Sympathetic Neural Mechanisms in Hypertension: Recent Insights.

PURPOSE OF REVIEW: To examine published and unpublished data documenting the role of sympathetic neural factors in the pathogenesis of different hypertensive phenotypes. These phenotypes relate to attended or unattended blood pressure measurements, to nighttime blood pressure profile alterations, and to resistant, pseudoresistant, and refractory hypertension. Results of original clinical studies as well as of recent meta-analyses based on the behavior of different sympathetic biomarkers in various hypertensive forms will be also discussed. RECENT FINDINGS: Studies performed in the past decade have shown that office blood pressure measurements, including in recent years those characterizing unattended or attended blood pressure assessment, are associated with profound changes in the behavior of different sympathetic biomarkers. This is the case for the clinical hypertensive phenotypes characterized by alterations in the nocturnal blood pressure profile and by sleep duration abnormalities. This is also the case for the clinical conditions defined as resistant, refractory, and pseudoresistant hypertension. Data reviewed in the present paper highlight the relevance of sympathetic neural factors in the development and progression of different clinical hypertensive phenotypes. This suggests that a common hallmark of the majority of the essential hypertensive states detectable in current clinical practice is represented by the alteration in the sympathetic blood pressure control.

Coffee consumption, clinic, 24-hour and home blood pressure. Findings from the PAMELA study.

BACKGROUND AND AIMS: Chronic coffee consuption has been reported to be associated with a modest but significant increase in blood pressure (BP), although some recent studies have shown the opposite. These data, however, largely refer to clinic BP and virtually no study evaluated cross-sectionally the association between chronic coffee consuption, out-of-office BP and BP variability. METHODS AND RESULTS: In 2045 subjects belonging to the population of the Pressioni Arteriose Monitorate E Loro Associazioni (PAMELA) study, we analyzed cross-sectionally the association between clinic, 24-hour, home BP and BP variability and level of chronic coffee consumption. Results show that when adjusted for confounders (age, gender, body mass index, cigarette smoking, physical activity and alcohol drinking) chronic coffee consumption does not appear to have any major lowering effect on BP values, particulary when they are assessed via 24-hour ambulatory (0 Cup/day: 118.5 ± 0.7/72.8 ± 0.4 mmHg vs 3 cups/day: 120.2 ± 0.4/74.8 ± 0.3 mmHg, PNS) or home BP monitoring (0 cup/day: 124.1 ± 1.2/75.4 ± 0.7 mmHg vs 3 cups/day: 123.3 ± 0.6/76.4 ± 0.36 mmHg, PNS). However, daytime BP was significantly higher in coffee consumers (about 2 mmHg), suggesting some pressor effects of coffee which vanish during nighttime. Both BP and HR 24-hour HR variability were unaffected. CONCLUSION: Thus chronic coffee consumption does not appear to have any major lowering effect either on absolute BP values, particulary when they are assessed via 24-hour ambulatory or home BP monitoring, or on 24-hour BP variability.

Uric Acid, Hypertensive Phenotypes, and Organ Damage: Data from the Pamela Study.

PURPOSE OF REVIEW: To examine published and unpublished data collected in the context of the Pressioni Arteriose Monitorate E Loro Associazioni (PAMELA) study on the relationships between serum uric acid (SUA), office and out-of-office blood pressure (BP), and organ damage. RECENT FINDINGS: SUA values were directly and significantly related to a large number of covariates that participate at cardiovascular risk determination, such as blood glucose, total serum cholesterol, serum triglycerides, body mass index, and serum creatinine. Additional variables included echocardiographically-determined left ventricular mass index and BP values, the latter not just when measured in the office but also when evaluated at home or over the 24-h period. White-coat hypertension and masked hypertension were characterized, as sustained hypertension, by a significant increase in SUA levels, which were also directly related to different indices of 24-h BP variability. No substantial difference in SUA levels was found when data were analyzed according to the dipping or non-dipping nocturnal BP profile. Data collected in the frame of the PAMELA study document the presence of a close relationship between SUA levels and BP values independently on the hypertensive phenotype patterns of BP increase (office, 24 h, or both) and nighttime BP profile. They also document the increase in SUA as a potential factor favoring the occurrence of new hypertension and new left ventricular hypertrophy.

Autonomic cardiovascular alterations as therapeutic targets in chronic kidney disease.

