Intra-arterial Blood Pressure Recording Research Articles

Accuracy of Non-Invasive Measurement of Mean Arterial Blood Pressure in Patients with Continuous Flow Left Ventricular Assist Devices: A Systematic Review

To determine the accuracy of non-invasive blood mean blood pressure (MAP) assessment in patients with continuous flow left ventricular assist devices. Systematic electronic search was performed on four online databases (PubMed, Scopus, Embase, and Web of Knowledge) for the terms "Blood Pressure" AND ("Heart-Assist Devices" OR "Left ventricular Assist Devices"). Only studies where a non-invasive blood pressure measurement was compared with intra-arterial blood pressure recording were included. A total of 12 studies with 502 participants were included, of those 402 had intra-arterial blood pressure measurement. The median number of participants per study was 30.5 (range: 5-154). The mean age of participants was 53 years old and 77% were male. All were single center prospective studies and intra-arterial blood pressure recordings were performed in the context of routine medical care in the Intensive Care Unit. Characteristics of the included studies are shown in figure 1. Intra-arterial recording was obtained using fluid filled catheter in all studies. Statements regarding the leveling and calibration of transducer 6 (50%) studies. Simultaneous recording occurred in 4 (30%) studies. The correlations between non-invasive and intra-arterial recordings are shown in Figure 2 CONCLUSION: Standardization of quality of signal acquisition and assessment of pulsatility was variable among studies. Non-invasive MAP has variable accuracy and this may adversely influence patients outcomes.

Correlation of Noninvasive Blood Pressure and Invasive Intra-arterial Blood Pressure in Patients Treated with Vasoactive Medications in a Neurocritical Care Unit.

The correlation between noninvasive (oscillometric) blood pressure (NBP) and intra-arterial blood pressure (IAP) in critically ill patients receiving vasoactive medications in a Neurocritical Care Unit has not been systematically studied. The purpose of this study is to examine the relationship between simultaneously measured NBP and IAP recordings in these patients. Prospective observational study of patients (N=70) admitted to a neurocritical care unit receiving continuous vasopressor or antihypertensive infusions. Paired NBP/IAP observations along with covariate and demographic data were abstracted via chart audit. Analysis was performed using SAS v9.4. A total of 2177 paired NBP/IAP observations from 70 subjects (49% male, 63% white, mean age 59years) receiving vasopressors (n=21) or antihypertensive agents (n=49) were collected. Paired t test analysis showed significant differences between NBP versus IAP readings: ([systolic blood pressure (SBP): mean=136 vs. 140mmHg; p<0.0001], [diastolic blood pressure (DBP): mean=70 vs. 68mmHg, p<0.0001], [mean arterial blood pressure (MAP): mean=86 vs. 90mmHg, p<0.0001]). Bland-Altman plots for MAP, SBP, and DBP demonstrate good inter-method agreement between paired measures (excluding outliers) and demonstrate NBP-IAP SBP differences at extremes of blood pressures. Pearson correlation coefficients show strong positive correlations for paired MAP (r=0.82), SBP (r=0.84), and DBP (r=0.73) recordings. An absolute NBP-IAP SBP difference of >20mmHg was seen in ~20% of observations of nicardipine, ~25% of observations of norepinephrine, and ~35% of observations of phenylephrine. For MAP, the corresponding numbers were ~10, 15, and 25% for nicardipine, norepinephrine, and phenylephrine, respectively. Despite overall strong positive correlations between paired NBP and IAP readings of MAP and SBP, clinically relevant differences in blood pressure are frequent. When treating with vasoactive infusions targeted to a specific BP goal, it is important to keep in mind that NBP and IAP values are not interchangeable.

