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Biomedical subjects

B Denef

Publications and source records attributed to B Denef.

At least 19 recordsLinked to original sources
PubMed2000

A 72 year old woman with ALCAPA.

ALCAPA syndrome (anomalous origin of the left coronary artery from the pulmonary artery), which causes the left coronary artery to grow with an anomalous origin from the pulmonary artery, is a rare disease which may result in myocardial infarction, congestive heart failure, and sometimes death during the early infantile period. A 72 year old woman with ALCAPA syndrome is presented. The asymptomatic patient presented with a cardiac murmur which was discovered during a routine check up for a gynaecological intervention. Coronary cineangiography established the diagnosis. Although surgical correction is the usual treatment for such cases, medical treatment was preferred for this patient because she was asymptomatic without clinical signs of heart failure.

Aged↗
PubMed1996

Small-angle X-ray scattering of kappa- and iota-carrageenan in aqueous and in salt solutions.

Aqueous and saline (0.03-0.08 M NaCl) solutions of the Na(+)-salt of kappa- and iota-carrageenan (3-17 mg/ml) have been investigated using small-angle X-ray scattering (SAXS). Investigation of the SAXS curves normalized for concentration allows to detect the transition from the dilute to the semidilute regime. Some of the experimental curves exhibit a clear maximum. In the case of kappa-carrageenan, the position of this maximum is proportional to the cube root of polysaccharide concentration. The fluctuation theory of Borue and Erukhimovich (BE theory), which predicts a maximum in the scattering curves for low ionic strength, gives a good fit for all our experiments. An increase of the polymer concentration or the ionic strength causes the appearance of two subsystems in solution exhibiting a different characteristic screening scale of Coulombic interaction for ideal Gaussian chains (and two different segment lengths). The condition for an increase of the relative contribution of the subsystem with the larger segment length correlates with the one for the disorder-order transition of carrageenan. In the most concentrated (17.1 mg/ml) solution of Na(+)-iota-carrageenan, the increase of NaCl molarity above 0.06 M gives rise to additional scattered intensity at the smallest angles, indicating molecular association.

Carrageenan↗
PubMed1996

Influence of ionic effects on the ordering and association phenomena in dilute and semidilute carrageenan solutions.

A small angle X-ray scattering (SAXS) study was made on Na(+)-kappa- and Na(+)- or Li(+)-iota-carrageenan in aqueous solutions with and without added salt in the dilute (approximately 6 mg/ml) and semidilute (approximately 16 mg/ml) regime close to the critical concentration (approximately 9-11 mg/ml). This concentration should be understood to be determined by contacts between blobs rather than between isolated molecules. The SAXS data of carrageenan solutions are described in terms of the fluctuation model of Borue-Erukhimovich rather than by a particle-type model, although the latter form of scattering appears when aggregates of ordered fragments are formed. According to current models of carrageenan the ordered fragments are single or double chain helices. In conditions favorable for the appearance of the ordered conformation, two polymer subsystems with a different characteristic screening scale of Coulombic interaction for the ideal Gaussian chain are detected. The system with the larger characteristic screening scale corresponds to molecular fragments with an ordered conformation. The contribution of both systems to the scattering can be separated which allows for discussion of their behaviour in the framework of the fluctuation theory. The SAXS results suggest that in all dilute and in the semidilute solutions with added NaCl or LiCl for both kappa- and iota-carrageenans there is a transformation from short-length correlated (disordered) to longer-length correlated (ordered) molecular fragments followed by the association of the ordered fragments, whereas a transformation from an association of disordered fragments to a structure with ordered fragments is detected in semidilute solutions of Li(+)-iota-carrageenan in Li(+)-iota-carrageenan in LiI and Na(+)-kappa-carrageenan in NaI. In the semidilute solutions of Na(+)-iota-carrageenan in NaI the formation of ordered fragments seems to follow an intermediate sequence.

Carbohydrate Conformation↗
PubMed1993

Changes in left ventricular filling after valve replacement for aortic stenosis.

