Component Of Blood Pressure Variability Research Articles

Determinants of short-term blood pressure variability – the value of arterial stiffness

Abstract. Increased blood pressure variability is a significant parameter that affects the prognosis in patients with arterial hypertension, and is an independent predictor of cardiovascular events and mortality. The arterial elasticity is an important factor in maintaining a constant average blood pressure for adequate blood supply to inner organs against the background of dynamic blood pressure fluctuations. A decrease in the elastic properties of the arteries, and therefore, an increase in the arterial stiffness can be one of the potential mechanisms for the blood pressure variability violation. Objective. The aim of the study was to evaluate the possible relationships between arterial stiffness indicators and blood pressure variability indices in patients with hypertension based on the results of ambulatory blood pressure monitoring. Patients and methods. The results of ambulatory blood pressure monitoring of 172 patients with hypertension were analyzed. Arterial stiffness was assessed using the ambulatory arterial stiffness index - symmetric and asymmetric. SD, SDw, CV, SV, ARV, and BPVR indices were calculated to assess blood pressure variability. Analysis of the obtained results was carried out using Microsoft Excel 2010 and the STATISTICA version 10.0 software. Differences between groups were assessed by the Mann-Whitney method, correlations among blood pressure variability indices and ambulatory arterial stiffness indices were evaluated using Spearman`s rank correlation analysis. Significance was set at p ˂ 0.05. The results. Awake asymmetric ambulatory arterial stiffness index was significantly higher than asleep one, no statistically significant difference between asleep and 24-hour asymmetric ambulatory arterial stiffness index was established. The asleep symmetric ambulatory arterial stiffness index did not significantly differ from the awake one and was significantly higher than the 24-hour one. In comparison with asymmetric, for symmetric ambulatory arterial stiffness index statistically significant relationships were established for a greater number of blood pressure variability indices. In all statistically significant cases, the direction of the established relationship with arterial stiffness was only direct for the systolic blood pressure variability indices. Variability of diastolic blood pressure had a clear inverse relationship with arterial stiffness. Conclusions. The presence of pathogenetic interrelationships between arterial stiffness and blood pressure variability have been proven in the present study. The obtained results allow to state that arterial elasticity is an important component of blood pressure variability.

Effect of Blood Pressure Variability on Outcomes in Emergency Patients with Intracranial Hemorrhage.

IntroductionPatients with spontaneous intracranial hemorrhage (sICH) have high mortality and morbidity, which are associated with blood pressure variability. Additionally, blood pressure variability is associated with acute kidney injury (AKI) in critically ill patients, but its association with sICH patients in emergency departments (ED) is unclear. Our study investigated the association between blood pressure variability in the ED and the risk of developing AKI during sICH patients’ hospital stay.MethodsWe retrospectively analyzed patients with sICH, including those with subarachnoid and intraparenchymal hemorrhage, who were admitted from any ED and who received an external ventricular drain at our academic center. Patients were identified by the International Classification of Diseases, Ninth Revision (ICD-9). Outcomes were the development of AKI, mortality, and being discharged home. We performed multivariable logistic regressions to measure the association of clinical factors and interventions with outcomes.ResultsWe analyzed the records of 259 patients: 71 (27%) patients developed AKI, and 59 (23%) patients died. Mean age (± standard deviation [SD]) was 58 (14) years, and 150 (58%) were female. Patients with AKI had significantly higher blood pressure variability than patients without AKI. Each millimeter of mercury increment in one component of blood pressure variability, SD in systolic blood pressure (SBPSD), was significantly associated with 2% increased likelihood of developing AKI (odds ratio [OR] 1.02, 95% confidence interval [CI], 1.005–1.03, p = 0.007). Initiating nicardipine infusion in the ED (OR 0.35, 95% CI, 0.15–0.77, p = 0.01) was associated with lower odds of in-hospital mortality. No ED interventions or blood pressure variability components were associated with patients’ likelihood to be discharged home.ConclusionOur study suggests that greater SBPSD during patients’ ED stay is associated with higher likelihood of AKI, while starting nicardipine infusion is associated with lower odds of in-hospital mortality. Further studies about interventions and outcomes of patients with sICH in the ED are needed to confirm our observations.