Arterial function can be obtained by noninvasive finger pressure waveform

Arterial function, expressed as augmentation index (AIx) and pulse wave velocity (PWV), predicts cardiovascular disease [1–4] and can be assessed by specific validated devices that subsequently record peripheral (carotid, radial, femoral) arterial waveforms. It could have practical implications to obtain the same information from easily applicable finger blood pressure monitors, which are commonly used to test autonomic function.Methods to obtain PWV from finger photoplethysmogram (PPG, [5]), or AIx from finger blood pressure [6] have been proposed.We tested whether reliable AIx and PWV data could be obtained from 5-minute recordings of noninvasive finger blood pressure (Finapres® 2300, Ohmeda, USA), and compared them with data simultaneously obtained from applanation tonometry (SphygmoCor®, Atcor, Australia). The protocol was approved by Helsinki University Ethical Committee, and written consent was obtained from each subject. To compare the twomethods over awide range of values we studied 46 consecutive unselected subjects of different ages (31 male, age 44 ± 16 yr, range 24–90, SBP: 129 ± 21 mmHg, DBP: 74 ± 16 mmHg, BMI: 24.8 ± 4.5 kg/m), in supine position, under spontaneous breathing at rest. Two reliable measurements were obtained from 29 (AIx) and 31 (PWV) participants by applanation tonometry (AIx-at, PWV-at), and one measurement in the remaining subjects. When two values were obtained their average was used for comparison. Measurementof AIx by transfer functionoffingerbloodpressure (AIx-f). In theory, thebestmethod toderivenoninvasiveAIx is throughsimultaneous recording of peripheral noninvasive and central intra-arterial blood pressure, with subsequent evaluation of the mathematical relationship (transfer function, TF) linking these two signals together (TF1). The TF1 can then be used to reconstruct the central blood pressure profile and obtain the AIx [2–4,6,7]. This rather complex approach requires expensive high-fidelitymicro-tiparterial catheters [7], butnowthisprocedure canbe simplified since our tonometer provided both the radial artery and the reconstructed central pressure waveforms (hence also TF1). Since the recordings of the radial artery and finger blood pressures were simultaneous, it was possible to obtain the TF that links the finger pressure to the central pressure (TF2)with the samedegree of precision as for TF1. By using TF2, the AIx-f can then be calculated (on-line supplement). The obtained TF1 was almost identical in all subjects, confirming that a single TF1 was used by the Sphygmocor® to link the central and radial pressures [7] (Fig. 1). Measurement of AIx by direct analysis of finger blood pressure contour (AIx-fbpc). From the previous considerations it follows that the blood pressure profile alone provides all the necessary information to directly derive AIx. To verify this we normalised the averaged amplitude of the finger blood pressure pulses (first systolic peak= 100, lowest point = 0) and determined the location of the dicrotic notch. Then we calculated the normalised amplitude at 21 equally-spaced points from the first systolic peak to the dicrotic notch (on-line supplement). Each of the amplitudes was comparedwith the AIx-at by regression analysis. The regression equation linking the PWV-at with the point showing the best correlation was used to an AIx estimate: AIx-fbpc. Pulse wave velocity from the finger blood pressure. Millasseau [5] described and validated a simple technique to estimate the PWV from the PPG without the need of two separate recordings at two different International Journal of Cardiology 175 (2014) 169–217

Pseudoresistant Hypertension Attributed to White-Coat Effect

See related article, pp 564–571 An increase in blood pressure (BP) when taken in the office setting was recognized as early as 1940, when Ayman and Goldshine1 reported that BP readings measured in the clinic were higher than BP recorded in the home. The authors attributed the increase in clinic BP to “the excitement and tension associated with the visit to the clinic or doctor's office.” In 1966, Sokolow et al2 using a noninvasive portable BP recording device showed that readings taken during usual daily activities (ambulatory BP) were lower than casual office BP. Floras et al3 subsequently confirmed these findings with continuous intra-arterial BP recordings by observing higher BP in the clinic compared with the awake ambulatory BP. Advances in ambulatory BP monitoring led to several studies by Pickering and his colleagues4,5 in which home BP and ambulatory BP were noted to be similar and BP lower during sleep and higher in the office setting. Based on these observations, they proposed the term “white-coat hypertension” (WCH) to describe the phenomenon of higher office BP and lower awake ambulatory BP.6 Pickering et al7 then proceeded to report on a series of 292 patients with untreated, borderline hypertension, finding that 21% exhibited WCH defined as a high office diastolic BP of 90 to 104 …

