Differences in blood pressure and heart rate variability between individuals with and without coronary artery calcification during prolonged high-intensity endurance exercise

Physical exercise is associated with increased life duration and improved life quality. Paradoxically, high exercise intensity is also associated with increased coronary artery calcification (CAC) and a small but significant increased risk of myocardial infarction and cardiac death during high-intensity exercise. This study compares cardiovascular hemodynamic measures and heart rate variability (HRV), which may impact cardiac function, during prolonged high-intensity exercise in individuals with and without CAC.

A total of 56 healthy, middle-aged (51.0 [43.0-58.0] years [median, (Q1-Q3)]) individuals (41 men/15 women) participating in a 91-km (251.2 [217.2-271.6] minutes) leisure sport mountain bike race were included in this study. Computer tomography coronary angiography after the race demonstrated CAC in 25 participants (20 men/5 women), defining them as CAC+. The other participants without CAC were defined as CAC-. The study subjects were assessed using hemodynamic measures and HRV at the top of the hardest hill (THH) towards the end of the race.

Comparing hemodynamic measures after THH demonstrated that CAC+ individuals had significantly higher systolic blood pressure (235.0 [225.0-245.0] mmHg vs 220.0 [192.5-237.5] mmHg, p=0.008), higher diastolic blood pressure (DBP) (105.0 [95.0-110.0] mmHg vs 95.0 [85.0-110.0] mmHg, p=0.006), higher pulse pressure (130.0 [125.0-140.0] mmHg vs 123.0 [110.0-130.0] mmHg, p=0.039), higher mean rate pressure product (33882 [30872-35053] bpm×mmHg vs 31028 [27392-33047] bpm×mmHg, p=0.028), and larger increase in DBP from baseline (20.0 [20.0-30.0] mmHg vs 10.0 [0.0-20.0] mmHg, p=0.001), compared with CAC- individuals. The CAC+ individuals had a significant reduction in the low frequency (LF) component of HRV (6.3 [2.4-11.5] ms² vs 12.4 [6.8-20.2] ms², p=0.044). In multivariate analysis, LF was an independent predictor of presence of CAC even after adjusting for established risk factors of atherosclerosis.

Individuals with calcified plaques had significant alterations in hemodynamic measures and LF following prolonged high-intensity exercise compared to individuals without CAC. LF was an independent predictor of presence of CAC suggesting a potentially pathological autonomic response to high intensity exercise in individuals with CAC.