An ounce of prevention is worth a pound of cure is wise counsel. Although not as lofty a goal, early detection of existing heart disease is worth at least half a pound of cure, agreed?
Why Get a Heart CT Scan?
The introduction of a simple, inexpensive, and safe screening test for silent CAD over a decade ago (coronary artery calcium CT scan or CACS) should have been a complete gamechanger in the approach to “winning the war” against CAD. The CACS was recommended as early as 2005 by the SHAPE society. The CACS does not involve injecting any chemicals or contrast, is painless, takes under a minute, and is widely available at hospitals worldwide. Unfortunately, the introduction of the CACS, sometimes called the “heart’s mammogram”, has been very slow and many have suffered heart attacks and deaths that could have been predicted months to years before their tragic events. The tide seems to be changing however as the cost of the CACS has dropped as low as $50 in some hospitals.
Updated practice guidelines have incorporated the exam into patient evaluation, and the press has highlighted examples of how the CACS has changed habits and even saved lives. There are useful summaries about the CACS exam that are worth reviewing.
What Do I Do With the Results?
Although getting the scan done is an important step, usually necessitating a prescription from a health care practitioner, the proper path after the CACS is less clear. There are simply not enough definite and prospective research studies. I have read thousands of the CACS exams, have ordered thousands more, and have managed patients from around the world for over 15 years who have an abnormal CACS. Their question, and maybe yours too, is always “what do I do about the CACS?” At the Kahn Center for Cardiac Longevity we take certain steps in the evaluation and treatment of patients with abnormal CACS and some of those protocols are listed here.
Step 1. Calculate Your Risk of Heart and Stroke Events After Your CACS
In a publication of the American College of Cardiology, two valuable statements are made that I am sharing here.
CAC progression is associated with a higher risk for myocardial infarction (heart attack) and all-cause mortality. CACS increase by about 20-25% per year and about 20% of subjects with a CACS = 0 progress to CACS >0 in 5 years and increases markedly with age, but less so in women. The best CAD prognosis is in patients with a CACS = 0 at baseline and 5 years later. ‘Double zero’ was associated with a 10-year risk of 1.4% followed by new-onset CAC at 5 years of 1.8%. After an initial abnormal CACS, a repeat scan after 5 years appears to be of additional value except for those with a double-zero or already high risk because of a CACS >400.
MESA Risk Score
A valuable and useful tool in support of CACS for risk assessment was developed in the MESA study, in which CACS was incorporated into a model using 10-year follow-up data of any coronary heart disease (CAD) outcome. The MESA risk score is available online and incorporates age 45-85 years. It provides 10-year CHD risk with and without the CACS.
A more update risk calculator you may want to use is called Astro-CHARM and is available online for free. You will have to know your blood pressure and some laboratory results. The Astronaut Cardiovascular Health and Risk Modification (Astro-CHARM) calculator is a tool that incorporates traditional risk factor information with coronary artery calcium (CAC) score results to provide an individual’s estimated 10-year risk of atherosclerotic disease (ASCVD) events, including fatal or non-fatal heart attack or stroke. It is intended for use in younger individuals (ages 40-65) without a prior history of ASCVD. The Astro-CHARM was developed using data from three large, population-based cohorts (the Multi-Ethnic Study of Atherosclerosis, Dallas Heart Study, and Prospective Army Coronary Calcium Project), and validated in a fourth cohort (the Framingham Heart Study).
I find calculating the Astro-CHARM with patients reassures them that a heart attack, stroke and death are not likely even with a high CACS. For example, if the calculator predicts a 5% risk of a heart attack, fatal or not, or a stroke over 10 years, that is a 95% chance of not having those events. If you assess that yearly, it is a 99.5% chance each year that a bad outcome will not occur in this example. It also helps discuss what therapies might be used versus the potential side effects. It is challenging to predict that a therapy will lower a 0.5% yearly risk to an even lower level particularly if side effects are common. Of course, the risk of diet and exercise changes discussed below is essentially absent so that is always the thrust of the long-term plan.
Step 2. Why Do I Have an Abnormal CACS?
This is a crucial question that must involve assessing any smoking history, fitness regimen, current diet, stress level, sleep and snoring history, weight, blood pressure, and routine laboratories. If there is loud snoring or apnea at night, a sleep study, often done in your own bed, is recommended. There are advanced labs I order on patients at the Kahn Center that include:
Advanced lipid profile (NMR Lipoprofile): Rather than giving you a calculated LDL cholesterol level, advanced panels measure LDL particle number and size, which are more predictive of future heart and stroke events. Two people with the same cholesterol levels can have widely different particle and size measurements, making for very different risks.
Hs-CRP: The middle of the word inflammation is flame and it means the immune system is turned on and increasing the risk of atherosclerosis, heart attack, stroke and even other conditions like cancer and dementia. Bloodwork for the hs-CRP and additional measures like MPO and Lp-Pla2 are recommended.
Lipoprotein (a): This is a genetic form of cholesterol that's elevated in about 20% of those tested. It's rarely drawn even though hundreds of research studies indicate that if it's high, the risk of heart attack and stroke skyrocket. It runs high in many families that have been decimated by heart disease.
Homocysteine: This amino acid is produced by a process called methylation. It can injure arteries when elevated. It may be due to a genetic defect in the MTHFR gene, which is easily measured. It can be treated with methylated B-complex vitamins.
Step 3. Do I Need a Stress Test?
I generally do not order the CACS when a patient has symptoms of classic angina, that is, pressure or tightness on exertion relieved quickly by rest. After a full evaluation, the decision is usually a stress test, a coronary CT angiogram (CCTA) with contrast injections, or directly to an invasive cardiac catheterization.
In the much larger population without angina but interested in the CACS for prevention, a stress test has been recommended even in the absence of any chest symptoms if the CACS is >400. This can be a routine treadmill test, a stress echo treadmill test, or rarely in my practice, a stress nuclear radioactive treadmill test. I reserve the nuclear examinations for obese patients and those with an EKG finding called a left bundle branch block and usually a “chemical” stress test is selected. If you score is over 400, I suggest you consider a stress test, usually a stress echo examination. If it is very abnormal for signs of reduced blood flow to the heart, a cardiology consultation, initiation of medical and lifestyle therapy, and an invasive cardiac catheterization or CCTA is usually appropriate.
There are some patients with low CACS results but still with symptoms that are concerning for angina pectoris. It is rare, but possible, to have a badly blocked heart artery with a low or even a zero CACS due to “soft” plaque. I always perform a complete history and physical examination to assess any chest symptoms.