Association between resting heart rate, VO₂max and carotid intima-media thickness in middle-aged men

Low resting heart rate (RHR) and high cardiorespiratory fitness (VO₂max) are associated with a reduction in cardiovascular events (CV). Carotid intima-media thickness (CIMT) has been suggested as a predictor of CV. The purpose of this study was to investigate the association between RHR, VO₂max and CIMT.

The subjects of this study were 707 males aged 40-50 who visited the National Health Center of South Korea, a health examination institution, from 2010 to 2016. RHR was measured using electrocardiogram. RHR was divided into 4 levels (<60 beats per minute; bpm, 60-69 bpm, 70-79 bpm, ≥80 bpm). VO₂max was measured by grade exercise test. Subject's VO₂max was divided into 3 levels (first, second and third tertiles). CIMT was measured by B-mode ultrasound. Carotid atherosclerosis was defined as CIMT >1 mm.

There was no significant difference in CIMT according to RHR level and there was no correlation between RHR and CIMT. High and middle VO₂max group had significant lower CIMT than low VO₂max group (P < 0.001). There was also a correlation between VO₂max and CIMT (R = -0.129, P < 0.001). The low VO₂max group showed 3.56-fold (95% CI, 1.77-7.16) higher relative risk of carotid atherosclerosis than the high VO₂max group.

These results suggest that cardiovascular fitness index VO₂max is associated to CIMT in middle-aged men. In addition, this study shows that VO₂max are important indicators for the prevalence of carotid atherosclerosis.