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D Matthys

Publications and source records attributed to D Matthys.

At least 19 recordsLinked to original sources
PubMed1999

The influence of low afterload on the nature of the stress-velocity relationship.

OBJECTIVES: Correct assessment of contractility by conventional methods during manipulation of afterload is often disappointing. To this purpose, the stress-velocity relationship offers assessment of contractility at different levels of afterload. We decided to study the influence of afterload on the nature of the stress-velocity relation. BACKGROUND: Although linear at baseline conditions in a population older than two years, data in newborns or after administration of low-dose dobutamine suggest a different nature of this relationship at low afterload. METHODS: Ten healthy piglets (five to six weeks; 11 to 13 kg) were studied. End-systolic meridional wall stress (ESWS) and rate-corrected velocity of circumferential fiber shortening (VcFc) were measured in these piglets at baseline, after balloon occlusion of the descending aorta, and at nitroprusside infusion rates of 1, 2 and 5 microg/kg/min. To eliminate inotropic influences mediated by reflex tachycardia, we subsequently studied five piglets and six adult pigs after bilateral cervical vagotomy. RESULTS: The ESWS changed from a baseline mean of 50 g/cm2 to 137 g/cm2 after balloon occlusion and to 19 g/cm2 at 5 microg/kg/min of nitroprusside. The VcFc changed from 1.19 c/s (circumference/second) to values of 0.9 c/s and 1.73 c/s, respectively. The ensuing stress-velocity regression line proved to be curvilinear instead of linear. The steeper slope at low afterload could suggest enhanced contractility compared to expected values had the relationship been linear. CONCLUSIONS: Data from young piglets and adult pigs suggest a curvilinear relationship of the stress-velocity relationship. This could probably explain some of the "hypercontractile states" encountered in conditions with low afterload.

Age Factors↗
PubMed1999

Effect of branched-chain amino acids (BCAA), glucose, and glucose plus BCAA on endurance performance in rats.

PURPOSE: The purpose of this study was to assess the effects of pre-exercise administration of branched-chain amino acids (BCAA), glucose, and glucose plus BCAA on time to exhaustion during treadmill exercise in rats. METHODS: Wistar rats were injected intraperitoneally with 1 mL of saline (0.9% NaCl), BCAA (30 mg), glucose (100 mg), or glucose plus BCAA 5 min before either 45 min of submaximal exercise (N = 32) or running to exhaustion (N = 24). After the submaximal exercise test, blood was collected for the measurement of ammonia, BCAA, free tryptophan (free TRP), glucose, free fatty acid, and lactic acid, and muscle samples were taken from the m. soleus for determination of glycogen content. RESULTS: Mean run time to exhaustion was significantly longer after BCAA administration (158+/-26 min) compared with that after saline (118+/-35 min)(P<0.05) but not compared with that after glucose administration (179+/-21 min). When glucose is administered before exercise, the supplementary administration of BCAA had no additional effect on performance (171+/-12 min). The data on blood ammonia, ratio of free TRP/BCAA, and muscle glycogen did not provide a clue for explaining the higher endurance performance after BCAA supplementation. CONCLUSION: The results support the hypothesis that the effect of BCAA administration on performance could be related to carbohydrate availability during exercise.

Amino Acids, Branched-Chain↗
PubMed1998

Low-dose dobutamine stress echocardiography in children and young adults.

Dobutamine stress echocardiography has become widely accepted in the evaluation of adult patients with coronary heart disease. We wanted to assess the feasibility and the physiologic responses of stress echocardiography at low doses of dobutamine in a population of normal children and adults. Once achieved, we submitted a group of post-anthracycline patients to the test to assess the sensitivity of low-dose dobutamine stress echocardiography in the detection of cardiac dysfunction. Thirty-two healthy children and young adults (19 male and 13 female subjects, median age 15 years [range 6 to 26]) were studied. After the initial study of normal subjects, we submitted a cohort of 39 patients (18 female and 21 male, aged 6 to 25 years), who completed anthracycline chemotherapy, to the same protocol. Dobutamine was infused at rates of 0.5 to 2.5 and 5 microg/kg/min and echocardiographic measurements were obtained at rest and at the end of each stage. The test could be completed in 100% of the subjects without major complications. Statistically significant differences between resting echocardiographic values of systolic and diastolic function and values at 2.5 and 5 microg/kg/min of dobutamine were found. Moreover, dobutamine revealed or enhanced differences between normal subjects and the post-anthracycline patients. Thus, low-dose dobutamine stress echocardiography is feasible and safe in older children. The test is very sensitive for the detection of subclinical cardiac dysfunction in post-anthracycline patients and could possibly assess functional myocardial reserve.

