Assessment of the relationship between dynamic pupillometry and exercise heart rate recovery among healthy subjects

Dynamic pupillometry (DP) is a simple, non-invasive computerized technique for assessment of pupillary light response which provides data concerning the balance of both branches of the autonomous nervous system (ANS). Heart rate (HR) recovery (HRR) after graded exercise reflects cardiac autonomic activity and predicts cardiovascular events. In this study, we aimed to evaluate the utility of DP as a predictor of cardiac autonomic activity assessed by HRR.

A total of 62 consecutive healthy subjects (mean age = 33.7 ± 8.6 years, 39 males and 23 females) were enrolled. Pupil diameters (R0, R1, R2 and R%): latency (Lc), amplitude (Ac), velocity (Vc) and duration of pupil contraction (Tc): latency (Ld), velocity (Vd) and duration of pupil dilatation (Td) were measured in DP. HRR indices were calculated by subtracting 1st (HRR1), 2nd (HRR2) and 3rd (HRR3) minute HR from the maximal HR during treadmill exercise stress test.

HRR1 was 32.9 ± 8.0 bpm, HRR2 was 55.1 ± 11.6 bpm and HRR3 was 58.3 ± 12.7 bpm, respectively. Correlation analysis revealed significant positive correlations of HRR1 with Vc (r = 0.660, p = 0.001), Ac (r = 0.559, p = 0.001) and Vd (r = 0.412, p = 0.001). HRR had significant negative correlations with Lc (r = -0.442, p = 0.001), R% (r = -0.384, p = 0.002) and Ld (r = -0.286, p = 0.025). Vc [β = 3.995 (1.040 to 6.951, 95% CI, p = 0.009)] and Lc [β = -0.032 (-0.056 to -0.008, 95% CI, p = 0.01)] were found to be significant independent predictors of HRR1.

Pupillary autonomic functions assessed by DP correlates with cardiac autonomic functions evaluated by HRR. Among the DP parameters analyzed, Vc and Lc were independent predictors of cardiac autonomic functions.