Change In Vessel Volume Research Articles

Assessing jugular venous compliance with optical hemodynamic imaging by modulating intrathoracic pressure.

The internal jugular veins (IJV) are critical cerebral venous drainage pathways that are affected by right heart function. Cardiovascular disease and microgravity can alter central venous pressure (CVP) and venous return, which may contribute to increased intracranial pressure and decreased cardiac output. Assessing jugular venous compliance may provide insight into cerebral drainage and right heart function, but monitoring changes in vessel volume is challenging. We investigated the feasibility of quantifying jugular venous compliance from jugular venous attenuation (JVA), a noncontact optical measurement of blood volume, along with CVP from antecubital vein cannulation. CVP was progressively increased through a guided graded Valsalva maneuver, increasing mouth pressure by 2mmHg every 2s until a maximum expiratory pressure of 20mmHg. JVA was extracted from a 1-cm segment between the clavicle and midneck. The contralateral IJV cross-sectional area (CSA) was measured with ultrasound to validate changes in the vessel size. Compliance was calculated using both JVA and CSA between four-beat averages over the duration of the maneuver. JVA and CSA were strongly correlated (median and interquartile range) over the Valsalva maneuver across participants (r = 0.986, [0.983, 0.987]). CVP more than doubled on average between baseline and peak strain (10.7 ± 4.4 vs. 25.8 ± 5.4 cmH2O; p < 0.01). JVA and CSA increased nonlinearly with CVP, and both JVA- and CSA-derived compliance decreased progressively from baseline to peak strain (49% and 56% median reduction, respectively), with no significant difference in compliance reduction between the two measures (Z = - 1.24, p = 0.21). Pressure-volume curves showed a logarithmic relationship in both CSA and JVA. Optical jugular vein assessment may provide new ways to assess jugular distention and cardiac function.

Monolithic InGaN/GaN photonic chips for heart pulse monitoring.

Photo-plethysmography (PPG) making use of a monochromic light source and a photoelectric sensor is a non-invasive detection method to record blood volume changes in vessels and can be used to extract cardiac-related heart pulse information. Here, we demonstrated the fabrication of a monolithic photonic chip by integrating light-emitting diodes (LEDs) with photodetectors (PDs) on the same GaN-on-sapphire wafer containing InGaN/GaN multi-quantum wells (MQWs). The MQWs simultaneously act as light emitters in the LEDs and detectors in the PDs, and their mechanism has been studied. The fabricated chip operating in reflection mode is flip-chip bonded on a flexible polydimethylsiloxane (PDMS) strip, enabling the sapphire surface in close contact with the skin. The optical and electrical properties of the LED and PD have been thoroughly characterized, confirming that the PDs using identical MQWs can detect the reflected light from the LEDs. By attaching the chip to the wrist, PPG heart pulse signals from the arterial blood flow can be obtained, thereby verifying the feasibility of the proposed monolithic chip.

Development of bioimpedance sensing device for wearable monitoring of the aortic blood pressure curve

Abstract Wearable devices that monitor our vital signs have been gaining more importance with each year. Non-invasive, continuous, accurate and precise blood pressure assessment method integrated in a wearable is a multidisciplinary challenge. This work presents an electrical bioimpedance (EBI) unit for multi-frequency measurements on pulsating artery for central aortic pressure (CAP) estimation. The developed device provides low complexity in the electronics design with a frequency range between 1 kHz and 200 kHz. It is able to register the impedance of blood vessel volume change simultaneously at different locations. Experiments were carried out in vivo by using the four-electrode configuration on human thorax, axillary artery and radial artery. Preliminary results show the applicability of the proposed impedance spectroscopy system to measure blood vessel volume changes. The impedance data can be later interpreted into the aortic blood pressure wave by using a generalized transfer function. In addition, experimental test-phantom and electrode design are introduced for testing purposes of the impedance system.

Assessment of a noninvasive optical photoplethysmography imaging device with dynamic tissue phantom models.