PURPOSE: The present paper will review the impact of different therapeutic interventions on the autonomic dysfunction characterizing chronic renal failure. METHODS: We reviewed the results of the studies carried out in the last few years examining the effects of standard pharmacologic treatment, hemodialysis, kidney transplantation, renal nerve ablation and carotid baroreceptor stimulation on parasympathetic and sympathetic control of the cardiovascular system in patients with renal failure. RESULTS: Drugs acting on the renin-angiotensin system as well as central sympatholytic agents have been documented to improve autonomic cardiovascular control. This has also been shown for hemodialysis, although with more heterogeneous results related to the type of dialytic procedure adopted. Kidney transplantation, in contrast, particularly when performed together with the surgical removal of the native diseased kidneys, has been shown to cause profound sympathoinhibitory effects. Finally, a small amount of promising data are available on the potential favorable autonomic effects (particularly the sympathetic ones) of renal nerve ablation and carotid baroreceptor stimulation in chronic kidney disease. CONCLUSIONS: Further studies are needed to clarify several aspects of the autonomic responses to therapeutic interventions in chronic renal disease. These include (1) the potential to normalize sympathetic activity in uremic patients by the various therapeutic approaches and (2) the definition of the degree of sympathetic deactivation to be achieved during treatment.

Effects of acute carotid baroreceptor stimulation on sympathetic nerve traffic in resistant and uncontrolled hypertension: a systematic review and meta-analysis.

In resistant hypertensive patients acute carotid baroreflex stimulation is associated with a blood pressure (BP) reduction, believed to be mediated by a central sympathoinhbition.The evidence for this sympathomodulatory effect is limited, however. This meta-analysis is the first to examine the sympathomodulatory effects of acute carotid baroreflex stimulation in drug-resistant and uncontrolled hypertension, based on the results of microneurographic studies. The analysis included 3 studies assessing muscle sympathetic nerve activity (MSNA) and examining 41 resistant uncontrolled hypertensives. The evaluation included assessment of the relationships between MSNA and clinic heart rate and BP changes associated with the procedure. Carotid baroreflex stimulation induced an acute reduction in clinic systolic and diastolic BP which achieved statistical significance for the former variable only [systolic BP: -19.98 mmHg (90% CI, -30.52, -9.43), P < 0.002], [diastolic BP: -5.49 mmHg (90% CI, -11.38, 0.39), P = NS]. These BP changes were accompanied by a significant MSNA reduction [-4.28 bursts/min (90% CI, -8.62, 0.06), P < 0.07], and by a significant heart rate decrease [-3.65 beats/min (90% CI, -5.49, -1.81), P < 0.001]. No significant relationship was detected beween the MSNA, systolic and diastolic BP changes induced by the procedure, this being the case also for heart rate. Our data show that the acute BP lowering responses to carotid baroreflex stimulation, although associated with a significant MSNA reduction, are not quantitatively related to the sympathomoderating effects of the procedure. This may suggest that these BP effects depend only in part on central sympathoinhibition, at least in the acute phase following the intervention.

Ambulatory Blood Pressure Phenotypes, Arterial Stiffness And Cardiac Remodelling.

BACKGROUND: Evidence on the association of arterial stiffness and left ventricular (LV) concentric remodelling/ LVH assessed by echocardiography, with abnormal blood pressure (BP) phenotypes, defined by office and ambulatory BP monitoring (ABPM) in the community is scanty. We investigated this issue in the participants to the Pressioni Monitorate E Loro Associazioni (PAMELA) study. METHODS: The study included 491 participants who attended the second and third survey of the PAMELA study performed after 10 and 25 years from the initial evaluation. Data collection included medical history, anthropometric parameters, blood examinations, office, ABPM, echocardiographic and Cardio-Ankle Vascular Index (CAVI) measurements. RESULTS: In the whole study sample (age 66 + 10 years, 50% males), the prevalence rates of sustained normotension (NT), white coat hypertension (WCH), masked hypertension (MH), sustained hypertension (SH) and non-dipping (ND) were 31.2, 10.0, 24.2, 34.6, and 35.8% and respectively. The likelihood of having SH, the BP phenotype carrying the greatest CV risk, was four times higher (OR= 4.31, CI:2.39-7.76, p<0.0001) in participants with increased CAVI and LV remodelling/LVH compared to their counterparts without organ damage. This association showed an incremental value in discriminating SH compared to both isolated markers of organ damage (OR=1.92,p=0.03 for increased CAVI and OR= 2.02, p=0.02 for LV remodelling/LVH). The presence of isolated but also combined organ damage was unrelated to ND. CONCLUSIONS: Our study provides new evidence of the incremental value of looking for both vascular and cardiac organ damage to optimize the identification and clinical management of SH in the general population.

