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Biomedical subjects

S G Carlier

Publications and source records attributed to S G Carlier.

At least 19 recordsLinked to original sources
PubMed2006

Influence of arterial compliance on presence and extent of ischaemia during stress echocardiography.

OBJECTIVE: To seek an association between total arterial compliance (TAC) and the extent of ischaemia at stress echocardiography. DESIGN: Cohort study. SETTING: Regional cardiac centre. METHODS: 255 consecutive patients (147 men; mean (SD) age 58 (8)) presenting for stress echocardiography for clinical indications were studied. Wall motion score index (WMSI) was calculated and ischaemia was defined by an inducible or worsening wall motion abnormality. Peak WMSI was used to reflect the extent of dysfunction (ischaemia or scar), and DeltaWMSI was indicative of extent of ischaemia. TAC was assessed at rest by simultaneous radial applanation tonometry and pulsed wave Doppler in all patients. RESULTS: Ischaemia was identified by stress echocardiography in 65 patients (25%). TAC was similar in the groups with negative and positive echocardiograms (1.08 (0.41) v 1.17 (0.51) ml/mm Hg, not significant). However, the extent of dysfunction was associated with TAC independently of age, blood pressure, risk factors, and use of a beta blocker. Moreover, the extent of ischaemia was determined by TAC, risk factors, and use of a beta blocker. CONCLUSION: While traditional cardiovascular risk factors are strong predictors of ischaemia on stress echocardiography, TAC is an independent predictor of the extent of ischaemia.

Blood Pressure↗
PubMed2005

Coronary circulation and interventional cardiology.

Cardiovascular disease has long been the leading cause of death in developed countries and it is rapidly becoming the number one killer in developing countries. Sudden heart attacks remain the primary cause of death in the United States: over 1.4 million attacks are suffered every year, more than half of which prove fatal. Interventional Cardiology is aimed to alleviate symptoms of cardiac pains and poor coronary circulation, and reduce the risk of death and nonfatal myocardial infarction. Our understanding of the coronary circulation has improved several folds due to the introduction of advance technologies. Yet, the microcirculatory flow needs future investigation.

Angioplasty, Balloon, Coronary↗
PubMed2005

Ultrafiltration improves aortic compliance in haemodialysis patients.

An elevated pulse pressure leads to an increased pulsatile cardiac load, and results from arterial stiffening. The aim of our study was to test whether a reduction in volume overload by ultrafiltration (UF) during haemodialysis (HD) leads to an improvement of aortic compliance. In 18 patients, aortic compliance was estimated noninvasively before and after HD with UF using a pulse pressure method based on the Windkessel model. This technique has not been applied before in a dialysis population, and combines carotid pulse contour analysis by applanation tonometry with aortic outflow measurements by Doppler echocardiography. The median UF volume was 2450 ml (range 1000-4000 ml). The aortic outflow volume after HD (39 ml; 32-53 ml) was lower (P=0.01) than before (46 ml; 29-60 ml). Carotid pulse pressure after HD (42 mmHg; 25-85 mmHg) was lower (P=0.01) than before (46 mmHg; 35-93 mmHg). Carotid augmentation index after HD (22%; 3-30%) was lower (P=0.001) than before (31%; 7-53%). Carotid-femoral pulse wave velocity was not different after HD (8.7 m/s; 5.6-28.9 m/s vs 7.7 m/s; 4.7-36.8 m/s). Aortic compliance after HD (1.10 ml/mmHg; 0.60-2.43 ml/mmHg) was higher (P=0.02) than before (1.05 ml/mmHg; 0.45-1.69 ml/mmHg). The increase in aortic stiffness in HD patients is partly caused by a reversible reduction of aortic compliance due to volume expansion. Volume withdrawal by HD moves the arterial wall characteristics back to a more favourable position on the nonlinear pressure-volume curve, reflected in a concomitant decrease in arterial pressure and improved aortic compliance.

Adult↗
PubMed2005

Pulse pressure vs. total arterial compliance as a marker of arterial health.

