By the time plaques have formed in arteries, the process of atherosclerosis, a condition that can lead to heart attacks and strokes, is already well underway. Now, by using advanced imaging technology to spot artery inflammation, scientists have for the first time found a way to track the condition before the plaques develop.
The finding, which appears in a recent Journal of the American College of Cardiologypaper, should lead to better, earlier diagnosis and treatment of atherosclerosis, say the study's researchers, who work at the Centro Nacional de Investigaciones Cardiovasculares (CNIC) in Spain.
Although scientists now understand atherosclerosis to be a persistent, inflammatory disease, it is not clear how much inflammation exists, and how it develops, in the early stages of the condition.
The recent study addresses this shortfall by using an advanced form of positron emission tomography/magnetic resonance imaging (PET/MRI) to detect the beginnings of artery inflammation in people who already had some atherosclerotic plaques in some of their arteries.
The study is part of the Progression of Early Subclinical Atherosclerosis (PESA) trial that is evaluating the pre-symptom stages of atherosclerosis in more than 4,000 middle-aged employees of the Banco de Santander Group in Madrid, Spain.
Study author Dr. Valentín Fuster, director of the CNIC, is the lead investigator of the PESA trial, which is the first to use PET/MRI techniques on such a large cohort of people.
He explains that it was not very long ago that all the knowledge of how atherosclerosis developed came only from autopsies.
"Today for the first time," he adds, "we present, with very advanced imaging technology, how atherosclerotic disease develops in people."
He remarks that while the individuals may appear to be healthy, "we can already see how different aspects of the atherosclerotic process are evolving."
Arteries and atherosclerosis
Arteries are the vessels that carry nutrient- and oxygen-rich blood to the heart and the rest of the body.
As time goes on, the plaques harden. Hardening plaques stiffen and narrow the arteries, reducing blood flow and the supply of oxygen and nutrients to cells and tissues.
This process can lead to potentially fatal cardiovascular consequences, such as heart disease, heart attack, and stroke.
According to figures that the American Heart Association help to compile, heart disease, stroke, and other cardiovascular conditions were the "underlying cause" of 840,678 deaths in the United States in 2016, accounting for around 1 in 3 deaths in the U.S. that year.
"We are talking about the number one killer today in the world," says Dr. Fuster.
Potential predictor of atherosclerotic plaques
Dr. Fuster and his colleagues demonstrated that inflammation of the arteries "is highly prevalent in middle-aged individuals with known subclinical atherosclerosis." This was particularly apparent in artery regions that had not yet developed plaques.
They suggest that "an arterial inflammatory state" could be a predictor for the later development of plaques and atherosclerotic disease.
The investigation involved analyzing advanced PET/MRI imaging results for 755 participants in the PESA trial. Their average age was 49 years, and they had all undergone exams that had revealed the presence of calcium buildup or plaques in some arteries.
First study author Leticia Fernández-Friera, who is a cardiologist at CNIC and the University Hospital HM Monteprincipe Madrid, says that they examined three main types of artery — "the carotid arteries, which supply blood to the head; the aorta, the body's largest artery; and the iliofemoral arteries, which supply blood to the legs."
Using the advanced imaging technology, the team found inflammation was evident in only around 10 percent of plaques that had already formed.
Most of the inflammation was in artery regions with no atherosclerotic plaques at all. More than half of individuals had this type of plaque-free inflammation, with most of it occurring in femoral arteries.
Where plaques did show signs of inflammation, they tended to be larger, contained more cholesterol, and were more likely to be in the branches of the femoral arteries.
Inflammation linked to more risk factors
Dr. Fernández-Friera says that they also found that "inflammation was associated with the presence of more risk factors; obesity and smoking, in particular, were independent predictors of the presence of arterial inflammation."
Dr. Fuster explains that the findings show how, because of the power of the technology, it is now possible to have "live images" of inflammation that can lead to atherosclerosis as it is happening.
This should help to diagnose the condition sooner and to identify people who are most likely to reap the benefits of early treatment.
Dr. Fuster proposes that further research should now "investigate whether inflammation precedes the development of the plaque and assess how the quantification of inflammation might contribute to the evaluation of cardiovascular risk."
He and his team are already looking in more detail at the process of arterial inflammation, and how it might contribute to plaque formation. They hope that this will result in an improvement in the anti-inflammatory treatment of atherosclerosis.
"Thanks to the PET/MRI technology, inflammation could be visualized at earlier stages of atherosclerosis disease, especially in regions free of atherosclerotic plaques."
Dr. Leticia Fernández-Friera