Intra‐arterial blood pressure reading in intensive care unit patients in the lateral position

Routine lateral turning of patients has become an accepted standard of care to prevent complications of immobility. The haemodynamic and oxygenation effects for patients in both lateral positions (45°) are still a matter of debate. We aimed to study the effect of these positions on blood pressure, heart rate and oxygenation in a general intensive care population. Observational study. Twenty stable intensive care unit patients had intra-arterial blood pressure recordings in the supine and lateral positions with the correction of hydrostatic height compared with a fixed reference point (phlebostatic level). A multilevel model was used to analyse the data. Mean arterial pressure readings in the lateral positions were, on average, 5 mmHg higher than in the supine position (p < 0.001). There were no significant differences between mean arterial pressure recordings in the left and right lateral position (p = 1.0). No important differences in oxygenation and heart rate were observed. After correction for covariates, the effects persisted. Our study demonstrated an increase, albeit small, in blood pressure in the lateral positions. No major differences between the left and right lateral position were found. No important differences in oxygenation and heart rate were observed. Turning haemodynamically stable patients in the intensive care unit has no important effects on blood pressure measurements when continuous hydrostatic height correction is applied.

Impact of sleep on arrhythmogenesis.

Sleep is generally considered to be a protected period, when the cardiovascular system benefits from the restorative influences of the sleeping brain. However, the dynamics of cardiovascular control during sleep can tax the capacity of the diseased coronary circulation and myocardium with surges in sleep-state–related autonomic activity and disruptions in airway function and central nervous system regulation. In this regard, sleep may constitute an autonomic stress test for the heart. The scope of sleep-related risk for atrial and ventricular arrhythmias is substantial. The major subgroups susceptible to adverse influences of surges in autonomic activity during sleep are those with ischemic heart disease, heart failure, and channelopathies (Table).1 It is significant that 20% of myocardial infarctions and 15% of sudden deaths occur at night in the United States.2 Most atrial arrhythmias in patients younger than 61 years of age have nocturnal onset.3 The young are not immune to risk, as sudden infant death syndrome (SIDS) claims 2500 lives in the United States annually.4 Cardiovascular risk is compounded by comorbid factors, most notably apnea, which affects an estimated 4% to 9% of the general population5 and is considerably more prevalent among obese individuals.6 The more common form is obstructive sleep apnea (OSA), with partial or complete collapse of the pharynx. Half of heart failure patients experience either OSA or central sleep apnea (CSA) with central nervous system–mediated periodic breathing, commonly referred to as Cheyne-Stokes respiration. Such cardiorespiratory disturbances profoundly alter autonomic nervous system activity and increase risk of arrhythmia, hypertension, and myocardial infarction. View this table: Table. Patient Groups at Potentially Increased Risk for Nocturnal Cardiac Events It is surprising, as recently underscored by Malhotra and Loscalzo,7 that the significance of cardiovascular risk during sleep may not be duly recognized within the cardiology community. The reasons are …

Adrenergic origin of very low-frequency blood pressure oscillations in the unanesthetized rat

Spectral analysis of cardiovascular signals has been extensively used to investigate circulatory homeostatic mechanisms. However, the nature of very low-frequency (VLF) fluctuations remains unclear. Because we previously observed enhanced VLF fluctuations in blood pressure (BP) in the sympathectomized rat (a model characterized by markedly increased plasma epinephrine levels), the aims of our study were to assess whether the genesis of VLF fluctuations in BP depends on circulating catecholamines and to determine which adrenergic receptor(s) and which membrane ion channel(s) are involved. We used continuous intra-arterial BP recordings from unanesthetized unrestrained rats to compute the power of VLF fluctuations in BP in the intact condition, during acute ganglionic blockade with hexamethonium, and after restoration of BP levels by infusion (in addition to hexamethonium) of adrenergic agonists (epinephrine, norepinephrine, and clonidine) or nonadrenergic vasoconstrictors (vasopressin). Effects of infusion of specific adrenergic receptor blockers (propranolol, prazosin, and yohimbine) with hexamethonium and catecholamines and infusion of various membrane ion channel blockers on VLF fluctuations in BP were also evaluated. Our results are as follows. 1) Ganglionic blockade drastically reduced BP levels and VLF fluctuations. 2) All vasoconstrictors restored BP levels, but only adrenergic vasoconstrictors generated striking VLF fluctuations in BP. 3) Catecholamine-induced fluctuations were abolished by alpha2-, but not alpha1- or beta-, adrenergic receptor blockade and by Ba2+-sensitive K+ channel or L-type Ca2+ channel, but not by other ion channel, blockers. We conclude that, in the conscious, unrestrained ganglion-blocked rat, catecholamine infusion generates VLF fluctuations in BP through stimulation of alpha2-receptors and activation of Ba2+-sensitive K+ channels. These fluctuations may have (patho)physiological relevance under conditions of disrupted circulatory homeostasis.

