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Pascal Verdonck

Publications and source records attributed to Pascal Verdonck.

At least 19 recordsLinked to original sources
PubMed2006

Cardiovascular haemodynamics and ventriculo-arterial coupling in an acute pig model of coronary ischaemia-reperfusion.

Although reperfusion after coronary occlusion is mandatory for myocardial salvage, reperfusion may trigger a cascade of harmful events (reperfusion injury) adding to myocardial injury. We investigated effects of reperfusion on left ventricular (LV) haemodynamics and ventriculo-arterial (VA) coupling in pigs following acute myocardial ischaemia induced by coronary artery occlusion. Experiments were performed in six animals, with measurements of cardiac and arterial function at baseline, after 60 min of ischaemia (T60) and after 2 (T180) and 4 h of reperfusion (T300). Ventriculo-arterial coupling was assessed using the ventriculo-arterial elastance ratio of paper, as well as using a 'stiffness coupling' and 'temporal coupling' index. Reperfusion following ischaemia (T180 versus T60) induced a progressive decline in cardiovascular function, evidenced by a decrease in mean arterial blood pressure, cardiac output and ejection fraction which was not restored at T300. Although reperfusion also induced an increase in slope of the end-systolic pressure-volume relationship (ESPVR), the ESPVR curve shifted to the right, associated with a depression of contractile function. Histology demonstrated irreversible myocardial damage at T300. The ventriculo-arterial elastance ratio and the 'stiffness coupling' index were unaffected throughout the protocol, but the 'temporal coupling' parameter indicated a relative shift between heart period and the time constant of the arterial system. It is unlikely that these alterations are attributable to ischaemic injury alone. The combination of both the stiffness and temporal coupling index may provide more information when studying ventriculo-arterial coupling than the more commonly used ventricular end-systolic stiffness/effection arterial elastance (E(es)/E(a)) ratio.

Animals↗
PubMed2006

Comparison of the hemodynamics in 6mm and 4-7 mm hemodialysis grafts by means of CFD.

The aim of our study is to investigate with computational fluid dynamics (CFD) whether different arterial anastomotic geometries result in a different hemodynamics at the arterial (AA) and venous anastomosis (VA) of hemodialysis vascular access grafts. We have studied a 6mm graft (CD) and a 4-7 mm graft (TG). A validated three-dimensional CFD model is developed to simulate flow in the two graft types. Only the arterial anastomosis (AA) geometry differs. The boundary conditions applied are a periodic velocity signal at the arterial inlet and a periodic pressure wave at the venous outlet. Flow rate is set to 1,000 ml/min. The time dependent Navier-Stokes equations are solved. Wall shear stress (WSS), wall shear stress gradient (WSSG) and pressure gradient (PG) are calculated. Anastomotic flow is asymmetric although the anastomosis geometry is symmetric. The hemodynamic parameters, WSS, WSSG and PG, values at the suture line of the arterial anastomosis of the TG are at least twice as much as in the CD. Comparing the parameters at the two AA indicate that little flow rate increase introduces the risk of hemolysis in the TG whereas the CD is completely free of hemolysis. The hemodynamic parameter values at the venous anastomosis of the CD are 24 till 35% higher compared to the values of the TG. WSS values (> 3 Pa) in the VA are in the critical range for stenosis development in both graft geometries. The zones where the parameters reach extreme values correspond to the locations where intimal hyperplasia formation is reported in literature. In all anastomoses, the hemodynamic parameter levels are in the range where leucocytes and platelets get activated. Our simulations confirm clinical results where TG did not show a better outcome when compared to the CD.

Anastomosis, Surgical↗
PubMed2006

Numerical assessment of the impact of a flow wire on its velocity measurements.

Blood flow velocities can be measured using a Doppler flow wire. This numerical study evaluates the impact of a 0.014" flow wire on the measured frequencies in a straight artery with diameters of 3 mm and 4 mm, under steady and pulsatile flow conditions. Simulations were performed with the wires positioned differently in the artery (perfectly centred and at an offset of 0.5 mm from the wall) and with different types of wire (tilted and straight). Measurements were taken at range gates from 4 mm to 10 mm. During simulations using a 3-mm vessel under pulsatile flow conditions, the relative error between the measured and reference maximum frequency (occurring in absence of the wire) decreased from 17.7% to 11.6% (with a mean value of 14.9%). During simulations using an off-centre 1.5 degree tilted wire, the mean error was approximately 5%. Therefore, our study suggests that that a centrally positioned flow wire is unfavourable for measuring flow velocities.