BACKGROUND: Brachial pulse pressure (BPP) is a predictor of outcome in epidemiologic studies, but brachial and aortic pulse pressure (AoPP) may not correspond and both are influenced by multiple parameters including arterial properties and cardiac output. We sought to what extent pulse pressure (PP) measurements reflected direct measurement of arterial properties, assessed as total arterial compliance (TAC). METHODS: We studied 123 patients (76 men; age 55 +/- 11); 31 normal controls, 46 patients with coronary artery disease and 46 patients with hypertension. PP was determined from brachial cuff pressure and TAC was measured by simultaneous radial applanation tonometry and pulsed wave Doppler of the LV outflow. AoPP was calculated using a transfer function from the radial waveform. RESULTS: There was a significant difference between BPP and AoPP (57 +/- 16 vs. 45 +/- 14; P < 0.0001), although TAC correlated with BPP (r = -0.72; P = 0.01) and AoPP (r = -0.66; P = 0.01). In a multiple linear regression, the difference between BPP and AoPP was predicted by cardiac output (CO) (P = 0.002) and gender (P = 0.03). Bland-Altman analysis showed the best correspondence between BPP and AoPP in the middle tertile (CO 4.7 to 5.7 L min(-1)) with less correlation in the low and high tertiles. The same analysis by gender showed a higher difference in women than men (14 +/- 6 vs. 10 +/- 5; P < 0.0001). The difference between BPP and AoPP showed the best correlation in the control group and the worst in the hypertension group. CONCLUSION: BPP correlates with TAC in men with normal cardiac function. However, in women, in patients at the low and high extremes of function, and in patients with preclinical and overt cardiovascular disease, there appears to be incremental value in measuring TAC.

Adult↗
PubMed2003

Sonotherapy, antirestenotic therapeutic ultrasound in coronary arteries: the first clinical experience.

We studied the safety and feasibility of intracoronary sonotherapy (IST) and its effect on the coronary vessel at 6 months. Thirty-seven patients with stable or unstable angina were included (40 lesions). The indication was de novo lesion (n = 26), restenosis (n = 2), in-stent restenosis (n = 11), and a total occlusion of a venous bypass graft. After successful angioplasty, IST was performed using a 5 Fr catheter with three serial ultrasound transducers operating at 1 MHz. IST was successfully performed in 36 lesions (success rate, 90%). IST exposure time per lesion was 718 +/- 127 sec. During hospital stay, one patient died due to a bleeding complication. At 6-month follow-up, one patient experienced acute myocardial infarction, eight patients underwent repeat PTCA. No patient underwent CABG. Late lumen loss was 1.05 +/- 0.70 mm with a restenosis rate of 25%. IVUS analysis revealed a neointima burden of 25% +/- 11%. IST can be applied safely and with high acute procedural success. Sonotherapy-related major adverse events were not observed. Late lumen loss and neointimal growth were similar to conventional PTCA approaches. These results justify the initiation of randomized clinical efficacy studies.

Aged↗
PubMed2002

Flow velocity and predictors of a suboptimal coronary flow velocity reserve after coronary balloon angioplasty.

AIMS: This study was conducted to analyse flow velocity parameters and predictors of a suboptimal coronary flow reserve (<2.5) following balloon angioplasty. METHODS: Two hundred and twenty-five patients underwent sequential intracoronary Doppler as part of the DEBATE I study. Of these, 183, with complete angiography and Doppler at the 6-month follow-up, were included. Univariate and multivariate logistic analysis was performed to identify independent predictors of post-procedural suboptimal coronary flow reserve, defined as coronary flow reserve <2.5. RESULTS: Forty-eight per cent (n=88) of the patients achieved a suboptimal coronary flow reserve. These patients had higher baseline velocities (cm.s(-1)) before balloon angioplasty (18+/-9 vs 14+/-6, P=0.004), after balloon angioplasty (22+/-11 vs 14+/-5, P<0.001) and at follow-up (19+/-9 vs 16+/-6, P=0.011) than the optimal coronary flow reserve group. Although the suboptimal group had lower hyperaemic velocities (cm.s(-1)) after balloon angioplasty than the optimal group (42+/-17 vs 49+/-16, P=0.008), these velocities became similar at follow-up. Increasing age (odds ratio, OR 1.071, P=0.0002), female gender (OR 2.52, P=0.014) and increasing pre-procedural baseline average peak velocities (OR 1.056, P<0.001) were found to be independent predictors of a suboptimal coronary flow reserve following balloon angioplasty. CONCLUSION: A suboptimal coronary flow reserve was associated with (1) a chronically elevated baseline average peak velocity (2) a transient deficit in the hyperaemic average peak velocity (3) the elderly, and female gender.

Angioplasty, Balloon↗
PubMed2002

Morphological and mechanical information of coronary arteries obtained with intravascular elastography; feasibility study in vivo.