Autonomic control of the heart and renal vascular bed during autonomic dysreflexia in high spinal cord injury.

Autonomic function and hemodynamics were studied in nine spinal cord injured (SCI) subjects, at rest and during peripheral afferent stimulation, bladder percussion. Nine able-bodied subjects were studied for comparison during unstimulated conditions. Spontaneous baroreceptor reflex sensitivity was calculated from recordings of ECG and intraarterial blood pressure. An index of sympathetic activity was provided by measuring total body noradrenaline (NA) spillover by isotope dilution technique. Renal vascular resistance was calculated from PAH-clearance.SCI subjects had lower total body NA spillover (1011 +/- 193 vs 2261 +/- 328 pmol/min, P < 0.01), but similar baroreceptor reflex sensitivity and hemodynamics compared to able-bodied subjects at rest. In SCI group, during bladder percussion, mean arterial pressure increased (79 +/- 5 vs 113 +/- 8 mm Hg, P < 0.01), whereas heart rate was reduced during the first minute of the manoeuvre (62 +/- 2 vs 56 +/- 2 bpm, P < 0.05). Baroreceptor reflex sensitivity remained unchanged. Total body NA spillover and renal vascular resistance increased by 332 % (from 1004 +/- 218 pmol/min, P < 0.05) and 55 % (from 0.078 +/- 0.011 mmHg/ml/min, P < 0.05), respectively.SCI subjects demonstrated lower total body sympathetic outflow but normal baroreceptor reflex sensitivity at rest, suggesting a balanced autonomic output to the heart. Bladder percussion caused a substantial increase in renal vascular resistance and blood pressure, which was partly due to marked generalised sympathetic activation. This activation was counterbalanced by an increased vagal activity as evidenced by reduction of the heart rate.

Role of the alpha1D-adrenergic receptor in the development of salt-induced hypertension.

In an attempt to elucidate whether there is a specific alpha1-adrenergic receptor (alpha1-AR) subtype involved in the genesis or maintenance of hypertension, the alpha1D-AR subtype was evaluated in a model of salt-induced hypertension. The alpha1D-AR-deficient (alpha1D-/-) and control (alpha1D+/+) mice (n=8 to 14 in each group) were submitted to subtotal nephrectomy and given 1% saline as drinking water for 35 days. Blood pressure (BP) was monitored by tail-cuff readings and confirmed at the end point by direct intraarterial BP recording. The alpha1D-/- mice had a significantly (P=0.0004) attenuated increase in BP response in this protocol (baseline 94.6+/-2.8 versus end point 107.4+/-4.5 mm Hg) compared with that of their wild-type counterparts (alpha1D+/+), from a baseline 97.4+/-2.9 to an end point 139.4+/-4.5 mm Hg. Seven of 15 alpha1D+/+ mice died with edema, probably owing to renal failure, whereas 14 of 15 alpha1D-/- mice were maintained for 35 days. Body weight, renal remnant weight, and residual renal function were similar in the 2 groups, whereas the values of plasma catecholamines (epinephrine, norepinephrine, and dopamine) were higher in alpha1D+/+ than in the alpha1D-/- mice. These data suggest that alpha1D-AR plays an important role in developing a high BP in response to dietary salt-loading, and that agents having selective alpha1D-AR antagonism could have significant therapeutic potential in the treatment of hypertension.

