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Biomedical subjects

J Roelandt

Publications and source records attributed to J Roelandt.

At least 37 records · Page 2Linked to original sources
PubMed1990

The reproducibility of continuous wave Doppler measurements in the assessment of mitral stenosis or mitral prosthetic function: the relative contributions of heart rate, respiration, observer variability and their clinical relevance.

The reproducibility of continuous wave Doppler echocardiographic measurements of transmitral diastolic flow velocity were studied in terms of bias and random error in 40 patients with either mitral stenosis or a Björk-Shiley mitral valve prosthesis. Twenty-seven patients were in sinus rhythm; 13 patients had atrial fibrillation. Intra- and interobserver differences in bias were small for the Doppler parameters studied i.e. early peak velocity (0.6% vs 3.6%), mean diastolic velocity (1.1% vs 8.6%), mean temporal velocity (2.3% vs 14.5%) and pressure half-time (2.7% vs 4.8%). The overall random error of the measurements (in terms of twice the standard deviation) was estimated separately in patients in sinus rhythm and atrial fibrillation: early peak velocity 5.6% and 9.2%, respectively, mean diastolic velocity 9.4% and 22%, mean temporal velocity 8.6% and 19% and pressure half-time 34% and 46%. The relative contributions to the overall random error of observer variation, heart rate dependency and respiratory variation were also studied. Heart rate dependency was demonstrated for both the mean diastolic velocity and the pressure half-time. Respiratory variation was found in the early peak velocity. From the results of this study the number of measurements to reduce the random error of the final average could be determined. Our results indicate that for the measurements in which a respiratory effect is present it is advisable to average the measurements taken over complete respiratory cycles.

Blood Flow Velocity↗
PubMed1990

Clinical perspectives of intravascular ultrasound.

The history of intravascular ultrasound imaging, recent developments in catheter technology, and the initial in vivo experience are reviewed. Additionally, the article also discusses the potential applications of intravascular ultrasound imaging in coronary and peripheral arterial atherosclerosis, hypertension, pulmonary arterial disorders, valvular heart disease, aortic abnormalities, and in congenital heart disorders. Possible future directions are outlined.

Coronary Artery Bypass↗
PubMed1990

The design, construction and clinical evaluation of a small phased array transducer for intraoperative echocardiography.

A small probe for cardiac surgery was developed and clinically tested. The probe is built as a phased array transducer with 64 elements with a centerfrequency of 5 MHz. The transducertip is connected with a handle by a flexible yet steerable shaft. This shaft has a length of 10 cm and can be set in a desired shape. Good quality images were obtained in all patients. The first study suggest many applications for a small probe in intraoperative echocardiography.

Cardiac Surgical Procedures↗
PubMed1989

Echocardiography in diagnosis of aortic dissection.

In a multicentre study the accuracy of echocardiography was measured in 164 consecutive patients with suspected aortic dissection. The diagnosis was subsequently proven (82 patients) on the basis of transthoracic and transoesophageal echocardiography and additional diagnostic procedures, including computed tomography (CT), aortic angiography, and surgery and/or necropsy. The sensitivity and specificity of echocardiography were 99% and 98%, respectively, with positive and negative predictive values of 98% and 99%. For CT sensitivity was 83%, specificity 100%, and positive and negative predictive values 100% and 86%, respectively. For aortography sensitivity and specificity were 88% and 94%, and the positive and negative predictive values 96% and 84%, respectively. Echocardiography, including the transoesophageal route, can provide accurate diagnosis of aortic dissection within 15 min. Diagnostic difficulties occur only in a few type II dissections, when complementary diagnostic procedures, including CT or angiography, may be needed. To clarify branch involvement angiography is required.

Acute Disease↗
PubMed1989

Arterial wall characteristics determined by intravascular ultrasound imaging: an in vitro study.

The feasibility of assessing arterial wall configuration with an intravascular 40 MHz ultrasound imaging device was investigated in an in vitro study of 11 autopsy specimens of human arteries. The system consists of a single element transducer, rotated with a motor mounted on an 8F catheter tip. Cross sections obtained with ultrasound were matched with the corresponding histologic sections. The arterial specimens were histologically classified as of the muscular or elastic type. Muscular arteries interrogated with ultrasound presented with a hypoechoic media, coinciding with the smooth muscle cells. In contrast, the media of an elastic artery densely packed with elastin fibers was as echogenic as the intima and the adventitia. On the basis of the cross-sectional image, it was possible to determine the nature of the atherosclerotic plaque. The location and thickness of the lesion measured from the histologic sections correlated well with the data derived from the corresponding ultrasound images. This study indicates that characterization of the type of artery and detection of arterial wall disease are possible with use of an intravascular ultrasound imaging technique.

Adult↗
PubMed1989

Intravascular ultrasonic imaging: histologic and echographic correlation.

