Central Sympathetic Inhibition Augments Sleep-Related Ultradian Rhythm of Parasympathetic Tone in Patients With Chronic Heart Failure

Sympathetic overactivity and nocturnal diuresis in obstructive sleep apnea alter the response to hypertension therapy

BACKGROUND

Obstructive sleep apnea (OSA) is associated with high blood pressure that responds poorly to usual antihypertensive therapy.

METHODS AND RESULTS

Forty-one subjects with OSA had 25% higher plasma norepinephrine and 42% higher epinephrine measured every 2 h over 24 h than 20 control subjects. They also excreted more sodium during sleep. This suggested that that a sympatholytic would be a more successful antihypertensive than a diuretic. To test this hypothesis we treated a second group of 23 hypertensive apneics with placebo, 6 weeks of the sympatholytic guanfacine and 6 weeks of hydrochlorothiazide in a crossover study. Guanfacine lowered 24-hour blood pressure by 9.6/6.7 mmHg, more than the 5.4/2.9 mmHg effect of hydrochlorothiazide (P < 0.05). Nighttime systolic blood pressure dipping was poor at 6.6 ± 1.8%. Hydrochlorothiazide did not alter blood pressure dipping but guanfacine improved dipping to 9.1 ± 1.2%, a better result (P = 0.03) than from the diuretic. Central aortic pressure by pulse wave analysis was 120/84 mmHg on hydrochlorothiazide and 109/72 on guanfacine, (P < 0.05). Guanfacine, but not hydrochlorothiazide, improved baroreflex sensitivity, heart rate variability and flow mediated vascular dilation, suggesting that decreasing the elevated sympathetic nerve activity of obstructive sleep apnea returned vascular function toward normal.

CONCLUSIONS

OSA is the most common condition associated with antihypertensive treatment failure. It increased sympathetic nerve activity day and night. Drugs that block sympathetic nerve function are not among the 4 most commonly recommended classes of antihypertensives but diuretics are. Sympatholytic therapy was superior to diuretic treatment for hypertension associated with sleep apnea.

TRIAL REGISTRATION

NCT, NCT02699125, Registered 26 February 2016 - Retrospectively registered, https://clinicaltrials.gov/study/NCT02699125 .

Day-night patterns in heart rate variability and complexity: differences with age and cardiopulmonary disease

STUDY OBJECTIVES

Heart rate variability (HRV) measures provide valuable insights into physiology; however, gaps remain in understanding circadian patterns in heart rate dynamics. We aimed to explore day-night differences in heart rate dynamics in patients with chronic cardiopulmonary disease compared with healthy controls.

METHODS

Using 24-hour heart rate data from patients with chronic obstructive pulmonary disease (COPD) and/or heart failure (n = 16) and healthy adult controls (older group: ≥50 years, n = 42; younger group: 20-49 years, n = 136), we compared day-night differences in conventional time and frequency domain HRV indices and a multiscale-entropy-based complexity index (CI1-20) of HRV among the 3 groups.

RESULTS

Twenty-four-hour HRV showed significant day-night differences (marked with "△") among younger healthy (mean age: 34.5 years), older healthy (mean age: 61.6 years), and cardiopulmonary patients (mean age: 68.4 years), including change in percentage of adjacent intervals that differ > 50 ms (△pNN50), high frequency (△HF), normalized low frequency (△nLF), ratio (△LF/HF), and △CI1-20. Among these, △LF/HF (2.13 ± 2.35 vs 1.1 ± 2.47 vs -0.35 ± 1.25; P < .001) and △CI1-20 (0.15 ± 0.24 vs 0.02 ± 0.28 vs -0.21 ± 0.27; P < .001) were significant in each pairwise comparison following analysis of variance tests. Average CI1-20 was highest in younger healthy individuals and lowest in cardiopulmonary patients (1.37 ± 0.12 vs 1.01 ± 0.27; P < .001). Younger healthy patients showed a heart rate complexity dipping pattern (night < day), older healthy patients showed nondipping, and cardiopulmonary patients showed reverse dipping (night > day).

CONCLUSIONS

As measures of 24-hour variability, traditional and complexity-based metrics of HRV exhibit large day-night differences in healthy individuals; these differences are blunted, or even reversed, in individuals with cardiopulmonary pathology. Measures of diurnal dynamics may be useful indices of reduced adaptive capacity in patients with cardiopulmonary conditions.

CITATION

Ma Y, Chang M-C, Litrownik D, Wayne PM, Yeh GY. Day-night patterns in heart rate variability and complexity: differences with age and cardiopulmonary disease. J Clin Sleep Med. 2023;19(5):873-882.

Guanfacine enhances cardiac acetylcholine release with little effect on norepinephrine release in anesthetized rabbits

An α2A-adrenergic agonist guanfacine improves autonomic imbalance in attention-deficit hyperactivity disorder, suggesting that it may be useful to correct autonomic imbalance in chronic heart failure (CHF) patients. To investigate the effects of guanfacine on cardiac autonomic nerve activities, a microdialysis technique was applied to anesthetized rabbit heart. Acetylcholine (ACh) and norepinephrine (NE) concentrations in atrial dialysates were measured as indices of cardiac autonomic nerve activities. Guanfacine at a dose of 100 μg/kg significantly decreased heart rate and increased dialysate ACh concentration without decreasing sympathetic NE release. Guanfacine may be useful for vagal activation therapy in CHF patients.

Effect of Daily Cold Water Immersion on Heart Rate Variability and Subjective Ratings of Well-Being in Highly Trained Swimmers

Purpose:

We investigated the effect of daily cold water immersion (CWI), during a typical training week, on parasympathetic activity and subjective ratings of well-being.

