Vascular characteristics in young women-Effect of extensive endurance training or a sedentary lifestyle

AIM

To explore whether high-level endurance training in early age has an influence on the arterial wall properties in young women.

METHODS

Forty-seven athletes (ATH) and 52 controls (CTR), all 17-25 years of age, were further divided into runners (RUN), whole-body endurance athletes (WBA), sedentary controls (SC) and normally active controls (AC). Two-dimensional ultrasound scanning of the carotid arteries was conducted to determine local common carotid artery (CCA) geometry and wall distensibility. Pulse waves were recorded with a tonometer to determine regional pulse wave velocity (PWV) and pulse pressure waveform.

RESULTS

Carotid-radial PWV was lower in WBA than in RUN (P < .05), indicating higher arterial distensibility along the arm. Mean arterial pressure was lower in ATH than in CTR and in RUN than in WBA (P < .05). Synthesized aortic augmentation index (AI@75) was lower among ATH than among CTR (-12.8 ± 1.6 vs -2.6 ± 1.2%, P < .001) and in WBA than in RUN (-16.4 ± 2.5 vs -10.7 ± 2.0%, P < .05), suggesting a diminished return of reflection waves to the aorta during systole. Carotid-femoral PWV and intima-media thickness (IMT), lumen diameter and radial distensibility of the CCA were similar in ATH and CTR.

CONCLUSION

Elastic artery distensibility and carotid artery IMT are not different in young women with extensive endurance training over several years and in those with sedentary lifestyle. On the other hand, our data suggest that long-term endurance training is associated with potentially favourable peripheral artery adaptation, especially in sports where upper body work is added. This adaptation, if persisting later in life, could contribute to lower cardiovascular risk.

The impact of using sagittal abdominal diameter to predict major cardiovascular events in European patients with type 2 diabetes

BACKGROUND AND AIMS

Obesity is associated with diabetes type 2 and one of the most important risk factors for cardiovascular disease. We explored if sagittal abdominal diameter (SAD) is a better predictor of major cardiovascular events than waist circumference (WC) and body mass index (BMI) in type 2 diabetes.

METHODS AND RESULTS

The CARDIPP study consists of a cohort of patients with type 2 diabetes. In this study we used data from 635 participants with no previous myocardial infarction or stroke, with a mean follow-up time of 7.1 years. SAD, WC and BMI were measured at baseline and the end-point was first cardiovascular event, measured as a composite of ICD-10 codes for acute myocardial infarction, stroke or cardiovascular mortality. SAD was significantly higher in the major cardiovascular event group compared to participants that did not suffer a major cardiovascular event during follow-up (p < 0.001). SAD >25 cm was the only anthropometric measurement that remained associated with major cardiovascular events when adjusted for modifiable and non-modifiable factors (hazard ratio 2.81, 95% confidence interval 1.37-5.76, p = 0.005).

CONCLUSION

SAD with the cut off level of >25 cm, if confirmed in larger studies, may be used as a more independent risk-assessment tool compared with WC in clinical practice, to identify persons with type 2 diabetes at high cardiovascular risk. ClinicalTrials.gov: NCT01049737.

Association between serum 25(OH)D3 and cardiovascular morbidity and mortality in people with Type 2 diabetes: a community-based cohort study

AIM

We aimed to explore the association between vitamin D and cardiovascular morbidity and mortality in people with Type 2 diabetes recruited from a community-based study because there is limited and inconsistent research of this group.

METHODS

A prospective community-based cohort study among people aged 55-66 years with Type 2 diabetes as part of The Cardiovascular Risk in Type 2 Diabetes - A Prospective Study in Primary Care (CARDIPP). We analysed serum 25-hydroxyvitamin D₃ [25(OH)D₃ ] at baseline. Cox regression analyses were used to calculate hazard ratios (HR) for the first myocardial infarction, stroke or cardiovascular mortality according to 25(OH)D₃ .

RESULTS

We examined 698 people with a mean follow-up of 7.3 years. Serum 25(OH)D₃ was inversely associated with the risk of cardiovascular morbidity and mortality: HR 0.98 [95% confidence interval (CI) 0.96 to 0.99, P = 0.001]. Compared with the fourth quartile (Q4) [25(OH)D₃ > 61.8 nmol/l], HR (with 95% CI) was 3.46 (1.60 to 7.47) in Q1 [25(OH)D₃ < 35.5 nmol/l] (P = 0.002); 2.26 (1.01 to 5.06) in Q2 [25(OH)D₃ 35.5-47.5 nmol/l] (P = 0.047); and 1.62 (0.70 to 3.76) in Q3 [25(OH)D₃ 47.5-61.8 nmol/l] (P = 0.26) when adjusting for age, sex and season. The results remained significant after adjusting also for cardiovascular risk factors, physiological variables including parathyroid hormone and previous cardiovascular disease (P = 0.027).

CONCLUSIONS

Low 25(OH)D₃ is associated with an increased risk of cardiovascular morbidity and mortality in people with Type 2 diabetes independent of parathyroid hormone. Vitamin D could be considered as a prognostic factor. Future studies are needed to explore whether vitamin D deficiency is a modifiable risk factor in Type 2 diabetes.

Abnormal mechanical properties of larger arteries in postmenopausal women with systemic lupus erythematosus

There is limited knowledge of potential defects in arterial wall properties in female systemic lupus erythematosus (SLE) patients without manifest cardiovascular disease (CVD) and significant atherosclerotic lesions. The aim of the present study was to investigate the mechanical properties of larger vessels in these patients and to compare them with healthy controls. B-mode ultrasound was used to assess vessel wall structure and to exclude presence of plaque. The ankle/brachial pressure index was measured to exclude occlusive arterial disease. An ultrasound echo-tracking system was used to determine stiffness of the abdominal aorta, common carotid artery (CCA) and popliteal artery (PA) in 39 female patientswith SLE and 55 female, healthy controls. SLE had an independent effect on stiffening of the CCA ( P = 0.01) and PA ( P = 0.005). In addition, larger vessel diameters were observed in the CCA (P = 0.002) after adjustments for the effects of mean arterial pressure and age. Thus, this investigation demonstrated an increased arterial stiffness and signs of premature vascular ageing in the SLE patients without manifest cardiovascular disease and without significant atherosclerotic lesions. The results of this study indicate that other mechanisms besides atherosclerosis might be involved in the pathogenesis of arterial stiffening in SLE patients.

Increased aortic pulse wave velocity in middle aged women with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a connective tissue disease where inflammatory activity affects several organ systems. An increased risk of cardiovascular disease has been identified in these patients, even after correction for traditional risk factors. The aim of the present study was to evaluate arterial stiffness and central hemodynamics in women with SLE in comparison to controls.

Arterial tonometry was used to measure aortic (carotid-femoral) and arm (carotid-radial) pulse wave velocity (PWV), reflected pressure waves, and aortic augmentation index (AIx) in 27 women with SLE (52 to 68 years) and 27 controls. Aortic PWV was higher in women with SLE than controls, 9.8 m/s versus 8.2 m/s ( P 0.01), after correction for mean arterial pressure and body mass index, 9.5 m/s versus 8.5 m/s ( P 0.05). Other parameters were similar, arm PWV, 8.4 versus 8.5 m/s, AIx 34 versus 33% and calculated central aortic pulse pressure 48 versus 43 mmHg, in SLE and controls, respectively (NS). Aortic PWV was positively associated to C-reactive protein (CRP) and complement factor 3 (C3).

Women with SLE have increased stiffness of their elastic central arteries. This may be one factor contributing to the increased cardiovascular risk seen in this cohort.

Pedometer-determined physical activity level and change in arterial stiffness in Type 2 diabetes over 4 years

AIM

To explore prospectively the correlation between the level of pedometer-determined physical activity at the start of the study and the change in pulse wave velocity from baseline to 4 years later in people with Type 2 diabetes.