Cardiovascular response to different types of acute stress stimulations.

Stress is an ubiquitous phenomenon in the modern world and one of the major risk factors for cardiovascular disease. e aim of our study was to evaluate the effect of various acute stress stimuli on autonomic nervous system (ANS) activity, assessed on the basis of heart rate (HRV) and blood pressure (BPV) variability analysis. the study included 15 healthy volunteers: 9 women, 6 men aged 20-30 years (23.3 ± 1.8). ANS activity was assessed by HRV and BPV measurement using Task Force Monitor 3040 (CNSystems, Austria). ECG registration and Blood Pressure (BP) measurement was done 10 minutes at rest, 10 minutes a er the stress stimulus (sound signal, acoustic startle, frequency 1100 Hz, duration 0.5 sec, at the intensity 95 dB) and 10 minutes after the cold pressor test. The cold pressor test (CPT) was done by placing the person's hand by wrist in ice water (0-4°C) for 120 s. Every kind of stress stimulation (acoustic startle; the CPT) caused changes of HRV indicator values. The time domain HRV analysis parameters (pNN50, RMSSD) decreased after acoustic stress and the CPT, but were significantly lower after the CPT. In frequency domain HRV analysis, significant differences were observed only after the CPT: (LF-RRI 921.23 ms2 vs. 700.09 ms2; p = 0.009 and HF-RRI 820.75 ms2 vs. 659.52 ms2; p = 0.002). The decrease of LF-RRI and HF-RRI value after the CPT was significantly higher than after the acoustic startle (LF-RRI 34% vs. 0.4%, p = 0.022; HF-RRI 19.7% vs. 7% ms2, p = 0.011). The decreased value of the LF and HF components of HRV analysis are indicative of sympathetic activation. Nonlinear analysis of HRV indicated a significant decrease in the Poincare plot SD1 (p = 0.039) and an increase of DFAα2 (p = 0.001) in response to the CPT stress stimulation. The systolic BPV parameter LF/HF-sBP increased significantly after the CPT (2.84 vs. 3.31; p = 0.019) and was higher than after the acoustic startle (3.31 vs. 3.06; p = 0.035). Significantly higher values of diastolic BP (67.17 ± 8.10 vs. 69.65 ± 9.94 mmHg, p = 0.038) and median BP (83.39 ± 8.65 vs. 85.30 ± 10.20 mmHg, p = 0.039) were observed in the CPT group than in the acoustic startle group. the Cold Pressor Test has a greater stimulatory effect on the sympathetic autonomic system in comparison to the unexpected acoustic startle stress. Regardless of whether the stimulation originates from the central nervous system (acoustic startle) or the peripheral nervous system (CPT), the final response is demonstrated by an increase in the low frequency components of blood pressure variability and a decrease in the low and high frequency components of heart rate variability.

Morning surge in blood pressure and blood pressure variability in Asia: Evidence and statement from the HOPE Asia Network.

Hypertension is a major risk factor for cardiovascular and cerebrovascular diseases. To effectively prevent end-organ damage, maintain vascular integrity and reduce morbidity and mortality, it is essential to decrease and adequately control blood pressure (BP) throughout each 24-hour period. Exaggerated early morning BP surge (EMBS) is one component of BP variability (BPV), and has been associated with an increased risk of stroke and cardiovascular events, independently of 24-hour average BP. BPV includes circadian, short-term and long-term components, and can best be documented using out-of-office techniques such as ambulatory and/or home BP monitoring. There is a large body of evidence linking both BPV and EMBS with increased rates of adverse cardio- and cerebrovascular events, and end-organ damage. Differences in hypertension and related cardiovascular disease rates have been reported between Western and Asian populations, including a higher rate of stroke, higher prevalence of metabolic syndrome, greater salt sensitivity and more common high morning and nocturnal BP readings in Asians. This highlights a need for BP management strategies that take into account ethnic differences. In general, long-acting antihypertensives that control BP throughout the 24-hour period are preferred; amlodipine and telmisartan have been shown to control EMBS more effectively than valsartan. Home and ambulatory BP monitoring should form an essential part of hypertension management, with individualized pharmacotherapy to achieve optimal 24-hour BP control particularly the EMBS and provide the best cardio- and cerebrovascular protection. Future research should facilitate better understanding of BPV, allowing optimization of strategies for the detection and treatment of hypertension to reduce adverse outcomes.