Arteries↗
PubMed2006

Hemodynamics of a pulsatile left ventricular assist device driven by a counterpulsation pump in a mock circulation.

The BCM (CardialCare, Minneapolis, MN, U.S.A.) is a pusher-plate pulsatile left ventricular assist device (LVAD) that is operated by counterpulsation pumps. The purpose of this work was to assess the fluid dynamics associated with operating the BCM in a mock circulation, and also to examine the similarities between hemodynamic parameters produced by this device in vitro and those produced by the left ventricle (LV) in vivo. The BCM was connected to a true size silicon rubber aorta and operated by an intra-aortic balloon pump. We examined the performance of the device at two system pressures (6.5 and 8 kPa); at three heart rates (60, 80, and 100 bpm); and at three pumping frequencies (1:1, 1:2, 1:3). Pressure and flow were measured in the upper descending aorta, and wave intensity analysis was used to calculate the peak intensity and energy of the compression and expansion waves. Pressure and flow waveforms produced by the BCM LVAD in vitro under different loading conditions were similar to those observed in vivo under similar loadings. Pusher-plate-type LVADs can produce compression and expansion waves similar to those generated by healthy LV in vivo.

Aorta↗
PubMed2006

Hydrodynamic evaluation of kangaroo aortic valve matrices for tissue valve engineering.

We evaluated the hydrodynamic performance of kangaroo aortic valve matrices (KMs) (19, 21, and 23 mm), as potential scaffolds in tissue valve engineering using a pulsatile left heart model at low and high cardiac outputs (COs) and heart rates (HRs) of 60 and 90 beats/min. Data were measured in two samples of each type, pooled in two CO levels (2.1 +/- 0.7 and 4.2 +/- 0.6 L/min; mean +/- standard errors on the mean), and analyzed using analysis of variance with CO level, HR, and valve type as fixed factors and compared to similar porcine matrices (PMs). Transvalvular pressure gradient (DeltaP) was a function of HR (P < 0.001) and CO (P < 0.001) but not of valve type (P = 0.39). DeltaP was consistently lower in KMs but not significantly different from PMs. The effective orifice area and performance index of kangaroo matrices was statistically larger for all sizes at both COs and HRs.

Animals↗
PubMed2006

Assessment of the tilting properties of the human mitral valve during three main phases of the heart cycle: an echocardiographic study.

RATIONALE AND OBJECTIVES: In experimental models of the left heart, the mitral valve (MV) is commonly implanted perpendicular to a central axis of the apex/MV. To adapt this to a more correct anatomical model, as well as for further studies of the left ventricle, we created a database of implantation angles of the MV and annulus during three main phases of the heart cycle, based on standard cardiac ultrasound measurements. MATERIALS AND METHODS: Twenty-eight patients were studied with the standard cardiac ultrasound equipment. From the apical echo window, an anteroposterior (AP) plane and a perpendicular commisure-commisure (CC) plane were generated during three critical moments in the heart cycle: systole (S); diastole early filling (E); and diastole late filling (A). In both planes, the angles between the annular plane and each mitral leaflet, as well as the angle between a theoretical longitudinal axis through the apex and center of the MV orifice and the mitral annulus plane, were measured with a custom-made application of Matlab R14. RESULTS: We observed an inclination of the angle mitral annulus/central left ventricle axis, with its lowest point in the direction of the aortic valve (AP plane) of 85 degrees+/-7 degrees in systole (S), 88 degrees+/-8 degrees in early diastole (E), and 88 degrees+/-7 degrees in late diastole (A). In the CC plane, we observed an almost horizontal implantation of 91 degrees+/-5 degrees in systole (S), 91 degrees+/-8 degrees in early diastole (E), and 91 degrees+/-7 degrees in late diastole (A).