METHODS

We analysed data from 135 men and 53 women with Type 2 diabetes, aged 54-66 years. Physical activity was measured with waist-mounted pedometers on 3 consecutive days and the numbers of steps/day at baseline were classified into four groups: <5000 steps/day, 5000-7499 steps/day, 7500-9999 steps/day and ≥10 000 steps/day. Pulse wave velocity was measured using applanation tonometry over the carotid and femoral arteries at baseline and after 4 years.

RESULTS

The mean (±sd; range) number of steps/day was 8022 (±3765; 956-20 921). The participants with the lowest level of physical activity had a more pronounced increase in the change in pulse wave velocity compared with the participants with the highest. When change in pulse wave velocity was analysed as a continuous variable and adjusted for sex, age, diabetes duration, HbA1c , BMI, systolic blood pressure, pulse wave velocity at baseline, β-blocker use, statin use, unemployment, smoking and diabetes medication, the number of steps/day at baseline was significantly associated with a less steep increase in change in pulse wave velocity (P=0.005). Every 1000 extra steps at baseline corresponded to a lower increase in change in pulse wave velocity of 0.103 m/s.

CONCLUSIONS

We found that a high level of pedometer-determined physical activity was associated with a slower progression of arterial stiffness over 4 years in middle-aged people with Type 2 diabetes.

The association between endostatin and kidney disease and mortality in patients with type 2 diabetes

AIM

Circulating endostatin, a biologically active derivate of collagen XVIII, is considered to be a marker of kidney disease and a risk factor for its related mortality. However, less is known of the role of endostatin in diabetes and the development of diabetic nephropathy. For this reason, our study investigated the associations between circulating endostatin and the prevalence and progression of kidney disease, and its mortality risk in patients with type 2 diabetes (T2D).

METHODS

This was a cohort study of 607 patients with T2D (mean age: 61 years, 44% women). Estimated glomerular filtration rate (eGFR), calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation, was used to assess the patients' kidney function decline and mortality.

RESULTS

Of the total study cohort, 20 patients declined by ≥20% in eGFR over 4 years, and 44 died during the follow-up (mean duration: 6.7 years). At baseline, participants with diabetic nephropathy (defined as eGFR<60mL/min/1.73m²) and/or microalbuminuria [defined as a urinary albumin-to-creatinine ratio (ACR)>3g/mol] had higher median levels of endostatin than those without nephropathy (62.7μg/L vs 57.4μg/L, respectively; P=0.031). In longitudinal analyses adjusted for age, gender, baseline eGFR and ACR, higher endostatin levels were associated with a higher risk of decline (≥20% in eGFR, OR per 1 SD increase: 1.73, 95% CI: 1.13-2.65) and a higher risk of mortality (HR per 1 SD increase: 1.57, 95% CI: 1.19-2.07).

CONCLUSION

In patients with T2D, circulating endostatin levels can predict the progression of kidney disease and mortality independently of established kidney disease markers. The clinical usefulness of endostatin as a risk marker in such patients merits further studies.

Abdominal obesity and low-grade systemic inflammation as markers of subclinical organ damage in type 2 diabetes

AIM

This study aimed to explore the associations between abdominal obesity, inflammatory markers and subclinical organ damage in 740 middle-aged patients with type 2 diabetes.

METHODS

Waist circumference (WC) and sagittal abdominal diameter (SAD) were measured, and blood samples were analyzed for C-reactive protein (CRP) and IL-6. Carotid intima-media thickness (IMT) was evaluated by ultrasonography, and aortic pulse wave velocity (PWV) measured with applanation tonometry.

RESULTS

Abdominal obesity as determined by SAD and WC was significantly correlated with IL-6 (WC: r=0.27, P<0.001; SAD: r=031, P<0.001), CRP (WC: r=0.29, P<0.001; SAD: r=0.29, P<0.001), IMT (WC: r=0.09, P=0.013; SAD: r=0.11, P=0.003) and PWV (WC: r=0.18, P<0.001; SAD: r=0.21, P<0.001). In multiple linear regressions with IMT and PWV as dependent variables, and age, gender, statin use, systolic blood pressure (SBP), body mass index (BMI), CRP and HbA1c as independent variables, both SAD and WC remained associated with IMT and PWV. On stepwise linear regression and entering both SAD and WC, the association between SAD and PWV was stronger than the association between WC and PWV.

CONCLUSION

Both SAD and WC are feasible measures of obesity, and both provide information on inflammation, atherosclerosis and arterial stiffness in type 2 diabetes, while SAD appears to be slightly more robustly associated with subclinical organ damage than WC.

Microalbuminuria, but not reduced eGFR, is associated with cardiovascular subclinical organ damage in type 2 diabetes

AIM

This study explored the association between reduced estimated glomerular filtration rate (eGFR) and microalbuminuria vs. subclinical organ damage in patients with type 2 diabetes.

METHODS

Data from middle-aged patients with type 2 diabetes (n=706) treated in primary care were analyzed for microalbuminura, defined as a urinary albumin/creatinine ratio (uACR)≥3.0mmol/mol, and reduced eGFR, defined as<60mL/min/1.73m(2), in relation to blood pressure, pulse wave velocity (PWV), left ventricular mass index (LVMI), and carotid intima-media thickness (IMT) and lumen diameter (LD).

RESULTS

Patients with microalbuminuria had significantly higher 24-h ambulatory systolic blood pressure (ASBP) compared with subjects with uACR<3mg/mmol: 137 vs. 128mmHg (P<0.001). There were no differences in ASBP in patients with eGFR<60mL/min/1.73m(2). However, patients with vs. without microalbuminuria had increased PWV (11.4 vs. 10.1m/s; P<0.001), LVMI (134.4 vs. 118.6g/m(2); P<0.001), LD (7.01±0.93 vs. 6.46±0.74mm; P<0.001) and IMT (0.78 vs. 0.74mm; P=0.047), respectively. The associations between uACR vs. PWV and LVMI were more robust after adjusting for age, diabetes duration, ASBP, HbA1c, LDL-cholesterol, and antihypertensive and lipid-lowering therapy compared with uACR vs. IMT. There were no statistically significant differences in PWV, LVMI or IMT between patients with reduced (<60mL/min/1.73m(2)) vs. normal eGFR.

CONCLUSION

Levels of urinary albumin excretion, but not reduced eGFR, were associated with increased arterial stiffness, left ventricular mass and atherosclerosis in patients with type 2 diabetes.

Cardiovascular function in adulthood following intrauterine growth restriction with abnormal fetal blood flow

OBJECTIVES

To examine whether intrauterine growth restriction (IUGR) is associated with increased cardiovascular risk later in life.

METHODS

We examined 19 young adults (aged 22-25 years) who were born at term after IUGR, along with 18 controls. All had been examined previously with fetal Doppler, and in the present follow-up with echocardiography, carotid echo-tracking ultrasound, applanation tonometry, blood pressure and laser Doppler, in order to characterize their cardiac and vascular geometry and/or function.

RESULTS

The diameter of the ascending aorta and the left ventricular diameter were smaller in the IUGR group, but only ascending aortic diameter remained significantly smaller after adjustment for body surface area (P < 0.05). The aortic pressure augmentation index was higher in the IUGR group (P < 0.05). The common carotid artery diameter, intima-media thickness and distensibility as well as left ventricular mass and function were similar in the two groups. IUGR status was found to be an independent predictor of ascending aortic diameter.

CONCLUSIONS

IUGR due to placental dysfunction seems to contribute to the higher systolic blood pressure augmentation and the smaller aortic dimensions that are observed in adults more than 20 years later, with possible negative consequences for future left ventricular performance due to increased aortic impedance.

Pedometer-determined physical activity is linked to low systemic inflammation and low arterial stiffness in Type 2 diabetes

AIMS

The aim of this study was to explore the association between pedometer-determined physical activity versus measures of obesity, inflammatory markers and arterial stiffness in people with Type 2 diabetes.

