Biomedical subjects

G Deklunder

Publications and source records attributed to G Deklunder.

35 records · Page 2Linked to original sources

PubMed1996

Helical CT angiography compared with arteriography in the detection of renal artery stenosis.

OBJECTIVE: The aim of the study was to improve the accuracy and detection rate for renal vascular lesions on helical CT angiography with an improved acquisition protocol and postprocessing. SUBJECTS AND METHODS: Fifty hypertensive patients (man age, 53 years old) referred because of clinical suspicion on renal artery stenosis were prospectively studied with digital renal arteriography and helical CT angiography. A 20-sec helical scan (collimation, 3 mm; pitch, 1) was obtained after injection of contrast medium. Interpretation was base on transverse sections, shaded-surface-display and maximum-intensity-projection reconstructions, and two-dimensional multiplanar reconstruction cuts obtained from shaded-surface-display reconstructions. RESULTS: Arteriography visualized 131 renal arteries (including 32 accessory arteries). Sixteen had significant (greater than 50% in diameter) stenosis. On helical CT angiography, 14 of these 16 stenoses were detected; two were missed (false-negatives), and two additional stenoses (false-positives) were reported. Sensitivity and specificity were 88% and 98%, respectively. Considering only main renal arteries, the sensitivity and the specificity of helical CT angiography were 100% and 98%, respectively. Helical CT angiography detected Conn's syndrome, which was responsible for hypertension, in two other patients. CONCLUSION: The accuracy and detection rate for renal artery stenosis on helical CT angiography compared with arteriography is improved with the described protocol.

Adult↗

PubMed1996

A prospective study of helical computed tomography angiography versus angiography for the detection of renal artery stenoses in hypertensive patients.

OBJECTIVE: To compare helical computed tomography angiography with arterial digital subtraction angiography in the diagnosis of renal artery stenoses. METHODS: Fifty hypertensives (24 men; mean age 53 years) were prospectively studied with computed tomography (Somaton Plus S, Siemens) and digital angiography (double-blind evaluation). Computed tomography was performed both in the sequential (the length of the abdomen) and in the helical (6 cm around renal arteries) modes during injection of 120 cm3 contrast medium. RESULTS: Digital angiography visualized 16 significant (< 50% on quantitative angiography) stenoses (16/131 renal arteries, including 32 accessory), in 14 (28%) patients. On helical computed tomography, 16 stenoses were detected, in 49 patients (16/122 renal arteries, seven accessory arteries were not identified because they were located out side the scan area); two patients had false-positive helical computed tomography results. The computed tomography sensitivity, specificity, positive and negative predictive values were 87.5% (14/16), 98.2% (111/114), 87.5% and 98.2%, respectively. In the sequential mode, two cases of bilateral adrenal hyperplasia, two aortic aneurysms and one renal neoplasm were detected. None of these patients had renal artery stenosis. CONCLUSIONS: Helical computed tomography is a suitable new non-invasive diagnostic modality for the detection of renal artery stenosis or adrenal pathology. With continued development and evaluation computed tomography could prove useful as a screening tool or as a replacement for digital angiography in patients with possible secondary hypertension.

Adolescent↗

PubMed1996

Transcranial high-intensity Doppler signals in patients with mechanical heart valve prostheses: their relationship with abnormal intracavitary echoes.

