Attenuation of wave reflection by wave entrapment creates a "horizon effect" in the human aorta

Wave reflection is thought to be important in the augmentation of blood pressure. However, identification of distal reflections sites remains unclear. One possible explanation for this is that wave reflection is predominately determined by an amalgamation of multiple proximal small reflections rather than large discrete reflections originating from the distal peripheries. In 19 subjects (age, 35-73 years), sensor-tipped intra-arterial wires were used to measure pressure and Doppler velocity at 10-cm intervals along the aorta, starting at the aortic root. Incident and reflected waves were identified and timings and magnitudes quantified using wave intensity analysis. Mean wave speed increased along the length of the aorta (proximal, 6.8±0.9 m/s; distal, 10.7±1.5 m/s). The incident wave was tracked moving along the aorta, taking 55±4 ms to travel from the aortic root to the distal aorta. However, the timing to the refection site distance did not differ between proximal and distal aortic measurement sites (proximal aorta, 48±5 ms versus distal aorta, 42±4 ms; P=0.3). We performed a second analysis using aortic waveforms in a nonlinear model of pulse-wave propagation. This demonstrated very similar results to those observed in vivo and also an exponential attenuation in reflection magnitude. There is no single dominant refection site in or near the distal aorta. Rather, there are multiple reflection sites along the aorta, for which the contributions are attenuated with distance. We hypothesize that rereflection of reflected waves leads to wave entrapment, preventing distal waves being seen in the proximal aorta.     

Quantification of wave reflection in the human aorta from pressure alone: a proof of principle

Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends not only on the magnitude of wave reflection but also on wave shapes and timing of incident and reflected waves. More accurate measures are obtainable after separation of pressure in its forward (P(f)) and reflected (P(b)) components. However, this calculation requires measurement of aortic flow. We explore the possibility of replacing the unknown flow by a triangular wave, with duration equal to ejection time, and peak flow at the inflection point of pressure (F(tIP)) and, for a second analysis, at 30% of ejection time (F(t30)). Wave form analysis gave forward and backward pressure waves. Reflection magnitude (RM) and reflection index (RI) were defined as RM=P(b)/P(f) and RI=P(b)/(P(f)+P(b)), respectively. Healthy subjects, including interventions such as exercise and Valsalva maneuvers, and patients with ischemic heart disease and failure were analyzed. RMs and RIs using F(tIP) and F(t30) were compared with those using measured flow (F(m)). Pressure and flow were recorded with high fidelity pressure and velocity sensors. Relations are: RM(tIP)=0.82RM(mf)+0.06 (R(2)=0.79; n=24), RM(t30)=0.79RM(mf)+0.08 (R(2)=0.85; n=29) and RI(tIP)=0.89RI(mf)+0.02 (R(2)=0.81; n=24), RI(t30)=0.83RI(mf)+0.05 (R(2)=0.88; n=29). We suggest that wave reflection can be derived from uncalibrated aortic pressure alone, even when no clear inflection point is distinguishable and AI cannot be obtained. Epidemiological studies should establish its clinical value.     

Distensibility and pulse wave velocity of the thoracic aorta in patients with juvenile idiopathic arthritis: an MRI study

OBJECTIVE: An increased incidence of cardiovascular disease has been found in rheumatic disorders. Changes in the variables of aortic elasticity in patients with juvenile idiopathic arthritis (JIA) were evaluated and their relationship to inflammation, anti-rheumatic drugs and traditional cardiovascular risk factors were investigated in this study. METHODS: Phase contrast MR was performed in 31 patients with JIA and 28 age and sex matched controls to evaluate the aortic distensibility and pulse wave velocity (PWV). Disease activity variables, plasma lipid profile, homocysteine, thyroid hormones, glucose and insulin were assessed in the patients. RESULTS: Eighteen patients had oligoarticular, 6 polyarticular and 7 systemic disease. Distensibility was lower (mean: 10.25; SD: 4.18) and PWV was higher (mean: 3.68; SD: 1.59) in the patients compared to the controls (mean: 13.4; SD: 4.99), (mean: 1.38; SD: 0.54) respectively (p < 0.01). A positive correlation between PWV and age was observed in the patients (rs = 0.47, p < 0.01) and controls (rs = 0.72, p < 0.01), and a negative correlation between distensibility and age in the patients (rs = -0.59, p < 0.01) and controls (rs = -0.63, p < 0.01). No statistically significant correlations were found between distensibility and PWV and metabolic and disease activity parameters. When distensibility and PWV were adjusted for age no significant differences were found between the three subtypes of JIA. CONCLUSION: JIA is associated with increased aortic stiffness that might suggest subclinical atherosclerosis. Early detection and follow-up by non-invasive methods may be useful in the prevention of future cardiovascular disease.     