Noncontact photoplethysmography (PPG) has been studied as a method to provide low-cost, noninvasive, two-dimensional blood oxygenation measurements and medical imaging for a variety of near-surface pathologies. To evaluate this technology in a laboratory setting, dynamic tissue phantoms were developed with tunable parameters that mimic physiologic properties of the skin, including blood vessel volume change, pulse wave frequency, and tissue scattering and absorption. Tissue phantoms were generated using an elastic tubing to represent a blood vessel where the luminal volume could be modulated with a pulsatile fluid flow. The blood was mimicked with a scattering and absorbing motility standard, and the tissue with a gelatin-lipid emulsion hydrogel. A noncontact PPG imaging system was then evaluated using the phantoms. Noncontact PPG imaging accurately identified pulse frequency, and PPG signals from these phantoms suggest that the phantoms can be used to evaluate noncontact PPG imaging systems. Such information may be valuable to the development of future PPG imaging systems.

Effects of Topical Icing on Inflammation, Angiogenesis, Revascularization, and Myofiber Regeneration in Skeletal Muscle Following Contusion Injury.

Contusion injuries in skeletal muscle commonly occur in contact sport and vehicular and industrial workplace accidents. Icing has traditionally been used to treat such injuries under the premise that it alleviates pain, reduces tissue metabolism, and modifies vascular responses to decrease swelling. Previous research has examined the effects of icing on inflammation and microcirculatory dynamics following muscle injury. However, whether icing influences angiogenesis, collateral vessel growth, or myofiber regeneration remains unknown. We compared the effects of icing vs. a sham treatment on the presence of neutrophils and macrophages; expression of CD34, von Willebrands factor (vWF), vascular endothelial growth factor (VEGF), and nestin; vessel volume; capillary density; and myofiber regeneration in skeletal after muscle contusion injury in rats. Muscle tissue was collected 1, 3, 7, and 28 d after injury. Compared with uninjured rats, muscles in rats that sustained the contusion injury exhibited major necrosis, inflammation, and increased expression of CD34, vWF, VEGF, and nestin. Compared with the sham treatment, icing attenuated and/or delayed neutrophil and macrophage infiltration; the expression of vWF, VEGF, and nestin; and the change in vessel volume within muscle in the first 7 d after injury (P < 0.05). By contrast, icing did not influence capillary density in muscle 28 d after injury (P = 0.59). The percentage of immature myofibers relative to the total number of fibers was greater in the icing group than in the sham group 28 d after injury (P = 0.026), but myofiber cross-sectional area did not differ between groups after 7 d (P = 0.35) and 28 d (P = 0.30). In conclusion, although icing disrupted inflammation and some aspects of angiogenesis/revascularization, these effects did not result in substantial differences in capillary density or muscle growth.

Effect of Reverse Vessel Remodeling on Regression of Coronary Atherosclerosis in Patients Treated With Aggressive Lipid- and Blood Pressure-Lowering Therapy - Insight From MILLION Study.

The MILLION study, a prospective randomized multicenter study, revealed that lipid and blood pressure (BP)-lowering therapy resulted in regression of coronary plaque as determined by intravascular ultrasound (IVUS). In the present study we performed additional analysis to investigate the associated factors with regression of coronary plaque.Methods and Results:We investigated serial 3D IVUS images from 68 patients in the MILLION study. Standard IVUS parameters were assessed at both baseline and follow-up (18-24 months). Volumetric data were standardized by length as normalized volume. In patients with plaque regression (n=52), plaque volumenormalizedsignificantly decreased from 64.8 to 55.8 mm3(P<0.0001) and vessel volumenormalizedsignificantly decreased from 135.0 to 127.5 mm3(P=0.0008). There was no difference in lumen volumenormalizedfrom 70.1 to 71.8 mm3(P=0.27). There were no correlations between % changes in vessel volume and cholesterol or BP. On the other hand, negative correlations between % change in vessel volume and vessel volumenormalizedat baseline (r=-0.352, P=0.009) or plaque volumenormalizedat baseline (r=-0.336, P=0.01) were observed. The current data demonstrated that in patients with plaque regression treated by aggressive lipid and BP-lowering therapy, the plaque regression was derived from reverse vessel remodeling determined by vessel volume and plaque burden at baseline irrespective of decreases in lipids and BP.