The feasibility of assessing arterial wall characteristics with an intravascular 40 MHz ultrasonic imaging device was determined in vitro. Ten autopsy specimens of human arteries, with and without atherosclerosis, were studied. A close relationship was observed between the histologic section and the corresponding ultrasonic cross-section with regard to the location, maximum plaque thickness and extent of the atherosclerotic lesion along the circumference of the vessel wall. Based on echogenicity of the atherosclerotic lesion, ultrasound could distinguish four basic types of atherosclerotic plaque components: 1. hypoechoic: a reflection of lipid deposits; 2. soft echoes: reflective of fibromuscular tissue; 3. bright echoes: representative of fibrous tissue; 4. bright echoes with shadowing behind the lesion: representative of calcium deposits. It is anticipated that development of such a catheter-tip imaging system combined with recanalisation methods will be of immense benefit for the precise localisation and identification of vessel wall pathology, precise positioning of a recanalisation instrument (laser device, atherectomy catheter) and subsequent use of this recanalisation procedure and for assessing the effect of recanalisation.

Adult↗
PubMed1989

What is the ideal orientation of a mitral disc prosthesis? An in vivo haemodynamic study based on colour flow imaging and continuous wave Doppler.

Doppler colour flow imaging demonstrates normal laminar flow to enter the left ventricle in diastole through the mitral inflow tract located posteriorly in the left ventricle. Laminar flow then passes around the left ventricular apex to the anteriorly located outflow tract. As this is the normal physiologic flow pattern, it would seem appropriate that in the surgical implantation of a mitral tilting disc prosthesis the greater orifice should be directed posteriorly to mimic the normal native valve flow pattern. To determine whether variable positioning of the greater orifice had any significant haemodynamic consequences, intracavitary blood flow patterns were studied in 30 patients with mitral Björk-Shiley prostheses variously orientated in the mitral orifice. The orientation of the greater orifice (OGO) of the prosthesis was determined by fluoroscopy and the pattern of the left ventricular inflow from Doppler colour flow imaging. Twelve patients had their OGO and inflow directed towards the inflow tract (orientation I): nine patients had their OGO and inflow directed anteriorly towards the outflow tract (orientation II) and nine patients had their prosthesis with OGO and inflow in an intermediate position (orientation III). The mean prosthetic diastolic gradient, calculated using continuous wave Doppler, averaged 2.8 mmHg (+/- 0.5 mmHg) for the 25-mm prosthesis in orientation I, but 6.0 mmHg (+/- 0.7 mmHg) for the same size prosthesis in orientation II and 5.8 mmHg (+/- 0.9 mmHg) with a 25-mm prosthesis in orientation III. Similarly, for prostheses of 27 mm and 29-31 mm the lowest mean diastolic gradient was found in orientation I (2.7 mmHg +/- 0.8 and 2.8 mmHg +/- 0.5, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

A comparison of two methods to measure coronary flow reserve in the setting of coronary angioplasty: intracoronary blood flow velocity measurements with a Doppler catheter, and digital subtraction cineangiography.

Intracoronary blood flow velocity measurements with a Doppler balloon catheter and the radiographic assessment of myocardial perfusion with contrast media, before and after the intracoronary administration of papaverine, have previously been used to investigate regional coronary flow reserve. In the present study we applied both techniques in 21 patients to measure coronary flow reserve in the setting of coronary angioplasty. Pre-angioplasty (N = 14) and post-angioplasty (N = 19) measurements of coronary flow reserve were obtained by digital subtraction cineangiography in the myocardial region supplied by the dilated coronary artery, and with the Doppler probe in the proximal part of the dilated vessel. The reactive hyperaemia following the final balloon inflation was recorded with the Doppler balloon catheter still positioned across the stenotic lesion. Coronary stenosis geometry was quantified with the Cardiovascular Angiography Analysis System. When the epicardial stenosis was the only factor causing a reduction in coronary flow reserve, flow reserve measured with both digital subtraction cineangiography and with the Doppler probe correlated well with the cross-sectional area at the site of obstruction, r = 0.88, SEE = 0.36 and r = 0.77, SEE = 0.45 respectively. In contrast, when other factors decreasing coronary flow reserve were present (intimal dissection, left ventricular hypertrophy, previous myocardial infarction, collaterals) measurements obtained with both techniques correlated poorly with cross-sectional area (r = 0.55, SEE = 0.57, and r = 0.59, SEE = 0.50). Flow reserve measurements obtained with digital subtraction cineangiography correlated well with the measurements obtained with the Doppler probe (r = 0.85, SEE = 0.38, and r = 0.87, SEE = 0.34), although the two approaches have methodologically nothing in common and their respective regions of interest (myocardium for the radiographic technique and intracoronary lumen for the Doppler technique) are basically different. Furthermore, the reactive hyperaemia following the final balloon inflation was related to the flow reserve measured with both the angiographic technique (r = 0.85, SEE = 0.34) and the Doppler technique (r = 0.83, SEE = 0.32) using pharmacologically induced coronary vasodilation with intracoronary papaverine. This suggests that the same quantity of coronary flow reserve that can be recruited pharmacologically can be recruited by ischaemia following a transluminal occlusion.

Adult↗
PubMed1989

Exercise Doppler echocardiography in patients with pure mitral stenosis.