BACKGROUND AND AIMS OF THE STUDY: In preceding studies, we reported that abnormal Doppler signals of high intensity (HITS) were frequently found in the cerebral arteries of patients with prosthetic mechanical heart valves. These signals should be attributed either to air microbubbles, possibly due to cavitations or to solid emboli elements. On the other hand, the presence of abnormal intracardiac echoes has been reported in patients with mechanical valves. These echoes should be also attributed to air microbubbles or to formed elements. Although in vitro experiments are in favor of the first explanation, the discussion of their origin remains open. METHODS: Among patients subjected to a transesophageal echocardiography (TEE), we selected subjects with mechanical prosthetic heart valves, according to the following criteria: (i) normally functioning valves; (ii) bright echoes suggesting microbubbles, inside the prosthetic valve and/or upstream from it (left ventricular outflow tract or left atrium); (iii) no morphological lesions that could generate solid microemboli at the prosthetic level; (iv) normal carotid arteries, as investigated by color echo-Doppler. RESULTS: Twenty patients were selected: 11 men and nine women of age range 40-64 years. They were implanted with mechanical heart valves (24 Saint-Jude Medical, three Björk-Shiley and one CarboMedics) in the mitral position (10), aortic position (two), or mitral and aortic position (eight) for periods ranging from 10 days to 17 years. There was no major left ventricular dysfunction (mean end-diastolic diameter 51.8 mm; mean ejection fraction 59%). The mean diameter of the left atrium was 46.1 mm. All but three patients were in sinus rhythm; seven had presented with a transient ischemic attack or amaurosis within the six months preceding the investigation. Immediately after TEE, Doppler signals were recorded on the middle cerebral arteries (MCA) during 10 minutes on each side, and the abnormal Doppler signals were counted. Seventeen subjects (85%) exhibited HITS repetition rate from 0.2 to 5.5 per min. CONCLUSION: The percentage of patients with HITS in a non-selected group with mechanical heart valves was about 50%, as observed in previous studies. It appears that in a selected group of patients the percentage with HITS is consistently higher. Therefore, HITS and abnormal intracardiac echoes could have a common origin.

Adult↗

PubMed1995

Cardiac output variations in supine resting subjects during head-out cold water immersion.

Five men, aged 31.2 years (SD 2.3), under semi-nude conditions and resting in a dorsal reclining position, were exposed to thermoneutral air for 30 min, followed immediately by a cold water (15 degrees C) immersion for 60 min. Cardiac output was measured using a dual-beam Doppler flow meter. During immersion in cold water, cardiac frequency (fc) showed an initial bradycardia. The lowest values were reached at about 10 min after immersion, 58.3 (SD 2.5) to 48.3 (SD 7.8) beats min-1 (P < 0.05). By the 20th min of exposure, fc had gradually risen to 70.0 beats min-1 (SD 6.6, P < 0.05). This change could be due to the inhibition of the initial vagal reflex by increased catecholamine concentration. Stroke volume (Vs) was significantly increased (P < 0.05) during the whole cold immersion period. Cardiac output, increased from 3.57 (SD 0.50) to 6.26 (SD 1.33) l min-1 (P < 0.05) and its change with time was a function of both Vs and fc. On the other hand, systolic flow acceleration was unchanged during the period of immersion. The changes in the respiratory variables (ventilation, oxygen uptake, carbon dioxide output and respiratory exchange ratio) during immersion showed an initial hyperventilation followed, as immersion proceeded, by a slower metabolic increase due to shivering.

Adult↗

PubMed1995

Comparative diagnostic value of ankle-to-brachial index and transcutaneous oxygen tension at rest and after exercise in patients with intermittent claudication.

BACKGROUND: Few studies have compared sensitivities of ankle-to-brachial index (ABI) and transcutaneous oxygen tension (TcPO2) in a large group of patients with Leriche stage II intermittent claudication. METHOD AND RESULTS: 111 patients (138 limbs) with a stable chronic (> three months) intermittent claudication and significant peripheral vascular disease (PVD) proved by angiography were studied. They performed a treadmill test (10%, 3 km/hr) limited by limb pain. ABI and TcPO2 were measured before, just after exercise, and after three and ten minutes of recovery in supine position. Sensitivities per patient for ABI and TcPO2 were respectively at rest: 82.9% and 28.8%, and after exercise: 88.3% and 62.2%. Sensitivities per leg (n = 138) for ABI and TcPO2 were respectively at rest: 73.9% and 26.8%, and after exercise: 82.6% and 34%. The sensitivity of TcPO2 increased to 56.5% after three minutes of recovery but was always less than that of ABI, which was maximal just after exercise (82.6%). The sensitivity of the regional perfusion index was similar to that of TcPO2. The sensitivity of TcPO2 increased with respect to the Leriche stage and the number of lesions but was always lower than that of ABI. There was a weak correlation between TcPO2 and ABI after exercise, but no correlation was noted between maximal walking distance, ABI, and TcPO2. CONCLUSION: TcPO2 is not required in patients with Leriche stage II intermittent claudication but might be useful either in severely affected patients (Leriche stage III or IV) or in selected patients.