Adult↗
PubMed2005

Noninvasive assessment of local pulse pressure: importance of brachial-to-radial pressure amplification.

The advocated SphygmoCor procedure uses a radial-to-aorta transfer function with calibration on brachial instead of radial artery pressure to assess the central pulse pressure. We compared these values with carotid artery pulse pressures obtained from a validated calibration method, assuming mean minus diastolic blood pressure constant throughout the large artery tree. From 44 healthy subjects (21 males; 22 to 68 years) pressure waves were obtained at the radial, brachial, and carotid artery with applanation tonometry. Using the calibration method, radial and carotid artery pressures were assessed from brachial artery waves and pressures. The effect of brachial-to-radial pulse pressure amplification, brachial pulse pressure, mean pressure, age, gender, height, body mass index, and smoking on differences between the 2 methods was assessed. Brachial artery pressure was 118+/-12/72+/-10 mm Hg. SphygmoCor central pulse pressure was 9.7+/-4.6 mm Hg lower (P<0.001) than the carotid artery pulse pressure (33.0+/-6.8 versus 42.7+/-8.9 mm Hg). The difference between the 2 methods strongly depended (P<0.001) on brachial-to-radial artery pulse pressure amplification (5.8+/-5.1 mm Hg; 12+/-11%) and less on brachial artery pulse pressure (P=0.005). After calibration of the radial pressure wave with radial instead of brachial artery pressures, the difference between SphygmoCor central pulse pressure and carotid pulse pressure decreased with 4 mm Hg. The advocated SphygmoCor procedure systematically underestimates the central pulse pressure with brachial-to-radial pulse pressure amplification as important determinant. Therefore, calibration of radial artery pressure waves on brachial artery pressures should be avoided. The underestimation of central aortic pulse pressure caused by the radial-to-aorta transfer function itself is much less than previously reported.

Adult↗
PubMed2005

Hemodynamics and complications encountered with arteriovenous fistulas and grafts as vascular access for hemodialysis: a review.

This review article describes the current state of affairs concerning in vivo, in vitro and in numero studies on the hemodynamics in vascular access for hemodialysis. The use and complications of autogenous and non-autogenous fistulas and catheters and access port devices are explained in the first part. The major hemodynamic complications are stenosis, initiated by intimal hyperplasia development, and thrombosis. The different in literature proposed conceivable causes of intimal hyperplasia development like surgical interventions, compliance mismatch, wall shear stress (WSS) and shear rate, vessel wall thrill and blood pressure are discussed on the basis of in vivo, in vitro and in numero studies.

Arteriovenous Anastomosis↗
PubMed2005

Carotid tonometry versus synthesized aorta pressure waves for the estimation of central systolic blood pressure and augmentation index.

OBJECTIVE: To assess the interchangeability of carotid tonometry and synthesized aorta pressure waveforms for estimating central systolic blood pressure (SBP) and augmentation index (AIx). METHODS: Tonometry waveforms were acquired with a custom built hardware and software platform in 276 subjects (179 men/97 women; aged 45.5 +/- 5.7 years; mean +/- standard deviation) at the radial (P(wf,ra)), brachial (P(wf,ba)), and carotid artery (P(wf,ca)). The P(wf,ba) was calibrated using systolic (SBP(ba)) and diastolic (DBP(ba)) sphygmomanometer pressure. The DBP(ba) and calculated mean (MAP(ba)) brachial pressure were subsequently used for calibration of P(wf,ra) and P(wf,ca). A central pressure waveform (P(wf,sao)) was synthesized from P(wf,ra) using a generalized pressure transfer function (TFF). The AIx and SBP were measured on P(wf,ra), P(wf,ca), and P(wf,sao). RESULTS: The SBP(ra), SBP(ca), and SBP(sao) were 138.5 +/- 16.8, 130.0 +/- 16.2, and 131.1 +/- 16.6 mm Hg, respectively. The SBP(ra) correlated well with the SBP(ca) (r = 0.93) and the SBP(sao) (r = 0.94), as did the SBP(ca) and the SBP(sao) (r = 0.97) with a mean bias of 1.35 +/- 3.90 mm Hg. The AIx derived from P(wf,ra), P(wf,ca), and P(wf,sao) were -20.8% +/- 14.5%, 12.4% +/- 13.9%, and 20.0% +/- 11.7%, respectively. The correlation between radial and carotid, and radial and central AIx was 0.72 and 0.94, respectively. The correlation between AIx derived from P(wf,ca) and P(wf,sao) was 0.75 with a bias of 11.0% +/- 14% (all correlations P < .001). CONCLUSIONS: The use of a generalized TFF in combination with well-calibrated radial pressure curves yields estimates of SBP in good agreement with carotid tonometry. Although AIx derived from a measured radial pressure curve correlates surprisingly closely with AIx measured on a synthesized aortic pressure curve, the correlation with a directly measured AIx on carotid signals is relatively poor.