Arterial wall properties and Womersley flow in Fabry disease.

Fabry disease is an X-linked recessive lysosomal storage disease resulting in the cellular accumulation of globotriaosylceramide particularly globotriaosylceramide. The disease is characterized by a dilated vasculopathy with arterial ectasia in muscular arteries and arterioles. Previous venous plethysomographic studies suggest enhanced endothelium-dependent vasodilation in Fabry disease indicating a functional abnormality of resistance vessels. We examined the mechanical properties of the radial artery in Fabry disease, a typical fibro-muscular artery. Eight control subjects and seven patients with Fabry disease had a right brachial arterial line placed allowing real time recording of intra-arterial blood pressure. Real time B-mode ultrasound recordings of the right radial artery were obtained simultaneously allowing calculation of the vessel wall internal and external diameter, the incremental Young's modulus and arterial wall thickness. By simultaneously measurement of the distal index finger-pulse oximetry the pulse wave speed was calculated. From the wave speed and the internal radial artery diameter the volume flow was calculated by Womersley analysis following truncation of the late diastolic phase. No significant difference was found between Fabry patients and controls for internal or external arterial diameters, the incremental Young's modulus, the arterial wall thickness, the pulse wave speed and the basal radial artery blood flow. Further, no significant difference was found for the radial artery blood flow in response to intra-arterial acetylcholine or sodium nitroprusside. Both drugs however, elevated the mean arterial flow. The current study suggests that no structural or mechanical abnormality exists in the vessel wall of fibro-muscular arteries in Fabry disease. This may indicate that a functional abnormality downstream to the conductance vessels is the dominant feature in development Fabry vasculopathy.

Effects of stress and behavioral interventions in hypertension--the effects of smoking and nicotine replacement therapy on blood pressure.

Effects of stress and behavioral interventions in hypertension--the effects of smoking and nicotine replacement therapy on blood pressure.

NONINVASIVE CHARACTERIZATION OF THE BLOOD PRESSURE RESPONSE TO THE DOUBLE-LEG PRESS

106 The goal of this study was to noninvasively characterize the blood pressure response to the double-leg press. High peak levels of blood pressure can be obtained during weight lifting, however, standard arm cuff and auscultatory methods can not accurately capture the peak dynamic responses. Thus, this study applied the Finpres™ (FP) continuous blood pressure monitor to measure beat-to-beat blood pressure values during the double-leg press. Seven healthy males, 25-35 yo, volunteered. Each 10 RM was determined on a double-leg press machine. Later, subjects performed three, 10 RM sets while blood pressure was continuously recorded with the FP blood pressure monitor. At rest, there was good agreement between FP and cuff (CF) systolic blood pressures (SBP). However, for diastolic blood pressure (DBP), the CF DBP was higher. During the leg press, CF SBP was less than the peak SBP with FP, and greater than the minimum SBP with FP. DBP was higher for the CF. FP blood pressures indicated increasing peak pressures with each repetition and with each successive set. FP blood pressures peaked as the weight was lowered (eccentric) and decreased as the weight was lifted (concentric). This pattern is similar to that previously reported with direct intra-arterial blood pressure recordings. Thus, the FP offers a potential method to assess peak pressures and patterns associated with various weight lifting protocols.

Cardiac output and pulmonary gas exchange at maximal exercise after atrial redirection for complete transposition.

To assess the determinants of exercise capacity and exercise oxygenation after atrial redirection for complete transposition. At graded bicycle ergometry, including respiratory and arterial blood gas analyses, intra-arterial blood pressure recording, and cardiac output determination (dye-dilution technique), we tested 17 post-Mustard/Senning patients, 8.9-22.0 years old (mean 14.5, SD 4.0). Reference data were obtained by similar methods. At maximal exercise, oxygen uptake (29.6 ml x kg(-1) x min(-1)) and heart rate (167 beats x min(-1)) were low (P<0.001). Right-to-left shunts were detected in five patients. Arterial oxygen partial pressure and saturation fell in all subjects (P<0.0001). In 15/16 (94%) the alveolar-arterial oxygen partial pressure difference was > +2 SD. In 13/15 (87%) stroke volumes fell during exercise. Cardiac output per oxygen uptake was low (P<0.0001), which implies a high arteriovenous oxygen difference and a low mixed venous oxygen content at peak exercise. The low exercise capacity was caused by a combination of low maximally attained heart rate and falling stroke volumes. The impaired arterial oxygenation may be caused by a combination of pulmonary ventilation/perfusion mismatch, a low mixed venous content and atrial shunting in some patients.