Mild Intermittent Hypoxia Improves Cardiovascular and Neurocognitive Function in Obstructive Sleep Apnea Patients

ObjectiveStudies in humans and other animals have provided compelling evidence that mild intermittent hypoxia (MIH) initiates long term facilitation of respiratory motor function and might offer cardiovascular, neurocognitive and metabolic protection. Despite this recognition, the beneficial responses to MIH in individuals with obstructive sleep apnea (OSA) have not been fully delineated. Hence, we aimed to determine if MIH coupled with continuous positive airway pressure (CPAP) therapy improves cardiovascular and neurocognitive function in OSA patients.MethodsData was collected from five hypertensive male participants who were diagnosed with OSA during overnight polysomnography at our laboratory and were subsequently treated with CPAP over a 3 week period of time. In addition, participants were treated with twelve 2‐minute episodes of hypoxia (PETO2 ≈ 50 mmHg) separated by 2‐minute intervals of normoxia for a period of 15 days over 3 weeks (i.e. 5 day/week). PETCO2 levels were sustained at 3 mmHg above baseline during MIH administration. Heart rate and beat to beat blood pressure measures obtained before exposure to MIH on the first and last day of the protocol were analyzed to determine if modifications in blood pressure and autonomic function were evident. Similarly, performance in neurocognitive tests designed to measure attention, learning and memory were also obtained pre‐ and post MIH therapy.ResultsPreliminary data suggests that daily exposure to MIH over 3 weeks led to a significant decrease in systolic blood pressure (before MIH vs. after MIH: 142.9 ± 4.4 vs. 132.7 ± 5.4 mmHg, p ≤ 0.05). Likewise, changes were observed in the high frequency (HF) component of heart rate variability (48.4 ± 5.7 vs. 60.0 ± 6.0 normalized units, p ≤ 0.01) and low frequency component of blood pressure variability (71.4 ± 5.7 vs. 63.8 ± 6.3 normalized units, p ≤ 0.06). The Buschke selective reminding test showed improvements in the number of trials required for recall (9 ± 0.9 vs. 2.2 ± 0.5, p ≤ 0.01) as well as long term recall (7.4 ± 1.4 vs. 17.8 ± 0.6, p ≤ 0.001) following MIH therapy. Daytime sleepiness did not show a significant change (7.5 ± 1.5 vs. 6.6 ± 1.6).ConclusionDespite being treated with CPAP for a short period of time (i.e. 3 weeks) significant modifications in cardiovascular, autonomic and neurocognitive modifications were evident. Typically this degree of change is not evident following treatment with CPAP for a short duration. We propose that repeated exposure to MIH was responsible for the significant modifications that were evident. Although data from control participants (i.e. CPAP alone) is required to support our results the data suggests that MIH may effectively treat cardiovascular co‐morbidities and improve memory in patients with OSA.Support or Funding InformationThis work is supported by the Department of Veterans Affairs, Veterans Health 507 Administration, Office of Research and Development (I01CX000125 & 15SRCS003 ‐ JHM).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Treating Visit-to-Visit Blood Pressure Variability to Improve Prognosis: Is Amlodipine the Drug of Choice?