Adolescent↗
PubMed1998

Inhaled salbutamol decreases blood ammonia levels during exercise in normal subjects.

The present study examines the effect of salbutamol, a beta2-adrenoreceptor agonist, on blood ammonia levels during an incremental cycle exercise test in healthy non-asthmatic subjects. Blood ammonia levels were lower after inhalation of 400 mcg of salbutamol than after placebo during submaximal exercise: 33+/-2 micromol x l(-1) v.s. 48+/-9 micromol x l(-1) at 220 W and 39+/-2 micromol x l(-1) v.s. 50+/-4 micromol x l(-1) at 260 W. At peak exercise there were no significant differences. The results suggest that beta2-adrenoreceptors are involved in the regulation of blood ammonia during exercise.

Administration, Inhalation↗
PubMed1998

Influence of age and low afterload on the stress-velocity relation of the left ventricle.

The relation between systolic meridional wall stress (WS) and velocity of circumferential fiber shortening (VcFc) is widely accepted as a preload-independent index of contractility, with a linear relation in most subjects older than 2 y. However, this relation seems to become different in infants and after administration of inotropic agents. We decided to study the nature of the stress-velocity relation by a cross-sectional assessment of the influence of age, low afterload, and increased contractility. Study subjects were 30 healthy infants, 32 healthy older children, and 35 asymptomatic older children after completion of anthracycline chemotherapy. WS and VcFc at rest were studied in these infants and children. WS and VcFc were also studied after dobutamine infusion in both groups of older children. Linear regression analysis of the stress-velocity relation showed parallel slopes between the older children at rest and the post anthracycline children after dobutamine. The regression lines between the infants at rest and the healthy older children after dobutamine were also parallel, but with a different and steeper slope compared with the former groups. When comparing the stress-velocity relation of the overall population at rest with the overall population after dobutamine, the resulting regression lines are curvilinear and parallel, with a steeper slope at low afterload. The stress-velocity relation in infants and after dobutamine, resulting in low afterload is different compared with the stress- velocity relation in older children at rest and at higher afterload. Data of the overall population at rest and after dobutamine suggest a curvilinear relation.

Adult↗
PubMed1998

Entrapment of a guide wire during percutaneous occlusion of a coronary artery fistula.

Coronary artery fistulas are extremely rare and coil occlusion by intervention techniques seems to be the therapy of choice. We describe the case of a 3-month-old infant with a coronary artery fistula. During occlusion of the fistula a coronary guide wire got entrapped in a small coronary branch, but could be successfully retrieved with a microsnare without damage to the heart. The microsnare technique prevented rupture of the guide wire.

Angioplasty, Balloon, Coronary↗
PubMed1997

Simultaneous delivery of two patent arterial duct coils via one venous sheath.

A female child, 10 months of age, weighing 7.2 kg, was catheterised for closure of a patent arterial duct. Aortography was performed in the lateral projection and the minimum diameter of the arterial duct was assessed by comparing it to the size of the catheter. The duct size was estimated between 3 and 3.5 mm at the narrowest point, therefore, it was decided to deliver two 5 mm patent arterial duct coils to avoid placement of an 8 mm coil in this small child. Similar operations were subsequently performed in two further children. Simultaneous delivery of two coils via a single long venous sheath is easy, fast, and safe. This simple and inexpensive procedure can reduce irradiation and anaesthesia time.

Ductus Arteriosus, Patent↗
PubMed1996

Effects of acute cardioselective and non-selective beta-adrenergic blockade on plasma ammonia levels in exercising dogs.

The aim of this study was to assess plasma ammonia levels during acute treadmill exercise in dogs after intravenous administration of a single dose of different cardioselective (atenolol) and non-selective (sotalol and propranolol) beta-adrenergic blocking drugs. The experiments were performed on 6 male mongrel dogs (20-25 kg) trained to run on a motor driven treadmill. After administration of saline or atenolol, there was no significant increase in plasma ammonia during exercise; propranolol and sotalol however, both non-selective beta-blockers, produced a significant increase in plasma ammonia. Plasma levels of alanine and glutamine were not altered during exercise compared with resting values, and were not modified by the administration of beta-blockers. It is not clear whether the different effects on exercise induced hyperammonemia are due to different effects on muscle ammonia formation or on the ammonia clearance by the liver.