In order to evaluate the short- and long-term effects of aortic valve replacement on the pattern of left ventricular inflow velocity, pulsed wave Doppler analysis was performed in 20 patients with isolated aortic stenosis. Complementary, left ventricular wall thickness was measured, using M-mode echocardiography. One week after operation, left ventricular wall thickness is not changed significantly. The Doppler findings suggest some improvement of left ventricular filling. Six months and 1 year postoperatively, there is a significant, but incomplete regression of left ventricular hypertrophy. Left ventricular filling improved only partially, compared to preoperatively.

Aged↗
PubMed1993

The differentiation between restrictive cardiomyopathy and constrictive pericarditis: the impact of the imaging techniques.

The differentiation between constrictive pericarditis and restrictive cardiomyopathy remains a difficult problem for clinical cardiologists. Recent advances in imaging techniques and the understanding of diastolic function have created a new diagnostic approach to this problem. In this article we will summarize the recent advances in the understanding of the pathophysiology of both disorders and how this is reflected mainly in the use of flow imaging techniques, such as Doppler echocardiography and radionuclide angiography. Combined with the advances in the radiological imaging of the pericardium by means of computed tomography and magnetic resonance imaging, an integrated approach to the differential diagnostic problem is proposed and an algorithm for clinical use has been designed.

Algorithms↗
PubMed1992

Influence of short atrioventricular delay on late diastolic transmitral flow and stroke volume.

Atrial transport function and the corresponding transmitral flow and stroke volume depend on the timing of atrial contraction. To study the influence of short atrioventricular delay (AVD) on these hemodynamic parameters, transmitral flow velocity (by pulsed wave Doppler) and aortic flow (by electromagnetic technique) were studied and compared (paired t test) during normal and short AVD at fixed rate DDD pacing (80 bpm) in AV-blocked, open-chest canine preparations (n:16). The short AVD resulted in a shorter acceleration (difference 4.1 +/- 4.9 msec, mean +/- SD, p less than 0.05), a lower peak velocity (difference: 7.1 +/- 3.2 cm/sec, p less than 0.001), a shorter (difference: 26.9 +/- 16.2 msec, p less than 0.001) and more rapid deceleration (difference: 220.7 +/- 291.7 cm/sec2, p less than 0.005) of the late diastolic transmitral flow elicited by atrial systole. Stroke volume decreased (7.8 +/- 5.2%, p less than 0.001) during short AVD as a consequence of a reduced left ventricular filling due to the interruption of the active atrial transport by the onset of the ventricular contraction.

Animals↗
PubMed1990

Effect of short atrioventricular delay on cardiac output.

Short atrioventricular (AV) delay modifies late diastolic filling dynamics. The effect of this change on cardiac output (CO) was studied in closed chest, AV blocked canine preparations (N:10), during AV sequential pacing (80 bpm). CO (thermodilution technique) and transmitral flow velocity (TMFV, pulsed-wave Doppler) were measured and compared (paired t-test) on the basis of TMFV pattern, when atrial contraction (A wave) started just after early diastolic transmitral flow deceleration (PR: 219 +/- 25 ms, mean +/- SD) and when A wave occurred at the end of late diastole and shortened due to the next ventricular contraction (PR: 56 +/- 11 ms). The short AV delay resulted in 12.0 +/- 5.9% decrease of CO, reflecting the interrupted late diastolic atrial transport. Properly timed atrial contraction is necessary for optimal AV sequential pacing.

Animals↗
PubMed1990

Early and 3 months follow-up results in 22 adult patients undergoing percutaneous transvenous mitral valvuloplasty.

Between April 1988 and October 1989, 22 adult patients with isolated or predominant severe mitral stenosis underwent Percutaneous Transvenous Mitral Valvuloplasty (PTMV). In 20 patients, a transseptal double balloon technique was used; in the last 2 patients, dilatation was performed using the Inoué balloon. Immediately after the procedure, the mitral valve area (MVA) rose from 1.2 +/- 0.3 to 2.2 +/- 0.8 cm2 (p less than 0.0001) using the hemodynamic method and from 1.1 +/- 0.4 to 1.9 +/- 0.4 cm2 (p less than 0.0001) using a Doppler technique. The mean left atrial pressure decreased from 20.3 +/- 6.0 to 10.5 +/- 5.0 mm Hg (p less than 0.0001). After the procedure, severe mitral regurgitation or significant iatrogenic interatrial septum defect did not occur. Two cerebral accidents were observed. One patient had a severe stroke with aphasia and hemiplegia but recovered within 3 months. The other patient had a minor dysarthric event, which resolved completely after 24 hours. Three months follow-up data in 16 patients revealed that they all were in NYHA class I or II. Restenosis occurred in 1 case. In the whole group of patients the MVA calculated by Doppler examination was similar to immediately after PTMV (1.9 +/- 0.4 versus 1.9 +/- 0.7 cm2).

