affected parts of the arteries with calcium. The calcium hardens like cement and creates a bony structure to protect the diseased arteries.

Calcium plaque accumulation in the coronary arteries is one of our body's most tightly regulated protective mechanisms that ultimately fails when inflammation escalates. Soon, other compounds such as sterols and inflammatory cells forming a denser plaque within an artery wall may (or may not) narrow the artery over time.

This escalation is the inflexion point at which a completely normal artery progresses to an atherosclerotic one with the potential of becoming "clogged."

More specifically, artery-clogging lipoprotein particles, called ApoBs, get past the innermost ("sub-endothelial") layer of the artery where the particles' cholesterol content is retained and oxidized, and immune cells flock to the area. The oxidization process turns an initially-beneficial bodily function into a maladaptive response.

Whether this disease process affects the artery diameter (or "lumen") depends on how advanced the inflammatory response is and how fast the condition progresses, hence why angiograms can be normal in some people with atherosclerosis.

As the plaque increases, it can narrow the artery to between 70 and 75%, causing impaired oxygen delivery to tissues ("ischemia") or rupture leading to a thrombotic event and infarction—as it did with my dad.

This is where calcium scoring comes in. The amount of calcium in the arteries correlates directly and fairly reliably to the amount of plaque, diseased tissues and, ultimately, the number of cardiac events a patient is likely to have in the future.


How Is Calcium Detected?

As mentioned, calcium is imaged by a computerized tomography (CT) scan or CAC scan.

A CAC scan is a high-speed x-ray of the heart which, in a couple of minutes, and thanks to an electron beam technology, senses the density of calcium plaques in arteries and shows it as white deposits on an image that represents a slice of a patient's torso.

Unlike a regular x-ray, which would be blurry with heartbeats, the CT scan is so fast that it accurately sees all the calcium around the heart—acting almost like a strobe to "freeze" heart movement.

Radiologists then add up several slices from the scans to obtain a score for the total amount of calcification in coronary arteries.

A high score means a lot of artery calcification is present, while a zero score has been referred to in the past as a "15-year warranty against heart disease for a human."

An abnormal calcium score can be schematized as anything greater than an absolute score of 300, with various risk thresholds:

  • 1-10 = minimal levels of calcium detected and low coronary disease risk (less than 10%).
  • 11-100 = mild plaque levels detected with some arteries narrowing.
  • 101-300 = moderate plaque detected with a relatively high risk of a heart attack within 3-5 years.
  • 300-400 and > 400 = extensive plaque detected and very high risk of vascular problems and adverse cardiac events.
CAC scans offer 360-degree views (through 180 degrees of rotation) of the calcification in the heart's arterial network and its exact location, facilitating closer monitoring between repeat scans.

CAC scans offer 360-degree views (through 180 degrees of rotation) of the calcification in the heart's arterial network and its exact location, facilitating closer monitoring between repeat scans.

CAC Scanning Goes a Long Way Back in History

There is a long history of heart calcification scanning. It started at The University of California, San Francisco (UCSF) in the 1970s.

A physicist named Douglas Boyd told cardiologist Bruce Brundage, dubbed the "Father of Calcium Scanning," that he wanted to build a heart scanner performing differently than scanners did in those days.

Back then, the English physicist Peter Mansfield had developed the leading scanning technology and approach to medical imaging.

These scanners imaged with accuracy, but they needed a faster shutter speed to fulfil Boyd's vision. Otherwise, whatever they captured had to be perfectly still—unlike the heart's motion.

Boyd eventually designed the ancestor CT scan of CAC scanning using electron beam tomography (EBT) technology in the early 1980s, and Brundage regarded it as a powerful cardiac diagnostic tool.

He first saw coronary calcium deposits when he used the technology to measure blood flow within the heart muscle in healthy tissue versus scar tissue in recovering heart attack patients.

Immediately, Brundage paralleled this discovery with findings from a collection of publications on atherosclerosis dating back to the late 1960s by Dr David H. Blankenhorn, a professor of medicine at the University of Southern California.

Blanckenhorn wrote about how during autopsies performed on heart attack victims, he noticed a correlation between the amount of calcium and atherosclerotic damage found in the arteries.

The first paper on CAC scanning to show that the relationship between the amount of plaque and atherosclerosis is linear was the National Institutes of Health (NIH)-funded Multi-Ethnic Study of Atherosclerosis (MESA) trial published in the mid-2000s.

In MESA, the cardiac risk was re-classified based on the calcium score 25 per cent of the time, and nearly half of the patients with typical intermediate-risk scores were re-classified as high-risk with CAC scanning.

UCSF's Ambulatory Care Center circa 1973.

UCSF's Ambulatory Care Center circa 1973.

How CAC Scans Compare to Other Risk Calculators

The benefits of a CAC scan go above and beyond what other risk calculators can deliver. There is a difference in the granularity and specificity of the results.

Health practitioners widely use the Framingham risk score assessment model in the UK as a first-line cardiovascular risk check for patients. This 10-year risk prediction test is based on the Framingham observational study and measures health parameters that tend to correlate with heart attacks.

