Frédéric Roche

Relation between heart rate variability and training load in middle-distance runners

PURPOSE Monitoring physical performance is of major importance in competitive sports. Indices commonly used, like resting heart rate, VO2max, and hormones, cannot be easily used because of difficulties in routine use, of variations too small to be reliable, or of technical challenges in acquiring the data. METHODS We chose to assess autonomic nervous system activity using heart rate variability in seven middle-distance runners, aged 24.6 +/- 4.8 yr, during their usual training cycle composed of 3 wk of heavy training periods, followed by a relative resting week. The electrocardiogram was recorded overnight twice a week and temporal and frequency indices of heart rate variability, using Fourier and Wavelet transforms, were calculated. Daily training loads and fatigue sensations were estimated with a questionnaire. Similar recordings were performed in a sedentary control group. RESULTS The results demonstrated a significant and progressive decrease in parasympathetic indices of up to -41% (P < 0.05) during the 3 wk of heavy training, followed by a significant increase during the relative resting week of up to +46% (P < 0.05). The indices of sympathetic activity followed the opposite trend, first up to +31% and then -24% (P < 0.05), respectively. The percentage increasing mean nocturnal heart rate variation remained below 12% (P < 0.05). There was no significant variation in the control group. CONCLUSION This study confirmed that heavy training shifted the cardiac autonomic balance toward a predominance of the sympathetic over the parasympathetic drive. When recorded during the night, heart rate variability appeared to be a better tool than resting heart rate to evaluate cumulated physical fatigue, as it magnified the induced changes in autonomic nervous system activity. These results could be of interest for optimizing individual training profiles.

Screening of Obstructive Sleep Apnea Syndrome by Heart Rate Variability Analysis

BACKGROUND Enhanced nocturnal heart rate variability (HRV) has been evoked in sleep-related breathing disorders. However, its capacity to detect obstructive sleep apnea syndrome (OSAS) has not been systematically determined. Thus, we evaluated the discriminant power of HRV parameters in a first group of patients (G1) and validated their discriminant capacity in a second group (G2). METHODS AND RESULTS In G1, 39 of 91 patients (42.8%) were identified as diseased by polysomnography, as were 24 of 52 patients (46%) in G2. Time-domain HRV variables (SD of NN intervals [SDNN], mean of the standard deviations of all NN intervals for all consecutive 5-minute segments of the recording [SDNN index], square root of the mean of the sum of the squares of differences between adjacent normal RR intervals [r-MSSD], and SD of the averages of NN intervals in all 5-minute segments of the recording [SDANN]) were calculated for daytime and nighttime periods, as well as the differences between daytime and nighttime values (Delta[D/N]). Correlations between HRV variables and OSAS status were analyzed in G1 by use of receiver-operating characteristic (ROC) curves and logistic regression analysis. By ROC curve analysis, 7 variables were significantly associated with OSAS. After adjustment for other variables through multiple logistic regression analysis, Delta[D/N]SDNN index and Delta[D/N] r-MSSD remained significant independent predictors of OSAS, with ORs of 8.22 (95% CI, 3.16 to 21.4) and 2.86 (95% CI, 1.21 to 6.75), respectively. The classification and regression tree methodology demonstrated a sensitivity reaching 89.7% (95% CI, 73.7 to 97.7) with Delta[D/N] SDNN index and a specificity of 98.1% (95% CI, 86.4 to 100) with Delta[D/N] SDNN using appropriate thresholds. These thresholds, applied to G2, yielded a sensitivity of 83% using Delta[D/N] SDNN index and a specificity of 96.5% using Delta[D/N] SDNN. CONCLUSIONS Time-domain HRV analysis may represent an accurate and inexpensive screening tool in clinically suspected OSAS patients and may help focus resources on those at the highest risk.