Methods:

Over two different weeks, eight highly trained swimmers (4 men; 19.6 ± 3.2 y) performed their usual training load (5 d/wk, approx. 21 h/wk). Last training session of each training day was immediately followed by 5 min of seated recovery, in randomized order, with CWI (15°C) or without (CON). Each morning before the first training session (6:30 AM) during the two experimental weeks, subjective ratings of well-being (eg, quality of sleep) were assessed and the R-R intervals were recorded for 5 min in supine position. A vagal-related index (ie, natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals; Ln rMSSD) was calculated from the last 3-min segment.

Results:

Compared with CON, CWI effect on Ln rMSSD was rated as possibly beneficial on day 2 [7.0% (–3; 19)], likely beneficial on day 3 [20.0% (1.5; 43.5)], very likely beneficial on day 4 [30.4% (12.2; 51.6)] and likely beneficial on day 5 [24.1% (–0.4; 54.8)]. Cold water immersion was associated with a likely greater quality of sleep on day 2 [30.0% (2.7; 64.6)], very likely on day 3 [31.0% (5.0; 63.1)] and likely on day 4 [38.6% (11.4; 72.4)] when compared with CON.

Conclusion:

Five minutes of CWI following training can reduce the usual exercise-induced decrease in parasympathetic activity and is associated with improved rating of perceived sleep quality.

Medetomidine, an α(2)-adrenergic agonist, activates cardiac vagal nerve through modulation of baroreflex control

BACKGROUND

Although α(2)-adrenergic agonists have been reported to induce a vagal-dominant condition through suppression of sympathetic nerve activity, there is little direct evidence that they directly increase cardiac vagal nerve activity. Using a cardiac microdialysis technique, we investigated the effects of medetomidine, an α(2)-adrenergic agonist, on norepinephrine (NE) and acetylcholine (ACh) release from cardiac nerve endings.

METHODS AND RESULTS

A microdialysis probe was implanted into the right atrial wall near the sinoatrial node in anesthetized rabbits and perfused with Ringer's solution containing eserine. Dialysate NE and ACh concentrations were measured using high-performance liquid chromatography. Both 10 and 100µg/kg of intravenous medetomidine significantly decreased mean blood pressure (BP) and the dialysate NE concentration, but only 100µg/kg of medetomidine enhanced ACh release. Combined administration of medetomidine and phenylephrine maintained mean BP at baseline level, and augmented the medetomidine-induced ACh release. When we varied the mean BP using intravenous administration of phenylephrine, treatment with medetomidine significantly steepened the slope of the regression line between mean BP and log ACh concentration.

CONCLUSIONS

Medetomidine increased ACh release from cardiac vagal nerve endings and augmented baroreflex control of vagal nerve activity.

The impact of chronic primary insomnia on the heart rate--EEG variability link

OBJECTIVE

To determine if chronic insomnia alters the relationship between heart rate variability and delta sleep determined at the EEG.

METHODS

After one night of accommodation, polysomnography was performed in 14 male patients with chronic primary insomnia matched with 14 healthy men. ECG and EEG recordings allowed the determination of High Frequency (HF) power of RR-interval and delta sleep EEG power across the first three Non Rapid Eye Movement (NREM)-REM cycles. Interaction between normalized HF RR-interval variability and normalized delta sleep EEG power was studied by coherency analysis.

RESULTS

Patients showed increased total number of awakenings, longer sleep latency and wake durations and shorter sleep efficiency and REM duration than controls (p<.01). Heart rate variability across first three NREM-REM cycles and sleep stages (NREM, REM and awake) were similar between both groups. In each group, normalized HF variability of RR-interval decreased from NREM to both REM and awake. Patients showed decreased linear relationship between normalized HF RR-interval variability and delta EEG power, expressed by decreased coherence, in comparison to controls (p<.05). Gain and phase shift between these signals were similar between both groups.

CONCLUSIONS

Interaction between changes in cardiac autonomic activity and delta power is altered in chronic primary insomniac patients, even in the absence of modifications in heart rate variability and cardiovascular diseases.

SIGNIFICANCE

This altered interaction could reflect the first step to cardiovascular disorders.

Long-Term follow-up of the circadian rhythm of heart rate and heart rate variability in healthy elderly patients

BACKGROUND

The long-term age-related changes in circadian rhythm of heart rate variability (HRV), that is, autonomic nervous activity, remain unknown in elderly people.

METHODS AND RESULTS

Holter monitoring was conducted twice at an interval of 15 years in 15 healthy elderly patients (age: 70.0 +/- 4.1 years, at first monitoring, female: 10) and assessed the age-related changes in 24-h mean and hourly mean normal sinus R-R interval (mean NN), HRV (high frequency (HF) component, low frequency (LF) component and LF/HF) and the circadian rhythms. As a result, 24-h mean mean NN (0.976 +/- 0.115 vs 0.903 +/- 0.117 (s), p = 0.0019), LF/HF (1.681 +/- 0.731 vs 0.962 +/- 0.442, p = 0.0022), and LF (278.88 +/- 176.43 vs 179.19 +/- 132.33 (ms2), p = 0.0039) significantly decreased 15 years later, although 24-h mean HF (221.20+/-138.89 vs 310.78+/-296.73 (ms2), p = 0.1102) increased slightly. The hourly mean NN closely correlated with hourly HF and LF/HF throughout circadian rhythms both at first and second monitoring. In the morning hours, amplitude rates of all HRV indices increased significantly 15 years later.

CONCLUSION

In elderly people, age-related changes in the 24-h mean heart rate (HR) were conversely dissociated from those of the 24-h mean HRV. However, the close correlation between hourly HR and HRV was preserved, even in very elderly patients. Additionally, the amplitude rates in HRV in the morning increased with age. These age-related changes of HR and HRV might be characteristic of elderly people.