Exercise increases heart rate and cardiac output and is helpful in the determination of dynamic mitral gradient in patients with mitral stenosis. However exercise is difficult to perform during cardiac catheterization in a premedicated recumbent patient and is only feasible when the brachial approach is used. Therefore, in the haemodynamic laboratory, exercise has important practical limitations. In order to obtain similar information using a reproducible and non-invasive technique, we tested the feasibility of combined two-dimensional and continuous wave Doppler echocardiography during exercise in a selected number of patients with pure mitral stenosis and in sinus rhythm. Seven patients, ranging from 14 to 48 years (average: 35 +/- 13), underwent baseline two-dimensional and continuous wave Doppler examinations, repeated after 2 minutes of supine bicycle exercise at a workload of 25, 50, 75 watts. The following parameters were derived and averaged: mean velocity of flow across the mitral valve, mean mitral valve gradient, diastolic filling period and heart rate. The increase in mitral valve flow was from 1.5 +/- 0.3 to 2.2 +/- 0.5 m/s (p less than 0.001); the corresponding increase in mean pressure gradient was from 11 +/- 3 to 21 +/- 8 mmHg (p less than 0.001). The decrease in the diastolic filling period was from 424 +/- 170 to 272 +/- 73 msec (p less than 0.005). The increase in heart rate was from 60 +/- 10 to 100 +/- 18 beats/minute (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Coronary blood flow velocity during percutaneous transluminal coronary angioplasty as a guide for assessment of the functional result.

To investigate the clinical usefulness of intracoronary Doppler recordings during percutaneous transluminal coronary angioplasty (PTCA), the changes of intracoronary blood flow velocity during PTCA were assessed in 20 patients with single proximal coronary stenosis, using a Doppler probe end-mounted on the tip of a PTCA catheter. A mean of 4 inflations was performed in each patient. Intracoronary velocities were measured before and after each inflation and during peak reactive hyperemia after each transluminal occlusion. Quantitative analysis of the coronary stenosis was assessed before and after PTCA, and the dilatation resulted in an increase in minimal luminal cross-sectional area from 1.1 +/- 0.8 to 2.7 +/- 1.2 mm2. A gradual and significant improvement in velocities was observed after the first 3 dilatations, but in 15 of the 20 patients the resting and hyperemic velocities were not affected by the fourth dilatation. Coronary flow reserve measured during reactive hyperemia after the last dilatation with the PTCA catheter across the lesion was 1.9. This value of coronary flow reserve is compatible with the residual stenosis measured after PTCA when corrected for the presence of the Doppler balloon catheter (0.68 mm2). This application of the Doppler technique may provide a new method of on-line functional monitoring of the PTCA procedure in individual patients, but does not yet allow an accurate prediction of the change in coronary geometry brought about by PTCA.

Adult↗
PubMed1988

The role of intraoperative two-dimensional echocardiography in the assessment of thoracic aorta pathology.

The role of intraoperative two-dimensional echocardiography is discussed in 15 consecutive patients with thoracic aorta pathology undergoing cardiac surgery. A 5 MHz mechanical scanner was used before and immediately after cardiopulmonary bypass. In 5 patients intraoperative two-dimensional studies revealed crucial morphologic information which, consequently, had a marked influence on their planned surgical procedure. In 3 patients the findings provided additional information whereas in the remaining patients the intraoperative echocardiographic findings confirmed the preoperative diagnosis. Following surgery the adequacy of cardiac repair was assessed and, in one patient, epicardial echocardiography indicated the necessity for reoperation. The application of intraoperative two-dimensional echocardiography leads to a better understanding of the pathology involved and facilitates a more appropriate decision concerning the surgical procedure.

Adolescent↗
PubMed1988

Is the rate of disappearance of echo contrast from the interventricular septum a measure of left anterior descending coronary artery stenosis?

Although myocardial contrast echo has been used recently in human studies, no study is available at the present time which relates contrast echo findings to the degree of coronary artery stenosis. The present study is the first attempt to determine whether a quantitative relationship exists between regional myocardial echo contrast disappearance rate ('washout') and the severity of coronary artery stenosis. Manual injection of sonicated iopamidol (Iopamiro 370) into the left main coronary artery with simultaneous cross-sectional echo registration provided the myocardial echo-contrast images. From the digitized images, an echo contrast time-intensity curve was constructed for the proximal basal interventricular septum (region I) and the mid-distal portion of the interventricular septum (region II). From these curves, T50 was calculated after Fourier transformation and mono-exponential curve fitting. The percentage stenosis area (%A) of the left descending coronary artery (LAD) was calculated from routine coronary arteriograms using a computer-based system. Thirty patients (22 men, 8 women; mean age 58 +/- 10 years) were included in the study. Group I (n = 7) had normal LAD, group II (n = 18) had LAD stenosis of varying degrees. Five patients were not suitable for quantitative evaluation. A curvilinear relation was found between T50 and %A. (T50 = 3.0 x e0.01%A; r = 0.78; P less than 0.05). Patients with asynergy had significantly longer T50 (8.2 +/- 2.5 s) than did patients without asynergy (4.2 +/- 1.5 s) (P less than 0.05). All patients with greater than 75% LAD %A had prolonged T50. T50 might be useful index for studying regional myocardial perfusion during cardiac catheterization.

Adult↗