Even a low-dose of moderate-to-vigorous physical activity reduces mortality by 22% in adults aged ≥60 years: a systematic review and meta-analysis

Background The health benefits of 150 min a week of moderate-to-vigorous-intensity physical activity (MVPA) in older adults, as currently recommended, are well established, but the suggested dose in older adults is often not reached. Objectives We aimed to determine whether a lower dose of MVPA was effective in reducing mortality, in participants older than 60 years. Methods The PubMed and Embase databases were searched from inception to February 2015. Only prospective cohorts were included. Risk ratios of death were established into four doses based on weekly Metabolic Equivalent of Task (MET)-minutes, defined as inactive (reference), low (1–499), medium (500–999) or high (≥1000). Data were pooled and analysed through a random effects model using comprehensive meta-analysis software. Results Of the 835 reports screened, nine cohort studies remained, totalling 122 417 participants, with a mean follow-up of 9.8±2.7 years and 18 122 reported deaths (14.8%). A low dose of MVPA resulted in a 22% reduction in mortality risk (RR=0.78 (95% CI 0.71 to 0.87) p<0.0001). MVPA beyond this threshold brought further benefits, reaching a 28% reduction in all-cause mortality in older adults who followed the current recommendations (RR=0.72 (95% CI 0.65 to 0.80) p<0.0001) and a 35% reduction beyond 1000 MET-min per week (RR=0.65 (95% CI 0.61 to 0.70) p<0.0001). Conclusions A dose of MVPA below current recommendations reduced mortality by 22% in older adults. A further increase in physical activity dose improved these benefits in a linear fashion. Older adults should be encouraged to include even low doses of MVPA in their daily lives.

Automatic Cardiac Event Recorders Reveal Paroxysmal Atrial Fibrillation after Unexplained Strokes or Transient Ischemic Attacks

Background: The etiology of stroke or transitory ischemic attack (TIA) remains frequently unknown. While paroxysmal atrial fibrillation (PAF) is often suspected, its presence remains difficult to establish. Therefore, we investigated the occurrence of PAF episodes in such a population using a long‐term automatic cardiac event recorder.

Relationship Among the Severity of Sleep Apnea Syndrome, Cardiac Arrhythmias, and Autonomic Imbalance

ROCHE, F., et al.: Relationship Among the Severity of Sleep Apnea Syndrome, Cardiac Arrhythmias, and Autonomic Imbalance. The relationship between obstructive sleep apnea syndrome (OSAS), cardiac arrhythmias, and conduction disturbances in adults remains controversial. Early studies showed a higher prevalence than more recent and designed epidemiological studies. To clarify the actual prevalence of cardiac arrhythmias and conduction disturbances in patients referred for assessment of OSAS, a prospective cohort study was conducted: 147 consecutive patients (103 men; mean age of 54.5 ± 10.7 years) underwent time‐synchronized polysomnography and ECG Holter monitoring. OSAS was diagnosed in 66 (44.9%) of them based on an apnea hypopnea index (AHI) ≥10. Prevalence of heart failure, of prior myocardial infarction, of hypertension, and of ventricular arrhythmias were similar in patients with or without OSAS. Nocturnal paroxysmal asystole was significantly more prevalent in OSAS patients (10.6 vs 1.2%; P < 0.02) and the number of episodes of bradycardia and pauses increased with the severity of the syndrome. Almost all bradycardic events occurred in patients with severe OSAS (AHI > 30), prolonged periods of arterial oxyhemoglobin desaturation, and low diurnal awake PaO2. Moreover, using heart rate variability analysis, nocturnal sinusal dysfunction contrasted with a blunted diurnal parasympathetic modulation of the sinus node. Frequent nocturnal nonsustained supraventricular tachycardias were predominantly found in patients with severe sleep related breathing disorders; however, an increased risk of ventricular arrhythmias was not found. Under continuous positive airway pressure treatment, the 1‐year follow‐up of OSAS patients with nocturnal pauses did not reveal any arrhythmic event justifying a specific intervention. (PACE 2003; 26:669–677)

Predicting sleep apnoea syndrome from heart period: a time-frequency wavelet analysis

