Sat | Nov 18, 2017

Calcium scoring - the gateway to coronary artery disease imaging

Published:Wednesday | March 15, 2017 | 12:00 AMDr Duane Chambers
Sudden cardiac death can happen to you
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The mainstay of Caribbean cardiac imaging has long been echocardiography, done by the cardiologists. A handful of radiologists throughout the region have offered limited CT and nuclear cardiac imaging, all while CT and MR cardiac imaging have experienced an explosion throughout the rest of the world.

The limiting factor for us has been the cost of the multi-detector CTs and the MRI machines necessary to achieve diagnostic imaging. The rapid technological advancement of imaging equipment has resulted in a lowering of the cost of older generation MDCT and MRIs capable of cardiac imaging.

Many radiology centres throughout the region now possess 64-slice MDCTs as well as MRI machines capable of handling cardiac imaging protocols. As a result, the Caribbean is poised to enjoy a period of rapid evolution in the sophistication of cardiac imaging and, by extension, medical and surgical cardiac care.

NUMBER ONE CAUSE OF GLOBAL DEATH

Cardiovascular diseases (CVD) are the number one cause of death globally. According to World Health Organization, an estimated 17.5

million people died from cardiovascular diseases in 2012, representing 31 per cent of all global deaths. Of these deaths, an estimated 7.4 million were due to coronary heart

disease. Over three-quarters of

CVD deaths occur in low and

middle-income countries.

What are the major risk factors for cardiovascular disease?

• High blood pressure

• High cholesterol and fats in the blood

• Diabetes

• Obesity

• Smoking

• Alcohol abuse

• Stress

All these risk factors accelerate the rate of formation of atherosclerotic plaque within the coronary arteries and increase the likelihood of a myocardial infarct (heart attack).

WHY WAIT UNTIL YOU ARE HAVING SYMPTOMS?

Coronary artery calcium scoring measures the amount of calcium in the coronary arteries. A score is generated which is directly related to the severity of atherosclerotic disease. By combining the CAC score with certain biometric parameters such as age, sex, race, presence of diabetes, systolic blood pressure, smoking history, family history of heart attack, total cholesterol, HDL cholesterol, presence of lipid lowering medication and hypertension medication, a 10-year risk of developing coronary heart disease can be calculated. This calculated risk could then be followed as the patients risk factors are managed.

The test is performed by doing a low dose CT scan of the heart. There is no pain or contrast injection and the entire test takes less than two minutes to perform. The only requirement for this test is the ability to lie flat and breath hold for 20 seconds. Multiple studies have shown that a patient is more likely to take steps to improve their risk factors if he or she can see the effect on the coronary arteries as well as how lifestyle modification and/or appropriate medications can change the CAC score.

The CAC score has emerged as the strongest risk prediction tool currently available.

In fact, from as early as 2010, the American Heart Association published guidelines which categorized CAC measurement as reasonable in:

(a) Asymptomatic adults with an intermediate risk of coronary artery disease.

(b) In low risk individuals with a family history of premature disease and

(c) In all diabetic patients 40 years or older. In addition to early detection, patient viewing of the CAC scan has been shown to increase adherence to the statin and aspirin treatment, to diet and exercise and to improve lipids, BP and weight. CAC score detection of high-risk patients and subsequent implementation of early management has been projected to decrease coronary events by as much as 30 per cent.

Knowing the calcium score also provides technical benefits for further imaging:

• A high calcium score selects patients for further imaging of the coronary artery lumen

• Calcium scores above 400 are associated with poor quality CT coronary angiograms; therefore catheter angiograms would be more appropriate for these patients.

Interpretation of the risk associated with CAC score is as follows: (2016 SCCT/STR guidelines)

0 = no CAC, very mild risk

1-99 =mild CAC,

mildly increased risk

100-299 =moderate CAC,

moderately increased risk

>300= moderate to severe CAC, moderate to severely increased risk

TAKE-HOME POINTS

• CAC scoring is the best non-invasive test for determining coronary artery calcium content.

• CAC scoring predicts the risk of hard cardiovascular disease.

• The test uses CT. It is fast and painless.

WHO SHOULD DO IT?

• Male over 45 years of age, female over 55 years of age.

• All diabetic patients over 40 years of age.

• Family or personal history of heart disease.

• Past or present cigarette

smoking.

• History of high cholesterol or high blood pressure.

• Overweight or obese.

• High stress levels.

• Inactive or sedentary life.

While it is impossible to eliminate the possibility of having a heart attack, there is now an accepted method of predicting your risk. Steps can therefore be taken to lower this risk sooner rather than later. KNOW YOUR SCORE BEFORE THE GAME IS OVER.

n Dr Duane Chambers, MB,BS DM radiology, is a founding partner for Imaging and Intervention Associates; senior radiologist at Radiology West