Adult↗
PubMed1990

Percutaneous transluminal valvuloplasty of calcific aortic stenosis in elderly patients. Role of noninvasive evaluation by Doppler echocardiography.

Between October 1986 and January 1989, 57 attempts of percutaneous transluminal valvuloplasty were made in 51 elderly patients, mean age 76.7 +/- 6.2 years, with symptomatic aortic stenosis; this included 3 failures and 6 repeat valvuloplasties. The procedure resulted in a significant immediate decrease of the peak-to-peak transaortic pressure gradient from 94.6 +/- 26.5 to 42.6 +/- 17.9 mm Hg (p less than 0.002) and an increase of the surface of the aortic valve from 0.4 +/- 0.1 to 0.6 +/- 0.2 cm2 (p less than 0.001). Cardiac output remained unchanged: 3.8 +/- 0.9 vs 3.8 +/- 0.8 lit/min. Complications included local vascular injury requiring surgical repair in 7 patients, cerebral events in 3 patients and disruption of the aortic annulus, the aortic wall and the pulmonary artery each in 1 patient, and resulted in 4 in-hospital deaths (8%). Follow-up data were available for all patients for a mean duration of 12.7 +/- 5.4 months. Fifteen patients (30%) died on average 9.0 +/- 4.9 months after discharge. Recurrence of symptoms and early restenosis were documented in the majority of the patients. Restenosis was successfully treated by repeat valvuloplasty in 4 and by valve replacement in 4 patients. Doppler echocardiography predicted the severity of the aortic stenosis before valvuloplasty and was very useful to assess follow-up results. Because of the limited hemodynamic results, the numerous procedural complications and the development of early restenosis balloon valvuloplasty of aortic stenosis should be restricted to selected symptomatic elderly patients.

Aged↗
PubMed1988

Cardiac chamber growth pattern determined by two-dimensional echocardiography.

Two-dimensional echocardiographic measurements of the right and left ventricles from the parasternal long-axis and apical four-chamber views and an estimated right ventricular-left ventricular dimensional ratio were obtained in 173 normal subjects, ranging from 1 day to 15 years of age. The end-diastolic dimensions of both the right and left ventricles increases in proportion to the logarithmic function of body surface area. The right ventricular-left ventricular dimensional ratio decreases immediately after birth and continues to decrease during the first months of life. Newborns have altered ventricular shapes as seen in the pathological conditions of right ventricular volume or pressure overload. After the first months of life, the ventricular shapes remain constant throughout childhood. The 95% prediction intervals for the data were computed, and we suggest that the confidence limits of the normal data may be useful for quantitative echocardiographic evaluation in childhood.

Adolescent↗
PubMed1987

Cross sectional echocardiographic assessment of great artery diameters in infants and children.

The pulmonary trunk and aortic root were measured on cross sectional echocardiograms in 173 normal subjects aged from one day to 15 years. Fifteen neonates were reexamined 3-6 days later. The great vessels were visualised in the parasternal long axis and short axis views. All measurements were made in end diastole and end systole by the leading edge method. The internal diameter (inner surface to inner surface) of the pulmonary trunk was also measured. The diameters of the great vessels correlated best with the square root of body surface area. Individual variability in cardiac growth gave a wide scatter of normal values. This was controlled for by calculating the ratio of the pulmonary trunk to aortic root for each subject. This ratio showed little individual variability and, except for the neonatal period, was remarkably constant throughout infancy and childhood (1.06 (0.06)). In the first 24 hours of life the ratio of the pulmonary trunk to the aortic root was significantly larger (1.29 (0.12)) but within one week it decreased to the "normal" ratio found in the older age groups. These normal data should be useful in assessing patients with congenital heart disease, particularly those in whom pulmonary blood flow is abnormal.