Accurate Measurement of Cross-Sectional Area of Femoral Artery on MRI Sequences of Transcontinental Ultramarathon Runners Using Optimal Parameters Selection

In clinics an accurate vessel segmentation method is important to quantize the vessel volume change with respect to time for artery elasticity measurement. This study proposes a modified version on 3D-expanded dynamic programming to find an optimal surface in a 3D matrix. The aim of this study is to discover the robustness against noises in measuring the cross-sectional area of the femoral artery on MRI datasets of ultra-endurance runners as accurately as possible. To do this, we use phantom images with different added noises and different image contrasts to find out the optimal parameters using grid search. The contrast between the vessel lumen and its background in phantom study is changed to simulate the real MRI dataset. We also add a plaque in phantom images to test the accuracy of the proposed algorithm in dealing pathologic cases. The phantom studies and grid search on selecting optimal parameters can offer an alternative way on parameter selection. In application to MRI, the accuracy is performed via comparisons between the manual tracings of experts and automated results. The mean relative error is 2.1%±2.1% on testing 11 MRI datasets (total 550 images). The phantom studies and grid search on selecting optimal parameters can offer an alternative way on parameter selection.

Six-month intravascular ultrasound analysis of the DESolve FIM Trial with a novel PLLA-based fully biodegradable drug-eluting Scaffold

Background: The DESolve Bioresorbable Coronary Scaffold is a novel drug-eluting device combining a PLLA-based scaffold coated with a bioresorbable polylactide-based polymer and the drug Myolimus. Myolimus, a macrocyclic lactone mTOR inhibitor, has demonstrated potent anti-proliferative properties in two First-in-Man (FIM) trials using Elixir's metallic coronary stents. The drug dose is 3 mcg per mm of scaffold length. We aimed to present the IVUS results of the first-in-man evaluation of this novel scaffold. Methods: The DESolve FIM trial enrolled 15 patients, treated with a single 3.0x14 mm DESolve at 3 centers. IVUS was performed at the end of the procedure and repeated at six-month invasive follow-up. Complete and adequate IVUS images at baseline and follow-up were obtained for 11 cases. Serial changes in vessel volume, scaffold area and the degree of NIH formation were assessed. All analyses were performed by an independent core laboratory. Results: From baseline to 6 months, IVUS showed a small increase in scaffold mean area (from 5.35±0.78mm2 to 5.61±0.81mm2). Additionally, there was no significant change in vessel volume (from 148.0±37.0 mm3 to 150.03±35.38 mm3) or area, demonstrating the absence of constrictive or expansive remodelling. There was very low neointimal volume (5.6±2.8 mm3) and % scaffold obstruction (7.18±3.37%) and no cases of incomplete strut apposition. Also no scaffold discontinuity (e.g.: fracture) was observed in this sample. Conclusions: The DESolve scaffold demonstrated a unique property of expansion and no chronic recoil from baseline to follow-up. Results at 6 months showed effective neointimal suppression and no late strut malapposition thus suggesting a very efficacious and novel bioresorbable scaffold.