AIMS: Plaque composition is a major determinant of coronary related clinical syndromes. In vitro experiments on human coronary and femoral arteries have demonstrated that different plaque types were detectable with intravascular ultrasound elastography. The aim of this study was to investigate the feasibility of applying intravascular elastography during interventional catheterization procedures. METHODS AND RESULTS: Data were acquired in patients (n=12) during PTCA procedures with an EndoSonics InVision echoapparatus equipped with radiofrequency output. The systemic pressure was used to strain the tissue, and the strain was determined using cross-correlation analysis of sequential frames. A likelihood function was determined to obtain the frames with minimal motion of the catheter in the lumen, since motion of the catheter prevents reliable strain estimation. Minimal motion was observed near end-diastole. Reproducible strain estimates were obtained within one pressure cycle and over several pressure cycles. Validation of the results was limited to the information provided by the echogram. Strain in calcified material (0.20%+/-0.07) was lower (P<0.001) than in non-calcified tissue (0.51%+/-0.20). CONCLUSION: In vivo intravascular elastography is feasible. Significantly higher strain values were found in non-calcified plaques than in calcified plaques.

Adult↗
PubMed2002

Value of coronary stenotic flow velocity acceleration in prediction of angiographic restenosis following balloon angioplasty.

INTRODUCTION: Quantitative angiographic assessment after balloon angioplasty is a poor predictor of immediate and long-term outcome. However, the measurement of blood flow velocity during angioplasty has been proved clinically useful. AIMS: To analyse the value of the maximal stenotic flow velocity and the presence of stenotic flow velocity acceleration (aSV) for the long-term outcome after balloon angioplasty. METHODS AND RESULTS: Patients undergoing single lesion angioplasty within the DEBATE trial were included. aSV was defined as acceleration in the stenotic coronary flow velocity >50% baseline velocity assessed at a reference site of the target vessel. After balloon angioplasty diameter stenosis, minimal lumen diameter (MLD) and coronary flow velocity reserve were similar between the aSV (n=54) and non-aSV group (n=125). At follow-up, the aSV group had a higher restenosis rate (52% vs 30%, P=0.006) The presence of aSV was the strongest independent predictor of restenosis (OR 3.08, 95% CI 1.35 to 7.05, P=0.008). The best predictive cut-off value of SV was 101cm.s(-1) (sensitivity of 46%, specificity of 81%, positive predictive value of 85% and a negative predictive value of 58%). CONCLUSION: Following angioplasty, SV appears to be exquisitely sensitive to the changes experienced at the treated area without depending on the status of the microcirculation.

Angioplasty, Balloon↗
PubMed2001

Advancing intravascular ultrasonic palpation toward clinical applications.

This paper describes the first reported attempt to develop a real-time intravascular ultrasonic palpation system. We also report on our first experience in the catherization laboratory with this new elastographic imaging technique. The prototype system was based on commercially available intravascular ultrasound (US) scanner that was equipped with a 20-MHz array catheter. Digital beam-formed radiofrequency (RF) echo data (i.e., 12 bits, 100 Hz) was captured at full frame rate from the scanner and transferred to personal computer (PC) memory using a fast data-acquisition system. Composite palpograms were created by applying a one-dimensional (1-D) echo tracking technique in combination with global motion compensation and multiframe averaging to several pairs of RF echo frames that were obtained in the diastolic phase of the cardiac cycle. The quality of palpograms was assessed by conducting experiments on vessel phantoms and on patients. The results demonstrated that robust and consistent palpograms could be generated in almost real-time using the proposed system. Good correlation was observed between low strain values and regions of calcification as identified from the intravascular US (IVUS) sonograms. Although the clinical results are clearly preliminary, it was concluded that the prototype system performed sufficiently well to warrant further and more in-depth clinical investigation.

Calcium↗
PubMed2001

Value of coronary stenotic flow velocity acceleration on the prediction of long-term improvement in functional status after angioplasty.

BACKGROUND: The coronary flow velocity acceleration at the stenotic site (SVA), defined as a > or = 50% increase in resting stenotic velocity when compared with the reference segment, has been shown to be highly sensitive and specific for the diagnosis of a hemodynamically significant stenosis. In this study, we describe the value of postprocedural SVA for the prediction of a lack of improvement in functional activity at long-term follow-up balloon angioplasty (BA). METHODS: We investigated the improvement in functional activity in patients undergoing single native vessel angioplasty and intracoronary Doppler (before BA, after BA, and again at 6-month follow-up) as part of the Doppler Endpoints Balloon Angioplasty Trial Europe (DEBATE) I trial. Lack of improvement was defined as no change in Duke Activity Status Index (DASI) at 6-month follow-up, whereas SVA was defined as > or = 50% elevation in resting velocity at the treated area compared with the distal measurement. RESULTS: SVA was found more frequently in patients without improvement in DASI (45% vs 31%, P =.03). Similar percent diameter stenosis and coronary flow velocity reserve were observed in patients with and those without improvement in DASI at follow-up. By multivariate regression analysis, the presence of SVA (P = .029; odds ratio, 1.97; 95% confidence interval, 1.07 to 3.63) and an elevated DASI at baseline (P < .001; odds ratio, 1.05; 95% confidence interval, 1.03 to 1.07) were associated with a lack of improvement at follow-up. CONCLUSIONS: The detection of SVA was associated with failure of improvement in functional activity at follow-up after coronary intervention.