Estimation of systolic pulmonary artery pressure with continuous wave Doppler pressure gradient method: a simultaneous Doppler and catheter correlative study

To estimate more precisely the systolic pulmonary artery pressure (PASP), continuous wave Doppler pressure gradient method and catheter measurement were performed simultaneously in 85 patients. There were 30 patients with tricuspid regurgitation (TR), 35 with ventricular septal defect (VSD), and 20 with patent ductus arterosus (PDA). For maximal transtricuspid pressure gradient (TRPG) determined by continuous wave Doppler and catheter determined PASP in TR group, the correlation coefficient (r) was as high as 0.99. For Doppler determined PASP (subtracting pressure gradient across PDA from systemic arterial pressure measured by cuff sphygmomanometer) and catheter determined PASP in PDA group, r was 0.95. Doppler determined PASP in VSD group (subtracting pressure gradient across VSD from systemic arterial pressure) also correlated well with catheter determined PASP (r = 0.97). This study demonstrates that continuous wave Doppler pressure gradient method can accurately estimate PASP in patients with TR, PDA, and VSD.     

Continuous wave Doppler determination of right ventricular pressure: a simultaneous Doppler-catheterization study in 127 patients

Simultaneous continuous wave Doppler echocardiography and right-sided cardiac pressure measurements were performed during cardiac catheterization in 127 patients. Tricuspid regurgitation was detected by the Doppler method in 117 patients and was of adequate quality to analyze in 111 patients. Maximal systolic pressure gradient between the right ventricle and right atrium was 11 to 136 mm Hg (mean 53 +/- 29) and simultaneously measured Doppler gradient was 9 to 127 mm Hg (mean 49 +/- 26); for these two measurements, r = 0.96 and SEE = 7 mm Hg. Right ventricular systolic pressure was estimated by three methods from the Doppler gradient. These were 1) Doppler gradient + mean jugular venous pressure; 2) using a regression equation derived from the first 63 patients (Group 1); and 3) Doppler gradient + 10. These methods were tested on the remaining 48 patients with Doppler-analyzable tricuspid regurgitation (Group 2). The correlation between Doppler-estimated and catheter-measured right ventricular systolic pressure was similar using all three methods; however, the regression equation produced a significantly better estimate (p less than 0.05). Use of continuous wave Doppler blood flow velocity of tricuspid regurgitation permitted determination of the systolic pressure gradient across the tricuspid valve and the right ventricular systolic pressure. This noninvasive technique yielded information comparable with that obtained at catheterization. Approximately 80% of patients with increased and 57% with normal right ventricular pressure had analyzable Doppler tricuspid regurgitant velocities that could be used to accurately predict right ventricular systolic pressure.     

The effect of TNF-a antagonists on aortic stiffness and wave reflections: a meta-analysis

Clinical Rheumatology - Patients with rheumatoid arthritis (RA) have higher aortic stiffness and cardiovascular risk. Tumor necrosis factor alpha (TNF-a) antagonists reduce inflammation in RA and...     

Glycosaminoglycans in the human aorta in diabetes mellitus: a study of tunica media from areas with and without atherosclerotic plaque

Summary Alterations in the connective tissue of the arterial wall have been suggested to play a role in the development of macrovascular disease in diabetes mellitus. The present study deals with changes in the content of GAG in aortic tunica media in human diabetes by separately analysing normal areas and areas with fibrous plaques. The thoracic aorta from 15 diabetic patients (7 with IDDM, 8 with NIDDM), and 30 sex- and age-matched non-diabetic subjects were collected at autopsy. Tunica intima was removed and GAG were isolated from the dried defatted and pulverized tunica media. GAG were quantified by uronic acid analysis and characterized by electrophoresis on cellulose acetate. Results showed that IDDM patients had a relative and absolute increase in hyaluronic acid in normal tunica media compared to non-diabetic subjects. There was a significant positive correlation between hyaluronic acid content of normal tunica media and duration of diabetes, but not between hyaluronic acid content and age. When tunica media from plaque areas was compared to normal areas the same pattern was evident in diabetic patients as in non-diabetic patients — significantly increased proportion of dermatan sulphate and reduced hyaluronic acid. The data agree with the notion that the arterial wall is subject to different pathological processes in diabetes, one of classical atherosclerosis with changes in GAG similar to non-diabetic subjects, and the other seen in areas without plaques with dissimilar alterations in GAG. These data therefore support the concept of the presence of a macrovascular disease in diabetes different from atherosclerosis.Abbreviations NIDDM Non-insulin-dependent diabetes mellitus - IDDM insulin-dependent diabetes mellitus - GAG glycosaminoglycans     

Long-term culture and a morphological study of endothelial cells from human aorta

Endothelial cells from human aorta were successfully cultured first in this Lab in our country. Cells survived and passed through 10-15 generations. Long term cultured endothelial cells from human aorta were observed under phase-contrast microscope, scanning, transmission electron microscope, and investigated immunocytochemically by immunofluorescence of specific antibody against Factor-VIII related surface antigen, and ABC method using monoclonal antibody 9B9 against human angiotensin-converting enzyme. Medium RPMI-1640 supplemented with 20% human serum, endothelial cell growth factor 200 micrograms/ml, heparin 100 micrograms/ml and gelatin coated flasks were very important conditions for long term culture of human endothelial cell.     