Aged↗

PubMed1995

[Evaluation of spiral computed tomography of the renal arteries alone or combined with Doppler ultrasonography in the detection of renal artery stenosis. Prospective study of 114 renal arteries].

A renovascular etiology occurs in 0.2 to 2% of hypertensive patients. Recently, spiral computed tomography (CT) has evolved as a new minimally invasive tool for the diagnosis of vascular pathologic conditions. The purpose of this study was to compare both spiral CT and color Doppler ultrasonography (US) with intraarterial digital subtraction angiography (DA) in the detection of renal artery stenosis (RAS) in hypertensive patients. Between December 1993 and April 1994, 44 hypertensives (men 22, mean age 52 years) suspected secondary hypertension were prospectively studied with spiral CT (Somatom Plus S, Siemens) US (Acuson, 3.5 MHz probe) and DA (double-blind evaluation). DA visualized 11 significant (> 50%) stenoses (11/114 renal arteries, including 27 accessory). On spiral CT, 9/11 were detected and 2 additional stenoses considered false positive. On US 5 stenoses were detected whereas 11 were demonstrated by DA; 2 patients had false positive US results. [table: see text] We conclude that combined spiral CT and color Doppler ultrasonography is an effective and relatively non invasive alternative to intraarterial digital angiography for the detection of renal artery stenosis in a hypertensive population screened for renovascular hypertension.

Adolescent↗

PubMed1994

Gas bubble emboli detected by transcranial Doppler sonography in patients with prosthetic heart valves: a preliminary report.

After observing spikes in the Doppler signal of cerebral arteries of patients with neurologic symptoms and prosthetic heart valves, we then studied two groups of patients with prosthetic heart valves: seven patients with neurologic symptoms and 65 asymptomatic patients. Using transcranial Doppler sonography of the middle cerebral artery, we found Doppler spikes in six symptomatic and 24 asymptomatic patients with mechanical heart valves. No spikes were found in one symptomatic and 21 asymptomatic patients with biological valves or in 20 asymptomatic patients with mechanical valves. We concluded that gas cavitation during the opening or closure of the valve, producing bubble emboli, is the most probable explanation for these Doppler spikes in patients with mechanical prosthetic heart valves.

Aged↗

PubMed1993

Intracardiac hemodynamics in man during short periods of head-down and head-up tilt.

The intracardiac hemodynamic responses to short periods of 70 degrees head-down and head-up tilts were studied in 12 normal male subjects, ages 19-24 years. Echo-Doppler techniques were used to measure the transmitral and transaortic flow velocities as well as cardiac index, and to evaluate the peripheral impedance. Head-down tilt (HDT) rapidly induced an increase (9.7%, p < 0.05) in the early passive filling of the left ventricle (ME peak of the transmitral flow velocity curve) and in transaortic flow velocity (8%, p < 0.05), as well as in cardiac output (6%, p < 0.05). In spite of a peripheral vasodilation, the blood pressure increased (7%, p < 0.05 for the systolic; 15%, p < 0.01 for the diastolic) and remained at a high level for the 5 min of the experiment. Head-up tilt (HUT) induced inverse responses; i.e., a large initial decrease in the transmitral (-15%, p < 0.05) and transaortic (-16%, p < 0.001) flows. The shape of the arterial peripheral flow indicated an increased vascular impedance. After a short drop, the blood pressure rapidly recovered a level statistically close to that of the pretest. In both cases, tachycardia occurred. We conclude that, in man, the cardiac responses to the changes in posture appear to be related more to the passive changes in ventricular filling due to the blood shift than to the nervous regulation by the arterial baroreflexes, whereas these reflexes mainly act in the control of the vascular impedance.

