Evaluation of intima-media thickness and vascular elasticity of the common carotid artery in patients with isolated systolic hypertension using ultrasound radiofrequency-data technology

Background: Radiofrequency (RF) data technology is a newly developed method to evaluate vascular disease, especially subclinical atherosclerotic change. Data regarding predictors of intima‐media thickness (IMT) and vascular elasticity of the common carotid artery (CCA) in subjects with isolated systolic hypertension (ISH) using ultrasound RF‐data technology are scarce. Aims: We evaluated the change in IMT and vascular elasticity of the CCA in patients with ISH at an early phase using US RF‐data technology. Methods: Thirty‐nine patients with ISH and 41 age‐matched control subjects were the study population. The common carotid arterial systolic diameter (Ds), diastolic diameter (Dd), IMT, carotid distensibility (CD), local pulse wave velocity (PWVβ) and stiffness (β) were compared between the two groups, as were correlations between pulse pressure (PP) and parameters of vascular stiffness. Results: Common carotid arterial Ds, Dd, IMT, PWVβ and β increased whereas CD decreased more significantly in the ISH group than in age‐matched controls. The level of PP in the ISH group had significant positive correlations with PWVβ (r = 0·298, P<0·05) and β (r = 0·291, P<0·05), whereas significant correlations with CD were not observed. Conclusions: US RF‐data technology could be used to accurately and quantitatively evaluate increased IMT and decreased arterial elasticity of the CCA in patients with ISH compared with normal subjects.     

Can stroke volume and cardiac output be determined reliably in a tilt‐table test using the pulse contour method?

The applicability of the finger pressure‐derived pulse contour (PC) technique was evaluated in the measurement of stroke volume (SV), cardiac output (CO) and their changes in different phases of the tilt‐table test. The reference method was whole‐body impedance cardiography (ICG). A total number of 40 physically active patients, aged 41 ± 19 years, were randomly chosen from a pool of 230. Specifically speaking, 20 of the patients experienced (pre)syncope (tilt+ patients) during the head‐up tilt (HUT), and 20 did not (tilt–). A total number of three measurement periods, 30–60 s each, were analysed: supine position, 5 min after the commencement of HUT, and 1 min before set down. SV and CO values measured by PC underestimated significantly those measured by ICG (biases ± SD 19 ± 14 ml and 1·55 ± 1·14 l min^–1, respectively) in agreement with earlier reports. The bias between the methods was almost the same in the different phases of the test. However, the SD of the bias was bigger for tilt+ (P<0·05). When the bias between the methods was eliminated by scaling the first measurement to 100%, the agreement between the methods in the second and third measurements was clearly better than without scaling. Both methods showed a physiological drop in SV after the commencement of HUT. These results indicate that PC suffices in tracking the changes in CO and SV, but for absolute values it is not reliable.     

Effect of head-upright tilt on the dynamic of cerebral autoregulation

The effect of head-upright tilting on the rate of cerebral autoregulation was studied in 12 healthy volunteers (nine men and three women; age range 20–36 years). The dynamics of cerebral autoregulation was determined from the rate of change in cerebral resistance (RoR) during a drop in arterial blood pressure induced by rapid deflation of a 3-min ischaemic thigh cuff and from the ratio of changes in cerebral blood flow and arterial blood pressure (CAI) during the recovery period after the drop in arterial blood pressure. The test was performed supine and with 40° head-up tilt (40° HUT). Middle cerebral artery mean blood flow velocity was measured by transcranial Doppler simultaneously with peripheral arterial blood pressure using Finapres. The thigh cuff deflation induced a larger drop in arterial pressure during 40° HUT [median ?28% (25 percentile ?36, 75 percentile ?19)] than in the supine position [?16% (?23, ?15)] (P<0·01) and in cerebral resistance [supine: ?12% (?15, ?6); 40° HUT: ?15% (?20, ?12); P<0·05]. There was no significant change in RoR [15% s^?1 (12, 15)] and CAI [1·9 (1·5, 3·1)] measured supine and during 40° HUT [RoR: 13% s^?1 (12, 15); CAI: 1·3 (0·99, 1·9)]. During the drop in arterial pressure, the relationship between arterial blood pressure and systolic peak-to-peak interval exhibited an hysteresis loop, indicating a cardiopulmonary and/or baroreflex activation that was not observed with cerebral resistance. The rate of autoregulation is an intrinsic property of the cerebral vascular bed and is not affected by the vasodilator state in the range of arterial blood pressure changes induced by the tight cuff method.     