Blood pressure (BP) levels are linearly associated with cardiovascular risk, and hypertension is the most common modifiable risk factor for cardiovascular disease.1 Moreover, antihypertensive treatment-induced BP lowering has been associated with reduction in all outcomes (stroke, heart failure, coronary events, cardiovascular, and all-cause mortality).2 Apart from the established knowledge regarding the importance of hypertension and its effective treatment, during the last years, there has been an increasing interest in the possibility that BP variability (BPV) might carry an additional contribution to cardiovascular risk, on top of the impact of mean BP levels. BP fluctuates constantly and its variability not only may have diagnostic implications regarding the accurate assessment of hypertension but also seems to exert additional stress on the cardiovascular system over and above average BP levels.3 Different components of BPV have been identified, characterized by BP fluctuations between hours, days, or months/years, respectively, termed as short-, mid-, and long-term components.3 All these types of BPV have been shown to carry an independent prognostic value in terms of cardiovascular events and all-cause and cardiovascular mortality.4–10 Three interesting articles have been recently published in this journal regarding long-term visit-to-visit BPV (VVV). Tedla et al11 showed that an increased VVV among 1122 untreated individuals was predictive of arterial stiffness progression after 10 years of follow-up. The 2 remaining papers reported data on the prognostic value of systolic VVV coming from 2 major trials: the observational extension of the ADVANCE trial (Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation)12 and the SPRINT (Systolic Blood Pressure Intervention Trial).13 However, it seems that at the present time, despite the accumulating evidence on the clinical relevance of VVV, the latter still remains a research tool failing to provide clinical application in …

Abstract WP301: Noninvasive Beat-to-Beat Assessment of Blood Pressure Variability, Heart Rate Variability and Baroreflex Sensitivity: Which Parameters Best Predict Clinical Outcome After Acute Ischemic Stroke?

Background and Objectives: Blood pressure variability (BPV), heart rate variability (HRV) and baroreflex sensitivity (BRS) as measures of autonomic function might provide prognostic information in ischemic stroke. We aimed to study noninvasive beat-to-beat assessment of BPV, HRV and BRS in the acute phase of ischemic stroke to determine whether any of them predicted clinical outcome. Methods & Patients: Consecutive ischemic stroke patients within 7 days of symptom onset were enrolled. The frequency components of BPV and HRV by means of power spectral analysis [very low frequency (VLF; < 0.04 Hz); low frequency (LF; 0.04-0.15 Hz); high frequency (HF; 0.15-0.40 Hz); power spectral density (PSD; <0.40 Hz) and LF/HF ratio] were calculated from 10-minute recordings of beat-to-beat blood pressure and heart rate monitoring. The baroreflex slope and baroreflex effectiveness index (BEI) were determined using the sequence method for BRS. Clinical outcome was assessed at 3 months after stroke onset as good or poor by modified Rankin Scale (mRS) (good outcome, mRS ≤ 2). Results: 82 patients were recruited (mean age, 64.6 ± 9.9 years; 89.3% males). Univariate analysis showed that there were significant differences in National Institutes of Health Stroke Scale (NIHSS) at recruitment, VLF diastolic BPV, VLF, HF and PSD systolic BPV, and down ramp BEI between the good and poor outcome groups (all P < 0.05). After adjusting for NIHSS, multivariate logistic regression showed that only HF systolic BPV (OR 1.320; 95% CI, 1.050-1.659; P=0.017) and down BEI (OR 0.950; 95% CI, 0.912-0.990; P=0.014) were independently correlated with poor functional outcome. Conclusions: Beat-to beat highly variable systolic blood pressure and impaired BRS as evaluated by decreased down BEI are associated with an unfavorable functional outcome after acute ischemic stroke. Important prognostic information can be readily obtained from a short period of noninvasive hemodynamics monitoring in the acute stroke patient.