Ambulatory intraarterial blood pressure in essential hypertension: Effects of age, sex, race, and body mass—the northwick park hospital database study

Twenty-four-hour recordings of intraarterial blood pressure (IABP) from 723 untreated hypertensive patients were analyzed for the effects of age, sex, race, and body mass index on the level of IABP and its circadian variation. Age had a highly significant positive relationship (P < .001) with the cuff systolic and diastolic blood pressures, with regression coefficients (SE) of +0.83 (0.07) and -0.24 (0.04) mm Hg/year, respectively. There was a similar (P < .001) positive relationship between age and 24-h mean systolic IABP, measuring +0.71 (0.07) mm Hg/year, but 24-h mean diastolic IABP did not increase significantly with age. There was a significant (P < .001) inverse relationship between age and 24-h mean heart rate (HR), at -0.17 (0.03) beats/min/year. Nocturnal fall in systolic and diastolic IABP, calculated as the difference between daytime and nighttime mean IABP, had a significant (P < .001) negative relationship with age. Nocturnal fall in HR, calculated similarly, also significantly (P < .001) decreased with age. Age did not affect long-term systolic and diastolic IABP variability but did decrease long-term HR variability significantly (P < .001). Hypertensive men and women of similar age, had comparable daytime mean systolic and diastolic IABP (P = .15 and P = .03 respectively), but women had significantly (P < .001) lower nighttime mean systolic and diastolic IABP than men. The nocturnal fall in systolic and diastolic IABP was significantly (P < .002) greater in women as compared to men. Women also had significantly (P < .01) greater long-term systolic and diastolic IABP variability than men. Women had significantly (P < .001) greater 24-h, daytime mean and nighttime mean HR than men. Twenty-four-hour, daytime and nighttime mean IABP were all significantly higher (P < .01) in Afro-Caribbeans as compared to whites and Asians. No significant differences were observed in the magnitude of nocturnal IABP fall or long-term IABP variability between the three races. Asians and Afro-Caribbeans had significantly (P < .001) lower nocturnal HR falls and long-term HR variability (P < .01) than whites. Body mass index (BMI) did not relate directly to the level of daytime blood pressure, clinic cuff, or daytime mean IABP, in either men or women. BMI did have a highly significant (P < .001) positive relationship with nighttime mean IABP in men, but not in women. The degree of nocturnal fall of IABP had a significant (P < .001) inverse relationship with BMI in hypertensive men.

Sympathectomy and Cardiovascular Spectral Components in Conscious Normotensive Rats

We examined the extent to which sympathetic influences are reflected by spectral powers of blood pressure and pulse interval in specific frequency bands in spontaneously behaving Wistar-Kyoto rats subjected to continuous intraarterial blood pressure recording. The rats were pretreated with 6-hydroxydopamine (150 mg/kg twice in 1 week, n = 19) to produce chemical sympathectomy or received vehicle (n = 15). In the sympathectomized group, additional monitoring sessions were performed with rats under alpha-adrenergic receptor blockade with phenoxybenzamine (n = 8), beta-receptor blockade with propranolol (n = 7), or cholinergic receptor blockade with atropine (n = 8). Blood pressure signals were analyzed by a computer to calculate spectral powers (fast Fourier transform) in the low-frequency (0.025 to 0.1 Hz), mid-frequency (0.1 to 0.6 Hz), and high-frequency (0.8 to 3.0 Hz) bands. In sympathectomized rats, low-frequency power of blood pressure was 70% greater than in intact rats, whereas mid-frequency power was 60% smaller (P < .05 for both) and high-frequency power was unchanged. High-frequency power of pulse interval was also unchanged in sympathectomized rats, whereas low- and mid-frequency powers were reduced by approximately 50% (P < .05). No further alterations in spectral powers were observed by adding alpha- or beta-adrenergic blockade to sympathectomy, whereas adding cholinergic blockade caused a striking reduction in all pulse interval powers. Thus, mid-frequency blood pressure power depends on sympathetic but also to a substantial extent on nonsympathetic influences. Sympathetic influences do not contribute to low-frequency blood pressure power, having instead a restraining effect. The low- and mid-frequency pulse interval powers depend on both sympathetic and vagal influences. Thus, no blood pressure or pulse interval power in the mid- and low-frequency ranges can be regarded as a specific marker of sympathetic activity.