In aged men,central vessel transmural pressure is reduced by brief Valsalva manoeuvre during strength exercise

A brief Valsalva manoeuvre, lasting 2–3 s, performed by young healthy men during strength exercise reduces transmural pressure acting on intrathoracic arteries. In this study, we sought to verify this finding in older men. Twenty normotensive, prehypertensive and moderately hypertensive otherwise healthy men 46–69 years old performed knee extensions combined with inspiration or with brief Valsalva manoeuvre performed at 10, 20 and 40 mmHg mouth pressure. Same respiratory manoeuvres were also performed at rest. Non‐invasively measured blood pressure, knee angle, respiratory airflow and mouth pressure were continuously registered. In comparison to inspiration, estimated transmural pressure acting on thoracic arteries changed slightly and insignificantly during brief Valsalva manoeuvre at 10 and 20 mmHg mouth pressure. At 40 mmHg mouth pressure, transmural pressure declined at rest (?8·8 ± 11·4 mmHg) and during knee extension (?12·1 ± 11·9 mmHg). This decline ensued, as peak systolic pressure increase caused by this manoeuvre, was distinctly <40 mmHg. Only a main effect of mouth pressure was revealed (P<0·001) and neither exercise nor interaction between these factors, what suggests that transmural pressure decline, depended mainly on intrathoracic pressure developed during brief Valsalva manoeuvre. Resting blood pressure did not influence the effect of brief Valsalva manoeuvre on transmural pressure.     

Arterial stiffness, but not endothelium-dependent vasodilation, is related to a low Ankle-Brachial index. The Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS)

Background: Arterial compliance and endothelium‐dependent vasodilation are two characteristics of the vessel wall. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study we studied the relationships between arterial compliance and endothelium‐dependent vasodilation versus the Ankle‐Brachial index (ABI), a clinically used index of peripheral artery disease. Methods: In the population‐based PIVUS study (all aged 70), arterial compliance was determined by ultrasound as the distensibility of the carotid artery and the stroke volume to pulse pressure (SV/PP) ratio by echocardiography, while endothelium‐dependent vasodilation was assessed by the invasive forearm technique with acetylcholine (EDV) and brachial artery ultrasound (FMD) in 519 subjects in whom the Ankle‐Brachial index was investigated. Results: After adjustments for gender and Framingham risk score, distensibility in the carotid artery and the SV/PP ratio were significantly reduced in subjects with a reduced ABI (<0·9) in both legs (n = 15, P = 0·0006 and P = 0·0003, respectively). Endothelium‐dependent vasodilation was not significantly related to a reduced ABI. Conclusion: A reduced arterial compliance, but not endothelium‐dependent vasodilation, was related to a low ABI in both legs after adjustment for major risk factors, suggesting that atherosclerosis in the leg arteries is associated with arterial compliance also in other parts of the vasculature.     

Brachial artery hyperemic blood flow velocities are related to carotid atherosclerosis

Objective: Cardiovascular (CV) risk relates to the blood flow velocity pattern in the brachial artery during hyperemia, especially to the hyperaemic systolic to diastolic mean blood flow velocity (SDFV) ratio. Here, we investigated the relations between SDFV in the brachial artery and different characteristics of carotid atherosclerosis. Material and methods: Data were collected from 1016 70‐year‐olds participating in the Prospective Investigation of Uppsala Seniors study. Doppler recordings of blood flow velocity during hyperemia were analysed in the brachial artery. In the carotid artery, intima‐media thickness (IMT) was recorded together with an assessment of echogenicity by the Grey scale median (GSM) method in both overt plaques and in the intima‐media complex (IM‐GSM). Results: The SDFV ratio was related to the number of carotid arteries affected by plaque (P = 0·018) and inversely to plaque echogenicity (P = 0·0003). The SDFV ratio was also related to IMT (P = 0·0022) and inversely to IM‐GSM (P = 0·0001). These relations were statistically significant also after adjusting for major CV risk factors, individually as well as summarised as the Framingham risk score. Conclusion: Our results indicate that the hyperemic systolic to diastolic blood flow velocity ratio in the brachial artery is related to atherosclerosis in the carotid artery.     

