Twenty-four-hour blood pressure and heart rate variability are reduced in patients on left ventricular assist device support

BACKGROUND

Limited data exist on the circadian blood pressure (BP) and heart rate (HR) variations that occur in heart failure (HF) patients on left ventricular assist device (LVAD) support.

METHODS

We prospectively recorded clinic and 24-hour ambulatory BP and HR data in patients on HeartMate II LVAD support. Results were compared to HF patients with ejection fraction ≤30% and controls with no history of cardiovascular disease. Physiologic nocturnal BP and HR dipping was defined as a ≥10% decline compared to daytime values.

RESULT

Twenty-nine LVAD patients (age 59 ± 15 years, 76% male, 38% ischemic etiology), 25 HF patients (age 64 ± 13 years, 84% male, 32% ischemic etiology) and 26 controls (age 56 ± 9 years, 62% male) were studied. Normal nocturnal BP dipping was less frequent in LVAD patients (10%) than in HF patients (28%) and controls (62%) and reversed BP dipping (BP increase at night) was more common in LVAD patients (24%), compared to HF (16%) and controls (8%), (p < 0.001, for all comparisons). Physiologic HR reduction was less frequent in LVAD patients (14%), compared to HF (16%) and controls (59%) (p < 0.001, for all comparisons). Among LVAD patients, 36% exhibited sustained hypertension over the 24-hours and 25% had white-coat hypertension.

CONCLUSIONS

Treatment of advanced HF with an LVAD does not restore physiologic circadian variability of BP and HR; additionally, BP was not adequately controlled in more than a third of LVAD patients, and a quarter of them exhibited white-coat hypertension. Future studies are warranted to confirm these findings and investigate prognostic and management implications in this population.

Prenatal Hypoxia Affects Foetal Cardiovascular Regulatory Mechanisms in a Sex- and Circadian-Dependent Manner: A Review

Prenatal hypoxia during the prenatal period can interfere with the developmental trajectory and lead to developing hypertension in adulthood. Prenatal hypoxia is often associated with intrauterine growth restriction that interferes with metabolism and can lead to multilevel changes. Therefore, we analysed the effects of prenatal hypoxia predominantly not associated with intrauterine growth restriction using publications up to September 2021. We focused on: (1) The response of cardiovascular regulatory mechanisms, such as the chemoreflex, adenosine, nitric oxide, and angiotensin II on prenatal hypoxia. (2) The role of the placenta in causing and attenuating the effects of hypoxia. (3) Environmental conditions and the mother's health contribution to the development of prenatal hypoxia. (4) The sex-dependent effects of prenatal hypoxia on cardiovascular regulatory mechanisms and the connection between hypoxia-inducible factors and circadian variability. We identified that the possible relationship between the effects of prenatal hypoxia on the cardiovascular regulatory mechanism may vary depending on circadian variability and phase of the days. In summary, even short-term prenatal hypoxia significantly affects cardiovascular regulatory mechanisms and programs hypertension in adulthood, while prenatal programming effects are not only dependent on the critical period, and sensitivity can change within circadian oscillations.

Patients with Parkinson disease present high ambulatory blood pressure variability

Patients with Parkinson disease (PD) present blunted nocturnal blood pressure fall and similar ambulatory blood pressure variability (ABPV) measured by standard deviation (SD) and coefficient of variation (CV) compared with healthy subjects. However, these classical indices of ABPV have limited validity in individuals with circadian blood pressure alterations. New indices, such as the average of daytime and night-time standard deviation weighted by the duration of the daytime and night-time intervals (SD_dn ) and the average real variability (ARV), remove the influence of the daytime and the night-time periods on ABPV. This study assessed ABPV by SD_dn and ARV in PD. Twenty-one patients with PD (11 men, 66 ± 2 years, stages 2-3 of modified Hoehn & Yahr) and 21 matched controls without Parkinson disease (9 men, 64 ± 1 years old) underwent blood pressure monitoring for 24 h. ABPV was analysed by 24 h, daytime and night-time SD and CV, and by the SD_dn and ARV. Systolic/diastolic 24-h and night-time SD and CV were similar between the patients with PD and the controls. The patients with PD presented higher daytime systolic/diastolic CV and SD than the controls (10·4 ± 0·9/12·3 ± 0·8 versus 7·0 ± 0·3/9·9 ± 0·5%, P<0·05; 12·6 ± 1·0/9·1 ± 0·5 versus 8·6 ± 0·4/7·5 ± 0·3 mmHg, P<0·05, respectively) as well as higher systolic/diastolic SD_dn (10·9 ± 0·8/8·2 ± 0·5 versus 8·2 ± 0·3/7·1 ± 0·2 mmHg, P<0·05, respectively) and ARV (8·8 ± 0·6/6·9 ± 0·3 versus 7·2 ± 0·2/6·0 ± 0·2 mmHg, P<0·05, respectively). In conclusion, patients with PD have higher ABPV than control subjects as assessed by SD_d , CV_d , SD_dn and AVR.