Angioplasty, Balloon↗
PubMed2001

Uncomplicated moderate coronary artery dissections after balloon angioplasty: good outcome without stenting.

OBJECTIVE: To study the relation between moderate coronary dissections, coronary flow velocity reserve (CFVR), and long term outcome. METHODS: 523 patients undergoing balloon angioplasty and sequential intracoronary Doppler measurements were examined as part of the DEBATE II trial (Doppler endpoints balloon angioplasty trial Europe). After successful balloon angioplasty, patients were randomised to stenting or no further treatment. Dissections were graded at the core laboratory by two observers and divided into four categories: none, mild (type A-B), moderate (type C), severe (types D to F). Patients with severe dissections (n = 128) or without available reference vessel CFVR (n = 139) were excluded. The remaining 256 patients were divided into two groups according to the presence (group A, n = 45) or absence (group B, n = 211) of moderate dissection. RESULTS: Following balloon angioplasty, there was no difference in CFVR between the two groups. At 12 months follow up, a higher rate of major adverse cardiac events was observed overall in group A than in group B (10 (22%) v 23 (11%), p = 0.041). However, the risk of major adverse events was similar in the subgroups receiving balloon angioplasty (group A, 6 (19%) v group B, 16 (16%), NS). Among group A patients, the adverse events risk was greater in those randomised to stenting (odds ratios 6.603 v 1.197, p = 0.046), whereas there was no difference in risk if the group was analysed according to whether the CFVR was < 2.5 or >/= 2.5 after balloon angioplasty. CONCLUSIONS: Moderate dissections left untreated result in no increased risk of major adverse cardiac events. Additional stenting does not improve the long term outcome.

Aortic Dissection↗
PubMed2001

Current management of primary pulmonary hypertension.

Primary pulmonary hypertension (PPH) is a rare disorder of the lung vasculature characterised by an increase in pulmonary artery pressure. Although the aetiology of this disease remains unknown, knowledge of the pathophysiology of the disease has advanced considerably. Diagnosis of PPH is largely by exclusion. The clinical symptoms associated with PPH are aspecific and similar to those seen in other cardiovascular and pulmonary diseases. Electrocardiography, echocardiography, pulmonary function tests, and a lung perfusion scan are necessary to exclude secondary forms of pulmonary hypertension and also help to confirm the diagnosis of PPH. A definite diagnosis of PPH is established by right-heart catheterisation which gives a precise measure of the blood pressure in the right side of the heart and the pulmonary artery, right ventricular function and cardiac output. Once a diagnosis of PPH is established, treatment involving drug therapy or surgery is commenced on the basis of the New York Heart Association functional class. Conventional treatment consists of lifetime administration of anticoagulants, oxygen, diuretics, and digoxin. Vasodilator therapy with calcium channel antagonists is indicated in patients who are 'vasoreactive' to acute vasodilator challenge as assessed by right-heart catheterisation. Promising results are obtained by continuous intravenous administration of epoprostenol (prostacyclin). Newer therapies for PPH include prostacyclin analogues, endothelin receptor antagonists, nitric oxide, phosphodiesterase-5 inhibitors, elastase inhibitors, and gene therapy. Surgical treatment consists of atrial septostomy, thromboendarterectomy, and lung or heart-lung transplantation.

Humans↗
PubMed2001

Total arterial compliance is a major determinant of peak oxygen uptake.

Total arterial compliance (TAC, defined as dV/dP), is a major component of the arterial system. A decreased TAC increases left ventricular load and has a detrimental effect on coronary perfusion. We sought to assess the influence of TAC on the functional reserve (VO2max). Fourteen patients (mean age 64 +/- 14y) with known or suspected coronary artery disease and eleven controls (34 +/- 5y) underwent supine bicycle exercise echocardiography. Audio Doppler signal output of the echocardiographic machine was digitized with a customized hardware and software interface simultaneously with carotid tonometry and ECG. TAC at rest was calculated by the pulse pressure method (PPM). By step-wise forward multivariate analysis, independent predictors of VO2max were patient versus control status, peak exercise cardiac output and TAC. The described PC-based acquisition system for tonometry and Doppler signals permits the assessment of ventricular function and arterial biomechanics.