Pulse wave analysis on fingertip arterial pressure: effects of age, gender and stressors on reflected waves and their relation to brachial and femoral artery blood flow

OBJECTIVES: Analysis of the contour of the arterial pressure pulse (pulse wave analysis; PWA) adds information about arterial stiffness etc., beyond that obtained from absolute pressures. Peripheral pulses normally show an anterograde systolic peak and two reflected peaks: one in systole and one in diastole. The amplitudes and timings of these were estimated from finger pressure recordings in three study groups. We studied the usefulness of continuous digital pressures for PWA. METHODS: First, PWA from intra-arterial (brachial) and non-invasive finger pressure recordings was compared. Secondly, stress-induced (mental arithmetics and cold pressor test) changes in pressure pulse reflection were compared with blood flow changes in brachial and femoral arteries (ultrasound). Thirdly, the influence of age and gender on digital pulse pressures was investigated at rest and during exercise. RESULTS AND CONCLUSION: Pulse wave analysis results from brachial and digital pressures correlated strongly. Stress induced changes in systolic reflection were associated with changes in brachial artery flow patterns, whereas diastolic reflection was associated with femoral artery flow changes. At rest, age increased systolic reflection without affecting diastolic reflection. Exercise increased systolic reflection and reduced diastolic reflection more in older subjects (>40 years) than in younger (<40 years). In conclusion, PWA from continuous, digital pressure recordings is a convenient technique to study the arterial function at rest and during exposure to stressors in broad populations. The two reflected waves are differently regulated, which may indicate different anatomical origin.     

Evaluation of impaired dynamic cerebral autoregulation by the Mueller manoeuvre

Arterial blood pressure (ABP) shows polyphasic changes during the Mueller manoeuvre (voluntary negative intrathoracic pressure). The aim of the present study was to investigate (1) whether these changes could be applied to detect impaired dynamic cerebral autoregulation (dCA) in carotid stenosis and (2) whether the degree of indicated impairment correlates with transfer function phase as another current measure for dCA (deep breathing method) and CO₂‐reactivity. We examined 13 patients with severe unilateral carotid artery stenosis and 16 age‐matched controls during 15‐s Mueller manoeuvres (MM) at ?30 mmHg using bilateral transcranial Doppler sonography and non‐invasive ABP recordings (Finapres, 2300, Ohmeda, Englewood, CO, USA). After an initial biphasic oscillation, cerebral blood flow velocity (CBFV) and ABP decreased to below baseline. CBFV reincreased in controls and on contralateral sides in patients 6·0 s (3·8–9·5 s, median and range) after the onset of the decrease, despite a further fall in ABP. CBFV over the affected side revealed a significantly delayed reincrease (8·0 (5·6–10·3) s; P<0·01) combined with a relatively flat and inertial amplitude behaviour. An applied autoregulation index derived from the MM (mROR), phase shift and CO₂‐reactivity were severely reduced on the affected side in patients (P<0·01). Reduction of the mROR correlated significantly with reduction of phase shift (r=0·69; P=0·002) and CO₂‐reactivity (r=0·78; P=0·002). In conclusion, the different cerebral haemodynamic pattern during the MM in patients is likely to reflect impaired dCA. The degree of indicated impairment correlates with that of transfer function phase and CO₂‐reactivity. Therefore, the MM represents a convenient method for grading of compromised cerebral haemodynamics in patients with carotid artery stenosis.     

Cholinergic blockade and the mesenteric artery response to head-up tilt-induced central hypovolaemia

The influence of muscarinic blockade on the superior mesenteric artery (SMA) response to head-up tilt (HUT) was assessed by Doppler ultrasound in eight healthy adults pretreated with i.v. glycopyrron. During supine rest, cholinergic blockade increased heart rate from 58 ± 3 to 106 ± 6 beats min^?1 (mean ± SE) and mean arterial pressure from 81 ± 3 to 97 ± 4 mmHg (P<0·01) and it reduced the cardiac stroke volume from 89 ± 6 to 59 ± 7 ml (P<0·01) with no significant effect on the SMA diameter and blood flow velocities. HUT provoked a further increase in heart rate to 134 ± 5 beats min^?1(P<0·01) and a reduction in stroke volume to 45 ± 4 ml (P<0·01). The early diastolic velocity increased from ?51 ± 4 to 6 ± 8 cm s^?1 during the normotensive stage of HUT and further to 21 ± 9 cm s^?1 during the hypotensive stage with a reduction in mean arterial pressure from 97 ± 4 to 73 ± 7 mmHg (P<0·01) but, in contrast to control HUT (without cholinergic blockade), the end-diastolic velocity did not change significantly. Maintenance of blood velocity and diameter in spite of an increase in arterial pressure at rest indicates increased SMA impedance. Likewise, during hypovolaemia, a glycopyrron-induced inhibition in diastolic velocity supports an increase in SMA impedance. The results indicate cholinergic vasorelaxing influence on the superior mesenteric artery both at rest and during normotensive central hypovolaemia.     

