Cardiac Biomarkers Jump After Marathons in Recreational Runners

 Steve Stiles

May 01, 2017

PARIS, FRANCE — Most marathon runners aren't pros, but many who regularly enter them do put in some hours a week training for the big events. Is it enough to protect the heart?

Many such regular but recreational runners have higher-than-normal chronic levels of troponin T by high-sensitivity assay (hs-TnT) and acute jumps in that biomarker right after a marathon, suggests an admittedly small but provocative study[1].

The research may be unusual for prospectively tracking the stress, fibrosis, and cardiac remodeling biomarker ST2 in amateur athletes when they run marathons and for seeing signs that it may become chronically elevated when they repeatedly train for the event at a less-than-elite level.

In the study of 79 such recreational runners on the day of the 2016 Barcelona Marathon, about half had above-normal ST2 levels before the race and showed significant but transient further increases right afterward.

Emma R Roca

About a tenth of them also had above-normal levels of troponin T by hs-TnT before the event, and the prevalence went to almost 90% right afterward before tapering off over the next 48 hours, reported Emma R Roca (Polytechnic University of Catalonia, Barcelona, Spain) here at European Society of Cardiology (ESC) Heart Failure 2017.

Runners who trained at lower levels and who had the longest marathon running times also had the greatest increases in hs-TnT and ST2, Roca told heartwire from Medscape. Therefore, it may take more training to protect the heart during marathons than perceived necessary by many recreational runners.

Put another way, significant increases in the two biomarkers were associated with lower levels of training and the poorest performance. "The runners who trained more and so were more prepared had less of an increase in ST2," said Roca, a biochemist and avid marathoner.

That so many runners started out with high ST2 levels suggests that such elevations may become chronic, "an adaption of their training" that could be cardioprotective and may represent the reason acute elevations weren't more pronounced, said Roca, noting that scenario is only speculation.

Also from speculation, she said, is the concern that persistently elevated ST2 reflects a chronic adverse stress effect on the myocardium from repeated undertraining for prolonged endurance events like marathons, with acceleration of fibrosis or other changes that could become clinical later in life.

There is a tendency not to serially measure such biomarkers in healthy, exercising people, she noted, so not much is known about their dynamics with intense prolonged exertion and its possible cardiac effects. And most people who run marathons probably do not train nearly enough to gain the cardiac and vascular benefits observed when elite athletes train.

Other studies have suggested that even amateur athletes can train for marathons in a way that improves cardiac structure and function so as to respond well to intense endurance exercise, but that such training has tended to be structured, intense, and prolonged .

In the current study, concentrations of N-terminal pro-B-type natriuretic peptide (NT-proBNP), hs-TnT, and ST2 were measured in 79 persons just prior, right after, and 48 hours after running the marathon; 72% were men and 71% were at least 35 years of age (mean 39).

Biomarker Changes From Baseline in 79 Marathon Runners

Biomarker Baseline Immediately after marathon (P vs baseline) 48 h after marathon (P vs baseline)
NT-proBNP (ng/L) 70 92 (<0.001) 70 (0.29)
ST2 (ng/mL) 34.2 54.2 (<0.001) 33.7 (0.53)
hs-TnT (ng/L) 2.9 46.9 (<0.001) 4.7 (<0.001)
% >ULN
NT-proBNP (% >125 ng/L) 0 30.7 (<0.001) 1.4 (1.00)
ST2 (% >35 ng/mL) 48.7 86.7 (<0.001) 48.6 (1.00)
hs-TnT(% >14 ng/L) 10.4 88.3 (<0.001) 17.9 (0.03)
ULN=upper limit of normal in people without cardiac disease

They had been running marathons for a mean of 7 years and trained for an average of 6 hours per week, and their mean body mass index was 22.8. Their average time for finishing the marathon was 3:32:44 h/min/s: good but not elite, observed Roca.

At baseline, levels of hs-TnT correlated directly with hours trained per week (P=0.01) and inversely with individuals' race completion time (P=0.009); no biomarkers correlated with past years of training, according to Roca.

On the other hand, the more training, the less the ST2 response; weekly training hours were inversely proportional to rises in that biomarker (P=0.007).

And race finishing time, which was longer in the less well-trained, was directly proportional to levels of hs-TnT (P<0.001) and ST2 (P<0.05).

That troponin levels climbed steeply during the race and stayed somewhat elevated in the hours afterward could suggest exercise-induced myocardial injury in this group, Roca said, so it would make sense in practice to screen recreational runners for changes in these biomarkers. Or barring actual screening, she said, it might be prudent to get at least baseline levels in case there are clinical issues later.

Offering a more general public-health message, Roca said that recreational runners who want to do marathons and perceive their training levels as appropriate will likely need to up their training if they want to level out cardiac biomarker responses, although it isn't really known whether that will improve their health later.

Roca had no relevant financial relationships.

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