METHODS

We analysed data from 224 men and 103 women with Type 2 diabetes, aged 54-66 years. Physical activity was measured with waist-mounted pedometers during three consecutive days and the number of steps/day were calculated and classified in four groups: < 5000 steps/day, 5000-7499 steps/day, 7500-9999 steps/day and ≥ 10000 steps/day. Blood samples were analysed for lipids, HbA(1c), inflammatory markers including C-reactive protein and interleukin-6. Nurses measured blood pressure and anthropometrics. Aortic pulse wave velocity was measured with applanation tonometry over the carotid and femoral arteries.

RESULTS

Mean steps/day was 7683 ± 3883 (median 7222, interquartile range 4869-10,343). There were no differences in age, diabetes duration, blood pressure, lipids or glycaemic control between the four groups of pedometer-determined physical activity. Subjects with higher steps/day had lower BMI (28.8 vs. 31.5 kg/m(2), P < 0.001), waist circumference (101.7 vs. 108.0 cm, P < 0.001), lower levels of C-reactive protein (1.6 vs. 2.6 mg/l, P = 0.007), lower levels of interleukin-6 (1.9 vs. 3.8 pg ml, P < 0.001) and lower pulse wave velocity (10.2 vs. 11.0 m/s, P = 0.009) compared with less physically active people.

CONCLUSIONS

We conclude that physical activity measured with pedometer was associated not only with less abdominal obesity, but also with decreased systemic low-grade inflammation as well as with low arterial stiffness, in people with Type 2 diabetes.

Impaired abdominal aortic wall integrity in elderly men carrying the angiotensin-converting enzyme D allele

OBJECTIVE

A polymorphism in the angiotensin-converting-enzyme gene (ACE I/D) has been associated with abdominal aortic aneurysm and a link between aortic aneurysm and aortic stiffness has been suggested. This study aimed to explore the links between ACE I/D polymorphism, circulating ACE and abdominal aortic wall integrity as reflected by abdominal aortic wall stiffness.

MATERIAL

A total of 212 men and 194 women, aged 70-88 years, were studied.

METHODS

Mechanical properties of the abdominal aorta were determined using the Wall Track System, ACE genotype using the polymerase chain reaction (PCR) and circulating ACE level by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In men, pulsatile diameter change differed between genotypes (II 0.70, ID 0.55 and DD 0.60 mm, P = 0.048), whereas a tendency was seen for distensibility coefficient (DC) (II 10.38, ID 7.68 and ID 8.79, P = 0.058). Using a dominant model (II vs. ID/DD), men carrying the ACE D allele had lower pulsatile diameter change (P = 0.014) and DC (P = 0.017) than II carriers. Multiple regression analyses showed additional associations between the D allele and increased stiffness β, and reduced compliance coefficient.

CONCLUSION

Men carrying the ACE D allele have stiffer abdominal aortas compared with II carriers. Deranged abdominal aortic stiffness indicates impaired vessel wall integrity, which, along with other local predisposing factors, may be important in aneurysmal disease.

In vivo estimation of the contribution of elastin and collagen to the mechanical properties in the human abdominal aorta: effect of age and sex

The mechanical properties of the aorta affect cardiac function and are related to cardiovascular morbidity/mortality. This study was designed to evaluate the isotropic (mainly elastin, elastiniso) and anisotropic (mainly collagen, collagenani) material parameters within the human aorta in vivo. Thirty healthy men and women in three different age categories (23–30, 41–54, and 67–72 yr) were included. A novel mechanical model was used to identify the mechanical properties and the strain field with aid of simultaneously recorded pressure and radius in the abdominal aorta. The magnitudes of the material parameters relating to both the stiffness of elastiniso and collagenani were in agreement with earlier in vitro studies. The load-bearing fraction attributed to collagenani oscillated from 10 to 30% between diastolic and systolic pressures during the cardiac cycle. With age, stiffness of elastiniso increased in men, despite the decrease in elastin content that has been found due to elastolysis. Furthermore, an increase in stiffness of collagenani at high physiological pressure was found. This might be due to increased glycation, as well as changed isoforms of collagen in the aortic wall with age. A marked sex difference was observed, with a much less age-related effect, both on elastiniso and collagenani stiffness in women. Possible factors of importance could be the effect of sex hormones, as well as differing collagen isoforms, between the sexes.

Masked nocturnal hypertension--a novel marker of risk in type 2 diabetes

AIMS/HYPOTHESIS

This study was designed to evaluate the prevalence of masked nocturnal hypertension (MNHT) and its impact on arterial stiffness and central blood pressure in patients with type 2 diabetes.

METHODS

Middle-aged patients (n = 414) with type 2 diabetes underwent clinic and ambulatory BP measurements and applanation tonometry.

RESULTS

MNHT (clinic BP < 130/80 mmHg and night-time BP > or = 120/70 mmHg) was found in 7.2% of patients (n = 30). Compared with patients with both clinical and nocturnal normotension (n = 70), patients with MNHT had higher aortic pulse wave velocity (PWV) (10.2 +/- 1.8 m/s vs 9.4 +/- 1.7 m/s; p = 0.03) and higher central BP (117.6 +/- 13.9/74.0 +/- 9.1 mmHg vs 110.4 +/- 16.4/69.7 +/- 9.6 mmHg, p = 0.04). In patients with clinical normotension, night-time systolic BP correlated significantly with PWV.

CONCLUSIONS/INTERPRETATION

Thirty per cent of patients with clinical normotension had nocturnal hypertension. This was accompanied by increased arterial stiffness and higher central BP. We conclude that in clinically normotensive patients with type 2 diabetes, ambulatory BP measurement may help clinicians to identify patients with increased cardiovascular risk.

Carotid intima-media thickness and apolipoprotein B/apolipoprotein A-I ratio in middle-aged patients with Type 2 diabetes

AIMS

To explore the association between carotid intima-media thickness (IMT) and the apolipoprotein B (apoB)/apolipoprotein A-I (apoA-I) ratio compared with conventional lipids in middle-aged patients with Type 2 diabetes.

METHODS

We analysed data from 247 patients with Type 2 diabetes, aged 55-66 years, in the Cardiovascular Risk factors in Patients with Diabetes-a Prospective study in Primary care (CARDIPP-1) study. Primary care nurses measured blood pressure and anthropometric characteristics. Blood samples were taken for laboratory analyses. The carotid IMT was determined by ultrasonography at the University Hospital in Linköping and at the County Hospital Ryhov, Jönköping, Sweden.

RESULTS

The ApoB/apoA-I ratio (r = 0.207, P = 0.001), apoB (r = 0.166, P = 0.009) and non-high-density lipoprotein cholesterol (non-HDL-c) (r = 0.129, P = 0.046) correlated with IMT. Conventional lipids, high-sensitivity C-reactive protein (hsCRP), glycated haemoglobin (HbA(1c)) and systolic blood pressure were not significantly correlated to IMT. A stepwise logistic regression analysis was conducted with IMT as the dependent variable and the apoB/apoA-I ratio, HbA(1c), hsCRP, low-density lipoprotein cholesterol (LDL-c), total cholesterol, non-HDL-c and treatment with statins as independent variables. Following adjustment for age and gender, only the apoB/apoA-I ratio remained significantly associated with IMT (odds ratio 4.3, 95% confidence intervals 1.7-10.8, P = 0.002).

CONCLUSIONS

We conclude that there was a significant association between the apoB/apoA-I ratio and IMT in middle-aged patients with Type 2 diabetes. The association was independent of conventional lipids, hsCRP, glycaemic control and use of statins.

Association of genetic variation on chromosome 9p21.3 and arterial stiffness

OBJECTIVES

Genome wide association studies have consistently reported associations between a region on chromosome 9p21.3 and a broad range of vascular diseases, such as coronary artery disease (CAD), aortic and intracranial aneurysms and type-2 diabetes (T2D). However, clear associations with intermediate phenotypes have not been described so far. To shed light on a possible influence of this chromosomal region on arterial wall integrity, we analysed associations between single nucleotide polymorphisms (SNPs) and degree of stiffness of the abdominal aorta in elderly individuals.

