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Read enough radiology reports and eventually you will find one that mentions calcifications in the heart or the aorta. When it appears in black and white, it sounds worrisome and can generate an emergency referral. But both patients and referring physicians are usually surprised to learn that the finding is not quite as dangerous as it sounds.
Unfortunately, as we age, plaque accumulates in our arteries. This starts as soft, cholesterol-laden plaque that eventually calcifies and hardens. Even though the process effectively begins at birth, most people do not have clinically significant blockages in their arteries until they are well into middle age.
Interestingly, and somewhat counterintuitively, calcified plaque is probably the less dangerous of the two. When a heart attack happens it is due to the sudden rupture of a soft, unstable plaque that might be obstructing only 10 or 20 per cent of the artery. Longstanding, calcified 90-per-cent blockages don鈥檛 cause heart attacks. They may cause angina 鈥� chest pain on exertion 鈥� but a stable plaque won鈥檛 suddenly rupture and provoke a myocardial infarction.
Thus, you might wonder why we should care about calcium in our arteries at all. Coronary artery calcium (CAC) testing is potentially useful for patient care. It鈥檚 just not useful for diagnosis. .
The problem with CAC is that most people conflate the calcium score with a coronary CT scan. The confusion is understandable since both tests are done with a CT machine and are often done at the same time.
A coronary CT is a more involved scan that requires intravenous injection of contrast dye to diagnose blocked arteries. Measuring CAC is done with a quicker, simpler scan that requires no contrast and just looks for calcium accumulation in the arteries of the heart.
For practical and logistical reasons, the two tests are often done simultaneously as the patient is 鈥渁lready in the machine鈥� but we often forget that the tests provide complementary pieces of information. A coronary CT scan is a non-invasive way to diagnose a potentially blocked artery. Getting a CAC score tells you something different. It tells you if someone needs to be treated more aggressively.
The general purpose of measuring someone鈥檚 coronary artery calcium is to decide whether to treat their risk factors. For example, if you were on the fence about whether you wanted to start someone on blood pressure medication or treat their high cholesterol, then a high calcium score might push you to treat, whereas a low calcium score wouldn鈥檛. CAC score performs that have been proposed over the years, and it does help better identify high-risk patients who would benefit from prophylactic treatment.
I鈥檝e personally always been a bit less enthusiastic about sending patients for CAC scores. Although to be fair, by the time a patient gets to me they鈥檝e likely already been identified as high risk, which makes the value of the test is moot. Its primary purpose is for risk refinement in intermediate-risk patients. Very low-risk and very high-risk patients don鈥檛 benefit much from the test because you won鈥檛 treat them or will continue to treat them regardless of the result. And while CAC scores are fairly easy to do with little major downside, they cost money, use up medical resources and scanner time that could be used for more urgent cases and expose patients to an admittedly small dose of radiation that could otherwise be avoided.
Occasionally, . A patient may get a lung scan because of a nodule seen on an X-ray and the report will comment on coronary calcifications. This is increasingly common but shouldn鈥檛 be seen with any additional worry. CAC, whether measured deliberately or seen incidentally, has the same prognostic value. It lets you fine tune patient鈥檚 preventative cardiac care. It shouldn鈥檛 be a cause for alarm.