Cardiovascular regulation during head-up tilt in healthy 20-30-year-old and 70-75-year-old men

This study compared the heart rate, finger arterial pressure (AP) and electromyographic (EMG) activity of selected anti-gravity muscles during the initial and prolonged phases of orthostatic stress in healthy young and older men. Beat-by-beat recordings of heart rate, finger systolic pressure, diastolic pressure and mean AP were made during supine rest and 5 min of 90 degrees head-up tilt (HUT) in 18 young (23+/-1 years) and 15 older (73+/-1 years) men. The EMG activity of the soleus, tibialis anterior and vastus medialis muscles was recorded. During the first 30 s following 90 degrees HUT (immediate response), the young men exhibited significant (P<0.05) decreases in finger systolic pressure, diastolic pressure and mean AP, followed by a sustained increase in finger AP during the 5 min following 90 degrees HUT (prolonged response). The immediate and prolonged finger AP and diastolic pressure responses were not significantly different (P>0.05) from the values at supine rest for the older men. The mean root mean square EMG activity of the soleus, tibialis anterior and vastus medialis muscles during 90 degrees HUT was not significantly different (P>0.05) from that at supine rest for either group. These results demonstrate that, when compared with healthy older men, young men show larger reductions in finger AP during the initial phase of orthostatic stress. However, during the prolonged phase of orthostatic stress, older men maintain resting finger AP, whereas young men demonstrate a reflex overshoot in finger AP. Finally, differences in lower-limb anti-gravity muscle activation do not account for the contrasting finger AP responses of healthy young and older men.     

Simultaneous quantification of myocardial perfusion,oxidative metabolism,cardiac efficiency and pump function at rest and during supine bicycle exercise using 1‐11C‐acetate PET – a pilot study

Background: PET using 1‐¹¹C‐acetate (ACE‐PET) applied at rest is used for measuring absolute myocardial blood flow (MBF) and oxidative metabolic rate (k_mono). We evaluated the feasibility of quantitative ACE‐PET during exercise. Methods: Five endurance athletes underwent dynamic PET scanning at rest and during supine bicycle stress. Exercise was maintained at a workload of 120 Watt for 17 min. The rate‐pressure product (RPP) was recorded repeatedly. MBF, k_mono in left (LV) and right (RV) ventricular wall, cardiac output (CO), cardiac efficiency and a lung uptake value reflecting left heart diastolic pressures were calculated from the PET data using previously validated models. Results: MBF increased from 0·71 ± 0·17 to 2·48 ± 0·25 ml min^?1 per ml, LV‐k_mono from 0·050 ± 0·005 to 0·146 ± 0·021 min^?1, RV‐k_mono from 0·023 + 0·006 to 0·087 + 0·014 min^‐1, RPP from 4·7 ± 0·8 to 13·2 ± 1·4 mmHg × min^?1 × 10³ and Cardiac Output from 5·2 ± 1·1 to 12·3 ± 1·2 l min ^?1 (all P < 0·001). Cardiac efficiency was unchanged (P = 0·99). Lung uptake decreased from 1·1 ± 0·2 to 0·6 ± 0·1 ml g^?1 (P < 0·001). Discussion: A number of important parameters related to cardiac function can be quantified non‐invasively and simultaneously with a short scanning protocol during steady state supine bicycling. This might open up new opportunities for studies of the integrated cardiac physiology in health and early asymptomatic disease.     