Adult↗
PubMed2005

Middle molecule removal in low-flux polysulfone dialyzers: impact of flows and surface area on whole-body and dialyzer clearances.

Some studies found that the removal of middle molecules has a long-term effect on mortality and, even more, is enhanced by high-flux dialysis. In order to enhance middle molecule removal in a low-flux dialyzer, the present study aimed at investigating the combined impact of dialyzer flows and membrane surface area. Blood and dialysate flows were varied within the clinical range 300-500 and 500-800 mL/min, respectively, while the ultrafiltration rate was kept constant at 0.1 L/hr. Single-pass tests were performed in vitro in a single Fresenius F6HPS dialyzer (3 tests) and serially (5 tests) and parallel (3 tests) connected dialyzers. The blood substitution fluid consisted of dialysis fluid in which radioactive-labeled vitamin B12 (molecular weight 1355 Da) was dissolved. Dialyzer clearance as well as whole-body clearance was calculated from radioactivity concentrations of samples taken from the inlet and outlet bloodline. Adding a second dialyzer in series or parallel ameliorated the overall dialyzer and whole-body clearance significantly, except for the highest applied blood flows of 500 mL/min. Better solute removal was also obtained with higher dialysate flows, while the use of higher blood flows seemed advantageous only when using a single dialyzer. Analysis of the ultrafiltration profiles in the different configurations illustrated that enhancing the internal filtration rate ameliorates convective transport of middle molecules. Adequate solute removal results from a number of interactions, as there are blood and dialysate flows, membrane surface area, filtration profile and concentration profiles in the blood and dialysate compartment.

Hemodialysis Solutions↗
PubMed2005

Kinetic behavior of urea is different from that of other water-soluble compounds: the case of the guanidino compounds.

BACKGROUND: Although patients with renal failure retain a large variety of solutes, urea is virtually the only currently applied marker for adequacy of dialysis. Only a limited number of other compounds have up until now been investigated regarding their intradialytic kinetics. Scant data suggest that large solutes show a kinetic behavior that is different from urea. The question investigated in this study was whether other small water-soluble solutes, such as some guanidino compounds, show a kinetic behavior comparable or dissimilar to that of urea. METHODS: This study included 7 stable conventional hemodialysis patients without native kidney function undergoing low flux polysulphone dialysis (F8 and F10HPS). Blood samples were collected from the inlet and outlet bloodlines immediately before the dialysis session, after 5, 15, 30, 120 minutes, and immediately after discontinuation of the session. Plasma concentrations of urea, creatinine (CTN), creatine (CT), guanidinosuccinic acid (GSA), guanidinoacetic acid (GAA), guanidine (G), and methylguanidine (MG) were used to calculate corresponding dialyzer clearances. A two-pool kinetic model was fitted to the measured plasma concentration profiles, resulting in the calculation of the perfused volume (V(1)), the total distribution volume (V(tot)), and the intercompartmental clearance (K(12)); solute generation and overall ultrafiltration were determined independently. RESULTS: No significant differences were observed between V(1) and K(12) for urea (6.4 +/- 3.3 L and 822 +/- 345 mL/min, respectively) and for the guanidino compounds. However, with respect to V(tot), GSA was distributed in a smaller volume (30.6 +/- 4.2 L) compared to urea (42.7 +/- 6.0L) (P < 0.001), while CTN, CT, GAA, G, and MG showed significantly higher volumes (54.0 +/- 5.9 L, 98.0 +/- 52.3 L, 123.8 +/- 66.9 L, 89.7 +/- 21.4 L, 102.6 +/- 33.9 L, respectively; P= 0.004, = 0.033, = 0.003, < 0.001, = 0.001, respectively). These differences resulted in divergent effective solute removal: 67% (urea), 58% (CTN), 42% (CT), 76% (GSA), 37% (GAA), 43% (G), and 42% (MG). CONCLUSION: The kinetics of the guanidino compounds under study are different from that of urea; hence, urea kinetics are not representative for the removal of other uremic solutes, even if they are small and water-soluble like urea.