A Single Session of Neuromuscular Electrical Stimulation Enhances Vascular Endothelial Function and Peripheral Blood Circulation in Patients With Acute Myocardial Infarction

This study aimed to investigate whether a single session of neuromuscular electrical stimulation (NMES) can enhance vascular endothelial function and peripheral blood circulation in patients with acute myocardial infarction (AMI). Thirty-four male patients with AMI were alternately assigned to 2 groups, and received NMES with muscle contraction (NMES group, n = 17) or without muscle contraction (control group, n = 17) after admission. NMES was performed for quadriceps and gastrocnemius muscles of both legs for 30 minutes. We measured systolic blood pressure as a parameter of cardiovascular responses and the low-frequency component of blood pressure variability as an index of sympathetic activity. Reactive hyperemia peripheral arterial tonometry (RH-PAT) index and transcutaneous oxygen pressure in foot (Foot-tcPO2) were also measured as parameters of vascular endothelial function and peripheral blood circulation, respectively. All patients completed the study without severe adverse events. Systolic blood pressure and the low-frequency component increased significantly during the NMES session in both groups (P < 0.01 and P < 0.05, respectively). However, elevation from systolic blood pressure at rest was < 10 mmHg in both groups. In the NMES group, the RH-PAT index and Foot-tcPO2 increased significantly after NMES (P < 0.05 and P < 0.001, respectively). No significant changes were observed in these parameters throughout the session in the control group. In conclusion, a single session of NMES with muscle contraction enhanced vascular endothelial function, leading to improvement in peripheral blood circulation without inducing excessive cardiovascular and autonomic responses in patients with AMI (UMIN000014196).

Autonomic impairment after myocardial infarction: Role in cardiac remodelling and mortality

1. Impairmant of baroreflex sensitivity (BRS) has been implicated in the reduction of heart rate variability (HRV) and in the increased risk of death after myocardial infarction (MI). In the present study, we investigated whether the additional impairment in BRS induced by sinoaortic baroreceptor denervation (SAD) in MI rats is associated with changes in the low-frequency (LF) component of HRV and increased mortality rate. 2. Rats were randomly divided into four groups: control, MI, denervated (SAD) and SAD + MI rats. Left ventricular (LV) function was evaluated by echocardiography. Autonomic components were assessed by power spectral analysis and BRS. 3. Myocardial infarction (90 days) reduced ejection fraction (by approximately 42%) in both the MI and SAD + MI groups; however, an increase in LV mass and diastolic dysfunction were observed only in the SAD + MI group. Furthermore, BRS, HRV and the LF power of HRV were reduced after MI, with an exacerbated reduction seen in SAD + MI rats. The LF component of blood pressure variability (BPV) was increased in the MI, SAD and SAD + MI groups compared with the control group. Mortality was higher in the MI groups compared with the non-infarcted groups, with an additional increase in mortality in the SAD + MI group compared with the MI group. Correlations were obtained between BRS and the LF component of HRV and between LV mass and the LF component of BPV. 4. Together, the results indicate that the abolishment of BRS induced by SAD in MI rats further reduces the LF band of HRV, resulting in a worse cardiac remodelling and increased mortality in these rats. These data highlight the importance of this mechanism in the prognosis of patients after an ischaemic event.

Hemodynamic responses and linear and non-linear dynamics of cardiovascular autonomic regulation following supramaximal exercise

The purpose of this study was to examine hemodynamic responses and cardiovascular autonomic regulation following supramaximal exercise. Electrocardiographic R-R intervals and beat-to-beat hemodynamics were recorded before and for 10 min after a 30-s Wingate test in 11 males. Spectral analysis of heart rate (HR) and arterial pressure variability, analysis of HR complexity, the sequence technique and the cross-spectral transfer function were used to quantify autonomic regulation and baroreflex sensitivity. After exercise, the high frequency component of HR variability (vagal-related index) was lower than pre-exercise values, whereas the ratio low frequency to high frequency (index of sympathovagal balance) and the low frequency component of blood pressure variability (index of sympathetic vasomotor tone) were greater than baseline (p < 0.05). Post-exercise HR complexity and baroreflex sensitivity were reduced compared to baseline, p < 0.05. Cardiovascular autonomic control requires more than 10 min to fully recover after intense physical exertion of only 30-s in young healthy males.