Effects of aging on 24-h dynamic baroreceptor control of heart rate in ambulant subjects

The effects of aging on the dynamic modulation of baroreflex sensitivity over 24 h was assessed in eight elderly (mean age +/- SD, 63.9 +/- 3.2 yr) and in eight young (23.9 +/- 6.1 yr) mild or moderate essential hypertensive patients, who were subject to a 24-h intra-arterial (Oxford technique) blood pressure recording in ambulatory conditions. The sensitivity of baroreflex control of the heart rate was dynamically assessed by quantifying 1) the slope of the regression line between pulse interval (the reciprocal of heart rate) and systolic blood pressure changes over spontaneously occurring hypertension-bradycardia or hypotension-tachycardia sequences (time domain analysis) and 2) the ratio between spectral-powers of pulse interval and systolic blood pressure around 0.1 Hz (alpha-coefficient: frequency domain analysis). The 24-h average sequence slope was lower in old than in young individuals (4.4 +/- 0.5 vs. 9.9 +/- 1.3 and 4.8 +/- 0.7 vs. 8.4 +/- 1.4 ms/mmHg for hypertension-bradycardia and hypotension-tachycardia sequences, respectively; P < 0.05 for both). Similar results were obtained by using the alpha-coefficient approach. The marked nighttime increase in baroreflex sensitivity observed in young individuals was much less evident in the elderly. Thus 24-h baroreflex sensitivity is markedly impaired by aging. The impairment becomes manifest also as an inability to increase baroreflex sensitivity at night.

Dependency of blood pressure upon cardiac filling in patients with severe postural hypotension.

Autonomic denervation of the vascular bed results theoretically in a stronger dependency of blood pressure upon intravascular volume, and the study described aimed at an investigation of the relation between cardiac filling and arterial blood pressure in patients with severe postural hypotension. Seven patients were studied during head-up tilt at three different tilt angles using intra-arterial blood pressure recordings and estimates of left ventricular volumes by radioisotope ventriculography. Blood pressure fell dramatically during head-up tilt due to reductions in cardiac output unopposed by vasoconstriction. The reduction in cardiac output resulted from reductions in left ventricular end-diastolic volumes with unchanged left ventricular ejection fractions and only moderate increments in heart rate. The study was demonstrated that blood pressure is strongly dependent upon cardiac filling in severe autonomic dysfunction, and that volume expansion is an important measure against postural hypotension.

Cardiovascular reactivity, coronary risk factors, and sympathetic activity in young men.

We have previously demonstrated that awareness of high blood pressure may increase blood pressure, plasma catecholamine levels, and stress responses. In the present study, three groups of 19-year-old men, all unaware of their blood pressure status, were selected from the first (group-1, 62 +/- 2 mm Hg, [mean +/- SEM], n = 15), 50th (group-50, 90 +/- 4 mm Hg, n = 15), and 99th (group-99, 123 +/- 5 mm Hg, n = 14) percentiles in causal mean blood pressure at a screening. They were studied (blinded examiners) with intra-arterial blood pressure recordings and multiple measurements of arterial plasma epinephrine and norepinephrine during a mental arithmetic challenge and cold pressor test. Despite high mean blood pressure at the screening, group-99 did not differ from group-50 either in intra-arterial mean blood pressure after 30 minutes of supine rest (89 +/- 3 versus 86 +/- 2 mm Hg) or in serum lipids and resting plasma epinephrine and norepinephrine. However, in group-99 resting plasma epinephrine showed a positive hyperbolic relation to resting diastolic blood pressure (r = .73, P = .004) and a negative hyperbolic relation to the ratio of high-density lipoprotein cholesterol to total cholesterol (r = -.75, P = .002). None of these correlations were present in the two other groups. Furthermore, the three groups differed in heart rate responses (P < .0005) and systolic (P < .0005) and diastolic (P < .05) blood pressure responses to mental arithmetic challenge, group-99 being hyperreactive compared with the other two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelation of cardiac and vascular structure in young men with borderline hypertension.