Adult↗

PubMed1992

Reversal of cold induced haemoconcentration.

Classically, cold induced plasma volume reduction is explained by an increased diuresis which is generated by an inhibition of antidiuretic hormone release. However, most of the haemoconcentration appears to be reversible during rewarming. This observation weakens the former statement. The aim of this study was to clarify the mechanisms involved in the reversal of the cold induced haemoconcentration. Six young males, resting in a dorsal reclining position, were exposed successively to a thermoneutral environment (30 min), a cold environment (1 degrees C; cold) or thermoneutrality (control) for 120 min, and during a 60-min recovery period in thermoneutral conditions. During cold stress, a reduction of 15% (i.e. 510 ml) of the plasma volume was observed, and osmolality was unchanged. After the 60-min recovery under thermoneutral conditions, plasma volume variation between the Cold and the Control experiments was reduced and reached 3% (i.e. 100 ml). This volume equalled the increased amount of urine production observed during the cold stress experiment. Haemoconcentration cannot be explained by increased urinary water loss (+/- 100 ml) alone. Therefore a transient shift of plasma water from vascular to interstitial spaces, due to an increase of blood pressure, could be involved in the reduction of plasma volume.

Adult↗

PubMed1992

Cold exposure and ischemic heart disease.

Exposure to cold causes a vasoconstriction and a tachycardia, both resulting in a rise of blood pressure and cardiac work. This last effect may have a deleterious influence on people suffering from ischaemic heart disease (IHD). Moreover, coronary artery spasm could occur if vasoconstriction extends to the heart vessels. Epidemiologic studies have shown that mortality from IHD was correlated to the ambient temperature. There will be more deaths per day in the winter, and fewer in the summer. However, the daily number of deaths also increases during the heat waves. During a cold test, the coronary blood flow remains normal or slightly increased in normal subject. There is never a coronary artery spasm. Subjects who suffer from angina but have normal coronary arteries behave in the same way as normal subjects. Patients with IHD show a decrease in coronary blood flow. In a few cases, those patients may exhibit a coronary spasm with chest pain and even myocardial infarction. It is concluded that people with normal cardiovascular function are unaffected by cold stress whereas those with IHD may be crippled, although rarely, by exposure to cold, especially if they perform a physical work.

Blood Pressure↗

PubMed1992

Factors enhancing cardiac output in resting subjects during cold exposure in air environment.

Six young males, in semi-nude conditions, resting in dorsal reclining position, were exposed successively to a thermoneutral environment (30 min), a cold environment (1 degree C) (Cold) or thermoneutrality (Control) (120 min), and during 60 min recovery in thermoneutral conditions. Cardiac output has been measured using a Dual Beam Doppler. During cold stress a significant increase of heart rate (66.4 +/- 6.4 to 91.0 +/- 14.9 beats.min-1), systolic blood pressure (119.5 +/- 7.8 to 218.7 +/- 18.7 mmHg), diastolic blood pressure (68.1 +/- 11.7 to 114.3 +/- 28.3 mmHg) and cardiac output (5.42 +/- 0.96 to 8.08 +/- 1.28 l.min-1) were observed. On the contrary initial systolic aorta flow acceleration is significantly lowered (1130 +/- 120 to 840 +/- 170 cm.s-2). Systolic ejection volume remained unchanged throughout the whole experiment. Increase in cardiac output during cold air (1 degree C) exposure is thus only imputed to the higher heart rate partly due to hypersecretion of catecholamines. The diminution of the blood flow acceleration could be related to a lesser arterial compliance and/or to the cold induced hemoconcentration. Enhanced heart's mechanical work due to sympathetic stimulation, seems thus to be absorbed by the increase in the peripheral resistance.

Adult↗

PubMed1991

Influence of ventilation of the face on thermoregulation in man during hyper- and hypothermia.