METHODS AND RESULTS

A total of 400 subjects, 212 men and 188 women, aged 70-88 years were included. Arterial stiffness was examined at the midpoint between the renal arteries and the aortic bifurcation. Two CAD- and aneurysm-associated SNPs (rs10757274 and rs2891168) and one T2D-associated SNP (rs1081161) within the 9p21.3 region were genotyped. Aortic compliance and distensibility coefficients were higher in carriers of the rs10757274G and rs2891168G alleles in men reflecting a decrease in aortic stiffness. Adjustment for age and mean arterial pressure had no effect on these associations. The two SNPs were not associated with intima-media thickness or lumen diameter of the abdominal aorta. There were no associations between the rs10811661 SNP and any measure of aortic stiffness.

CONCLUSIONS

Impaired mechanical properties of the arterial wall may explain the association between chromosome 9p21.3 polymorphisms and vascular disease.

Lower capacitance response and capillary fluid absorption in women to defend central blood volume in response to acute hypovolemic circulatory stress

Acute hemorrhage is a leading cause of death in trauma, and women are more susceptible to hypovolemic circulatory stress than men. The mechanisms underlying the susceptibility are not clear, however. The aim of the present study was to examine the compensatory mechanisms to defend central blood volume during experimental hypovolemia in women and men. Twenty-two women (23.1 ± 0.4 yr) and 16 men (23.2 ± 0.5 yr) were included. A lower body negative pressure (LBNP) of 11–44 mmHg induced experimental hypovolemic circulatory stress. The volumetric technique was used to assess the capacitance response (redistribution of peripheral venous blood to the central circulation) as well as to assess net capillary fluid transfer from tissue to blood in the arm. Plasma norepinephrine (NE) and forearm blood flow were measured before and during hypovolemia, and forearm vascular resistance (FVR) was calculated. LBNP created comparable hypovolemia in women and men. FVR increased less in women during hypovolemic stress, and no association between plasma NE and FVR was seen in women ( R2 = 0.01, not significant), in contrast to men ( R2 = 0.59, P < 0.05). Women demonstrated a good initial capacitance response, but this was not maintained with time, in contrast to men [e.g., decreased by 24 ± 4% (women) vs. 4 ± 5% (men), LBNP of 44 mmHg, P < 0.01], and net capillary fluid absorption from tissue to blood was lower in women (0.086 ± 0.007 vs. 0.115 ± 0.011 ml·100 ml−1·min−1, P < 0.05). In conclusion, women showed impaired vasoconstriction, reduced capacitance response with time, and reduced capillary fluid absorption during acute hypovolemic circulatory stress, indicating less efficiency to defend central blood volume than men.

Vascular mechanical properties and endothelial function in pre-eclampsia with special reference to bilateral uterine artery notch

OBJECTIVES

To assess whether women with pre-eclampsia (PE) have different properties of the blood vessel wall compared to healthy pregnant controls. Further, to evaluate endothelial function and vascular mechanical properties in women with PE with special regard to its association with bilateral uterine artery notch and placental histopathology.

PARTICIPANTS

Some 57 Caucasian pregnant women: 23 with uncomplicated pregnancies and normal uterine artery Doppler, and 34 with PE, the PE group comprising 2 subgroups according to the presence (n=20) or absence (n=14) of bilateral uterine artery notches.

METHODS

Ultrasonic echo-tracking assessed the elastic properties of the common carotid artery, abdominal aorta and popliteal artery. Flow-mediated dilatation (FMD) of the brachial artery was measured by ultrasonography. Histopathological examination of the placenta was carried out in 46 pregnancies: 18 uncomplicated pregnancies, 15 with PE with bilateral notch, and 13 with PE without bilateral notch.

RESULTS

There were no significant differences in carotid, aortic or popliteal vessel wall stiffness either between women with PE and controls or within the PE group. FMD was significantly lower in women with PE than in controls (p=0.03). The lowest FMD was observed in pre-eclamptic women with bilateral uterine artery notches 9.5% (SD: 5.3) compared to 11.6% (SD: 5.4) in pre-eclamptic women without bilateral uterine artery notch, and 13.4% (SD: 4.0) in controls (p=0.01). Bilateral uterine artery notching was significantly associated with a lower FMD (OR: 0.87; 95% CI: 0.77-0.98). There were significantly more placentas with high ischaemic score in the bilateral notch group than in the group with PE and normal circulation.

CONCLUSIONS

There were no differences in vessel wall stiffness between women with PE and healthy controls. Women with PE showed signs of endothelial dysfunction, significantly more pronounced in women with bilateral uterine artery notch. Bilateral uterine artery notch was associated with ischaemic pathology of the placenta. Notwithstanding, a significant number of placentas in the PE group failed to show noteworthy ischaemic or other morphological changes that could explain the role of the placenta in the development of PE.

Sex-related effects on venous compliance and capillary filtration in the lower limb

Recent studies in humans have suggested sex differences in venous compliance of the lower limb, with lower compliance in women. Capillary fluid filtration could, however, be a confounder in the evaluation of venous compliance. The venous capacitance and capillary filtration response in the calves of 12 women (23.2 ± 0.5 years) and 16 men (22.9 ± 0.5 years) were studied during 8 min lower body negative pressure (LBNP) of 11, 22, and 44 mmHg. Calf venous compliance is dependent on pressure and was determined using the first derivative of a quadratic regression equation that described the capacitance-pressure relationship [compliance = β1 + (2·β2· transmural pressure)]. We found a lower venous compliance in women at low transmural pressures, and the venous capacitance in men was increased ( P < 0.05). However, the difference in compliance between sexes was reduced and not seen at higher transmural pressures. Net capillary fluid filtration and capillary filtration coefficient (CFC) were greater in women than in men during LBNP ( P < 0.05). Furthermore, calf volume increase (capacitance response + total capillary filtration) during LBNP was equivalent in both sexes. When total capillary filtration was not subtracted from the calf capacitance response in the calculation of venous compliance, the sex differences disappeared, emphasizing that venous compliance measurement should be corrected for the contribution of CFC.

Reduced aortic wall stress in diabetes mellitus

OBJECTIVE

Most risk factors are similar for abdominal aortic aneurysm (AAA) and atherosclerosis, e.g. smoking, male gender, age, high blood pressure, hyperlipidemia. Diabetes mellitus however, is a risk factor for atherosclerosis, but diabetic patients seldom develop AAA. The reason for this discrepancy is unknown. Increased aortic wall stress seems to be an etiologic factor in the formation, growth and rupture of AAA in man. The aim of our study was to study the wall stress in the abdominal aorta in diabetic patients compared with healthy controls.

METHODS

39 patients with diabetes mellitus and 46 age - and sex matched healthy subjects were examined with B-mode ultrasound to determine the lumen diameter (LD) and intima-media thickness (IMT) in the abdominal aorta (AA) and the common carotid artery (CCA). Diastolic blood pressure (DBP) was measured non-invasively in the brachial artery. LaPlace law was used to calculate circumferential wall stress.

RESULTS

Age, DBP, and LD in the abdominal aorta were not significantly different in the diabetic patients compared to controls. IMT in the AA was larger in the diabetic patients, 0.89+/-0.17 vs 0.73+/-0.11 mm (p<.001). Accordingly aortic wall stress was reduced in the diabetics, 7.8+/-1.7 x 10(5) vs 9.7+/-1.9 x 10(5)dynes/cm(2) (p<.001).

CONCLUSIONS

Wall stress in the abdominal aorta is reduced in diabetes mellitus. This is mainly due to a thicker aortic wall compared to healthy controls. The reduced aortic wall stress coincides with the fact that epidemiological studies have shown a decreased risk of aneurysm development in diabetic patients.