It is not established whether left ventricular hypertrophy and structural vascular changes are primary phenomena or secondary consequences of raised blood pressure. In this study we investigated 54 borderline hypertensive men (BH) (SBP 140-160 mmHg and/or DBP 84-95 mmHg) and 20 normotensive men (NC) (SBP 110-130 mmHg and DBP 60-80 mmHg), recruited from an unbiased population sample (age 20 +/- 2 years). Blood pressure (BP) levels were confirmed by i.a. BP recordings. Left ventricular mass (LVM) was determined with M-mode echocardiography and minimal vascular resistance (Rmin) was calculated from the blood flow in the calf and forearm after maximal ischaemic work. Central haemodynamics were assessed by intra-arterial blood pressure recordings and cardiac output determinations by the dye dilution technique. In the BH group, LVM and Rmin were strongly correlated to body size, especially weight and body surface area. However, LVM and Rmin were only weakly correlated to blood pressure. In the normokinetic BH subgroup (NBH) (n = 38) minimal forearm vascular resistance was significantly higher than in the hyperkinetic BH individuals (HBH) (n = 16), indicating the presence of structural vascular changes in the former. Furthermore, in the NBH group there was a significant correlation between LVM and Rmin both in the calf (r = 0.490 P = 0.002) and in the forearm (r = 0.520 P = 0.001). This association remained after correction for body size. No such correlation was seen in the HBH subgroup or in the NC group. The present study does give long-reaching conclusions as regards the aetiological factors underlying the cardiovascular remodelling. However, our data show that (1) cardiovascular changes appear early in the course of blood pressure elevation, (2) the cardiac and vascular changes develop in parallel, and (3) structural remodelling is not solely explained by the degree of blood pressure elevation since blood pressure was similar in the two BH subgroups. Thus, other factors than blood pressure appear to be important determinants of structural adaptation in mildly hypertensive states.

Brain natriuretic peptide: natriuretic and endocrine effects in essential hypertension

Documentation of the renal, hormonal and haemodynamic effects and plasma clearance of human brain natriuretic peptide (BNP) given (in a dose inducing increases in plasma BNP concentrations to pathophysiological levels) to patients with essential hypertension. Six male patients with untreated, uncomplicated, mild-to-moderate essential hypertension underwent placebo-controlled single-blind studies in balanced random order. Human BNP (2 pmol/kg per min) and vehicle were given as constant intravenous infusions in a volume of 15 ml/h for 2 h. Continuous recording of intra-arterial blood pressure and heart rate, together with serial blood samples (for hormone assays) and 30-min urine collections, were obtained throughout the studies from 90 min before commencement of infusions to 90 min after completion of infusions. Achieved intra-infusion plasma BNP immunoreactivity (20-30 pmol/l) was similar to levels previously observed in heart failure. Plasma cyclic GMP was increased. Sodium excretion rose to 2.5-fold placebo values. Plasma aldosterone fell to 50% of placebo values. Blood pressure and heart rate were unchanged. The metabolic clearance rate (5.0 +/- 0.4 l/min) and plasma half-life (19.5 min) indicated that BNP has a large volume of distribution (141 +/- 16 litre). In essential hypertension pathophysiological plasma concentrations of human BNP have significant acute effects promoting natriuresis and suppressing plasma aldosterone. These effects are similar to those of ANP, but the plasma half-life and volume of distribution of BNP are considerably greater than those of atrial natriuretic peptide. These two hormones may play separate complementary roles in fluid volume and blood pressure homeostasis.