Gravity, the hydrostatic indifference concept and the cardiovascular system

Gravity, like any acceleration, causes a hydrostatic pressure gradient in fluid-filled bodily compartments. At a force of 1G, this pressure gradient amounts to 10 kPa/m. Postural changes alter the distribution of hydrostatic pressure patterns according to the body's alignment to the acceleration field. At a certain location--referred to as hydrostatically indifferent--within any given fluid compartment, pressure remains constant during a given change of position relative to the acceleration force acting upon the body. At this specific location, there is probably little change in vessel volume, wall tension, and the balance of Starling forces after a positional manoeuvre. In terms of cardiac function, this is important because arterial and venous hydrostatic indifference locations determine postural cardiac preload and afterload changes. Baroreceptors pick up pressure signals that depend on their respective distance to hydrostatic indifference locations with any change of body position. Vascular shape, filling volume, and compliance, as well as temperature, nervous and endocrine factors, drugs, and time all influence hydrostatic indifference locations. This paper reviews the physiology of pressure gradients in the cardiovascular system that are operational in a gravitational/acceleration field, offers a broadened hydrostatic indifference concept, and discusses implications that are relevant in physiological and clinical terms.

Abstract 2314: Altered Metabolism of Asymetric Dimethylarginine (ADMA) is Associated with Endothelial Dysfunction and Negative Arterial Remodelling After Heart Transplantation

Cardiac allograft vasculopathy (TAV) is a diffuse and progressive form of coronary artery disease occurring after heart transplantation (HT) characterized by endothelial dysfunction (ED) and negative arterial remodeling. However, TAV risk factors are not well understood. We hypothesized that asymmetric dimethylarginine (ADMA), a circulating inhibitor of nitric oxide synthase, mediates HT related ED and remodeling. Methods and Results Forty eight consecutive cardiac transplant recipients underwent baseline angiography within 8 weeks of cardiac transplantation and at 1 year after transplantation. Intravascular ultrasound indices were measured at baseline and 1 year in all and coronary response to infused acetylcholine and glyceryl trinitrate at 1 year as a measure of ED in 31 subjects. ADMA and its circulating metabolite symmetric DMA (SDMA) were measured at 8 weeks and 1 year by LC-mass spectroscopy. Rejection was diagnosed histologically in endomyocardial biopsies and subjects were subdivided into those with without treated rejection in the first year after HT. Responses to Ach were significantly impaired in patients with a history of treated rejection in the first year after transplant versus those without rejection (mean % change vessel diameter ± SD; −19.4 ± 12.7 versus −8.4 ± 10.2, p = 0.026). There was no difference in response to glyceryl trinitrate in those with and without rejection. Plasma ADMA levels decreased significantly after HT (0.55 ±0.12 versus 0.48 ± 0.09 micromol/l, p &lt;0.001). Using stepwise multivariate regression in a model including age, gender, lipid levels, glucose and blood pressure, plasma ADMA was an independent correlate of Ach coronary artery response 1 year after transplant (p = 0.004, R2 = 46%). Other predictors were female gender and rejection. The ADMA/SDMA ratio (a marker of ADMA breakdown) was correlated inversely with change in vessel volume and change in lumen volume as measured by IVUS between baseline and 1 year (r = −0.036, p = 0.04). Conclusion Levels of ADMA correlated with impaired endothelial function as did episodes of treated rejection. The ADMA/SDMA ratio, a marker of ADMA breakdown, correlated with negative arterial remodeling. Abnormalities in ADMA metabolism may contribute to the pathogenesis of CAV.

Acute Rejection and Cardiac Allograft Vascular Disease Is Reduced by Suppression of Subclinical Cytomegalovirus Infection