It has been suggested that a thermal countercurrent exchange may occur in the cerebral vascular bed of humans, thereby creating for the brain a state of relative thermal independence with regard to the rest of the body. However, worrying questions have arisen concerning this suggestion. Experiments were carried out on seven young male volunteers. Hyper- and hypothermic conditions were produced by immersion in water at 38.5 degrees C and 25 degrees C, respectively. During the last few minutes of immersion, the face was cooled or warmed by ventilation with a 200 l.min-1 air flow at 5 degrees C or 40 degrees C, respectively. Internal and peripheral temperatures were recorded. Blood flow in the anastomotic vessels between face and brain was measured by Doppler techniques associated with computerized frequency analysis. The general responses were as classically described, i.e. an increase in peripheral and central temperatures during immersion in the warm bath and a decrease in these variables in the cold bath. The reactions produced by cooling or warming the face were small and easily explained by the direct changes of the heat load they induced. Whatever the thermal conditions, the blood flow in the anastomotic vessels between the vascular bed of the face and that of the brain was never reversed. It was concluded that there was no experimental evidence for an efficient thermal counter-current exchange in the vascular bed of the human head.

Adult↗

PubMed1990

[Blood flow measurement in arteriovenous fistula. Comparison of 2 ultrasonic methods, direct and indirect by compression of the fistula].

Measuring blood flow in arteriovenous fistulae in patients under chronic dialysis is of interest to evaluate the repercussions of the fistula on the heart. The apparently simplest method is direct measurement of the mean blood flow velocity by the pulsed doppler technique and ot the cross-section area by ultrasonography, the product of these two values being the blood flow rate. Another method has been proposed, which consists of measuring the cardiac output before and after compression of the fistula, the difference between the two values being supposed to represent the blood flow rate in the fistula. A comparative study of these two methods was conducted in 17 patients aged from 2 to 21 years (mean: 14 years). The direct method gave a figure of 475 ml.min-1.m-2 (SD = 240), while the figure obtained with the indirect method was 471 ml.min-1.m-2 (SD = 227); the difference was statistically not significant. In terms of concept, however, the indirect method is open to much more severe criticism than the direct method, and whenever possible the latter should be preferred when measuring blood flow in arteriovenous fistulae.

Adolescent↗

PubMed1990

[Constrictive pericarditis: study by Doppler echography of blood flow in the supra-hepatic veins].

The blood flow rate in the supra-hepatic veins has been measured by Doppler ultrasound in 11 subjects suffering from more or less advanced constrictive pericarditis; the results were compared to those obtained with normal subjects. In all the pathological cases, the flow rate curve shows the following modifications: a slight decrease in the X peak, which is related to the blood "demand" caused by the decrease in the ventricular volume during the ejection, and a correlative increase in the Y peak, contemporaneous of the ventricular filling up. In the patients in which the pericarditis has not reached a marked stage of constriction, the intra-thoracic ventilatory pressure variations still exert a certain influence on the supra-hepatic blood flow rate; on the other hand, this influence is suppressed when the constriction is complete. These phenomena are parallel to the pressure modifications observed by catheterism and to those of the mitral and tricuspid transvalvular flow. The advantage of measuring the blood flow rate in the supra-hepatic veins lies in the fact that the access, for ultrasound analysis, to these vessels is quicker and more constant than to the heart valves. This method seems therefore to be an interesting one to assess the stage of development of the constricting pericarditis.

Hepatic Veins↗

PubMed1988

[Doppler effect in cardiology. Continuous Doppler, pulsed Doppler, Doppler color].

Echocardiography has contributed to the exploration of the heart by providing much information, and it has even given rise to new semiological concepts. However, abnormalities of intracardial blood flow, notably shunts and regurgitations, could only be diagnosed indirectly from their effects on cardiac cavities. A new step forward was the advent of pulsed and continuous doppler ultrasound, since from that moment it has been possible to demonstrate abnormal blood flows, to measure their velocity and to determine, albeit with some reservation, such crucial values as pressure gradients. Yet even when these two techniques were combined in the doppler-echotomography systems blind areas persisted, and a blood flow of strongly abnormal direction could in fact escape doppler velocimetry. This is where another development came to the rescue, for it enabled both normal and abnormal flows to be visualized in colours. Owing to this visualization, and provided all possible projections are used, it has become exceptional to "miss" an abnormal blood flow. The diagnosis is now easier and more accurate, and in a second stage the flow can be quantified by pulsed or continuous doppler ultrasound. The colour-coded doppler technique therefore has not superseded the previous one: one may say that it has merely increased diagnostic reliability, but is this not a decisive improvement?