Influence of fibrillin-1 genotype on the aortic stiffness in men

Aortic stiffness is a predictor of cardiovascular mortality. The mechanical properties of the arterial wall depend on the connective tissue framework, with variation in fibrillin-1 and collagen I genes being associated with aortic stiffness and/or pulse pressure elevation. The aim of this study was to investigate whether variation in fibrillin-1 genotype was associated with aortic stiffness in men. The mechanical properties of the abdominal aorta of 79 healthy men (range 28–81 yr) were investigated by ultrasonographic phase-locked echo tracking. Fibrillin-1 genotype, characterized by the variable tandem repeat in intron 28, and collagen type I alpha 1 genotype characterized by the 2,064 G>T polymorphism, were determined by using DNA from peripheral blood cells. Three common fibrillin-1 genotypes, 2-2, 2-3, and 2-4, were observed in 50 (64%), 10 (13%), and 11 (14%) of the men, respectively. Those of 2-3 genotype had higher pressure strain elastic modulus and aortic stiffness compared with men of 2-2 or 2-4 genotype ( P = 0.005). Pulse pressure also was increased in the 2-3 genotype ( P = 0.04). There was no significant association between type 1 collagen genotype and aortic stiffness in this cohort. In conclusion, the fibrillin-1 2-3 genotype in men was associated with increased aortic stiffness and pulse pressure, indicative of an increased risk for cardiovascular disease.

Impaired vascular growth in late adolescence after intrauterine growth restriction

BACKGROUND

Abnormal blood flow in a fetus small for gestational age indicates true fetal intrauterine growth restriction (IUGR). We tested the hypothesis that IUGR with abnormal fetal blood flow is associated with long-term abnormal vascular morphology and function in adolescence.

METHODS AND RESULTS

In a prospective study, vascular mechanical properties of the common carotid artery (CCA), abdominal aorta, and popliteal artery (PA) were assessed by echo-tracking sonography in 21 adolescents with IUGR and abnormal fetal aortic blood flow and in 23 adolescents with normal fetal growth and normal fetal aortic blood flow. Endothelium-dependent and -independent vasodilatation of the brachial artery was measured by high-resolution ultrasound. After adjustment for body surface area and sex, the IUGR group had significantly smaller end-diastolic vessel diameters than the referents in the abdominal aorta and PA (mean difference, 1.7 mm [95% CI, 0.62 to 2.74] and 0.6 mm [95% CI, 0.25 to 1.02], respectively) (P=0.003 and P=0.002, respectively), with a similar trend in the CCA (P=0.09). A higher resting heart rate was observed in the IUGR group (P=0.01). No differences were found in stiffness or in endothelium-dependent and -independent vasodilatation between the 2 groups.

CONCLUSIONS

IUGR caused by placental insufficiency appears to be associated with impaired vascular growth persisting into young adulthood in both men and women. The smaller aortic dimensions and the higher resting heart rate seen in adolescents with previous IUGR may be of importance for future cardiovascular health.

Increased aortic stiffness is persistent in type 1 diabetic women: a follow-up study

AIMS/HYPOTHESIS

We have previously reported that women, not men, with type 1 diabetes have increased aortic stiffness. Increased arterial stiffness may explain why diabetic women have a particularly high risk of developing cardiovascular complications. We have now followed up our previously investigated patients after 7 years, with a view to evaluating whether the sex difference was persistent, and also evaluating the degree of progression with time and the relationship between stiffness versus intima media thickness of the aorta.

METHODS

Stiffness (beta) of the abdominal aorta (echo-tracking sonography) and intima media thickness (B-mode ultrasound) were assessed in 23 women and 19 men with type 1 diabetes and compared with matched healthy individuals.

RESULTS

At follow-up, aortic stiffness was still higher (60%) (p=0.0016) in diabetic than in control women, whereas there was no similar difference (p=0.4) between diabetic and control men. No progression of stiffness had occurred over the 7 years. At follow-up, the intima media thickness was increased and the internal diameter of the aorta was decreased in diabetic men and women without any sex-related difference.

CONCLUSIONS/INTERPRETATION

The increased aortic stiffness that affects type 1 diabetic patients seems to be an early event that soon reaches a plateau without any further increase. Increased aortic stiffness in type 1 diabetic women seems to be a sex-specific functional disorder unrelated to the degree of underlying atherosclerosis.

Increased stiffness of the abdominal aorta in women with rheumatoid arthritis

OBJECTIVE

To study the distensibility and the diameter of the abdominal aorta and the common carotid artery (CCA) in patients with rheumatoid arthritis (RA), and investigate the relation between mechanical properties of these arteries and disease severity.

METHODS

One hundred and one patients with RA (33 consecutive cases with extra-articular manifestations, and 68 subjects with non-extra-articular disease, matched for age, sex and disease duration) were investigated. Echo-tracking ultrasonography was used to measure stiffness and mean diameter of the abdominal aorta and the CCA. The patients were compared with healthy individuals from the corresponding age group (n=74 for measurements of the aorta, n=64 for the CCA). Predicted values for stiffness and mean diameter, based on age and sex, were calculated.

RESULTS

Stiffness of the abdominal aorta was increased in women with RA [mean percentage of predicted value (% predicted) 180; 95% confidence interval (95% CI) 150-211] but not in men (% predicted 99; 95% CI 75-122). CCA stiffness was less markedly increased, and mean diameters of the aorta and the CCA were not different from the expected. In the RA cohort, patients with extra-articular manifestations tended to have greater stiffness of the aorta (P=0.11), and disability, as indicated by a higher Health Assessment Questionnaire score, was associated with increased aortic stiffness (P=0.04).

CONCLUSION

RA is associated with decreased distensibility of the abdominal aorta in females, and such changes seem to correlate with disease severity. We suggest that arterial stiffness is an important factor in cardiovascular co-morbidity in RA.

The effect of sympathetic stimulation on proximal brachial artery mechanics in humans - differential behaviour within the length of the brachial artery?

AIMS

The mechanical properties of arteries play a major role in the regulation of blood pressure and cardiac performance. The effect of sympathetic stimulation on the mechanical properties of the proximal brachial artery was analysed in 18 healthy volunteers, nine young (25 +/- 2 years) and nine elderly (69 +/- 2 years).

METHODS

A non-invasive ultrasonic echo-tracking system for measurement of systolic/diastolic variation of the proximal brachial artery diameter in combination with intra-arterial pressure measurements was used to determine wall mechanics. The pressure-diameter (P-D) relationship, distensibility coefficient (DC), compliance coefficient (CC) and stiffness(beta) were obtained at rest and during sympathetic stimulation induced by lower body negative pressure (LBNP).

RESULTS

The peripheral vascular resistance increased by 100 and 72%, respectively in the young and elderly during LBNP (P < 0.001). Simultaneously, the mechanical properties of the proximal brachial artery remained unaltered, as estimated from both P-D relationship and stiffness in young (beta-index rest: 5.2 +/- 0.9, LBNP: 5.5 +/- 1.3, NS) as well as elderly (beta-index rest: 13.6 +/- 4.6, LBNP: 16.1 +/- 4.7, NS).

CONCLUSIONS

LBNP-induced sympathetic activation does not change proximal brachial artery mechanics, in contrast to earlier reports on the muscular distal brachial artery. This may imply that the transition between elastic and muscular artery behaviour is within the length of the brachial artery, where the site of transition from elastic to muscular wall structure needs to be specified in future studies.

The popliteal artery, an unusual muscular artery with wall properties similar to the aorta: implications for susceptibility to aneurysm formation?

OBJECTIVE

The popliteal artery is, after the aorta, the most common site for aneurysm formation. Why the popliteal artery is more susceptible than other peripheral muscular arteries is unknown. An important factor may be differences in arterial wall composition as compared with other peripheral muscular arteries, which in turn affect wall properties. These are however unknown. We studied the mechanical wall properties of the popliteal artery in healthy subjects.

MATERIAL AND METHODS

An ultrasound echo-tracking system was used to measure pulsatile changes in popliteal diameter in 108 healthy subjects (56 female, 52 male; age range, 9-82 years). In combination with blood pressure, stiffness (beta), strain, cross-sectional artery wall compliance coefficient (CC), and distensibility coefficient (DC) were calculated. Intima-media thickness (IMT) was registered with a Philips P700 ultrasound scanner.