The Framingham test determines the predisposition to heart disease by computing parameters including gender, a person's diabetes history, body mass index (BMI), total cholesterol levels, blood pressure, and smoking habits.

The predictive value of CAC screening has been tested against some of these markers. For example, one study examined smokers and non-smokers and found that calcium blows away even smoking versus non-smoking as a risk. Non-smokers who came in with a high score had 6 or 7 times the risk of smokers with a low score.

One issue with multifactorial risk calculators like Framingham is that they introduce the potential for discordant risk markers, making it more challenging to predict CAD risk.

In the US, heart disease guidelines recommend looking at four modalities when there is uncertainty about a patient: coronary calcium, family history, CRP and the ankle-brachial index. Of those four, the most robust data are for coronary calcification scoring.

The most important aspect of the predictive value of the CAC scanner is its immediacy. The scan actually sees the atherosclerotic plaque, eliminating the margin of error from relying on proxy markers in the blood that are highly variable.

An algorithm known as the Agastson Score, put together by Florida-based cardiologist, Arthur S. Agatston, can even correlate the CAC screening score to plaque size and cross-reference the calcium levels with age and other data to refine sudden cardiac death risk prediction.

Going one step further, the management of CAD could improve by using a vascular age derived from calcification scoring and added to a patient's chronological age.


Making a Case for CAC Scans

CAC scanning prevention statistics are clear-cut and unambiguous. For example, a zero-scoring person of a given age has less than a 1% chance of an adverse atherosclerotic event in the subsequent ten years.

In contrast, someone who scores in the 100 to 300 range has about a 20 per cent likelihood of suffering a heart attack over the next three to five years.

Although CAC scoring has been in the European Society of Cardiology (ESC) guidelines for middle-risk people since 2013, it's as if hardly anyone knows.

There were initiatives in the following years to spread the word about this important addition to the guidelines.

David Bobbett, a Dublin-based entrepreneur, business leader and founder of the Irish Heart Disease Awareness Society, funded The Widowmaker (2015), an American movie released by Netflix to show what calcium scanning can offer to the millions with hidden CAD.

He commissioned the film to tell the story of how his world came to a halt when he learned that he had a calcium score of 906 and a one-in-four chance of having a massive heart attack within the following year.

Bobbett was a non-smoking, healthy-eating 51-year-old man in the top 10 per cent of his age group for fitness, with no bad markers, running five times a week and weighing the same as he did when he was 20 years old.

His calcification score could have been much worse if he had waited another couple of years to get tested. With CAC scoring, the progression rate matters, and it is possible to monitor it closely.

Monitoring Coronary Calcium Scores

As the artery-wall thickness ("sclerosis") clears up, through lifestyle modification or treatment, the calcium should slowly erode and naturally absorb back into the rest of the body.

The calcium might slowly decrease, stay the same, or increase even with lifestyle intervention and treatment. But research suggests that a low yearly increase may not be worrying. On the other hand, a rapid increase in calcium deposits is more problematic and dangerous.

One of the frequently cited studies where researchers tracked all the calcium at the start and then followed yearly how much their calcium increased over three to six years illustrates this concept.

They looked at patients with a calcium score of around 500 to 720 at baseline, increasing at over 15 per cent a year, and compared them with others whose calcification rate was increasing less than 15 per cent.

Among those whose calcification rate increased at greater than 15 per cent a year, 50 per cent had a heart attack in the next three and a half years. But, only three per cent of those who increased at less than 15 per cent a year had heart events after six years.

They had a similar risk ratio to healthy people because their calcium count was stable, no matter how high their initial score was.


Why Is CAC Scanning So Underutilized?

Doctors usually only resort to CAC scoring to check whether a genetic predisposition translates into excessive CAD, if a patient has an inflammatory disorder or autoimmune condition such as lupus or rheumatoid arthritis, or if they are on the fence about committing them to lifelong statins therapy.

Outside of these provisions, they may defer using CAC scanning until a patient has failed numerous other calculators or tests.

While CAC scanning was proven valuable relatively early, its more widespread adoption and seamless integration into standard care could be faster.

A longstanding unfounded argument against CAC scanning that slowed its adoption rate is radiation dose, which is only as high as 3 mSv, compared with 12 mSv for an angiography, for a scan that is required far less often and with a more decisive result.

CAC Screening in the UK

Since 2013, European guidelines have supported using CAC scoring in patients found to be of intermediate risk from a Framingham risk assessment.

The National Institute for Health and Clinical Excellence (NICE) issued additional guidance on calcium scoring in 2016 as one of the preferred first-line investigation tests in some low-risk groups.

Depending on the hospital or clinic, patients can self-refer for a CAC scan if they have one or more traditional risk factors. However, without any apparent predisposition to heart disease, a cardiology referral from a GP is required.

Alternatively, Nuffield Health offers more flexible screening as a primary prevention diagnostic tool in many locations around the UK for around £300.

Based on current care pathways, a patient could get very sick before a referral is granted and a scan performed, and that has got to change.

CAC scanning is an accurate lifesaving prevention tool that needs to be better known and used by healthcare practitioners and should be more readily available for all patients.

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2023 Camille Bienvenu