Changes in left ventricular ejection time and pulse transit time derived from finger photoplethysmogram and electrocardiogram during moderate haemorrhage

Objectives: Early identification of haemorrhage is difficult when a bleeding site is not apparent. This study explored the potential use of the finger photoplethysmographic (PPG) waveform derived left ventricular ejection time (LVET_p) and pulse transit time (PTT) for detecting blood loss, by using blood donation as a model of controlled mild to moderate haemorrhage. Methods: This was a prospective, observational study carried out in a convenience sample of blood donors. LVET_p, PTT and R‐R interval (RRi) were computed from simultaneous measurement of the electrocardiogram (ECG) and the finger infrared photoplethysmogram obtained from 43 healthy volunteers during blood donation. The blood donation process was divided into four stages: (i) Pre‐donation (PRE), (ii) first half of donation (FIRST), (iii) second half of donation (SECOND), (iv) post‐donation (POST). Results and conclusions: Shortening of LVET_p from 303+/?2 to 293+/?3 ms (mean+/?SEM; P<0·01) and prolongation of PTT from 177+/?3 to 186+/?4 ms (P<0·01) were observed in 81% and 91% of subjects respectively when comparing PRE and POST. During blood donation, progressive blood loss produced falling trends in LVET_p (P<0·01) and rising trends in PTT (P<0·01) in FIRST and SECOND, but a falling trend in RRi (P<0·01) was only observed in SECOND. Monitoring trends in timing variables derived from non‐invasive ECG and finger PPG signals may facilitate detection of blood loss in the early phase.     

Lower limb vascular conductance and resting popliteal blood flow during head‐up and head‐down postural challenges

This study hypothesized that central and local reflex mechanisms affecting vascular conductance (VC) through the popliteal artery compensated for the reduction in muscle perfusion pressure (MPP) to maintain popliteal blood flow (PBF) during head‐down tilt (35? HDT), but not in head‐up tilt (45? HUT). Resting measurements were made on 15 healthy men in prone position to facilitate the access to the popliteal artery, on two separate days in random order during horizontal (HOR), HDT or HUT. In each body position, the body was supported, and the ankles were maintained in relaxed state so that there was no muscle tension, as with normal standing. Popliteal blood flow velocity and popliteal arterial diameter were measured by ultrasound, and PBF was calculated. MPP was corrected to mid‐calf from measured finger cuff pressure, and VC was estimated by dividing PBF by MPP. The MPP in HDT (48 ± 2 mmHg) was ~100mmHg less than in HUT (145 ± 2 mmHg). PBF was similar between HOR (51 ± 18 ml min^?1) and HDT (47 ± 13 ml min^?1), but was lower in HUT (30 ± 9 ml min^?1). VC was different between HDT (1·0 ± 0·3 ml min^?1 mmHg^?1), HOR (0·6 ± 0·2 ml min^?1 mmHg^?1) and HUT (0·2 ± 0·1 ml min^?1 mmHg^?1). In conclusion, the interactions of central and local regulatory mechanisms resulted in a disproportionate reduction of VC during HUT lowering PBF even though MPP was higher, while in HDT, increased VC contributed to maintain PBF at the same level as the HOR control condition.     

Atherosclerosis measured by whole body magnetic resonance angiography and carotid artery ultrasound is related to arterial compliance,but not to endothelium‐dependent vasodilation – the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study

Background: Arterial compliance and endothelium‐dependent vasodilation are two characteristics of the vessel wall. In the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study, we studied the relationships between arterial compliance and endothelium‐dependent vasodilation versus atherosclerosis as measured with two imaging modalities. Methods: In the population‐based PIVUS study (1016 subjects aged 70), arterial compliance was determined by ultrasound in the carotid artery and the stroke volume to pulse pressure ratio by echocardiography, while endothelium‐dependent vasodilation was assessed by the invasive forearm technique with acetylcholine and brachial artery ultrasound. Intima‐media thickness was evaluated by ultrasound in the carotid artery (n = 954). Stenosis in the carotid, aorta, renal, upper and lower leg arteries were determined by magnetic resonance angiography in a random subsample of 306 subjects. Results: After adjustments for gender, Framingham risk score, obesity, myocardial infarction and stroke, distensibility in the carotid artery and the stroke volume to pulse pressure ratio were both significantly related to a weighted index of stenosis in the five arterial territories evaluated by magnetic resonance angiography (p<0·02 for both). Distensibility in the carotid artery (P = 0·021), but not the stroke volume to pulse pressure ratio (P = 0·08), was also significantly related to intima‐media thickness. Conclusion: In the elderly population, atherosclerosis is mainly related to arterial compliance, but not to endothelium‐dependent vasodilation in peripheral conduit or resistance vessels.     