RESULTS

The popliteal diameter increased with age, and was larger in male subjects than in female subjects (P<.001). Fractional diameter change (strain) decreased with age (P<.001), and strain values were lower in male subjects than in female subjects (P<.01). Accordingly, stiffness increased with age (P<.001), with higher stiffness values in male subjects (P<.01). DC decreased with age (P<.001), with lower DC values in male subjects (P<.01). CC decreased with age, with no difference between genders (P<.001). IMT increased with age (P<.001), with higher IMT values in male subjects (P<.001). The increase in IMT did not affect distensibility.

CONCLUSION

The wall properties of the popliteal artery are affected by age and gender, not only with an increase in diameter, but also with an age-related decrease in distensibility, with male subjects having lower distensibility than in female subjects. This seems not to be the behavior of a true muscular artery, but of a central elastic artery, such as the aorta, and might have implications for susceptibility to arterial dilatation, as well as the association of aneurysm formation between the aorta and the popliteal artery.

CLINICAL RELEVANCE

The popliteal artery is, after the abdominal aorta, the most common location for aneurysm formation in the arterial system. Why it is more susceptible than other arteries is unknown. This study shows that the wall function of the popliteal artery differs from other peripheral arteries, and instead show striking similarities to the abdominal aorta, indicating that the functional arrangement of arterial wall components are similar in the two arteries. This may have implications for the susceptibility to aneurysm formation, as well as the association of dilating disease between the popliteal artery and the abdominal aorta.

Influence of glucose and insulin on transcapillary fluid absorption from the arm during lower body negative pressure in man

This study examined the influence of insulin and glucose on the transcapillary fluid absorption during lower body negative pressure (LBNP) in humans. Ten healthy males [23 (1) years] were exposed to LBNP of 45 cmH(2)O on two occasions: (1) before and during a hyperinsulinaemic clamp (HI) and (2) before and during a hyperglycaemic clamp (HG). Transcapillary fluid absorption and blood flow were recorded with volumetric technique. Forearm blood flow increased during HI from 2.3 (0.3) ml (100 ml)(-1) min(-1) to 3.3 (0.5) ml (100 ml)(-1) min(-1) ( P<0.05). The haemodynamic response to LBNP was similar during HI and HG compared with control LBNP. Transcapillary fluid absorption during LBNP increased during HG from 0.044 (0.007) ml (100 ml)(-1) min(-1) to 0.059 (0.009) ml (100 ml)(-1) min(-1 )( P<0.01), whereas it was unchanged during HI. In conclusion, hyperglycaemia augments transcapillary fluid absorption from skeletal muscle and skin during LBNP whereas hyperinsulinaemia has no such effect. This indicates that in human hyperglycaemia contributes to plasma volume restitution during hypovolaemic circulatory stress.

Female gender increases stiffness of elastic but not of muscular arteries in type I diabetic patients

The reason for the particularly increased risk for cardiovascular complications in diabetic women is still unclear. We have previously found decreased distensibility of elastic arteries in type I diabetic women, indicating increased cardiac load, not seen in type I diabetic men, which might be one contributing factor. Whether the effect of gender is different in muscular arteries in type I diabetic patients has not been assessed. As estimates of arterial distensibility we measured stiffness (beta) and pressure strain elastic modulus (Ep) in the muscular common femoral artery using echo-tracking sonography in 30 women (mean age 34 years, range 20-61) and 26 men (mean age 38 years, range 22-56) with type I diabetes. The results were compared with those of 89 healthy individuals of corresponding age and gender and with previously published results from elastic arteries in these patients obtained at the same occasion. The internal common femoral diameter was significantly decreased in both diabetic men and women. In sharp contrast to the highly significant decreased distensibility of the elastic abdominal aorta and common carotid artery in the type I diabetic women, the distensibility of the common femoral artery did not clearly differ between patients and controls, neither for women nor for men. Thus, the gender difference in changes of arterial distensibility found in elastic arteries was absent or far less obvious in the femoral artery. In conclusion, female gender seems to affect the mechanical properties of elastic, but not of large muscular arteries in type I diabetic patients. Thus, putative gender differences in arterial changes in type I diabetes are to be sought in elastic rather than muscular arteries.

Altered vascular function in healthy normotensive pregnant women with bilateral uterine artery notches

OBJECTIVES

To assess endothelial function and vascular mechanical properties in normotensive pregnant women with high resistance in the uteroplacental circulation.

DESIGN

Cross-sectional prospective study.

SETTING

Doppler ultrasound laboratory at university department of obstetrics and gynaecology referral centre for high risk pregnancies.

PARTICIPANTS

Forty-two caucasian normotensive pregnant women: 23 with uncomplicated pregnancies and 19 with bilateral uterine artery notches.

METHODS

Flow-mediated dilatation of the brachial artery was measured by ultrasonography at 25 gestational weeks. Concentrations of nitrite and nitrate in the plasma were established at 25 and 32 gestational weeks. The elastic properties of the common carotid artery, abdominal aorta and popliteal artery were measured with an ultrasonic echo-tracking system.

RESULTS

Flow-mediated dilatation at two minutes after cuff deflation was significantly lower in the bilateral notch group compared with the control group, 8.3% and 13.7%, respectively (P = 0.0007). The ability to sustain vasodilatation was reduced in the bilateral notch group (P = 0.02). Lower values of nitrite and nitrate in the plasma were found at 32 gestational weeks in the bilateral notch group than in the control group (mean 24.76 microM/L (SD 5.6) and 30.93 microM/L (8.2), respectively; P = 0.008). Nitrite and nitrate levels tended to be lower in the bilateral notch group even at 25 gestational weeks (29.45 microM/L (8.3) and 35.73 microM/L (11.0) in the bilateral notch and control group, respectively; P = 0.09). There was no difference in aortic, carotid or popliteal elasticity between the two groups.

CONCLUSIONS

Healthy normotensive pregnant women with bilateral uterine artery notches show impaired endothelial function, but no differences in vascular mechanical properties.

Arterial dimensions in the lower extremities of patients with abdominal aortic aneurysms--no indications of a generalized dilating diathesis

PURPOSE

This study assessed whether there is a dilating diathesis in peripheral arteries of patients with abdominal aortic aneurysms (AAAs).

METHODS

The anteroposterior diameters of the common femoral artery (CFA) and popliteal artery (PA) were measured in 183 consecutive patients with an AAA (158 men, 25 women; age range, 57-78 years) before elective surgery on the AAA and compared with that of healthy age-matched control subjects. The diameter registrations were performed on the right leg by using a noninvasive echo-tracking ultrasound scanning technique.

RESULTS

Eight CFA aneurysms and four PA aneurysms were found in the male patients with AAAs. Of the patients with AAAs in the CFA and in the PA who were investigated, 46% and 49%, respectively, were affected by peripheral vascular occlusive disease (PVOD). The CFA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = not significant [NS]). After exclusion of the CFA aneurysms, the diameters were 92.7% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the CFA diameters were 95.2% of those in healthy control subjects (P = .022). The PA diameters in the patients with AAAs were 97.8% of those in healthy control subjects (P = NS). If PA aneurysms were excluded, the diameters were 94.4% of those in healthy control subjects (P = .0003). If patients with PVOD were also excluded, the PA diameters were 96.1% of those in healthy control subjects (P = NS).

CONCLUSION

After excluding the few patients with AAAs who had peripheral aneurysmal disease and the patients with PVOD, no dilating diathesis in CFAs and PAs was found. This supports the hypothesis that specific genetic, or other factors, not present in most AAAs are responsible for the occurrence of concomitant peripheral aneurysms. Furthermore, the generalized vascular dilating diathesis seen in some patients seems to be a specific entity that was not necessarily affiliated with AAA disease.

Dynamic behaviour of the common femoral artery: age and gender of minor importance

The distensibility of elastic arteries has been extensively studied, while studies of muscular arteries are sparse. The influences of age and gender on the mechanical properties of the common femoral artery (CFA) were studied. The pulsatile diameter changes of the CFA were noninvasively measured using echo-tracking sonography in 173 healthy volunteers (95 females, 78 males, range 7-81 years). In combination with blood pressure measurements, stiffness (beta) and pressure strain elastic modulus (Ep) were calculated. Neither beta nor Ep was related to age or gender and a considerable interindividual variation was present. The CFA diameter increased with age. In conclusion, the distensibility of this muscular artery is not clearly affected by age or gender, although the diameter increases with age. This indicates remodelling of the arterial wall and an impact of vascular smooth muscles on long-term wall mechanics. Thus, there appear to be fundamental differences in the dynamic behaviour of the common femoral artery when compared to elastic arteries, such as the aorta and the common carotid artery.