Anticytomegalovirus (CMV) prophylaxis prevents the acute disease but its impact on subclinical infection and allograft outcome is unknown. We sought to determine whether CMV prophylaxis administered for three months after heart transplant would improve patient outcomes. This prospective cohort study of 66 heart transplant recipients compared aggressive CMV prophylaxis (n = 21, CMV hyperimmune globulin [CMVIG] plus four weeks of intravenous ganciclovir followed by two months of valganciclovir); with standard prophylaxis (n = 45, intravenous ganciclovir for four weeks). Prophylaxis was based on pretransplant donor (D) and recipient (R) CMV serology: R-/D+ received aggressive prophylaxis; R+ received standard prophylaxis. Outcome measures were: CMV infection assessed by DNA-polymerase chain reaction on peripheral blood polymorphonuclear leukocytes, acute rejection, and cardiac allograft vascular disease (CAV) assessed by intravascular ultrasound. All patients completed one year of follow-up. RESULTS.: CMV infection was subclinical in all but four patients (two in each group). Aggressively treated patients had a lower incidence of CMV infection (73 +/- 10% vs. 94 +/- 4%; P = 0.038), and an independent reduced relative risk for acute rejection graded > or =3A (relative risk [95% CI] = 0.55 [0.26-0.96]; P = 0.03), as compared with the standard prophylaxis group. Aggressively prophylaxed patients also showed a slower progression of CAV, in terms of coronary artery lumen loss (lumen volume change=-21 +/- 13% vs. -10+/-14%; P = 0.05); and vessel shrinkage (vessel volume change = -15 +/- 11% vs. -3 +/- 18%; P = 0.03). Prolonged (val)ganciclovir plus CMVIG reduces viral levels, acute rejection, and allograft vascular disease, suggesting a role for chronic subclinical infection in the pathophysiology of the most common diseases affecting heart transplant recipients.

NONINVASIVE DETERMINATION OF ARTERIAL PRESSURE-DEPENDENT COMPLIANCE IN YOUNG SUBJECTS USING AN ARTERIAL TONOMETER

The objective of this study is to determine the pressure-dependent compliance of human radial artery in young subjects. The arterial blood pressure and the change in vessel volume of the radial artery in ten normotensive volunteers were simultaneously measured with an arterial tonometer. The arterial global compliance was calculated as the division of change in vessel volume by the difference between the systolic and the diastolic blood pressures. The arterial global compliance measured from the ten young volunteers was found to be 4.645 ± 2.739 uL/mmHg. When the arterial pressure-volume relation was assumed to be of natural logarithm, a correlation coefficient of 0.996 was yielded by curve-fit methods. Similarly, when the arterial compliance-pressure relation was fit in a natural logarithmic form, a correlation coefficient of 0.998 was obtained. In conclusion, the arterial vessel volume varies with the arterial blood pressure logarithmicly and positively, whereas a logarithmic and negative relation between the arterial global compliance and arterial blood pressure is present in human radial arteries. Thus, it is for all time necessary to take the pressure level into account if we want to compare compliance values obtained from distinct physiological situations.

Optimization of dose prescription protocol and its impact on delivered dose and vascular response after β-radiation for in-stent restenosis. A randomized trial with serial volumetric intravascular ultrasound and dose volume histograms

The incidence of restenosis within stented segment after intravascular brachytherapy with recommended dose prescription protocols is up to 25%. Therefore, we designed a randomized trial comparing recommended dose prescription protocol with dosing adjusted for the source-to-target distance. Fifty-one in-stent restenosis (ISR) lesions in 48 patients underwent centered source beta-irradiation with serial intravascular ultrasound. Patients randomly received 20 Gy at 1 mm either beyond lumen surface [n=25, standard group (S)] or external elastic membrane [n=26, dosing-adjusted (DA) group]. Minimum dose absorbed by 90% of adventitia (DV(90%Adv)) was calculated. DV(90%Adv) was higher for the DA group than for the S group (21.63+/-5.67 vs. 12.05+/-4.88 Gy, P<.001). After 8.9+/-4.5 months there was complete lumen preservation in DA vs. lumen decrease subsequent to neointimal hyperplasia (NIH) in S group (0.10+/-1.20 vs. -0.61+/-1.29 mm3/mm, P<.05). Vessel volume increased significantly in the DA group and was unchanged in S group (+1.73, P=.002 vs. 0.14 mm3/mm, P=NS). DV(90%Adv) correlated inversely with NIH volume and positively with vessel volume change (r=-.405, P=.007 and r=.363, P=.017, respectively). For beta-irradiation of ISR, dosing adjusted for the source-to-target distance leads to significant increase in target delivered doses, which is associated with complete NIH inhibition and induction of positive vessel remodeling.