Obesity accentuates circadian variability in breathing during sleep in mice but does not predispose to apnea

Obesity is a primary risk factor for the development of obstructive sleep apnea in humans, but the impact of obesity on central sleep apnea is less clear. Given the comorbidities associated with obesity in humans, we developed techniques for long-term recording of diaphragmatic EMG activity and polysomnography in obese mice to assess breathing patterns during sleep and to determine the effect of obesity on apnea generation. We hypothesized that genetically obese ob/ob mice would exhibit less variability in breathing across the 24-h circadian cycle, be more prone to central apneas, and be more likely to exhibit patterns of increased diaphragm muscle activity consistent with obstructive apneas compared with lean mice. Unexpectedly, we found that obese mice exhibited a greater circadian impact on respiratory rate and diaphragmatic burst amplitude than lean mice, particularly during rapid eye movement (REM) sleep. Central apneas were more common in REM sleep (42 ± 17 h(-1)) than non-REM (NREM) sleep (14 ± 5 h(-1)) in obese mice (P < 0.05), but rates were not different between lean and obese mice in either sleep state. Even after experimentally enhancing central apnea generation by acute withdrawal of hypoxic chemoreceptor activation during sleep, central apnea rates remained comparable between lean and obese mice. Last, we were unable to detect patterns of diaphragmatic burst activity suggestive of obstructive apnea events in obese mice. In summary, obesity does not predispose mice to increased occurrence of central or obstructive apneas during sleep, but does lead to a more pronounced circadian variability in respiration.

Long-term and within-day variability of working memory performance and EEG in individuals

OBJECTIVE

Assess individual-subject long-term and within-day variability of a combined behavioral and EEG test of working memory.

METHODS

EEGs were recorded from 16 adults performing n-back working memory tasks, with 10 tested in morning and afternoon sessions over several years. Participants were also tested after ingesting non-prescription medications or recreational substances. Performance and EEG measures were analyzed to derive an Overall score and three constituent sub-scores characterizing changes in performance, cortical activation, and alertness from each individual's baseline. Long-term and within-day variability were determined for each score; medication effects were assessed by reference to each individual's normal day-to-day variability.

RESULTS

Over the several year period, the mean Overall score and sub-scores were approximately zero with standard deviations less than one. Overall scores were lower and their variability higher in afternoon relative to morning sessions. At the group level, alcohol, diphenhydramine and marijuana produced significant effects, but there were large individual differences.

CONCLUSIONS

Objective working memory measures incorporating performance and EEG are stable over time and sensitive at the level of individual subjects to interventions that affect neurocognitive function.

SIGNIFICANCE

With further research these measures may be suitable for use in individualized medical care by providing a sensitive assessment of incipient illness and response to treatment.

CIRCADIAN BLOOD PRESSURE VARIABILITY AND EXERCISE THERAPY

The objective of this study was to find if there was a relationship between the time when cardiovascular rehabilitation was running in the patients after myocardial infarction and an average daily value of systolic and diastolic blood pressure at 7-day ambulatory blood pressure monitoring.Systolic and diastolic pressures significantly increased in patients who underwent cardiovascular rehabilitation in the morning from 9.00 a.m. to 10.15 a.m., and significantly decreased in those who did their physical exercise in the afternoon from 1.30 p.m. to 2.45 p.m., compared to their blood pressure values on days without rehabilitation.