One for the heart
For nearly 45 years, medical experts have relied on well-known cardiovascular risk factors to determine how patients should be treated to ward off a heart attack or stroke.
When a patient has either no risk factors or many of them, treatment decisions are usually straightforward. Doctors typically tell patients with no risk factors to keep doing what they’re doing, while those at high or moderately high risk are often advised to start medications along with adopting lifestyle measures, like a heart-healthy diet and regular exercise.
But when patients are in the middle-ground of risk, or are known to be at elevated risk but resist advice to take medication or change their habits, there’s a test that can help clarify the best course of treatment and help convince reluctant patients to follow it.
The test is a coronary calcium scan, which takes 10-15 minutes. It uses specialised CT X-rays to assess the presence and amount of calcium (actually bony deposits of plaque that signal atherosclerosis or hardening of the arteries) in the blood vessels that feed the heart.
The radiation dose is low, about the amount in a mammogram, and calcium scores can range from zero up into the thousands. The higher the level of calcium in coronary arteries, the greater the patient’s likelihood of suffering a cardiovascular event like a heart attack or stroke within the next decade.
In 2018, the United States Preventive Services Task Force acknowledged that the calcium test can indeed help doctors assess a patient’s cardiovascular risk. But the agency concluded that there was not yet adequate evidence to show that the test’s results improved patient outcomes above what is typically recommended, based on standard risk factors alone.
Still, many who practise preventive cardiology believe otherwise.
Dr Sadiya S. Khan, a preventive cardiologist at the Feinberg School of Medicine at Northwestern University, US, said that she and many other cardiologists follow the American College of Cardiology/American Heart Association’s conclusion that the calcium test can help guide therapeutic options, especially for patients with a borderline or intermediate risk of developing cardiovascular disease.
Results of a calcium scan can also be important for younger men and women — and sometimes for their physicians, who may not take risk factors in younger patients as seriously as they should. Dr Khan explained in an interview, “The presence of any calcium in coronary arteries is a sign of having heart disease.”
When atherosclerosis starts to develop, the arterial lesions — called plaque — are not calcified, explained Dr Philip Greenland, also a preventive cardiologist at Northwestern. Rather, the lesions acquire the bony deposits over time that gradually increase when the plaque ruptures and is repaired. The healing process causes calcification, he said.
Dr Greenland cautioned that patients and doctors should never assume that a calcium score of zero means there’s nothing to worry about. He said in men under 40 and women under 50, “you can’t rely on coronary artery calcium alone, because the level is typically zero even in the presence of atherosclerosis.”
Rather, he and Dr Khan said that in younger adults, follow-up tests and medical advice should be based on the extent of patients’ cardiovascular risk, including whether they have any symptoms of heart disease, like shortness of breath when climbing stairs or chest pain when exerting themselves.
Dr Greenland said that people with “a low-risk factor profile and a calcium score of zero have a kind of warranty that they won’t have a heart attack within 10 years.”
“But,” he continued, “if risk factors put you above a 20 per cent 10-year risk of a cardiovascular event, even zero calcium is not sufficient to provide such a warranty.” You can determine your risk profile, which considers such factors as age, gender and race, using the calculator at cvriskcalculator.com.
The value of this advice is underscored by the findings of a large study, published in October in JAMA Cardiology. A cardiology team from Aarhus University Hospital in Denmark reported that among nearly 24,000 high-risk patients who had symptoms of cardiovascular disease, 14 per cent of those with obstructions in their coronary arteries nonetheless had no evidence of coronary calcium.
For patients in the 10-year study who were younger than 60, a “sizeable proportion” of obstructive coronary artery disease occurred among those with no coronary artery calcium, yet they faced a seriously increased risk of heart attack and death, the Danish team wrote.
Dr Khan emphasised that regardless of calcium score, all patients at high risk, especially those with symptoms of heart disease, should be treated with medication and lifestyle changes. Among helpful measures are lowering elevated levels of blood pressure, cholesterol and glucose; adopting a heart-healthy diet; getting regular physical exercise; and striving to achieve and maintain a normal body weight.