Renal Denervation in End-Stage Renal Disease: Current Evidence and Perspectives.

In patients with end-stage renal disease (ESRD) undergoing haemodialysis, hypertension is of common detection and frequently inadequately controlled. Multiple pathophysiological mechanisms are involved in the development and progression of the ESRD-related high blood pressure state, which has been implicated in the increased cardiovascular risk reported in this hypertensive clinical phenotype. Renal sympathetic efferent and afferent nerves play a relevant role in the development and progression of elevated blood pressure values in patients with ESRD, often leading to resistant hypertension. Catheter-based bilateral renal nerves ablation has been shown to exert blood pressure lowering effects in resistant hypertensive patients with normal kidney function. Promising data on the procedure in ESRD patients with resistant hypertension have been reported in small scale pilot studies. Denervation of the native non-functioning kidney's neural excitatory influences on central sympathetic drive could reduce the elevated cardiovascular morbidity and mortality seen in ESRD patients. The present review article will focus on the promising results obtained with renal denervation in patients with ESRD, its mechanisms of action and future perspectives in these high risk patients.

Relationships between sympathetic markers and heart rate thresholds for cardiovascular risk in chronic heart failure.

BACKGROUND: Results of recent clinical trials have shown that in heart failure (HF) heart rate (HR) values > 70 beats/minute are associated with an increased cardiovascular risk. No information is available on whether the sympathetic nervous system is differently activated in HF patients displaying resting HR values above or below this cutoff. METHODS: In 103 HF patients aged 62.7 ± 0.9 (mean ± SEM) years and in 62 heathy controls of similar age we evaluated muscle sympathetic nerve traffic (MSNA, microneurography) and venous plasma norepinephrine (NE, HPLC assay), subdividing the subjects in different groups according to their resting clinic and 24-h HR values. RESULTS: In HF progressively greater values of clinic or 24-h HR were associated with a progressive increase in both MSNA and NE. HR cutoff values adopted in large scale clinical trials for determining cardiovascular risk, i.e., 70 beats/minute, were associated with MSNA values significantly greater than the ones detected in patients with lower HR, this being the case also for NE. In HF both MSNA and NE were significantly related to clinic (r = 0.92, P < 0.0001 and r = 0.81, P < 0.0001, respectively) and 24-h (r = 0.91, P < 0.0001 and r = 0.79, P < 0.0001, respectively) HR. The behavior of sympathetic markers described in HF was specific for this clinical condition, being not observed in healthy controls. CONCLUSIONS: Both clinic and 24-h HR values greater than 70 beats/minute are associated with an increased sympathetic activation, which parallels for magnitude the HR elevations. These findings support the relevance of using in the therapeutic approach to HF drugs exerting sympathomoderating properties.

Uric acid relationships with lipid profile and adiposity indices: Impact of different hyperuricemic thresholds.

Previous studies focused on the relationships between Serum Uric Acid (SUA) and lipids have found an association mainly with triglycerides. Furthermore, previous studies on adiposity indices have been focused on the evaluation of the Visceral Adiposity Index (VAI). The present study was aimed at providing within the same population a systematic evaluation of lipids and adiposity indices with SUA, employing both the classic cutoff for hyperuricemia and the newly one identified by the Uric Acid Right for Heart Health (URRAH) study. We analyzed data collected in 1892 subjects of the Pressioni Arteriose Monitorate E loro Associazioni (PAMELA) study with available SUA, lipid profile and variables necessary to calculate VAI, Cardio-Metabolic Index (CMI) and Lipid Accumulation Product (LAP). At linear regression model (corrected for confounders) SUA correlated with all the lipids values (with the strongest ß for triglycerides) and adiposity indices. When the two different cutoffs were compared, the URRAH one was significantly related to atherogenic lipids profile (OR 1.207 for LDL and 1.33 for non-HDL, P < 0.001) while this was not the case for the classic one. Regarding adiposity indices the classic cutoff displays highest OR as compared to the URRAH one. In conclusions, newly reported URRAH cutoff for hyperuricemia better relate to atherogenic lipoprotein (LDL and non-HDL) when compared to the classic one. The opposite has been found for adiposity indexes where the classic cut-off seems to present highest performance. Among adiposity indexes, LAP present the highest OR for the relationship with hyperuricemia.