Adult↗
PubMed2000

Residual plaque burden, delivered dose, and tissue composition predict 6-month outcome after balloon angioplasty and beta-radiation therapy.

BACKGROUND: Inhomogeneity of dose distribution and anatomic aspects of the atherosclerotic plaque may influence the outcome of irradiated lesions after balloon angioplasty (BA). We evaluated the influence of delivered dose and morphological characteristics of coronary stenoses treated with beta-radiation after BA. METHODS AND RESULTS: Eighteen consecutive patients treated according to the Beta Energy Restenosis Trial 1.5 were included in the study. The site of angioplasty was irradiated with the use of a beta-emitting (90)Sr/(90)Y source. With the side branches used as anatomic landmarks, the irradiated area was identified and volumetric assessment was performed by 3D intracoronary ultrasound imaging after treatment and at 6 months. The type of tissue, the presence of dissection, and the vessel volumes were assessed every 2 mm within the irradiated area. The minimal dose absorbed by 90% of the adventitial volume (D(v90)Adv) was calculated in each 2-mm segment. Diffuse calcified subsegments and those containing side branches were excluded. Two hundred six coronary subsegments were studied. Of those, 55 were defined as soft, 129 as hard, and 22 as normal/intimal thickening. Plaque volume showed less increase in hard segments as compared with soft and normal/intimal thickening segments (P<0.0001). D(v90)Adv was associated with plaque volume at follow-up after a polynomial equation with linear and nonlinear components (r = 0.71; P = 0.0001). The multivariate regression analysis identified the independent predictors of the plaque volume at follow-up: plaque volume after treatment, D(v90)Adv, and type of plaque. CONCLUSIONS: Residual plaque burden, delivered dose, and tiss composition play a fundamental role in the volumetric outcome at 6-month follow-up after beta-radiation therapy and BA.

Angioplasty, Balloon, Coronary↗
PubMed2000

Quantification of plaque volume, shear stress on the endothelium, and mechanical properties of the arterial wall with intravascular ultrasound imaging.

Present intravascular echographic imaging (IVUS) is based on either the mechanically rotated single element catheter or the multi-element phased array catheter principle. In both methods the ultrasonic beam is rotated through 360 degrees and the cross-sectional echo image of plaque and wall structures is visualised. A new development based on intravascular ultrasound is calculation of mechanical properties of the arterial wall. In this so-called elastographic approach, high frequency information obtained at identical positions in the arterial wall is compared under systolic and diastolic pressures. Minute shifts in the echo data indicate local compressibility. It thus becomes possible to indicate areas of high or low strain, which correspond to soft and hard material. Three-dimensional information can be obtained if the position of cross sectional slices is recorded with a pull-back device and slices are united into a 3D image. On the basis of such information it has become possible to view stents in 3D, and with interactive software, to calculate automatically plaque volume. With pull-back information only, the artery is reconstructed as a "straight pipe". Only when the biplane X-ray information is combined with the intravascular pull-back echo information can the true 3D reconstruction of the artery be constructed. Given the true geometric lumen information, it becomes possible, under certain assumptions, to derive the luminal fluid dynamics. From this, shear stress values close to the arterial wall can be calculated. Under the assumption that low values for local shear stress are areas prone to restenosis, predictions of endangered areas can be made.

Arteriosclerosis↗
PubMed2000

Flow estimation using an intravascular imaging catheter.

Coronary flow assessment can be useful for determining the hemodynamic severity of a stenosis and to evaluate the outcome of interventional therapy. We developed a method for measuring the transverse flow through the imaging plane of an intravascular ultrasound (IVUS) catheter. This possibility has raised great clinical interest since it permits simultaneous assessment of vessel geometry and function with the same device. Furthermore, it should give more accurate information than combination devices because lumen diameter and velocity are determined at the same location. Flow velocity is estimated based on decorrelation estimation from sequences of radiofrequency (RF) traces acquired at nearly the same position. Signal gating yields a local estimate of the velocity. Integrating the local velocity over the lumen gives the quantitative flow. This principle has been calibrated and tested through computer modeling, in vitro experiments using a flow phantom and in vivo experiments in a porcine animal model, and validated against a Doppler element containing guide wire (Flowire) in humans. Originally the method was developed and tested for a rotating single element device. Currently the method is being developed for an array system. The great advantage of an array over the single element approach would be that the transducer has no intrinsic motion. This intrinsic motion sets a minimal threshold in the detectable velocity components. Although the principle is the same, the method needs some adaptation through the inherent different beamforming of the transducer. In this paper various aspects of the development of IVUS flow are reviewed.

Animals↗