Adrenergic beta-Antagonists↗
PubMed1996

Reduced decrease of peripheral vascular resistance during exercise in young type I diabetic patients.

OBJECTIVE: In normal subjects, peripheral vascular resistance decreases during dynamic exercise. We studied blood pressure and peripheral vascular resistance responses to dynamic exercise in young normotensive type I diabetic patients. RESEARCH DESIGN AND METHODS: Thirty adolescent diabetic patients (9-19 years of age) underwent a maximal exercise test on a cycle ergometer. In a subset of 14 patients, cardiac output was measured by a CO2 rebreathing method and peripheral vascular resistance was calculated. Twenty-four normal individuals, age and sex matched, served as control subjects. RESULTS: Diastolic blood pressure was significantly higher in diabetic patients at intermediate workload (77 +/- 2 vs. 71 +/- 1 mmHg) and peak exercise (86 +/- 2 vs. 73 +/- 2 mmHg). Peripheral vascular resistance was significantly higher in diabetic patients at intermediate workload (17.0 +/- 1.1 vs. 12.6 +/- 0.5 mmHg.l-1.min-1.m-2) and peak exercise (16.3 +/- 1.3 vs. 11.4 +/- 0.5 mmHg.l-1.min-1.m-2). There were no significant correlations with the patient's age, diabetes duration, or diabetes control. CONCLUSIONS: We observed the decrease of vasodilator response during dynamic exercise in normotensive young type I diabetic patients.

Adolescent↗
PubMed1996

Cardiorespiratory variables during a continuous ramp exercise protocol in normal young adults.

The purpose of the present study was to determine whether the cardiorespiratory variables measured during an exercise test with a continuously increasing workload (ramp) protocol are reproducible and to compare them to the values obtained with a step-wise incremental (James) protocol. Twenty normal adolescents and young adults performed two exercise tests on a cycle-ergometer, one with each protocol, and twelve of these subjects additionally performed a second identical ramp test. The results show that the cardiorespiratory variables measured during exercise with ramp protocol are reproducible and that peak values are not different from those obtained with step-wise incremental exercise protocol, except for a higher peak power. At intermediate equivalent workloads, there were significant correlations between cardiorespiratory variables measured in steady-state conditions with the incremental protocol and those obtained in non-steady-state conditions with the ramp protocol.

Adolescent↗
PubMed1995

Effects of acute non-selective beta-adrenergic blockade on plasma ammonia levels in exercising dogs.

The purpose of the present study was to document exercise induced hyperammoniemia after blockade of the beta-adrenoceptors and to investigate the effect of administration of branched-chain amino acids (BCAA) and glucose in these conditions. Seven dogs, chronically instrumented with a catheter in the deep jugular vein and a Doppler probe around the carotid artery were trained to perform a ten-minute treadmill exercise test. Administration of propranolol i.v. prior to exercise increases plasma ammonia at peak exercise compared with placebo (78 +/- 7.9 vs 25 +/- 5.1 mumol/l; p < 0.05). This effect of propranolol on plasma ammonia during exercise is enhanced by the administration of BCAA (108 +/- 15 vs 78 +/- 7.9 mumol/l; p < 0.05), and diminished by the administration of glucose (42 +/- 7.7 vs 78 +/- 7.9 mumol/l; p < 0.05). These results suggest that increased metabolisation of BCAA is involved in the ammonia formation after beta-adrenergic blockade.

Adrenergic beta-Antagonists↗
PubMed1994

Adenosine-tri-phosphate treatment for supraventricular tachycardia in infants.

Adenosine is an endogenous nucleoside acting on coronary perfusion and myocardial conduction. Although the anti-arrhythmic effects of adenosine have been known for decades, interest in the use of adenosine or adenosine-triphosphate (ATP) (a precursor of adenosine) in termination of supraventricular tachycardia (SVT) has been renewed. We studied the use of striadyne (ATP and a mixture of other nucleosides including adenosine) in 22 infants younger than 6 months in order to evaluate efficiency and safety of the drug in this particular age group. Striadyne stopped SVT in 17 cases and was diagnostic in another 4 cases. Ten out of 17 successfully converted infants showed one or more reinitiations of SVT, which were easily controlled. The results support the efficiency of ATP for the termination of re-entry types of tachycardia, as well as its diagnostic value and its lack of serious side-effects.