Heart rate fluctuations are a typical finding during obstructive sleep apnoea, characterised by bradycardia during the apnoeic phase and tachycardia at the restoration of ventilation. In this study, a time-frequency domain analysis of the nocturnal heart rate variability (HRV) was evaluated as the single diagnostic marker for obstructive sleep apnoea syndrome (OSAS). The predictive accuracy of time-frequency HRV variables (wavelet (Wv) decomposition parameters from level 2 (Wv2) to level 256 (Wv256)) obtained from nocturnal electrocardiogram Holter monitoring were analysed in 147 consecutive patients aged 53.8±11.2 yrs referred for possible OSAS. OSAS was diagnosed in 66 patients (44.9%) according to an apnoea/hypopnoea index ≥10. Using receiver-operating characteristic curves analysis, the most powerful predictor variable was Wv32 (W 0.758, p<0.0001), followed by Wv16 (W 0.729, p<0.0001) and Wv64 (W 0.700, p<0.0001). Classification and Regression Trees methodology generated a decision tree for OSAS prediction including all levels of Wv coefficients, from Wv2 to Wv256 with a sensitivity reaching 92.4% and a specificity of 90.1% (percentage of agreement 91.2%) with this nonparametric analysis. Time-frequency parameters calculated using wavelet transform and extracted from the nocturnal heart period analysis appeared as powerful tools for obstructive sleep apnoea syndrome diagnosis.

Results From the Loire-Ardèche-Drôme-Isère-Puy-de-Dôme (LADIP) Trial on Atrial Flutter, a Multicentric Prospective Randomized Study Comparing Amiodarone and Radiofrequency Ablation After the First Episode of Symptomatic Atrial Flutter

Background— There is no published randomized study comparing amiodarone therapy and radiofrequency catheter ablation (RFA) after only 1 episode of symptomatic atrial flutter (AFL). The aim of the Loire-Ardèche-Drôme-Isère-Puy-de-Dôme (LADIP) Trial of Atrial Flutter was 2-fold: (1) to prospectively compare first-line RFA (group I) versus cardioversion and amiodarone therapy (group II) after only 1 AFL episode; and (2) to determine the impact of both treatments on the long-term risk of subsequent atrial fibrillation (AF). Methods and Results— From October 2002 to February 2006, 104 patients (aged 78±5 years; 20 women) with AFL were included, with 52 patients in group I and 52 patients in group II. The cumulative risk of AFL or AF was interpreted with the use of Kaplan-Meier curves and compared by the log-rank test. Clinical presentation, echocardiographic data, and follow-up were as follows: age (78.5±5 versus 78±5 years), history of AF (27% versus 21.6%); structural heart disease (58% versus 65%), left ventricular ejection fraction (56±14% versus 54.5±14%), left atrial size (43±7 versus 43±6 mm), mean follow-up (13±6 versus 13±6 months; P=NS), recurrence of AFL (3.8% versus 29.5%; P<0.0001), and occurrence of significant AF beyond 10 minutes (25% versus 18%; P=0.3). Five complications (10%) were noted in group II (sick sinus syndrome in 2, hyperthyroidism in 1, and hypothyroidism in 2) and none in group I (0%) (P=0.03). Conclusions— RFA should be considered a first-line therapy even after the first episode of symptomatic AFL. There is a better long-term success rate, the same risk of subsequent AF, and fewer secondary effects.

Frequent and prolonged asymptomatic episodes of paroxysmal atrial fibrillation revealed by automatic long-term event recorders in patients with a negative 24-hour holter