Adolescent↗
PubMed1986

Relationship between left ventricular pressure and the calibrated apexcardiogram during abrupt outflow obstruction.

In order to study the influence of sudden left ventricular pressure rise on the calibrated apexcardiogram, 181 acute aortic occlusions were performed during systole in 7 dog experiments. For each beat preceding (CO) an occlusion and each occlusion (OC), peak systolic amplitude of left ventricular pressure (CO: 118.5 +/- 17.8 mm Hg; OC: 205.8 +/- 38.7 mm Hg) and apexcardiogram (CO: 48.8 +/- 16.7 mm Hg; OC: 63.0 +/- 25.8 mm Hg) were measured. Pressure gradients, ratios and surface areas of all tracings were digitally calculated. The cross-correlation function between pressure and apexcardiogram was also calculated in order to determine time lags. Significant correlations were found: between surface ratios and pressure gradient of pressure (r = 0.80, p less than 0.001) and of apexcardiogram (r = 0.79, p less than 0.001); between surface ratios of pressure and surface of apexcardiogram (r = 0.52, p less than 0.001). The data suggest that during isovolumic systole, the time integral of the left ventricular pressure and its change during the ejection phase define to a large extent the general shape and size of the apexcardiogram.

Animals↗
PubMed1985

Usefulness of echocardiographic assessment of right ventricular and pulmonary trunk size for estimating magnitude of left-to-right shunt in children with atrial septal defect.

M-mode and 2-dimensional echocardiographic studies were performed in 42 patients, aged 1 to 16 years (mean 6), with a secundum or sinus venosus type atrial septal defect (ASD) and normal pulmonary artery pressure. Twenty normal children served as a control group. In patients with ASD the echocardiographic variables were correlated with the magnitude of the left-to-right shunt (Qp/Qs) calculated by the Fick principle. Although M-mode echocardiograms showed increased right ventricular (RV) dimension in 69% of the patients, the correlation between RV dimension index (RV dimension/body surface area) and Qp/Qs was weak (r = 0.49). When RV dimension was related to left ventricular (LV) dimension and expressed by the RV/LV ratio, 90% of the patients were found to have an abnormally large right ventricle. The correlation between the RV/LV ratio and Qp/Qs was fairly good (r = 0.64). In 33 patients (78%), the pulmonary trunk (PT) was adequately visualized and measured on 2-dimensional echocardiograms. The dimension of the PT was related to the aortic root dimension and expressed by the PT dimension/aortic dimension ratio. This ratio was 0.99 +/- 0.06 in normal children and 1.35 +/- 0.23 in patients with ASD (p less than 0.001). The PT/aortic ratio exceeded the upper limit of normal (the normal mean value + 2 standard deviations) in each of the 27 patients with a Qp/Qs of 1.5 or greater. In 5 of the 6 patients with a Qp/Qs of less than 1.5 the PT/aortic ratio was close to 1 and within the normal range. An excellent correlation (r = 0.89) was found between the PT/aortic ratio and Qp/Qs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Long-term echocardiographic assessment of dilated cardiomyopathy in children.

Left ventricular (LV) dimensions and function were assessed by echocardiography in 22 children with dilated cardiomyopathy. They had survived an initial episode of congestive heart failure in infancy for greater than or equal to 2 years. At the time of echocardiography, when they were 3 to 16 years old, 8 patients (Group 1) still had signs of dilated cardiomyopathy and 14 (Group 2) had lost all roentgenographic and electrocardiographic evidence of heart disease. All 8 patients in Group 1 (average follow-up 4.5 years) had significantly increased LV dimensions. The end-diastolic dimension averaged 144 +/- 18% of the normal value. Fractional LV shortening with systole was significantly reduced and averaged 23 +/- 3%. The E point-septal separation ranged from 7 to 17 mm (mean 12 +/- 4) and was far above the normal limit in all. Of the 14 patients in Group 2, seven (average follow-up 7 years) had normal ventricular dimensions and 7 (average follow-up 10 years) had LV dimensions larger than the upper range of the 95% prediction limit. In 6 of the latter patients the fractional LV shortening with systole was less than or equal to 31% and the E point-septal separation in excess of the upper limit of normal. These findings indicate that about half of the patients who had apparently recovered still had residual lesions as judged from the echocardiogram. In 6 patients in group 1, two-dimensional echo-cardiography allowed the visualization of a thickened endocardium. One of these 6 patients died. The echocardiographic image correlated well with the process of LV endocardial fibroelastosis found at necropsy.

