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Arnold Meshkov, MD, explores how discoveries and the advent of new technologies have influenced diagnosis of atherosclerosis throughout history.
It is surprising how little data are available telling us the incidence of asymptomatic, or “subclinical” atherosclerosis in the general population. Atherosclerosis imaging, by cardiac catheterization or noninvasive testing, is usually performed in patients with symptoms suggesting coronary artery disease. But just recently, the result of a large study of over 30,000 Swedes ages 50-64 was published in Circulation. Using a coronary artery calcium score and a CT angiogram of the coronary arteries, the study found that slightly over 40% of people had “silent” coronary artery atherosclerosis. The good news was that only about 5% had a significant blockage.
Prevention of heart attack and stroke are now commonplace, especially in those who had an acute cardiovascular event. More people are benefiting from “primary prevention” when they have multiple risk factors and an elevated blood LDL and cholesterol levels. But more needs to be done to identify those who have a mild degree of atherosclerosis, as the recommendations regarding treatment with statins will change if atherosclerosis is demonstrated by imaging. A blood test can express risk, but imaging atherosclerosis will likely have a significant psychological effect on both the patient and doctor, and improve compliance with long-term use of medication i.e., statins.
The history of the heart attack has had long periods of time of not knowing much of anything about its cause, treatment, and identification of atherosclerosis before someone had a myocardial infarction. Too often many did not survive. From the time of William Heberden’s report in London in 1776 about a group of patients with “angina pectoris,” 140 years passed until Nikolai Anichkov in Russia proved that atherosclerosis was due to cholesterol deposits, and in the same time frame William Herrick in the US described the multiple manifestations of coronary artery disease, with the new finding that in some patients, long term survival is possible.
The ability to determine the presence of atherosclerosis as a cause of chest pain and risk for a myocardial infarction has faced enormous challenges. Beginning in the 1930s, studies began using exercise to try to see it would cause EKG changes of ischemia. The results were not impressive, and even the Master “two-step” developed in the 1940s had such limited accuracy that it would be difficult to have the results published today in a peer-reviewed journal.
The work continued, first with the development of the motorized treadmill by Robert Bruce, MD, of the University of Washington in the late 1960s, followed by the ground-breaking work of the first “nuclear” cardiologists like Barry Zaret, MD, of Yale. Imaging as well the EKG changes dramatically improved the statistical sensitivity and specificity for significant coronary artery atherosclerosis. But even these two major changes in diagnostic testing proved to be of minimal predictive value for cardiac events in the general population.
At the present time, there are two other imaging technologies that allow for the noninvasive of atherosclerosis. First came the coronary artery score invented by Arthur Agatston, MD, in the 1980’s. This very simple imaging technique is shown to predict cardiac risk very well, with higher levels of coronary artery calcium indicating more advanced atherosclerosis. Equally important, a “0” calcium score indicates an excellent prognosis for the next several years.
In more recent years, CT angiography of the coronary arteries has developed into a more mature technology, initially overcoming the technical difficulty of creating CT images of the heart with a heart rate over sixty beats per minute. Although the problem of image “blooming” from areas of calcification can still be a problem, this modality has also proven its worth regarding prognosis, and assisting decision making between medical therapy and cardiac catheterization, with a final decision of angioplasty or coronary artery bypass surgery.
The use of these technologies will hopefully advance the diagnosis of atherosclerosis in the general population. We know that this disease begins at a young age and is too often progressive without treatment. These tests may lead people to the conclusion that a better diet, more exercise, and many times medication will reduce the risk. It may take decades to see if these two tests lead to better outcomes. Let’s hope the insurance companies and Medicare agree to let us use them.
Bergstrom, G, Perrson M, et al. Prevalence of subclinical atherosclerosis in the general population. Circulation 2021 144(12): 916-929.
Meshkov, A. Chasing the Widowmaker – The History of the Heart Attack Pandemic, 2021 KoehlerPublishing, Virginia Beach, Virginia. Chapter 6: Divining the Signals: The Creation of the Stress test; Chapter 18: Stopping Time: The Radioactive Heart Images.