Out-of-office blood pressure measurement in children and adolescents

Out-of-office blood pressure measurement in children and adolescents

Effects of magnesium infusion on hemodynamic and autonomic changes in healthy volunteers

Background: Magnesium has been used for treatments and preventions of various situations, such as cardiovascular disease and pre-eclampsia. And it also used for decreasing demands of anesthetics and analgesics during anesthesia. Activity of autonomic nervous system has important roles for homeostasis of cardiovascular system, and its dysfunction affects mortality and morbidity. Because there are few reports about effects of magnesium infusion on autonomic nervous system, we investigated effects of magnesium infusion on hemodynamic and autonomic changes using variable autonomic function tests in healthy volunteers. Methods: Hemodynamic parameters, heart rate variability, blood pressure variability, and baroreflex sensitivity were evaluated before and after magnesium infusion of 30 mg/kg during 20 min in twenty healthy volunteers. Cold face test, valsalva maneuver were also performed before and after magnesium infusion. Results: Low-frequency components of blood pressure variability decreased after magnesium infusion (P = 0.026). There were no significant differences in blood pressure, heart rate, cardiac output, stroke volume, total peripheral resistance, heart rate variablility and baroreflex sensitivity between before and after magnesium infusion. Increases of diastolic blood pressure during cold face test decreased significantly after magnesium infusion (P = 0.022). In addition, no significant hemodynamic and autonomic changes were found during valsalva maneuver. Conclusions: Central sympathetic vasomotor tone decreased after magnesium infusion of 30 mg/kg during 20 min in healthy volunteers. However, it had no effects on parasympathetic system and baroreflex sensitivity. (Korean J Anesthesiol 2008; 55: 691~9)

Long-Term Prognostic Value of Blood Pressure Variability in the General Population

The hypothesis has been advanced that cardiovascular prognosis is related not only to 24-hour mean blood pressure but also to blood pressure variability. Data, however, are inconsistent, and no long-term prognostic study is available. In 2012 individuals randomly selected from the population of Monza (Milan), 24-hour ambulatory blood pressure (Spacelabs 90207) was measured via readings spaced by 20 minutes. Systolic and diastolic blood pressure variability was obtained by calculating the following: (1) the SD of 24-hour, day, and night mean values; (2) the day-night blood pressure difference; and (3) the residual or erratic blood pressure variability (Fourier spectral analysis). Fatal cardiovascular and noncardiovascular events were registered for 148 months. When adjusted for age, sex, 24-hour mean blood pressure, and other risk factors, there was no relationship between the risk of death and 24-hour, day, and night blood pressure SDs. In contrast, the adjusted risk of cardiovascular death was inversely related to day-night diastolic BP difference (beta coefficient=-0.040; P<0.02) and showed a significant positive relationship with residual diastolic blood pressure variability (beta coefficient=0.175; P<0.002). Twenty-four-hour mean blood pressure attenuation of nocturnal hypotension and erratic diastolic blood pressure variability all independently predicted the mortality risk, with the erratic variability being the most important factor. Our data show that the relationship of blood pressure to prognosis is complex and that phenomena other than 24-hour mean values are involved. They also provide the first evidence that short-term erratic components of blood pressure variability play a prognostic role, with their increase being accompanied by an increased cardiovascular risk.

Variability in Response to Antihypertensive Drugs

Heterogeneity of treatment effects (HTE) is a measure of the variations in individual treatment response to the same agent across a population. Hypertension affords an appropriate model for investigators of HTE. Use of blood pressure measurement guidelines and consistent techniques help to reduce the potential variability associated with clinician measurements. Patient characteristics such as age and race/ethnicity can affect blood pressure, including patient response and adverse events observed with antihypertensive medication. Through pharmacogenetic advances, potential underlying causes for such variation are emerging. The growing number of clinical examples of mutations that affect antihypertensive response includes multiple polymorphisms within the components of the renin-angiotensin-aldosterone system. The most prominent examples of these polymorphisms exist in the genes coding for angiotensinogen, angiotensin-converting enzyme, and the angiotensin II type 1 receptor. An understanding of the components of blood pressure variability and sources of HTE in antihypertensive therapy is important for analyzing published reports on this topic. It is also helpful when designing treatment protocols for individual patients with hypertension and in assessing their response to therapy.