Cardiology↗

PubMedDate not supplied

[Effects of a sequential combination of estradiol valerate and cyproterone acetate on the functional properties of the arterial wall in menopausal women].

Several studies have shown that estrogen replacement therapy protects postmenopausal women against coronary artery disease. This protective effect has been ascribed to the hormone's effect on serum lipids, as well as a direct action on the vascular wall. Concurrent administration of a progestin to protect women from the risk of endometrial hyperplasia may alter the protective effects of estrogen. The aim of this study was to assess the evolution of the endothelial function in postmenopausal women given a sequential combination of oral 2 mg estradiol valerate for 11 days, followed by 2 mg estradiol valerate associated with 1 mg cyproterone acetate for ten days (Climène). Each 21-day sequence was followed by a seven-day treatment-free interval. The women received a three-month treatment course. Thirty-one healthy postmenopausal women participated in the study (median age: 51 years; range: 45-59 years). Flow-mediated dilatation (FMD), a reflection of endothelium-dependent vasomotor function, increased from 8.47% at baseline (range: 4.57-11.02%) to 9.64% (range: 7.07-13.12%) at the end of the first treatment cycle; i.e., a 15% increase over baseline (P < 0.0001). FMD further increased after three treatment cycles to 10.59% (range: 8.09-15.22%); i.e., a 28.6% increase over baseline (P < 0.0001). FMD at the end of the first combined sequence or after the 11 days of estradiol only were similar (delta = 0.25%; range: -2.31-5.81%; not significant). In conclusion, in postmenopausal women, a three-month sequential treatment combining estradiol valerate and estradiol valerate plus cyproterone acetate (Climène) has beneficial effects on endothelial function as demonstrated by the evolution of the FMD. There was no decrease in the effect of estradiol on FMD when cyproterone acetate was added to estradiol.

Arteries↗

PubMedDate not supplied

[Usefulness of magnetic resonance angiography in the screening of renal artery stenosis in hypertensive patients: proposition of a diagnostic algorithm: a study of 245 patients].

Usefulness of magnetic resonance angiography in the screening of renal artery stenosis in hypertensive patients: proposition of a diagnostic algorithm: a study on 245 patients. Different non-invasive techniques, including Duplex, spiral angioscan, and magnetic resonance angiography (MRA) are available for the diagnosis of renal artery stenosis (RAS). The aim of this study was to assess the diagnostic performances of MRA and the MRA-Duplex couple in the diagnosis of RAS. Between September 2003 and January 2005, 245 patients benefited from a renal MRA for the assessment of hypertension etiology. The MRA-Duplex couple was performed in 228 patients. Renal arteriography was performed in case of abnormalities observed with MRA and/or Duplex (n=41). The sensitivity and specificity of MRA were respectively at 100% and 23%. The sensitivity was notably higher in the right renal artery (100 vs. 73%). The sensitivity and specificity of Duplex were respectively at 71 and 85%. The concordance between the two exams was disappointing (kappa at 0.39 for the right side and 0.62 for the left side), leading to the interest of the MRA-Duplex association for excluding the presence of RAS (sensitivity and negative predictive value=100%). However, using the MRA-Duplex couple led to a high number of false positive cases, due to MRA, leading to 11 angiograms out of 41 exams, without any significant RAS. In case of suspicion of RAS, the MRA-Duplex couple permits to exclude definitely the diagnosis of RAS. In case of discordance between the 2 exams, it would be useful to require a spiral angioscan and/or redo a Duplex exam using contrast agents, prior to angiography with a therapeutic goal. These management modalities might be useful to avoid the number of normal angiograms, with an inherent risk of complications and cost excess.

Algorithms↗