Reduced capillary hydraulic conductivity in skeletal muscle and skin in Type I diabetes: a possible cause for reduced transcapillary fluid absorption during hypovolaemia

AIMS/HYPOTHESIS

Patients with Type I (insulin-dependent) diabetes mellitus have a reduced transcapillary fluid absorption from skeletal muscle and skin and thus defective plasma volume regulation during hypovolaemia. Our aim was to find whether a defective capillary filtration coefficient or impaired transcapillary driving force are aetiologic factors for this reduction.

METHODS

We investigated 11 diabetic patients (diabetes duration 6.9 +/- 1.1 years, age 26 +/- 1 years), without complications and 12 control subjects (26 +/- 1 years). Their capillary filtration coefficient was measured in the upper arm using a volumetric technique at rest and during lower body negative pressure (LBNP). We calculated the driving force for transcapillary fluid transfer.

RESULTS

The increase in heart rate and the decrease in systolic blood pressure during lower body negative pressure were similar in diabetic and control subjects. The resting capillary filtration coefficient was decreased in the diabetic subjects, 0.033 +/- 0.003 vs 0.051 +/- 0.007 ml x 100 ml(-1) x min(-1) x mmHg(-1) (p < 0.05). During lower body negative pressure, the capillary filtration coefficient increased 35 % in both groups compared with resting capillary filtration coefficient and was still decreased in diabetes; 0.046 +/- 0.004 compared with 0.069 +/- 0.006 ml x 100ml(-1) x min(-1) x mmHg(-1) (p < 0.01). The established driving force during lower body negative pressure was 1.37 +/- 0.11 vs 1.30 +/- 0.15 mmHg (NS) in diabetic and control subjects, respectively.

CONCLUSIONS/INTERPRETATION

Our study indicates that a reduced capillary filtration coefficient rather than defective regulation of transcapillary driving force, is the reason for the reduced transcapillary fluid absorption during hypovolaemic circulatory stress found in Type I diabetic patients.

Cardiovascular response to acute hypovolemia in relation to age. Implications for orthostasis and hemorrhage

Venous compliance in the legs of aging man has been found to be reduced with decreased blood pooling (capacitance response) in dependent regions, and this might lead to misinterpretations of age-related changes in baroreceptor function during orthostasis. The hemodynamic response to hypovolemic circulatory stress was studied with the aid of lower-body negative pressure (LBNP) of 60 cmH(2)O in 33 healthy men [18 young (mean age 22 yr) and 15 old (mean age 65 yr)]. Volumetric technique was used in the study of capacitance responses in the calf and arm as well as transcapillary fluid absorption in the arm. LBNP led to smaller increase in heart rate (P < 0.001) and peripheral resistance (P < 0.01) and reduced transcapillary fluid absorption in the arm (P < 0.05) in old subjects. However, blood pooling in the calf was reduced in old subjects (1.66 +/- 0.10 vs. 2.17 +/- 0.13 ml/100 ml tissue; P < 0. 01). Accordingly, during similar blood pooling in the calf (LBNP 80 cmH(2)O in old subjects), no changes in cardiovascular reflex responses with age were found. The capacitance response in the arm (mobilization of peripheral blood to the central circulation) was still reduced, however (0.67 +/- 0.10 vs. 1.37 +/- 0.11 ml/100 ml tissue; P < 0.01). Thus the reduced cardiovascular reflex response found in the elderly during orthostatic stress seems to be caused by a reduced capacitance response in the legs with age and a concomitant smaller central hypovolemic stimulus rather than a reduced efficiency of the reflex response. With similar hypovolemic circulatory stress, no changes in cardiovascular reflex responses are seen with age. The capacitance response in the arm (mobilization of peripheral blood toward the central circulation) is reduced, however, by approximately 50% in the elderly. This might seriously impede the possibility of survival of an acute blood loss.

Abdominal aortic aneurysm wall mechanics and their relation to risk of rupture

PURPOSE

to see whether aneurysmal aortic wall mechanics can be used as a predictor of abdominal aortic aneurysm (AAA) rupture.

METHOD

among 285 individuals, followed conservatively for AAA and monitored for aneurysm growth and wall mechanics on at least one occasion at our institution between January 1991 and January 1998, eleven subsequently ruptured. Wall mechanics were estimated as stiffness (beta). This was calculated from diameter and pulsatile diameter change, determined non-invasively by an ultrasonic echo-tracking system and blood pressure obtained by the auscultatory method. The results were compared with those of 121 individuals electively operated on for AAA.

RESULTS

no difference in aortic stiffness was found between those that subsequently ruptured (beta=35, median) compared to those non-ruptured (beta=38, median) AAAs (p=0.855). There was no difference in diameter in ruptured (58.8 mm) compared with non-ruptured (54.1 mm) AAAs (p=0.129). All ruptured AAAs showed an expansion of diameter over time.

CONCLUSION

this study shows no difference in aneurysmal aortic wall mechanics in those AAAs that subsequently ruptured compared with electively operated AAAs. The results indicate that it is not possible to use aneurysmal aortic wall stiffness as a predictor of rupture.

Reduced transcapillary fluid absorption from skeletal muscle and skin during hypovolaemia in insulin-dependent diabetes mellitus

OBJECTIVES

Diabetes mellitus is associated with a high cardiovascular morbidity which has been linked to disturbances in microvascular function. This study was designed to examine the transcapillary fluid absorption during experimental hypovolaemia in type 1 diabetes.

SUBJECTS

Twelve males with type 1 diabetes (age 25 +/- 3 years, duration 8 +/- 1 years) with no clinical microangiopathy and 12 healthy males (22 +/- 2 years).

INTERVENTIONS

As a model for hypovolaemic circulatory stress, lower body negative pressure (LBNP: 15, 30 and 60 cmH2O) was used. Transcapillary fluid absorption from tissue to blood in the upper arm, as well as forearm blood flow, was measured by volumetric technique.

RESULTS

Resting forearm blood flow, heart rate and blood pressure were similar in diabetic patients and controls. Basal plasma noradrenaline was reduced in the diabetics compared with controls (0.75 +/- 0.06 vs. 1.09 +/- 0.10 pmol L-1, P < 0.05), but the increase in plasma noradrenaline in response to LBNP was similar in the two groups. The haemodynamic responses to LBNP in the two groups were equal, showing a reduction of pulse pressure, an increase in heart rate and in peripheral resistance with a concomitant blood flow reduction. The transcapillary fluid absorption (mL 100 mL-1 min-1) was significantly reduced in the diabetic patients: LBNP 15 cmH2O, 0.024 +/- 0.004 vs. 0.036 +/- 0. 002; 30 cmH2O, 0.041 +/- 0.003 vs. 0.056 +/- 0.005; and 60 cmH2O, 0. 057 +/- 0.007 vs. 0.091 +/- 0.008 (diabetic patients vs. controls, P < 0.001).

CONCLUSIONS

The transcapillary fluid absorption from tissue to blood during hypovolaemic circulatory stress in type 1 diabetic patients is reduced by one-third compared with controls, which indicates impaired plasma volume regulation. This basic mechanism for plasma volume control is affected before clinical microcirculatory complications are found and could be one of the causes of the increased cardiovascular morbidity and mortality in IDDM.

Increased aortic stiffness in women with type 1 diabetes mellitus is associated with diabetes duration and autonomic nerve function

AIMS

The increase in risk for cardiovascular complications in diabetic women is even greater than that in diabetic men. We found arterial stiffness to be increased in women, but not in men, with Type 1 diabetes mellitus (DM). The aims of the present study were to evaluate whether the changes in arterial distensibility are influenced by diabetes duration and to evaluate any association between autonomic neuropathy and decreased arterial distensibility.