ROCHE, F., et al.: Frequent and Prolonged Asymptomatic Episodes of Paroxysmal Atrial Fibrillation Revealed by Automatic Long‐Term Event Recorders in Patients with a Negative 24‐Hour Holter. The presence, frequency, and duration of episodes of paroxysmal atrial fibrillation (PAF) is difficult to establish. This is caused by the limited duration of standard Holter recordings and to the unsatisfactory yield of patient‐triggered event recorders, because of asymptomatic events and of an inconsistent use of the patient dependent triggering function. A prospective cohort of 65 consecutive patients with recurrent palpitations and a negative 24‐hour ECG Holter was investigated by means of a cardiac event recorder bearing continuous automatic arrhythmia analysis and storage. Over a mean duration of 77 ± 36 hours, episodes of PAF were diagnosed in 20 (31%) patients, who had a total of 37 episodes; mean duration of PAF episodes was 7 hours 50 minutes ± 8/hours 45 minutes (minimum 45 minutes, maximum 28 hours). Eleven (55%) of these 20 patients were asymptomatic and would have remained undiagnosed without the automatic mode of the event recorder. Asymptomatic PAF episodes were longer than symptomatic ones (10 hours 30 minutes ± 6 hours 30 minutes vs 4 hours 50 minutes ± 4 hours, P < 0.05). In addition, episodes of sustained paroxysmal supraventricular tachycardia (PSVT) were diagnosed in 39 (57%) patients, of whom 34 (87%) were symptomatic. In this prospective cohort, a second standard 24‐hour monitoring would have missed 44% of the patients with PAF or PSVT and a classical patient‐triggered event recorder 13%. In patients still complaining of palpitations after one negative 24‐hour Holter, numerous, prolonged, and often asymptomatic episodes of PAF can be revealed by long‐term automatic event recorders. These devices should help clarify the clinical consequences of such episodes.

Cardiovascular variability during periodic leg movements: a spectral analysis approach

OBJECTIVE Changes in cardiovascular measures have been advocated as sensitive markers of phasic events arising from sleep. The current study was aimed to analyse the effects of periodic leg movements (PLMS) on heart rate variability (HRV) during NREM sleep in patients having restless legs syndrome and periodic leg movements during sleep. METHODS The absolute and normalized high- and low-frequency peaks from spectral analysis (FFT) of R-R intervals, the HRV changes using wavelet transform, the geometric and time domain HRV were measured in 14 patients with restless legs syndrome and PLMS. The analysis was done comparing one hundred, 10 min periods with PLMS (PLMS+) and 60 periods without PLMS (PLMS-) in stage 2 of NREM sleep. In 8 patients analysis was also done in slow wave sleep (SWS). RESULTS Occurrence of PLMS induced changes in geometrical indices of HRV, with a rise of the triangular index and the triangular interpolation of R-R intervals in PLMS+ periods (P < 0.0001). Small changes in time domain indices were found during PLMS+ periods, while the SD of the R-R intervals (SDNN), reflecting global HRV, was significantly higher (P = 0.001). While the low frequency (LF) power significantly increased in PLMS+ periods (P < 0.0001), high frequency (HF) power showed a weak and not significant reduction. The rise in sympathetic activity as detected by frequency domain HRV analysis was related to density and interval of PLMS. Comparison between sleep stages of NREM sleep demonstrated lower values of HRV measures when PLMS+ periods occur in SWS. CONCLUSIONS Overall, PLMS occurrence was associated with a shift to increased sympathetic activity without significant changes in cardiac parasympathetic activity. The frequency domain analysis of HRV appears to be an easy tool to estimate the autonomic changes related to PLMS and PLMS- arousals and to differentiate their occurrence during stage 2 and deep sleep. SIGNIFICANCE Spectral HRV measures may offer a simple approach to estimate the degree of autonomic changes occurring in relation to periodic leg movements in restless legs patients.

Sleep Apnea Syndrome and Cognition

Obstructive sleep apnea (OSA) is a sleep-related breathing disorder characterized by repetitive episodes of airflow cessation resulting in brief arousals and intermittent hypoxemia. Several studies have documented significant daytime cognitive and behavioral dysfunction that seems to extend beyond that associated with simple sleepiness and that persists in some patients after therapeutic intervention. A still unanswered question is whether cognitive symptoms in OSA are primarily a consequence of sleep fragmentation and hypoxemia, or whether they coexist independently from OSA. Moreover, very little is known about OSA effects on cognitive performances in the elderly in whom an increased prevalence of OSA is present. In this review we will consider recent reports in the association between sleep apnea and cognition, with specific interest in elderly subjects, in whom sleep disturbances and age-related cognitive decline naturally occur. This will allow us to elucidate the behavioral and cognitive functions in OSA patients and to gain insight into age differences in the cognitive impairment. Clinically, these outcomes will aid clinicians in the evaluation of diurnal consequences of OSA and the need to propose early treatment.