Plaque Progression Observed in Extreme Endurance Runners With Preexisting CAD

Runners free of cardiovascular disease who participate in extreme endurance exercise, in this case the 140-day Race Across the USA, do not show any signs of developing coronary artery disease or have any significant changes in their cardiovascular risk profile, according to the results of a small study.

For runners with subclinical CAD at baseline, though, measurements taken before and after the long-distance race show a progression of coronary disease, specifically an increase in noncalcified plaque at coronary sites with preexisting disease.

“The findings turned out to be not only interesting, but quite provocative,” senior researcher Aaron Baggish, MD (Massachusetts General Hospital, Boston), told TCTMD. “Going into this, we thought, best-case scenario, we’re going to show they run across the country, they have a little plaque when they start, and it gets better after all this running. But that’s not what we found.”

The new report, published in the July 11, 2017, issue of the Journal of the American College of Cardiology, is based on just eight runners who completed the months-long race from California to Maryland, a distance that saw runners average 26 miles per day 6 days per week (with 1 rest day).

Race Across the USA

While moderate-intensity exercise is widely known to protect against coronary disease, there have been some reports, mainly cross-sectional data, that suggest high levels of endurance exercise, such as marathon running, may promote or accelerate coronary disease. These concerns, however, remain largely speculative.

We thought, best-case scenario, we’re going to show they run across the country, they have a little plaque when they start, and it gets better after all this running. But that’s not what we found. Aaron Baggish

This analysis of Race Across the USA participants included seven men and one woman (average age 45.5 years). Three runners were former smokers, one had hypertension, and one was taking a statin.

Compared with baseline measurements, systolic blood pressure was 6% lower after the race, while diastolic blood pressure, body mass index, and LDL levels were unchanged. Levels of HDL and C-reactive protein (CRP), a marker of inflammation, were increased. For the runners without CAD at baseline, there was no evidence of coronary disease after the race.

For the four runners with subclinical CAD at baseline, each of whom had one preexisting cardiovascular risk factor, coronary stenoses were documented by CT angiography in the proximal or mid left anterior descending artery. Luminal stenosis ranged from 1% to 29% in two of the runners and 30% to 49% in the other two.

Twenty-four hours after the race, just one runner showed an increase in coronary stenosis, but coronary plaque volume increased in all four runners with CAD. For the three individuals with a progression in noncalcified plaque (the statin-treated runner had a small increase in calcified plaque), there were corresponding increases in CRP and HDL, although LDL levels remained unchanged from baseline. 

“It’s notable, though, that the four people who started disease-free stayed disease-free,” said Baggish. “So, if you don’t have any coronary disease, you can run up to a marathon a day, and even at that extremely high dose, it doesn’t seem to stimulate coronary injury. But if the coronaries aren’t perfect to begin with, and you superimpose a lot of running—enough running to live in a chronically inflamed state, which was what these guys were doing—it may well be that it slowly accelerates the [disease] process.” 

Despite the results, Baggish cautioned that the study was extremely small and should be viewed as hypothesis-generating only.

“It’s certainly not changing my approach in the clinic at all,” said Baggish. “I don’t caution people against too much running if they’re otherwise healthy or their heart disease is being well managed, but I do think it raises some questions, particularly along the lines of inflammation, and whether in certain people who might be predisposed to inflammation and who do a lot of exercise, if that can eventually catch up with them.”