METHODS

Stiffness of the abdominal aorta was measured noninvasively using echo-tracking sonography and parasympathetic function by heart rate variation during deep breathing (E/I ratio) in 40 women (mean age 33 years, range 20-61) and 38 men (mean age 36 years, range 22-56) with Type 1 DM.

RESULTS

There was a significant correlation between aortic stiffness and duration of diabetes in women (r = 0.41, P = 0.008), but not in men (r = 0.15, P = 0.35). There was also a significant correlation between aortic stiffness and the E/I ratio in women (r = -0.49, P = 0.002), but not in men (r = -0.14, P = 0.41). When adjusted for diabetes duration, the significant association between the E/I ratio and aortic stiffness remained in diabetic women (r = -0.44, P = 0.008) and was stronger than the association between diabetes duration and aortic stiffness. There were no significant correlations between aortic stiffness and triglycerides or total cholesterol, respectively.

CONCLUSIONS

Increased aortic wall stiffness found in women with Type 1 DM is related to diabetes duration. Further, in women with Type 1 DM there is a correlation between increased aortic stiffness and parasympathetic dysfunction. This may be of importance for the increased susceptibility to cardiovascular complications in diabetic women.

Acute renal impairment due to a primary aortocaval fistula is normalised after a successful operation

OBJECTIVES

To study renal function in patients with aortocaval fistula, before and after surgery.

DESIGN

Retrospective study.

MATERIAL AND METHODS

During the last 22 years nine male patients (median age 67, age range 50-72) with spontaneous aortocaval fistula in combination with AAA were operated upon. This constitutes 4% of the patients with ruptured AAA and 1.5% of all patients with AAA.

RESULTS

A preoperative diagnosis of aortocaval fistula was established in three of the nine cases. The medium duration of symptoms prior to surgery was 5 days (range 4 h-14 days). The fistula was combined with an extravasating ruptured AAA in only three patients. Seven of the patients had acute renal insufficiency, with creatinine levels of in median 292 mumol (IQR 218-342). Creatinine declined to 172 mumol/l (IQR 170-313) on the fifth postoperative day in uncomplicated cases and to 86 mumol at discharge. One patient died due to multi-organ failure, whereas the other left hospital well and alive with normal renal function.

CONCLUSION

Acute preoperative renal insufficiency due to an aortocaval fistula in patients with AAA is often due to venous congestion, and is normalised after successful surgery.

The diameter of the common femoral artery in healthy human: influence of sex, age, and body size

PURPOSE

To determine the relevance of dilatations of the common femoral artery (CFA), knowledge of the normal CFA diameter is essential. The diameter of the CFA in healthy male and female subjects of different ages was investigated.

METHODS

The diameter of the CFA was measured in 122 healthy volunteers (59 male, 63 female; 8 to 81 years of age) with echo-tracking B-mode ultrasound scan. The influence of age, sex, height, weight, body surface area (BSA), and systolic blood pressure was analyzed by means of a multiple regression model.

RESULTS

The CFA increased steadily in diameter throughout life. From 25 years onwards, the diameter was larger in men than in women. Significant correlations were found between the CFA diameter and weight (r = 0.58 and r = 0.57 in male and female subjects, respectively; P <.0001), height (r = 0.49 and r = 0.54 in male and female subjects, respectively; P <.0001), and BSA (r = 0.60 and r = 0.62 in male and female subjects, respectively; P <.0001). Age and BSA were used to create a model for prediction of the CFA diameter (r = 0.71 and r = 0.77 in male and female subjects, respectively; P <.0001).

CONCLUSION

The diameter of the CFA increases with age, initially during growth but also in adults. This is related to age, body size, and sex male subjects have larger arteries than female subjects. It is now possible to predict the normal CFA diameter, and nomograms that may be used in the study of aneurysmal disease are presented.

Is there a relationship between abdominal aortic aneurysms and alpha1-antitrypsin deficiency (PiZ)?

OBJECTIVE

To determine if the frequency of alpha 1AT deficiency (PiZ) is increased in patients with abdominal aortic aneurysm (AAA), and, to investigate whether aneurysmal stiffness and other clinical characteristics differ in AAA patients with and without alpha 1AT deficiency.

METHODS

We identified alpha 1AT-deficient individuals by a monoclonal-antibody ELISA technique, in 102 consecutive patients with AAA. Positive ELISA samples were further phenotyped by isoelectric focusing to differentiate between the heterozygosity (PiZ) and homozygosity (PiZZ) state. Aneurysmal diameter and stiffness was measured using echotracking sonography and blood pressure measurements.

RESULTS

The frequency of heterozygous alpha 1AT deficiency (PiZ) in patients with AAA was similar to that in the general population (6.8% and 4.7%, respectively, p > 0.3). The frequency of popliteal and femoral aneurysm was similar in male PiZ-carriers and non-carriers with AAA, as were age at diagnosis of AAA, aneurysmal diameter, aneurysmal stiffness, and presence of factors that may be associated with AAA (i.e. smoking, hypertension, diabetes mellitus, and family history of AAA). Occurrence of ischaemic heart disease was more frequent in male non-PiZ-carriers than in male PiZ-carriers with AAA (p = 0.03).

CONCLUSIONS

The frequency of alpha 1AT deficiency (PiZ) was not increased in our series of patients with AAA and patients in whom the two disorders coexisted did not appear to have different clinical characteristics except for the lower occurrence of ischaemic heart disease among the PiZ-carriers.

The fate of the infrarenal aortic neck after open aneurysm surgery

PURPOSE

The long-term success of the endovascular repair of abdominal aortic aneurysms is dependent on the secure fixation of the stent graft at the proximal and distal attachment sites. A progressive dilatation of the infrarenal neck may jeopardize this success. The data regarding this issue are scarce. However, the long-term fate of the infrarenal neck can be studied in patients who have undergone open aneurysm surgery. This was the purpose of the present investigation.

METHODS

Between January 1989 and December 1993, 64 patients underwent open repair of infrarenal abdominal aortic aneurysms. Of the 36 patients who were eligible for the study, 19 had preoperative computed tomography scans that were available. The 19 patients also underwent a new computed tomography scanning at a mean of 71 +/- 12 months after surgery.

RESULTS

The mean preoperative aortic diameter was 25.4 +/- 3.7 mm at the infrarenal neck, 24.8 +/- 3.4 mm at the level of the renal arteries, and 26.7 +/- 3.0 mm at the level of the superior mesenteric artery (SMA). The mean aortic diameter increased at all of the 3 levels: +2.8 +/- 3.1 mm (P =.0014) at the infrarenal neck, +2.8 +/- 3.0 mm (P =.0013) at the level of the renal arteries, and +1.3 +/- 3.0 mm (P = .080) at the level of the SMA. The annual growth rate was 0.48 mm/y (P = .0023) at the infrarenal neck, 0.46 mm/y (P =.0010) at the level of the renal arteries, and 0.21 mm/y (P = .5811) at the level of the SMA. No correlation was found between the preoperative infrarenal neck diameter (r = .295, P = .2194), the preoperative aortic diameter at the level of the renal arteries (r = .302, P = .2088), and the preoperative aortic diameter at the level of the SMA (r = .314, P =. 2043) and the corresponding growth rates. The patients were stratified into 2 groups one with a small annual growth rate at the infrarenal neck (n = 11; </= 0.3 mm/y) and one with a larger annual growth rate (n = 8; > 0.3 mm/y) and no differences in the preoperative infrarenal neck diameter or the clinical characteristics were found between the groups.

CONCLUSION

This investigation shows an aortic dilatation of the infrarenal neck and of the aorta at the level of the renal arteries of approximately 0.5 mm annually after open aneurysm surgery. This dilatation raises concern regarding the long-term success after endovascular repair. The data also indicate that 2 populations might exist with regard to the annual growth rate of the infrarenal neck one with low growth rate and one with higher growth rate. This might be of interest for the future selection of patients for endovascular repair.