IDENTIFICATION OF BLOOD PRESSURE CONTROL MECHANISMS BY POWER SPECTRAL ANALYSIS

1. Blood pressure and organ perfusion are controlled by a variety of cardiovascular control systems, such as the baroreceptor reflex and the renin-angiotensin system (RAS), and by local vascular mechanisms, such as shear stress-induced release of nitric oxide (NO) from the endothelium and the myogenic vascular response. Deviations in arterial blood pressure from its set point activate these mechanisms in an attempt to restore blood pressure and/or secure organ perfusion. However, the response times at which different cardiovascular mechanisms operate differ considerably (e.g. blood pressure control by the RAS is slower than blood pressure control via the baroreceptor reflex). 2. Owing to these different response times, some cardiovascular control systems affect blood pressure more rapidly and others more slowly. Thus, identifying the frequency components of blood pressure variability (BPV) by power spectral analysis can potentially provide important information on individual blood pressure control mechanisms. 3. Evidence is presented that the RAS, catecholamines, endothelial-derived NO and myogenic vascular function affect BPV at very low frequencies (0.02-0.2 Hz) and that low-frequency (LF) BPV (0.2-0.6 Hz) is affected by sympathetic modulation of vascular tone and endothelial-derived NO in rats. In humans, LF BPV (0.075-0.15 Hz) is affected by sympathetic modulation of vascular tone and myogenic vascular function. The impact of the RAS and endothelial-derived NO on BPV in humans requires further investigation. 4. In conclusion, power spectral analysis is a powerful diagnostic tool that allows identification of pathophysiological mechanisms contributing to cardiovascular diseases, such as hypertension, heart failure and stroke, because it can separate slow from fast cardiovascular control mechanisms. The limitation that some cardiovascular control mechanisms affect the same frequency components of BPV requires the combination of blood pressure spectral analysis with other techniques.

Evidence for Cardiovascular Autonomic Dysfunction in Neonates With Coarctation of the Aorta

Coarctation of the aorta (CoA) is associated with hypertension and abnormalities of blood pressure control, which persist after late repair. Assumptions that neonatal repair would prevent development of blood pressure abnormalities have not been supported by recent data. We hypothesized that early pathological adjustment of autonomic cardiovascular function may already be established in the neonate with coarctation. We studied 8 otherwise well neonates with simple CoA and compared measures of spontaneous baroreflex sensitivity, heart rate variability, and blood pressure variability with 13 healthy newborn babies. Spontaneous baroreflex sensitivity was calculated with sequence methodology from an ECG, and noninvasive blood pressure was recorded with a Portapres. Heart rate variability was determined with time- and frequency-domain measures. Blood pressure variability was measured in the frequency domain. In comparison with normal controls, neonates with CoA had raised blood pressure (78.9+/-3.8 versus 67.1+/-2.1 mm Hg), depressed baroreflex sensitivity (8.7+/-1.5 versus 13.8+/-1.1 ms/mm Hg), reduced heart rate variability (total power 16.5+/-3.1 versus 31.5+/-2.2 ms2), and an increase in the high-frequency component of blood pressure variability (3.1+/-0.3 versus 2.2+/-0. 2 mm Hg2). This is not the pattern expected if neonates with CoA simply had subclinical cardiac failure. These data suggest that infants with CoA already show signs of pathological adjustment of autonomic cardiovascular homeostasis. Further longitudinal studies are required to determine whether these alterations play a role in the increased risk of late hypertension in these patients.