Aged↗
PubMed2005

Dialysate partitioning in the Genius batch hemodialysis system: effect of temperature and solute concentration.

BACKGROUND: The Genius batch system contains a 75-L closed reservoir from which fresh dialysate is extracted at the top, and to which spent dialysate is returned at the bottom. In vivo studies have demonstrated that almost the entire amount of dialysate can be used before contamination of fresh with spent dialysate occurs. The question is raised whether density differences cause this separation, and what the relative contributions of temperature and solute content are. METHODS: As patient substitute, a container filled with dialysate was loaded with various amounts of urea. Temperature differences between spent and fresh dialysate were imposed by not heating the dialysate at the outlet line from the dialyzer (A), heating the outlet to obtain continuously equal temperatures at inlet and outlet (B), or to temperatures as in vivo (C). With a dialysate flow set at 300 mL/min, urea is not expected at the inlet before 250 minutes. RESULTS: With a urea concentration of 33 mg/dL, urea contamination at the dialysate inlet line occurred after 185 +/- 20 (A), 122 +/- 11 (B), and 175 +/- 12 minutes (C) of dialysis, whereas with 67 mg/dL, this happened at 219 +/- 5 (A), 162 +/- 11 (B), and 202 +/- 8 minutes (C). With 100 and 150 mg/dL, urea contamination appeared at 224 +/- 2 (A) and 204 +/- 14 minutes (B), and 227 +/- 5 (A) and 232 +/- 3 minutes (B), respectively. CONCLUSION: Both temperature differences between spent and fresh dialysate and solute content of spent dialysate contribute to dialysate partitioning in the Genius dialysis system.

Dialysis Solutions↗
PubMed2005

Accuracy of 4 different algorithms for the analysis of tomographic radionuclide ventriculography using a physical, dynamic 4-chamber cardiac phantom.

UNLABELLED: Various automatic algorithms are now being developed to calculate left ventricular (LV) and right ventricular (RV) ejection fraction from tomographic radionuclide ventriculography. We tested the performance of 4 of these algorithms in estimating LV and RV volume and ejection fraction using a dynamic 4-chamber cardiac phantom. METHODS: We developed a realistic physical, dynamic 4-chamber cardiac phantom and acquired 25 tomographic radionuclide ventriculography images within a wide range of end-diastolic volumes, end-systolic volumes, and stroke volumes. We assessed the ability of 4 algorithms (QBS, QUBE, 4D-MSPECT, and BP-SPECT) to calculate LV and RV volume and ejection fraction. RESULTS: For the left ventricle, the correlations between reference and estimated volumes (0.93, 0.93, 0.96, and 0.93 for QBS, QUBE, 4D-MSPECT, and BP-SPECT, respectively; all with P < 0.001) and ejection fractions (0.90, 0.93, 0.88, and 0.92, respectively; all with P < 0.001) were good, although all algorithms underestimated the volumes (mean difference [+/-2 SDs] from Bland-Altman analysis: -39.83 +/- 43.12 mL, -33.39 +/- 38.12 mL, -33.29 +/- 40.70 mL, and -16.61 +/- 39.64 mL, respectively). The underestimation by QBS, QUBE, and 4D-MSPECT was greater for higher volumes. QBS, QUBE, and BP-SPECT could also be tested for the right ventricle. Correlations were good for the volumes (0.93, 0.95, and 0.97 for QBS, QUBE, and BP-SPECT, respectively; all with P < 0.001). In terms of absolute volume estimation, the mean differences (+/-2 SDs) from Bland-Altman analysis were -41.28 +/- 43.66 mL, 11.13 +/- 49.26 mL, and -13.11 +/- 28.20 mL, respectively. Calculation of RV ejection fraction correlated well with true values (0.84, 0.92, and 0.94, respectively; all with P < 0.001), although an overestimation was seen for higher ejection fractions. CONCLUSION: Calculation of LV and RV ejection fraction based on tomographic radionuclide ventriculography was accurate for all tested algorithms. All algorithms underestimated LV volume; estimation of RV volume seemed more difficult, with different results for each algorithm. The more irregular shape and inclusion of a relatively hypokinetic RV outflow tract in the right ventricle seemed to cause the greater difficulty with delineation of the right ventricle, compared with the left ventricle.