Adenosine Triphosphate↗
PubMed1994

Adenosine triphosphate treatment for supraventricular tachycardia in infants.

UNLABELLED: Adenosine is an endogenous nucleoside acting on coronary perfusion and myocardial conduction. Although the anti-arrhythmic effects of adenosine have been known for decades, interest in the use of adenosine or adenosine triphosphate (ATP- a precursor of adenosine) in termination of supraventricular tachycardia (SVT) has been renewed. We studied the use of Striadyne (ATP and a mixture of other nucleosides including adenosine) in 22 infants younger than 6 months in order to evaluate efficacy and safety of the drug in this particular age group. Striadyne stopped SVT in 17 cases and was diagnostic in another 4 cases. Ten out of 17 successfully converted infants showed one or more reinitiations of SVT, which were easily controlled. The results support the efficacy of ATP for the termination of re-entry types of tachycardia, as well as its diagnostic value and its lack of serious side-effects. CONCLUSION: Adenosine or ATP could be the drug of choice for the treatment of junctional tachycardia in infants after vagal manoeuvres have failed. Provided continuous ECG monitoring is performed during injection, adenosine or ATP may be diagnostic in other types of supraventricular tachycardia and even in wide-complex tachycardia. We suggest a bolus injection of 0.5-1.0 mg/kg to be used prior to transport to the paediatric cardiology unit.

Adenosine Triphosphate↗
PubMed1994

Cardiovascular reactivity in isometric exercise and mental arithmetic in children.

In children, we studied noninvasively the cardiovascular stress responses, including changes over time of systolic blood pressure (SBP), heart rate (HR), and stroke volume (SV) in isometric handgrip (IHG) and mental arithmetic. Specifically, we asked whether 1) these cardiovascular stress responses were different for the two stress conditions in children, 2) these responses differed in boys and girls, and 3) the anthropometric variables related to these stress responses. SV differed significantly between IHG and mental arithmetic over the entire stress period. This may reflect higher systemic vascular resistance during IHG. HR in boys was lower than in girls over the entire period of stress in both stress tests. This observation cannot be attributed to differences in conditioning, because this should not influence responses to isometric or mental stress. A larger left ventricular mass was related to higher SVs. A marked relationship was found between HR and SBP and between HR and SV. No relationship was found between SBP and SV.

Blood Pressure↗
PubMed1993

Gender difference in aerobic capacity in adolescents after cure from malignant disease in childhood.

The aim of this study was to document gender difference in aerobic capacity after cure from malignant disease in childhood. We studied 18 males and 17 females aged 11-19 years and 10-18 years, respectively. They had all completed their treatment at least two years previously. Twelve males and 11 females received anthracyclines in comparable doses (range 150-500 mg/m2). Maximal exercise tests were performed on a cycle ergometer. Maximal oxygen consumption (ml/min/kg) was significantly (p < 0.001) lower only in females when compared to their controls. We postulate two causes: girls are smaller than their controls, possibly related to their higher vulnerability to cranial irradiation than boys; and girls were less involved than boys in sports. The influence of anthracycline treatment on aerobic capacity was only observed in males and not in females. This could be related to the higher exercise level in boys than in girls.

Adolescent↗
PubMed1993

Membranous subvalvular pulmonary stenosis in complete transposition of the great arteries: usefulness of serial exercise testing.

A 22-year-old male who had Mustard repair for complete transposition presented with progressive exercise intolerance, documented by a gradual decrease in exercise capacity on cycle ergometer. Cardiac catheterization and angiography demonstrated subvalvular pulmonary stenosis. After surgical relief of the obstruction, exercise capacity returned to previous level.

Adult↗
PubMed1992

Exercise-induced bradycardia after Mustard repair for complete transposition.

Impairment of sinus rhythm has been reported after the Mustard procedure for complete transposition. We observed two patients who developed severe bradycardia during or after exercise. The first had a 2.8 s sinus pause in the recovery period, the second had a drop in heart rate during exercise. Both eventually had a pacemaker implanted. Exercise testing can be helpful in detecting sick sinus syndrome.

Adolescent↗