Evaluation of endothelial function using finger plethysmography

Background: The aims of this study were to establish the optimum duration of blood flow occlusion to obtain maximal response and to compare the response after lower‐arm and upper‐arm occlusion. Methods: Pulse wave amplitude was analysed using a novel finger plethysmograph (EndoPat; Itamar). For measuring reactive hyperaemic index (RHI) induced by forearm cuff occlusion, 30 healthy subjects were examined at different days in a random order of four cuff occlusion times (1·5, 3, 5 and 8 min). RHI induced by 5 min upper‐arm cuff occlusion was also measured in 20 subjects. Results: Average RHI was lower with 1·5 and 3 min forearm occlusion compared with 8 min forearm occlusion (P = 0·002 and P = 0·024). There was no significant difference between values of 5 min and 8 min forearm occlusion and between 5 min forearm and 5 min upper‐arm occlusion (P = 0·1). All subjects reported less discomfort after forearm occlusion compared with upper‐arm occlusion. Conclusion: Maximum response was reached after 5 min of blood flow occlusion and therefore this occlusion time is recommended. The response after forearm and upper‐arm occlusion did not differ significantly. Forearm occlusion might be preferred as this caused less discomfort.     

Gait performance in relation to aortic pulse wave velocity,carotid artery elasticity and peripheral perfusion in healthy older adults

Arterial stiffening is a widely known physiological change that occurs with ageing, but the functional consequences of vascular ageing are unclear. The purpose of this study was to determine whether carotid–femoral pulse wave velocity (PWV), mechanical properties of the carotid and femoral arteries and/or peripheral perfusion was associated with gait performance measured using a 400‐m walk test. Twenty‐one healthy older (68 ± 5 years) adults without cardiovascular disease participated in this study. Applanation tonometry was used to measure PWV, and Doppler ultrasound was used to measure arterial wall properties of the left common carotid and common femoral artery along with femoral blood flow. The median walk distance in the first 2 min of the test was 585 ft, and the overall gait speed was 1·5 m s^?1. Gait performance was inversely correlated with PWV (distance: r = ‐0·51; speed: r = ?0·48; P<0·05) and carotid artery stiffness index β (distance: r = ?0·56; speed: r =  ? 0·51; P<0·05) after adjustment for age, body mass index, waist circumference and systolic blood pressure. No significant correlations were found between gait performance and femoral artery stiffness index β or femoral artery blood flow. These results found higher central arterial stiffness, as assessed by segmental arterial stiffness or local arterial wall properties, is associated with lower gait performance in older adults independent of other confounders.     

Hydration status influences the measurement of arterial stiffness

Consensus guidelines have attempted to standardize the measurement and interpretation of pulse wave velocity (PWV); however, guidelines have not addressed whether hydration status affects PWV. Moreover, multiple studies have utilized heat stress to reduce arterial stiffness which may lead to dehydration. This study utilized two experiments to investigate the effects of dehydration on PWV at rest and during passive heat stress. In experiment 1, subjects (n = 19) completed two trials, one in which they arrived euhydrated and one dehydrated (1·2[1·0]% body mass loss). In experiment 2, subjects (n = 11) began two trials euhydrated and in one trial did not receive water during heat stress, thus becoming dehydrated (1·6[0·6]% body mass loss); the other trial subjects remained euhydrated. Using Doppler ultrasound, carotid‐to‐femoral (central) and carotid‐to‐radial (peripheral) PWVs were measured. PWV was obtained at a normothermic baseline, and at a 0·5°C and 1°C elevation in rectal temperature (via passive heating). In experiment 1, baseline central PWV was significantly higher when euhydrated compared to dehydrated (628[95] versus 572[91] cm s^?1, respectively; P<0·05), but peripheral PWV was unaffected (861[117] versus 825[149] cm s^?1; P>0·05). However, starting euhydrated and becoming dehydrated during heating in experiment 2 did not affect PWV measures (P>0·05), and independent of hydration status peripheral PWV was reduced when rectal temperature was elevated 0·5°C (?74[45] cm s^?1; P<0·05) and 1·0°C (?70[48] cm s^?1; P<0·05). Overall, these data suggest that hydration status affects measurements of central PWV in normothermic, resting conditions. Therefore, future guidelines should suggest that investigators ensure adequate hydration status prior to measures of PWV.     