Algorithms↗
PubMed2004

Conductance catheter-based assessment of arterial input impedance, arterial function, and ventricular-vascular interaction in mice.

Global assessment of both cardiac and arterial function is important for a meaningful interpretation of pathophysiological changes in animal models of cardiovascular disease. We simultaneously acquired left ventricular (LV) and aortic pressure and LV volume (V(LV)) in 17 open-chest anesthetized mice (26.7 +/- 3.2g) during steady-state (BL) and caval vein occlusion (VCO) using a 1.4-Fr dual-pressure conductance catheter and in a subgroup of eight animals during aortic occlusion (AOO). Aortic flow was obtained from numerical differentiation of V(LV). AOO increased input impedance (Z(in)) for the first two harmonics, increased characteristic impedance (0.025 +/- 0.007 to 0.040 +/- 0.011 mmHg x microl(-1) x s, P < 0.05), and shifted the minimum in Z(in) from the third to the sixth harmonic. For all conditions, the Z(in) could be well represented by a four-element windkessel model. The augmentation index increased from 116.7 +/- 7.8% to 145.9 +/- 19.5% (P < 0.01) as well as estimated pulse-wave velocity (3.50 +/- 0.94 to 5.95 +/- 1.62 m/s, P < 0.05) and arterial elastance (E(a), 4.46 +/- 1.62 to 6.02 +/- 1.43 mmHg/microl, P < 0.01). AOO altered the maximal slope (E(max), 3.23 +/- 1.02 to 5.53 +/- 1.53 mmHg/microl, P < 0.05) and intercept (-19.9 +/- 8.6 to 1.62 +/- 13.51 microl, P < 0.01) of the end-systolic pressure-volume relation but not E(a)/E(max) (1.44 +/- 0.43 to 1.21 +/- 0.37, not significant). We conclude that simultaneous acquisition of Z(in) and arterial function parameters in the mouse, based solely on conductance catheter measurements, is feasible. We obtained an anticipated response of Z(in) and arterial function parameters following VCO and AOO, demonstrating the sensitivity of the measuring technique to induced physiological alterations in murine hemodynamics.

Animals↗
PubMed2004

Hemodynamics in a compliant hydraulic in vitro model of straight versus tapered PTFE arteriovenous graft.

BACKGROUND: Hemodialysis patients require a vascular access to deliver sufficient blood flow to the artificial kidney. Of these vascular accesses, 30% are prosthetic (mainly polytetrafluorethylene [PTFE]) graft implants. These grafts are prone to the development of stenosis in the vein due to intimal hyperplasia, subsequently leading to thrombosis and graft failure. AIM: We investigated the hemodynamics in a straight and a tapered PTFE-graft and compare the hydrodynamical behavior of both grafts. MATERIALS AND METHODS: Two different vascular access geometry models were examined: a 6-mm diameter straight graft and a 4- to 7-mm tapered graft. The grafts were sutured to a compliant silicon model of an artery and vein in a loop configuration. Flow rate varied between 500 and 1500 mL/min. Two conditions were tested: 1). control: mean pressure is 100 mm Hg at the arterial inlet; and 2). low resistance condition: pressure is 20 mm Hg at the venous outlet. Pulse pressure is 60 mm Hg at the arterial inlet for both conditions. Pressure and flow velocity are measured continuously, while flow rate is measured volumetrically. RESULTS: The pressure drop at the arterial anastomosis of the tapered graft is three times higher compared to the straight graft model. Intragraft pressure drops are similar in both graft types. Mean pressure and pulse pressure in the graft and vein are decreased in the low resistance condition. Also, the difference between maximum and minimum velocity is smaller in this. CONCLUSIONS: No significant differences are noted between the graft geometries: pressure drop over the graft is almost equal. The major difference is the higher pressure drop at the arterial anastomosis of the tapered graft.