DEVELOPMENT OF AN ARTERIAL APPLANATION TONOMETER FOR DETECTING ARTERIAL BLOOD PRESSURE AND VOLUME

Traditional arterial tonometry permits noninvasive and continuous recording of the arterial pressure waveform, by applanating a superficial artery supported by a bone. In the paper, we present an arterial tonometer to simultaneously register the blood pressure waveform and the arterial time-varying volume. The tonometer consisted mainly of a chamber filled with a conductive fluid, a flexible diphragm in touch with an artery, and a pressure sensor used to detect the underlying arterial pressure. In addition, four electrodes were in parallel diposed in the chamber, two of them were triggered with a constant-current source, and the voltage difference between the other two inner electrodes was assocated with the amount of change in the arterial volume. The pressure calibration curve performed with a mercury sphygmomanometer showed a fairly linear relationship (r = 0.998) between the tonometer's chamber pressure and the voltage output of the pressure-sensing circuit. The volume calibration was carried out with vessel-like cylinders of various diameters and a linear relationship (r = 0.884) of the change in vessel volume to the voltage output of the volume-sensing circuit was obtained. Clinical testing results revealed that the noninvasive blood pressure measurement with the tonometer was appreciably consistent with the invasive measurement with the catheter-tipped pressure transducer. In summary, the arterial applanation tonometer developed may be used to reliably determine the full arterial blood pressure waveform and the change in the arterial volume, and to make the wall compliance assessment of a superficial artery possible.

Volumetric remodeling of the proximal left coronary artery: Early versus late after heart transplantation

OBJECTIVESThe aim of this study was to characterize progression of cardiac allograft vasculopathy (CAV) with special respect to coronary artery geometry.BACKGROUNDAs previously shown by intravascular ultrasound (IVUS), CAV is characterized by a multifocal intimal hyperplasia. Little is known, however, about vascular remodeling processes influencing vessel geometry and luminal narrowing.METHODSIn 30 heart transplant recipients serial IVUS studies were performed at baseline (BL) and after a mean follow-up period of 12.5 ± 2.5 months. Changes in plaque, lumen and vessel volume were assessed in the proximal left anterior descending artery. Pattern of remodeling was analyzed in patients “early” (n = 15, BL study 1.4 ± 0.7 months after heart transplantation [HTX]) compared with “late” after HTX (n = 15, BL 46.1 ± 29.1 months).RESULTSPlaque volume was found to increase by a mean of 23.8 ± 25.9 mm3, not significantly different within and beyond the 1st year after HTX. Significant differences, however, were observed in changes in vessel volume with a mean decrease of −52.8 ± 70.9 mm3in the early group, whereas late follow-up group presented with an enlargement of 32.3 ± 46.0 mm3. Based on these changes, lumen volume decreased by −73.2 ± 69.8 mm3early, in contrast to a slight increase of 5.2 ± 32.6 mm3in the late group.CONCLUSIONSProgression of CAV is a complex process, modified by changes in the vascular geometry. Especially within the 1st year after HTX, luminal loss is influenced not only by an increase in plaque area but by a decrease in total vessel volume as well.

The contribution of vessel volume change and blood resistivity change to the electrical impedance pulse.

An impedance pulse, recorded noninvasively, has contributions due to both the change in blood volume of the arteries and to the change in the blood resistivity. Other researchers have tried to quantify the relative contributions and have either underestimated or overestimated the contributions since they did not simulate the physiological conditions. We have used an in vitro flow circulation system to more closely simulate the physiological conditions and quantify the two contributions. We find that the blood resistivity change contribution is strong enough (21.5 percent of the arterial volume change contribution) to change the morphology of the impedance pulse. There is, however, a phase difference between the two contributions. As a result of this, the blood resistivity change contribution to the height of the impedance pulse will be less than 5.5 percent.