Conventional treatment after myocardial infarction in routine clinical practice results in regression of left common carotid intima‐media thickness

This study aimed to evaluate the effect of standard medical treatment on the progression of atherosclerosis after a myocardial infarction, in an ordinary clinical setting, by measuring the right and left common carotid intima‐media thickness (IMT). The first investigation took place 3–12 months after the index event; the second took place 3·3–8·2 years after the first. In both investigations, the right and left carotid arteries of 102 patients were examined with an ultrasound duplex scanner. Common carotid IMT and calculated cross‐sectional intima‐media area (cIMa) were measured on both sides. More than 90% of the patients were treated with aspirin, beta‐blockers and statins. In the first investigation, IMT and cIMa were significantly greater on the left side compared to the right (IMT: 0·83 ± 0·22 and 0·74 ± 0·18 mm, P<0·001; cIMa: 18·2 ± 5·2 and 16·3 ± 5·1 mm², P<0·001). In the second investigation, IMT on the left side was significantly reduced compared to the first investigation (0·79 ± 0·22 and 0·83 ± 0·22 mm, P<0·05) with a corresponding tendency towards a decrease in cIMa on the same side. In our study, conventional medical treatment after a myocardial infarction in ordinary clinical routines resulted in regression of the common carotid IMT on the left side. The significant side difference in IMT emphasizes the importance of where and how the carotid IMT is measured in studies using this surrogate end point.     

Association of carotid arterial distensibility with Doppler indices of left ventricular filling in 50-year-old subjects

Doppler indices of left ventricular diastolic filling are associated with various cardiac and extracardiac factors. Afterload is one of the extracardiac factors influencing left ventricular diastolic filling. The distensibility of the great arteries is one of the components of afterload. In this study, the relation between Doppler indices of left ventricular filling and the distensibility of the common carotid arteries was investigated. We studied 237 subjects at 50 years of age with Doppler echocardiography and ultrasound examination of the common carotid arteries. The following Doppler indices of left ventricular filling were studied: peak early diastolic velocity E-wave, peak atrial diastolic velocity A-wave and early to atrial peak velocity ratio, E/A. Carotid arterial characteristics were: distensibility coefficient, carotid arterial diameter change in systole and fractional change in the carotid arterial diameter. The relation between Doppler indices of left ventricular filling and carotid arterial characteristics was assessed by univariate and multivariate regression analysis. There was a significant univariate, positive association between E/A ratio and carotid arterial distensibility (r = 0·27, P<0·001), carotid arterial systolic diameter change (r = 0·19, P<0·005) and fractional change of the carotid arterial diameter (r = 0·20, P<0·005). In multivariate analysis, E/A ratio was independently associated with carotid arterial distensibility (P<0·005), after adjusting for heart rate, body mass index and gender. Decreased carotid arterial distensibility was associated with a reduction in E/A ratio, suggesting that arterial distensibility may have an effect on left ventricular diastolic filling or that changes in the arterial elastic properties are associated with corresponding structural changes in the left ventricle.     

Cerebral haemodynamics during the Mueller manoeuvre in humans

Voluntary negative intra‐thoracic pressure (Mueller manoeuvre) is known to reduce arterial blood pressure (ABP). To investigate changes in cerebral blood flow velocity (CBFV) during 15 s Mueller manoeuvres at –30 mmHg intra‐thoracic pressure, 27 young (aged 21–31 years, group A) and 11 older (52–64 years, group B) healthy adults were studied using transcranial Doppler and non‐invasive ABP measurement (Finapres). After closely following the initial ABP drop, CBFV showed an overshoot during temporary recovery of ABP. Then ABP and CBFV decreased significantly to below baseline. While ABP declined further until the end of the manoeuvre, CBFV increased in group A 4·7 s (2·4–8·5) (median and range) and in group B 5·7 s (4·1–7·2) after the onset of the CBFV decrease. Critical closing pressure (CCP), calculated for each cardiac cycle from the dynamic pressure–flow relationship (DPFR), indicated a reduction of intra‐cranial pressure during the first half of the strain. DPFR‐related estimation of cerebrovascular resistance provided a more physiological response than the conventional cerebrovascular resistance quotient ABP/CBFV, and decreased about 1·5 s before the observed CBFV increase. A modification of the previously described dynamic auto‐regulation index ROR correlated significantly with CO₂ reactivity values (r=0·61, P=0·001). In conclusion, changes in CBFV during Mueller manoeuvres are likely to reflect dynamic cerebral auto‐regulation and may provide an estimate of dynamic cerebral auto‐regulation capacity. In older adults, the maximal dynamic auto‐regulatory response seems to be unchanged, but the onset of reaction is slightly delayed.