Impact of human immunodeficiency virus infection on arterial stiffness and wave reflections in the early disease stages

Background

Human immunodeficiency virus (HIV) infection is associated with subclinical inflammation and increased cardiovascular risk. Arterial stiffness and enhanced wave reflections are markers of cardiovascular disease and independent predictors of cardiovascular risk. The effect of HIV infection, per se, on aortic stiffness and wave reflections has not been clearly defined.

Methods

We studied 51 adults with a recent HIV infection, free of antiretroviral treatment and AIDS diagnosis, as well as 35 controls matched for age, sex and smoking status. Carotid-femoral pulse wave velocity (PWV) and timing of the reflected wave (Tr) were measured as indices of aortic stiffness, while aortic augmentation index (AIx) and augmented pressure (AP) were measured as indices of wave reflections.

Results

While PWV was similar in the two populations, Tr was significantly lower in HIV-infected subjects compared to controls (by 16.5 ms, p = 0.002). In addition, AIx and AP were decreased (by 6.4%, p = 0.048 and by 3.3 mmHg, p = 0.010, respectively) in subjects with HIV infection. Moreover, HIV-infected patients compared with controls had increased values of hs-CRP [1.37 (0.85-2.53) vs. 0.75 (0.41-1.90) mg/l, p = 0.007] and interleukin-6 [1.90 (0.91-3.9) vs. 1.28 (0.80-2.65) pg/ml, p = 0.048]. Tr was negatively correlated with hs-CRP (r = −0.283, p = 0.010) and interleukin-6 (r = −0.278, p = 0.018).

Conclusions

Our study provides evidence of decreased wave reflections and similar aortic stiffness, as assessed by PWV, in the early stages of HIV infection in treatment-naive patients compared to controls. Subclinical inflammation and resultant peripheral vasodilatation constitute potential mediators of the whole pathophysiological process.     

A simultaneous onset of organizing pneumonia and rheumatoid arthritis, along with a review of the literature

Organizing pneumonia (OP) is a specific type of interstitial pneumonia that has been noted as one of the pulmonary manifestations during the course of rheumatoid arthritis (RA). In this study, we report a case with a simultaneous development of OP and RA. The patient presented with concurrent flu-like symptoms and arthralgia of multiple joints, and antibiotic therapy was not effective. The rheumatoid factor (RF) and anti-cyclic citrullinated antibodies were both high. Multiple air-space opacities on chest radiographs and bilateral peripheral consolidations on high-resolution computed tomography films were evident. The histology of transbronchial lung biopsy samples was characterized by intra-alveolar buds of granulation tissue consisting of intermixed myofibroblasts and connective tissues. Treatment with prednisolone induced a complete recovery from OP without relapses. Our review of previous reports about RA-associated OP (RA-OP) suggested that the high titer of RF and increased disease activity of RA indicate a great risk of developing OP. This condition may represent a lung’s reaction in the RA-associated inflammatory and/or immune process. We should be aware of RA-OP cases in which pulmonary manifestations precede articular symptoms. In these cases, respiratory manifestations are the main evidence of RA activity. In most cases of steroid-resistant RA-OP, the use of immunosuppressants was effective. Since OP may progress to fibrotic lung disease during the course of RA, we may consider performing a second lung biopsy for steroid-resistant patients, even if they have once been diagnosed as OP.     

Pressure wave reflections, central blood pressure, and aortic stiffness in patients with Adamantiades-Behcet's disease: a cross-sectional case-control study underlining the role of chronic corticosteroid treatment

BACKGROUND: Adamantiades-Behcet's disease (ABD) is a multisystemic inflammatory/autoimmune disease involving both microcirculation and macrocirculation. Aortic stiffness index and aortic augmentation index (AI) are indices for the estimation of arterial stiffness and pressure wave reflections, respectively. The effect of anti-inflammatory and immunosuppressive drugs used in ABD on these indices is unknown. METHODS: In this cross-sectional study we examined 74 subjects with ABD (aged 40.1 +/- 12.5 years, 24 men) and 24 control subjects by using the noninvasive technique of radial artery applanation tonometry and pulse wave analysis for assessment of aortic AI by application of transfer functions. Echocardiography was used for assessment of aortic stiffness index. Classic cardiovascular (CV) risk factors, left ventricular and endothelial function of the brachial artery, as well as intima-media thickness of carotid artery, were also assessed. RESULTS: Corticosteroids were the only drug having a negative and independent effect on aortic AI, but not on aortic stiffness. Patients taking corticosteroids had lower aortic AI and central systolic blood pressure (BP), but not aortic stiffness and peripheral systolic BP, when compared to those without corticosteroids (21+/-14% v 12+/-14%, P < .050). Medication, traditional CV risk factors, and functional or structural CV parameters were all comparable among the two groups. The AI was similar between the control group and patients with ABD taking corticosteroids. CONCLUSIONS: The AI, but not aortic stiffness, is lower in patients with ABD taking corticosteroids compared to patients not taking corticosteroids and similar to the control group. These results imply a role of inflammation or immunomodulatory mechanisms in the regulation of pressure wave reflections.