By Gabe Mirkin, M.D.
Since heart attacks are usually caused by plaques breaking off from the inner linings of arteries leading to the heart, doctors use a test called Coronary Artery Calcium Score (CAC) to predict which people have the largest plaques and therefore are at high risk for suffering heart attacks that cause one out of four deaths in North America. The CAC test uses x-ray computed tomography (CT scan) to measure the extent of plaques in the arteries leading to the heart. This test categorizes patients into risk for suffering a heart attack by Agatson Units (named after the man who invented the test):
0 = no plaques
1-99 = mild plaques formation
100-399 = moderate plaque formation
>400 = severe plaque formation
CAC scores have been found to predict chances of dying of a heart attack in asymptomatic people (Ann Intern Med, Jul 7, 2015;163(1):14-21), and to correlate with heart attack risk factors such as high LDL cholesterol, low HDL cholesterol, high blood pressure, smoking, and high triglycerides (J Am College of Cardiology, July 5, 2005;46(1):158-165). However, not everyone with a high calcium score is at high risk for a heart attack, because a CAC can miss the plaques without calcium that are most likely to cause heart attacks.
One study showed that people who have no heart disease whatever have a 25 percent chance of having extensive plaques in their arteries, compared to 47 percent in people who have died from heart attacks (Atherosclerosis, Jul 2013;229(1):124-9). Among the people who died of heart attacks, more than half of the lesions leading to sudden death had no calcium. Since the CAC measures calcium, these people who died of heart attacks would have had a CAC score showing no plaques at all. Healthy people with low risk factors for heart attacks and a CAC score of zero, followed for 10 years, still have a 3.1 percent chance of suffering a heart attack (Eur Heart J, July 1, 2018;39(25):2401–2408).
CAC Images Can Predict Which Plaques Are Likely to Break Off
A radiologist can look at CAC images and predict which plaques are likely to break off to cause heart attacks. Most of the calcium is in the inner lining of the plaque that holds the plaque in place inside an artery. In effect, calcium is the glue that helps to keep the plaque in place and prevent it from breaking off. The more fat in the plaque, the weaker it is and the more likely it is to break off.
If the radiologist looks at a plaque on a CAC and it has lots of calcium, particularly on its inner lining, and very little fat inside the plaque, it is a stable plaque that is not likely to break off to cause a heart attack. Exercise helps to prevent heart attacks primarily by stabilizing plaques, and athletes who eat an anti-inflammatory diet can be at extremely low risk for heart attacks, even though they may have a relatively high calcium score.
Statins Can Increase CAC Scores Yet Help to Prevent Heart Attacks
Statins are known to help to prevent heart attacks, but they can increase CAC scores (Nature Partner Journals, Aging and Mechanisms of Disease, June 22, 2018;4(7)). Statins increase CAC scores because they stabilize plaques by depositing extra calcium in existing plaques, which lowers heart attack risk. This study showed that statins raise CACs by 29.7 percent each year, but adding another drug called a PCSK9 inhibitor to the statin drug slowed the rate that CAC scores rose to only 14.3 percent each year.
A 10-year-follow up showed that patients with CAC scores greater than zero benefit from statins, while those with CAC scores of zero had no reduction in heart attack rates whatever (Arteriosclerosis, Thrombosis, and Vascular Biology, Aug 29, 2019;39(10). Statins help to prevent heart attacks in other ways besides lowering LDL cholesterol, such as lowering inflammation, widening narrowed blood vessels and reducing oxidation.
High CAC scores are associated with increased risk for suffering a heart attack. However, some people, particularly athletes and people taking statins, may have high CAC scores even though they are at low risk for heart attacks, because both vigorous exercise and statins raise CAC scores in a way that helps to prevent heart attacks. In these people, a high calcium content in plaques can indicate stable plaques, with a reduced chance of breaking off to cause a heart attack.
A high CAC score also may not show increased risk for a heart attack because it can include calcifications in valves that do not increase risk for a heart attack. If you have a high calcium score, talk with your doctor and share these references with him or her, to see if any of these factors apply to you.
Joe Bee says
Hypothesis — Statins and HDL both “treat” plaque in same manner — increasing calcium score and reducing risk of coronary event physically fit and people on statins have high calcium scores and low risk.
Fred Campbell says
I’d sure appreciate your comments about my situation. Also wonder if you are a cardiologist and are taking new patients. If so, I suspect it’d have to be virtual appointments since I doubt you’re near Seattle.
20 months ago I had a CAC of 1,040. I’ve just had another scan and it’s now at 1,237 (RCA 838, LAD 229). The RCA alone increased at an annual rate of 16% and the overall score increased 11%. The LAD went down slightly. Soon after that first scan I began using Pravastatin at 20mg and Amlodipine at 5mg per day. I also consistently stayed with Dr. Caldwell Esselstyn’s plant based diet (with no oils). I exercise by playing lots of pickleball, walking and doing super slow weight training. I’m 76, 5’7″, 140lbs. My cholesterol is now 136, LDL 74 and HDL 45. Triglycerides are 82. Oxidized LDL is 194.
Thank you for any feedback you care to provide.
Fred, Get to Undoctored.com and start Dr William Davis’s protocol for plaque stabilization. There is much misinformation out there. He will lead you straight. He is the author of the ‘Wheatbelly’ and ‘ Undoctored’ books. Trust me on this and Best Wishes to you. Phil
Carolyn S says
Thank you for posting this. My husband is a cyclist and just received his report of high CAC and is pretty shocked. This article and your suggestion is very helpful! We are already cued up to Dr. Davis’s CT Heart Scan Workshop. ( I am very familiar with Dr. Davis and I can credit his Wheat Belly books with helping me eliminate my migraines – life changing.).
I realize this thread is old but I hope you get this info and I hope you’ve already changed your diet. A plant-based diet, especially one including grains, is the last thing you want to do. You need a diet more akin to the paleo diet. Do not fear meat and animal proteins, embrace them. Stay away from grains and foods that raise your insulin levels, and stay away from processed foods. It’s really quite simple. The other reply had it right.
No studies PROVE a correlation between diet and heart disease or prevention. If you don’t believe me, try to find one. A few “hint” or “suggest” at a link, and others show zero link. There was a review of 30-some diet studies and the authors (heart doctors) where stunned to conclude that no convincing evidence exists that diet plays a role in heart disease. I wish I had the link, but I don’t at this time. They did find diet DOES contribute to Diabetes.
I’ve never heard cardiologists can predict which plaques might break off and cause a heart attack. In fact I’ve read just the opposite in almost every thing I’ve read about CAC scans. Also statins, while perhaps not an out and out scam, are certainly a money-maker for big pharmaceutical and offer almost no prevention against heart attack according to multiple studies AND their own adverts. PLEASE read the small print in this Lipitor ad. These are THEIR words, not mine, not some “quacks.” The small print admits that said statin reduces heart attack risk about about 1%.
Brent S says
No link between diet and heart disease?? There are many factors to a person’s health, but there is plenty of evidence that longevity/health is related to diet. Heart disease causes more death than all the cancers combined. Poor diet and inactivity lead to obesity, diabetes, and heart disease. Genetics might be the longest lever, but those unfortunate enough to lose the genetic lottery (my CAC=1200 @57) can prolong and improve life with a mostly plant-based diet and daily exercise. I recommend Dr Fuhrman’s dietary guidance.