Intra-individual reproducibility of extreme values.

<p>Intra-individual reproducibility of abnormality, defined as the probability for an individual who was in a given quantile during EST1 to remain in the same quantile or to change of quintile during EST2. For example, intra-individual reproducibility of extreme values for ΔHR_ex (first quintile) and ΔHR_rec (fifth quintile) was 58% and 57%, respectively.</p

Heart rate profile and indices.

<p>A: Definition of heart rate (HR) profile and HR indices during the exercise stress test. The heart rate profile, x_HR(t) (solid dark line) is a function of time obtained by filtering the instantaneous heart rate (dots) with a median filter 15 beats long. HR_rest: Mean x_HR(t) over 15 sec resting pre-test; HR_ex: Maximum x_HR(t) during exercise; HR_rec: minimum x_HR(t) during recovery; ΔHR_ex = HR_ex − HR_rest: HR increase during exercise; ΔHR_rec = HR_rec − HR_ex HR decrease during the 1 min recovery phase. HR_m: Mean HR during the entire test; B: Distribution of the heart rate profile across all participants. Black solid line, dark and light shadowed areas represent median, 25th-75th percentiles and 5th-95th percentile intervals, respectively.</p

Intra-individual correlation of HR profile.

<p>Distribution of the Pearson’s correlation coefficients between heart rate profiles during EST1 and EST2 for all individuals (n = 821). First, second and third quartiles correspond to cases A, B and C, respectively. The HR profiles corresponding to these values are shown in panels (A)-(C). Each panel is composed of two sub-panels, one on the left showing x_HR(t) against time and using the same vertical axis for EST1 and EST2, and another one on the right showing x_HR(t) against EST phase (0 and 1 correspond to the beginning and end of each EST) and with different vertical scales adjusted to span the HR range of x_HR(t) during EST1 and EST2.</p

Influence of maximum workload differences on intra-individual correlation.

<p>Intra-individual correlation of HR indices was assessed considering individuals who underwent ESTs with maximum work load that did not differ more than |ΔWL|. Bars represent the Spearman’s correlation coefficient. The number of individuals for each group is reported on top of each bar. Horizontal line is the mean Spearman’s correlation coefficient for resting HR.</p

Distribution of heart rate indices.

<p>Distribution of heart rate indices during first and second exercise stress test (EST1 and EST2). Every HR index decreased during EST2 with respect to EST1. The decrease was small (<4%) but consistent across individuals. (***) p<5·10⁻⁴ (Paired, two-sided Wilcoxon signed rank test).</p

Правда коммунизма. 1988. № 106

<div><p>Background</p><p>The heart rate (HR) response to exercise provides useful information about the autonomic function and has prognostic value, but its reproducibility over a long period of time, a critical requirement for using it as a clinical biomarker, is undetermined.</p><p>Aim</p><p>To determine the intra-individual reproducibility of HR dynamics during sub-maximum exercise and one minute recovery.</p><p>Methods</p><p>1187 individuals from the Cardio physical fitness assessment test of the UK Biobank repeated a standard exercise stress test twice (recall time 34.2 ± 2.8 months) and were prospectively studied.</p><p>Results</p><p>821 individuals complied with inclusion criteria for reproducibility analysis, including peak workload differences between assessments ≤10 W. Intra-individual correlation between HR profile during the first and the second assessment was very high and higher than inter-individual correlation (0.92±0.08 vs 0.87±0.11, p<0.01). Intra-individual correlation of indices describing HR dynamics was: ρ = 0.81 for maximum HR during exercise; ρ = 0.71 for minimum HR during recovery; ρ = 0.70 for HR changes during both exercise and recovery; Intra-individual correlation was higher for these indices of HR dynamics than for resting HR (ρ = 0.64). Bland-Altman plots demonstrated good agreement between HR indices estimated during the first and second assessment. A small but consistent bias was registered for all repeated measurements. The intra-individual consistency of abnormal values was about 60–70%.</p><p>Conclusions</p><p>The HR dynamics during exercise and recovery are reproducible over a period of 3 years, with moderate to strong intra-individual reproducibility of abnormal values.</p></div

Intra-individual correlation of HR indices.

<p>Scatter-plots showing the correlation between HR indices at first (EST1) and second (EST2) assessment. The Spearman’s correlation coefficient, ρ_sp, and the coefficient of determination, R², quantify the intra-individual correlation for each HR index and are reported in each panel. Dashed grey and red lines represent the identity line and the linear regression line, respectively.</p

Dispersion of AT (left), ARI (middle) and RT (right) increased for short S1–S2 pacing intervals.

<p>Bars represent median and median absolute deviation of the dispersions across different protocols (n = 14). Dispersion was calculated as the difference between 95th and 5th percentile of each distribution.</p

APD restitution dispersion contributed to the increase of ARI dispersion and it is due to both repolarization and activation dynamics.

<p>Each point represents a restitution protocol (n = 14). Left: APD restitution dispersion correlated with the increase in the dispersion of ARI between the largest and the shortest pacing intervals (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161765#pone.0161765.g008" target="_blank">Fig 8</a>-middle panel). The dispersion of APDR slope <i>α</i> correlated better with dispersion (middle), i.e. the heterogeneity of AT restitution, than with dispersion (right), i.e. the heterogeneity of the slope between RT and S1–S2 PI.</p

Contribution of repolarization and activation dynamics to APDR slope <i>α</i>.

<p>The contribution of AT and RT was estimated as the sensitivity of <i>α</i> to changes in (rate of change of RT with respect to S1–S2 PI) and (rate of change of AT with respect to S1–S2 PI), respectively, as in Eqs (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161765#pone.0161765.e037" target="_blank">16</a>) and (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161765#pone.0161765.e038" target="_blank">17</a>). Bar and lines represent the median and median absolute deviation across n = 14 restitution protocols, of median and estimated within each restitution protocol. Differences between and are statistically significant (<i>P</i> < 0.0001, Wilcoxon rank-sum test).</p