Different effects on circulatory control during volatile induction and maintenance of anesthesia and total intravenous anesthesia: autonomic nervous activity and arterial cardiac baroreflex function evaluated by blood pressure and heart rate variability analysis

Study Objective To evaluate the different effects on autonomic circulatory control during volatile induction/maintenance of anesthesia (VIMA) vs total intravenous anesthesia (TIVA). Design Prospective study. Setting Operating theater of a university hospital. Patients Twenty patients, with American Society of Anesthesiologists physical status of I or II, were randomly allocated into the VIMA group (n = 10) or the TIVA group (n = 10). Interventions In the VIMA group, anesthesia was induced with 5% sevoflurane and 60% N 2O in oxygen and maintained with 2% sevoflurane and 60% N 2O in oxygen. In the TIVA group, anesthesia was induced with propofol 2.0 mg/kg intravenously by bolus injection and fentanyl 2 μg/kg, and maintained with an intravenous infusion of propofol 5 mg/kg·per hour and air-oxygen mixture. Measurements Monitoring included recordings of electrocardiographic and arterial blood pressure waveforms. Autonomic nervous activity and arterial cardiac baroreflex function were evaluated by analysis of blood pressure variability, heart rate variability, and transfer function analysis between these 2 variables. Main Results In the VIMA group, the low-frequency component of blood pressure variability (LF SBP) and low- and high-frequency components of the R-R interval variability (LF RR and HF RR) decreased significantly during anesthesia. In the TIVA group, LF SBP and LF RR decreased significantly. The degree of reduction in LF SBP was greater in the VIMA group than in the TIVA group. However, changes in R-R interval variability and cardiac baroreflex indices were not significantly different between the 2 groups. Conclusions Our results demonstrated that although reductions in autonomic nervous modulation to the heart might not be so different between the 2 groups, reduction in sympathetic nervous modulation to peripheral vasculature is greater in the VIMA group than in the TIVA group.

Assessing the prognostic relevance of blood pressure variability: discrepant information from different indices

Assessing the prognostic relevance of blood pressure variability: discrepant information from different indices

Measurement of the Low-frequency Component of Blood Pressure Variability Can Assist the Interpretation of Heart Rate Variability Data

Measurement of the Low-frequency Component of Blood Pressure Variability Can Assist the Interpretation of Heart Rate Variability Data

Contribution of the autonomic nervous system to blood pressure and heart rate variability changes in early experimental hyperthyroidism

A great deal of uncertainty persists regarding the exact nature of the interaction between autonomic nervous system activity and thyroid hormones in the control of heart rate and blood pressure. We now report on thyrotoxicosis produced by daily intraperitoneal (i.p.) injection of l-thyroxine (0.5 mg/kg body wt. in 1 ml of 5 mM NaOH for 5 days). Control rats received i.p. daily injections of the thyroxine solvent. In order to estimate the degree of autonomic activation in hyperthyroidism, specific blockers were administered intravenously: atropine (0.5 mg/kg), prazosin (1 mg/kg), atenolol (1 mg/kg) or the combination of atenolol and atropine. A jet of air was administered in other animals to induce sympathoactivation. Eight animals were studied in each group. The dose and duration of l-thyroxine treatment was sufficient to induce a significant degree of hyperthyroidism with accompanying tachycardia, systolic blood pressure elevation, increased pulse pressure, cardiac hypertrophy, weight loss, tachypnea and hyperthermia. In addition, the intrinsic heart period observed after double blockade (atenolol+atropine) was markedly decreased after treatment with l-thyroxine (121.5±3.6 ms vs. 141.2±3.7 ms, P<0.01). Of the autonomic indices, vagal tone (difference between heart period obtained after atenolol and intrinsic heart period) was negatively linearly related to intrinsic heart period ( r=0.71, P<0.05). Atenolol modified neither the heart period nor blood pressure variability in rats with hyperthyroidism and in these rats the jet of air did not significantly affect the heart period level. The thyrotoxicosis was associated with a reduction of the 0.4 Hz component of blood pressure variability (analyses on 102.4 s segments, modulus 1.10±0.07 vs. 1.41±0.06 mm Hg, P<0.01) and prazosin was without effect on this 0.4 Hz component in these animals. These data show a functional diminution of the vascular and cardiac sympathetic tone in early experimental hyperthyroidism. The marked rise in the intrinsic heart rate could be the main determinant of tachycardia. The blood pressure elevation may reflexly induce vagal activation and sympathetic (vascular and cardiac) inhibition.