Determinants of Interindividual Variation in Exercise-Induced Cardiac Troponin I Levels

Abstract

Background Postexercise cardiac troponin levels show considerable interindividual variations. This study aimed to identify the major determinants of this postexercise variation in cardiac troponin I (cTnI) following 3 episodes of prolonged high-intensity endurance exercise. Methods and Results Study subjects were recruited among prior participants in a study of recreational cyclists completing a 91-km mountain bike race in either 2013 or 2014 (first race). In 2018, study participants completed a cardiopulmonary exercise test 2 to 3 weeks before renewed participation in the same race (second race). Blood was sampled before and at 3 and 24 hours following all exercises. Blood samples were analyzed using the same Abbot high-sensitivity cTnI STAT assay. Fifty-nine individuals (aged 50±9 years, 13 women) without cardiovascular disease were included. Troponin values were lowest before, highest at 3 hours, and declining at 24 hours. The largest cTnI difference was at 3 hours following exercise between the most (first race) (cTnI: 200 [87-300] ng/L) and the least strenuous exercise (cardiopulmonary exercise test) (cTnI: 12 [7-23] ng/L; P<0.001). The strongest correlation between troponin values at corresponding times was before exercise (r=0.92, P<0.0001). The strongest correlations at 3 hours were between the 2 races (r=0.72, P<0.001) and at 24 hours between the cardiopulmonary exercise test and the second race (r=0.83, P<0.001). Participants with the highest or lowest cTnI levels showed no differences in race performance or baseline echocardiographic parameters. Conclusions The variation in exercise-induced cTnI elevation is largely determined by a unique individual cTnI response that is dependent on the duration of high-intensity exercise and the timing of cTnI sampling. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02166216.

Keywords: biomarkers; exercise physiology; troponin.

Conflict of interest statement

Ø.S. has received lecture fees from Abbott Diagnostics. The remaining authors have no disclosures to report.

Figures

Figure 1. Flowchart of the study.

CPX indicates cardiopulmonary exercise; T0, recruitment race; T1 cardiopulmonary exercise test 2018; and T2, 2018 race.

Figure 2. Cardiac troponin I (cTnI), at baseline, 3 h, and 24 h, after the cardiopulmonary exercise test in 2018 (T1), the North Sea Race in 2018 (T2), and the North Sea Race recruitment race in either 2013 or 2014 (T0).

Scale is log10‐transformed. Dotted lines indicate the 99th percentile of the high‐sensitivity cTnI assay (26 ng/L).

Figure 3. Consistency in ranking of cardiac troponin I (cTnI) values following the recruitment race (the North Sea Race in either 2013 or 2014) and the 2018 North Sea Race.

Low responders are defined as individuals with a cTnI value within the first quartile (Q1) of the recruitment race (T0), whereas high responders are defined as individuals with a cTnI value within the highest quartile (Q4) of the recruitment race (T0). The graph displays the number of individuals in each of the 4 quartiles based on the cTnI values achieved in the 2018 race (T2). T0 indicates recruitment race; T1 cardiopulmonary exercise test 2018; and T2, 2018 race.

Figure 4. Scatterplot shows individual cardiac troponin I (cTnI) response at baseline, 3 h, and 24 h after the cardiopulmonary exercise (CPX) test in 2018 (T1), the 2018 race (T2), and the recruitment race in either 2013 or 2014 (T0).

Spearman bivariate correlations were used to assess the correlations between time points. Dotted lines indicate the 99th percentile of the high‐sensitivity cTnI assay (26 ng/L).