Comparison of electrocardiographic versus echocardiographic detection of left ventricular mass changes over time and evaluation of new onset left ventricular hypertrophy.

We assessed the value of 3 electrocardiographic (EKG) voltage criteria in detecting variations of left ventricular mass (LVM) over time, taking echocardiographic (ECHO) LVM as reference, in the Pressioni Arteriose Monitorate E Loro Associazioni study. In 927 subjects (age 47 ± 13 years on entry, 49.9% men) an ECHO evaluation of LVM and EKG suitable for measurement of EKG-LVH criteria (Sokolow-Lyon voltage, Cornell voltage and R-wave voltage in aVL) were available at baseline and at a 2nd evaluation performed 10 years later. Δ (delta) LVM, Δ LVMI, and Δ EKG parameters values were calculated from 2nd evaluation to baseline. The sensitivity of the EKG criteria in the diagnosis of LVH, poor at baseline, becomes even worse after 10 years, reaching very low values. Only the sensitivity of R-wave amplitude exhibited slight increase over time but with unsatisfactory absolute values. Despite the prevalence of ECHO-LVH at the 2nd evaluation was threefold increased compared to baseline (29.3% and 33.7% for LVM indexed to BSA and height2.7 , respectively), the prevalence of EKG-LVH was unchanged when evaluated by Sokolow-Lyon criteria, significantly reduced when assessed by Cornell voltage index, while significantly increased using R-wave voltage in aVL criteria. Despite an ECHO-LVM increase over the time, mean EKG changes were of opposite sign, except for R-wave amplitude in aVL. Our study highlights the discrepancy between ECHO and EKG in monitoring LVM changes over the time, especially for Sokolow-Lyon and Cornell voltage. Thus, EKG is an unsuitable method for the longitudinal evaluation of LVM variations.

Impact of the Increase in Left Ventricular Mass on the Risk of Long-Term Cardiovascular Mortality: A Prospective Cohort Study.

BACKGROUND: Left ventricular hypertrophy (LVH) is an independent predictor of cardiovascular events, and evidence has been obtained that an increase of a normal left ventricular mass (LVM) or new-onset LVH over time augments cardiovascular outcomes. METHODS: We addressed this issue in a sample of a general population at relatively low cardiovascular risk. We analyzed subjects with normal echocardiographic LVM enrolled in the PAMELA (Pressioni Arteriose Monitorate E Loro Associazioni) study to follow the increase of LVM over time and assess the prognostic impact of this change on the incidence of cardiovascular events (mean follow-up 18.5 years). RESULTS: In 990 subjects with no LVH at baseline, there was a significant average increase of LVM (21.2%), LVMIBSA (18.9%), and LVMIHT (22.3%) more than 10 years later. About a quarter developed LVH. The LVMIBSA change exhibited an association with the cardiovascular risk mortality during the following 18.5 years, and the association remained significant after adjustment for confounders (hazard ratio, 1.2 [1.0-1.5]). Similar findings were obtained for LVM in absolute values or indexed for height. The association was seen in both genders, but the link with the cardiovascular risk was statistically significant in males only. CONCLUSIONS: Thus, although over 10 years, the LVM increase does not reach a LVH status, it is associated with an augmented cardiovascular mortality risk. This suggests that it might be important to consider periodical LVM assessment, even when LVM is within the normal range, to timely detect its increase and cope with the need of cardiovascular risk restratification.

Metronidazole-induced hepatotoxicity in a patient with xeroderma pigmentosum: A case report.

RATIONALE: Whereas metronidazole-induced hepatotoxicity is quite rare in the general population, in individuals carrying a nucleotide excision repair disorder, namely Cockayne syndrome, there is a high risk of developing this complication. PATIENT CONCERNS: We report the case of a 44-year-old man, affected by xeroderma pigmentosum, who was admitted to the hospital presenting aspiration pneumoniae caused by worsening dysphagia and with severe hepatotoxicity during the hospitalization. DIAGNOSES: Acute hepatitis, which was leading to acute liver failure, occurred during antibiotic treatment with metronidazole and ceftazidime with an elevation of liver enzymes consistent with hepatocellular damage pattern. INTERVENTIONS: Hydration with glucose 5% solution, pantoprazole and vitamin K were administered, meanwhile other causes of hepatitis were ruled out and the ongoing antibiotic treatment was stopped suspecting a drug-induced liver injury. OUTCOMES: Liver function nearly completely recovered 1 month later with a first rapid improvement, within few days, of aminotransferases and coagulation studies, and slower of cholestatic enzymes. LESSONS: We describe the first case available in the literature of hepatotoxicity associated with metronidazole treatment in a xeroderma pigmentosum patient. Clinicians therefore, based on this report and according to the possible underlying mechanism shared by other genetic diseases characterized by alterations in the pathway of DNA-repair, should consider such adverse event also in patients affected by this rare disease.

