Atherosclerosis: What’s Happening Inside Your Arteries?
Could atherosclerosis already be clogging your arteries?
Atherosclerosis: What's in Your Arteries?
Over years, continued exposure to risk factors tends to cause atherosclerosis. The process works like this:
1. Fatty Streaks
Low-density lipoprotein (LDL or "bad" cholesterol) works its way into the walls of arteries. Once inside, LDL is like toxic waste: hard to detect, hard to dispose of, and potentially disastrous down the road.
If we could see inside arteries, the LDL at this point would be visible in the wall as a fatty streak, like a smear of grease. Autopsies of young people show that fatty streaks develop as early as the teenage years.
2. Plaque Formation
Over time, more cholesterol accumulates in the artery. The body sends leukocytes, a cleanup crew of white blood cells. The cholesterol and the cells responding to it evolve into a "bump" on the artery wall. This is called a plaque.
3. Plaque Growth
Unfortunately, the ongoing "cleanup" doesn't shrink the plaque. In fact, just the opposite: as more cholesterol and cells gather, the plaque grows. What happens next inside your arteries can be a matter of life and death.
Growing Plaques: Arteries' Extreme Makeover
As plaques grow, arteries remodel themselves to keep blood flow. They thicken their walls, making room for the enlarging plaque. "The plaque grows but stays out of the way, like a car stranded at the side of the road," explains Schaefer.
Eventually, some plaques grow slowly into the flow of blood. Even so, they rarely cause symptoms until the artery is more than 70% blocked. "Given enough time, arteries can create collateral channels, a natural bypass around the blockage," says Schaefer.
When a plaque does limit blood flow, pain with exertion is the most common symptom. In the coronary arteries, this causes angina (chest pain), and in the legs, claudication (muscle pain).
Surprisingly, these near-complete blockages aren't the most dangerous plaques.
"Another paradox of atherosclerosis is that these severe blockages don't usually cause heart attacks," explains Schaefer.
Atherosclerosis: "Stable" and "Unstable" Plaques
In general, severe blockages that have occurred over decades are stable. They're the bad neighbor who everyone's gotten used to living with. (Or you just don't know he's there.)
Rather, the plaques to watch out for are the young punks down the block. "Most heart attacks occur because of sudden changes in plaques that only block 20% or 30% of an artery," says Jeff Borer, MD, professor of cardiovascular medicine at Weill Cornell Medical College in New York.
These small but deadly plaques are hard to detect, even with advanced tests for atherosclerosis. "Generally, we just have to infer they're there from the presence of bigger blockages elsewhere," says Borer.
Learning why these smaller plaques rupture is a key focus of ongoing research. Studies over the past decade have demonstrated that inflammation inside the plaque is the key