Adolescent↗
PubMed1983

Noninvasive determination of stiffness of the left ventricle by combined M-mode echo- and apexcardiography. An experimental method.

In order to compare an invasive with a noninvasive index of left ventricular stiffness during late diastole, M-mode echocardiogram, left ventricular pressure (LVP) and apexcardiogram (QLAC) were recorded simultaneously during acute dog experiments. The slope of the log pressure (P)-log volume (V) relationship is expressed by the ratio VdP/PdV. This index has been proven to be valid for the evaluation of left ventricular stiffness during late diastole. Diameter (D) changes were assumed to be proportional to volume changes. Continuous data from the ascending part of the A wave (due to atrial contraction) and the corresponding diameter change were used to calculate the slope (k1) of the log LVP--log D relation. During the same period the slope (k2) of the log QLAC--log D relation was also calculated. A significant linear correlation was found between values obtained semi-invasively from LVP-D (k1) and noninvasively from QLAC-D (k2) data: n = 21, r = 0.93, p less than 0.001. This shows the usefulness of VdP/PdV derived noninvasively from QLAC and M-mode echo for the assessment of stiffness of the left ventricle during late diastole.

Animals↗
PubMed1983

Diagnosis and treatment of obstruction of a tricuspid Björk-Shiley prosthesis.

Obstruction of a tricuspid Björk-Shiley prosthesis was diagnosed in 7 patients, caused by thrombus formation in 6, and tissue overgrowth in one. In 5 patients in whom the tilting disc had a ring shaped radiopaque marker, cineradiographic studies revealed incomplete opening (less than 60 degrees) and or closure of the prosthetic valve disc. In six patients the most reliable phonocardiographic signs were the presence of a delayed and prolonged diastolic mid-frequency rumble at the third left intercostal space, increasing on inspiration, and the absence of the opening sound of the tricuspid prosthetic valve. In 5 patients the M mode echocardiographic pattern of diastolic motion of the obstructed valve disc was very characteristic and showed a delayed and rounded upstroke and downstroke, and a reduced amplitude of diastolic excursion of the valve disc. In one patient in whom parasternal M mode echocardiography did not identify the obstructed valve, valve obstruction was clearly demonstrated by bidimensional echocardiography from the apical four chamber view. It is concluded that echocardiography is a useful tool for the diagnosis of tricuspid prosthetic valve obstruction, especially when the valve disc has no ring chaped radiopaque marker. Four patients were treated with streptokinase. This treatment was successful in 3 patients, but failed in the patient in whom the tricuspid valve obstruction was caused by tissue overgrowth. We recommend fibrinolytic therapy before surgical reintervention.

Echocardiography↗
PubMed1982

Relationship between apexcardiogram, left ventricular pressure and wall stress.

Simultaneous measurement of left ventricular dimension and wall thickness by M-mode echocardiography, of left ventricular pressure by a tip-transducer manometer, and of the calibrated apexcardiogram with a pixie beam transducer, were made during acute experiments on anaesthetized dogs. Instantaneous values for chamber dimensions and wall thickness were obtained throughout the heart cycle by digitizing the echo-mechanocardiograms. From these data myocardial stresses, derived from a thick shell theory (meridional and circumferential components) and from Laplace's law, were computed. Laplace stress if shown to be an adequate expression for average wall stress. Its value was correlated with the calibrated apexcardiogram. The present investigation suggests that to a certain extent, the apexcardiogram not only reflects pressure changes but also dimensional changes of the left ventricle.

Animals↗