Heart rate thresholds for cardiovascular risk and sympathetic activation in the metabolic syndrome.

AIMS: We examined whether to what extent resting heart rate (HR) values are capable to reflect in the metabolic syndrome (MS) a different degree of sympathetic activation. We also thought to determine at which HR cutoff values the sympathetic nervous system becomes more activated in the MS. METHODS: In 70 MS patients aged 55.5 ± 1.8 (mean ± SEM) years we evaluated muscle sympathetic nerve traffic (MSNA, microneurography) and venous plasma norepinephrine (NE, HPLC assay), subdividing the study population in three different subgroups according to resting clinic and 24-h HR values (< 70, 70-79 and ≥ 80 beats/min). RESULTS: MS patients with clinic HR values ≥ 80 beats/min displayed MSNA and NE values significantly increased when compared to those found in MS with HR between 70 and 79 beats/min or below 70 beats/min (MSNA: 55.2 ± 0.9 vs 44.6 ± 0.6 and 39.2 ± 0.6 bursts/min, P < 0.01, NE: 403.9 ± 6.9 vs 330.1 ± 4.3 and 258.3 ± 6.8 pg/ml, respectively, P < 0.01). A similar behavior was observed for 24-h HR. In the group as a whole both MSNA and plasma NE showed highly significant direct relationships with clinic HR, the correlation being similar for MSNA and NE (r = 0.89 and r = 0.91, P < 0.01 for both) Similar significant relationships were also found between 24-h HR values and MSNA or NE. CONCLUSIONS: In the MS HR values ≥ 80 beats/min are associated with an increased sympathetic activation, both when assessed by direct recording of MSNA and when evaluated as plasma NE. The sympathetic overdrive parallels for magnitude the HR elevations, this being the case for both clinic and 24-h HR.

Reproducibility of blood pressure phenotypes identified by office and ambulatory blood pressure in treated hypertensive patients. Data from the PHYLLIS study.

Previous studies have shown that white-coat and masked uncontrolled hypertension (WUCH and MUCH, respectively) are clinical conditions with very poor reproducibility over time. This is also the case for the different nighttime blood pressure (BP) patterns (dipping, nondipping, reverse dipping or extreme dipping). Whether and to what extent the phenomenon might depend on the type of antihypertensive treatment is unknown. In the present study, we addressed this issue by analyzing the data collected in the Plaque Hypertension Lipid-Lowering Italian Study (PHYLLIS), in which office and ambulatory BP were measured three times during an almost 3-year treatment period. The results showed that a limited number of WUCH or MUCH patients at an initial office measurement and 24-h systolic (S) BP measurement maintained the same status at a second set of measurements one or more years later. This was also the case for all dipping patterns, and only a minimal number of patients exhibited the same phenotype throughout all on-treatment SBP measurements. The results were similar for treatment with a thiazide diuretic or an ACE inhibitor and are in line with those of the European Lacidipine Study on Atherosclerosis (ELSA) trial, i.e., the only other available trial with multiple on-treatment office and ambulatory BP measurements, in which patients were treated with a calcium channel blocker or a beta-blocker. All the BP patterns identified in hypertensive patients treated by joint office and ambulatory BP measurements display poor reproducibility, and this is unrelated to the type of antihypertensive treatment used.

Association between Berlin questionnaire index and blood pressure, organ damage and metabolic profilein a general population.