Blood Flow Velocity↗
PubMed2004

Functional analysis of the common carotid artery: relative distension differences over the vessel wall measured in vivo.

OBJECTIVES: Absolute (DeltaD) and relative (DeltaD/D) arterial diameter distension, parameters related to the elasticity of the vessel, can be measured in superficial arteries using ultrasound-based vessel "wall tracking" techniques. Currently available systems (e.g. the Wall Track System; WTS) measure the displacement of the media-adventitia transition (outer wall). We hypothesize that, given volume incompressibility of the vessel wall, DeltaD and DeltaD/D measured at the outer wall, significantly underestimate vessel distension at the lumen-intima interface (inner wall). METHODS: We measured DeltaD and DeltaD/D at both the inner and outer wall of the common carotid artery in 39 subjects (aged 18-83 years) using a new prototype "wall tracking" system based on the Vivid-7 scanner (GE Vingmed Ultrasound, Horten, Norway). In addition, DeltaD and DeltaD/D were also measured using WTS. RESULTS: As anticipated, tracking the inner wall yielded lower diastolic diameters than when tracking the outer wall (Ddia = 5.70 +/- 0.80 and 6.91+/- 0.98 mm, respectively, P < 0.0001). DeltaD (0.54+/- 0.16 versus 0.49 +/- 0.16 mm; P < 0.0001) and DeltaD/D (0.096+/- 0.030 versus 0.071+/- 0.026, P < 0.0001) were indeed larger at the inner than at the outer wall. For WTS, Ddia, DeltaD and DeltaD/D were 7.04 +/- 1.02 mm, 0.45 +/- 0.14 mm and 0.066 +/- 0.022, respectively. CONCLUSIONS: On average, DeltaD and DeltaD/D are 10 and 25% higher on the inner than on the outer wall, respectively. Follow-up studies in larger cohort trials are mandatory to assess whether tracking the inner wall yields arterial function parameters with a higher cardiovascular prognostic potential.

Adolescent↗
PubMed2004

Accuracy of commercially available processing algorithms for planar radionuclide ventriculography using data for a dynamic left ventricular phantom.

BACKGROUND: Automatic and semi-automatic algorithms to calculate ejection fraction (EF) from planar radionuclide ventriculography (PRV) have been used for many years in nuclear medicine. Validation of these algorithms is scarce and often performed on outdated versions of the software. Nevertheless, clinical trials where PRV is being used as the 'gold standard' for EF are numerous. Because of the importance attributed to the EF calculated by these programs, the accuracy of the resulting EF was assessed with a dynamic left ventricular physical phantom. METHODS: A dynamic left ventricular phantom was used to simulate 21 combinations of various ejection fractions (7-66%) and end diastolic volumes (27-290 ml). For each combination, a planar radionuclide ventriculograph was acquired, converted to an interfile format and transferred into processing stations with 10 different contemporaneously available commercial algorithms. The gold standard was the 'real' EF of the phantom, derived from the exact volume of the ventricle in end diastolic and end systolic position. Correlation and Bland-Altman analysis was performed between the real EF and the calculated EF. RESULTS: The correlation for all data was excellent (r=0.98), the mean difference was very acceptable (0.98%). Nevertheless, Bland-Altman analysis showed a significant trend in the difference between real and calculated EF, with a growing underestimation for higher ranges of EF, due to an overestimation of background in larger volumes compared to smaller ones. CONCLUSION: The determination of EF from PRV, calculated with commercially available algorithms, correlates closely to the real EF of a dynamic left ventricular phantom. This phantom can be used in the development and validation of algorithms for PRV studies, in software audits and in quality assurance procedures.

Algorithms↗