We evaluated the relationships between Berlin questionnaire (BQ) scores, hypertension and other metabolic variables in 598 subjects (age: 65.8 ± 10 years, mean ± SD) enrolled in the PAMELA (Pressioni Arteriose Monitorate E Loro Associazioni) study representative of the general population, treated or untreated with antihypertensive drugs. Two hundred and eleven subjects (35%) had a positive BQ with two or more positive categories of the inquiry. Compared to those without sleep disorders these subjects showed a greater male prevalence (55.9%), worse serum cholesterol, triglycerides and glucose profile, greater body mass index (BMI) (28.9 ± 4.9 vs. 24.9 ± 3.4 kg/m2 ), higher office (and to a lesser extent 24-h) BP and HR values, higher serum creatinine values and greater rate of echocardiographic left ventricular (LV) hypertrophy (25% vs. 13%). These differences were not detected when the data analysis was restricted to treated hypertensive patients. Thus, BQ scores allow to identify among subjects belonging to a general population those with elevated BP, organ damage and altered metabolic. When antihypertensive drug treatment is present, however, the approach fails to detect differences between groups with low or high BQ index.

White-Coat Hypertension Without Organ Damage: Impact on Long-Term Mortality, New Hypertension, and New Organ Damage.

BACKGROUND: According to some guidelines, white-coat hypertension (WCH) carries little or no increase of cardiovascular risk in the absence of organ damage (OD), but no data are available on this issue. METHODS: Using the population data from PAMELA (Pressioni Arteriose Monitorate E Loro Associazioni), we evaluated cardiovascular and total mortality over a median follow-up of 29 years in WCH (elevated office and normal 24-hour or home blood pressure [BP]) and normotensive controls (normal in- and out-of-office blood pressure) with no echocardiographic left ventricular hypertrophy and no reduction of estimated glomerular filtration rate. Patients with sustained hypertension (SH, in- and out-of-office blood pressure elevation) and normotensive, WCH, and SH with cardiac and renal OD served as controls. RESULTS: In the 1423 subjects analyzed, there were 165 cardiovascular and 526 all-cause deaths. After adjustment for confounders, no-OD WCH exhibited a risk of fatal cardiovascular events lower than that of no-OD SH but greater than that of no-ODN (hazard ratio, 2.0 [95% CI, 1.1-3.6], P=0.02), this being the case also for all-cause mortality. Compared with no-OD normotensive, no-OD WCH also exhibited a greater 10-year adjusted risk to develop new SH or OD. Similar findings were obtained in normotensive, WCH, and SH with OD. CONCLUSIONS: The present study provides the first evidence that WCH with no OD is accompanied by a noticeable increase in long-term risk of mortality, new hypertension, and new OD, thereby differing from normotension.

Elevated resting heart rate as independent in-hospital prognostic marker in COVID-19.

BACKGROUND: Scarce and non-homogeneous data are available on the prognostic value of clinic heart rate (HR) in coronavirus disease 2019 (COVID-19). METHODS: The present study evaluated in 389 patients hospitalized for COVID-19 the in-hospital prognostic value of resting HR, assessed over different time periods, i.e., at hospital admission, during initial 3 days and 7 days of hospitalization. RESULTS: Results show that assessment of this hemodynamic variable during hospitalization provides information on the clinical outcome of the patients, greater HR values being associated with a worse inhospital prognosis. The prognostic value of elevated HR during COVID-19: 1) was independent on other confounders such as age, gender, comorbidities and fever, 2) appeared to be strengthened by repeated measurements of HR during the initial 3/7 days of hospitalization, and 3) was detectable in patients in which the therapeutic intervention did not include drugs, such as beta-blockers, calcium antagonists, digoxin, ivabradine and antiarrhythmic compounds known to interfere with HR. CONCLUSIONS: Heart rate may represent an important marker of a patient's outcome in COVID-19.

Transient effects of carotid baroreflex stimulation via the neck chamber device on central venous pressure.

We examined in 11 young subjects (age 29.7±3.6 years, mean±SEM) whether carotid baroreceptor stimulation via the neck chamber device may affect central venous pressure (CVP), thus potentially involving other reflexogenic areas in the examined responses. Application of progressively greater neck chamber subatmospheric pressures caused a progressive lengthening in RR interval, which reached a peak at the maximal value of negative neck chamber pressure applied. This was accompanied by significant and progressively greater reduction in CVP values when the data were calculated considering the early changes occurring within the first 2 seconds of the stimulus. There was a weak correlation between the early changes in CVP and the RR interval responses when all stimuli were pooled together (r = 0.32, P < .05). The results of the present study suggest that the neck chamber technique employed to assess carotid baroreceptor-heart rate sensitivity can transiently affect via the CVP reduction cardiopulmonary receptors activity, which may participate at the integrated reflex responses.

Sympathetic Neural Mechanisms Underlying Attended and Unattended Blood Pressure Measurement.

[Figure: see text].