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Biomedical subjects

H Verhaaren

Publications and source records attributed to H Verhaaren.

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↗
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

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

Dobutamine stress echocardiography in the evaluation of late anthracycline cardiotoxicity in childhood cancer survivors.

Late anthracycline cardiotoxicity has been of increasing concern to pediatric oncologists. An increasing number of patients with cardiac dysfunction has been reported without a good correlation between cardiac function or symptoms and routine echocardiographic follow-up. We studied dobutamine stress echocardiography in patients who had received moderate doses of anthracyclines years before. Twenty-three patients (14 male, 9 female; 7-25 y) who completed chemotherapy with moderate doses of anthracyclines (180-380 mg/m2) more than 2 y previously underwent dobutamine stress echocardiography and were compared with a control group of 26 healthy young people (15 male, 11 female; 6-26 y) matched for age and weight. Dobutamine was administered in three periods up to a rate of 5 micro g/kg/min. Eighty-five percent of the patients showed an abnormal response to dobutamine. Both systolic and diastolic functions were affected. The systolic dysfunction was not related to diminished contractility but to an elevated systolic wall stress due to inadequate cardiac muscle thickening. The diminished wall thickening was related to the length of follow-up. Dobutamine proved to be a very sensitive method to detect clinical and subclinical cardiac dysfunction in patients post anthracycline chemotherapy and questions the concept of a safe dose.

Adolescent↗
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↗
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↗
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

Membranous subvalvar pulmonary stenosis in complete transposition; advantage of biplane transoesophageal echocardiography for the diagnosis in a young adult.

A young adult who had previously undergone a Mustard repair for complete transposition developed symptomatic left ventricular outflow tract obstruction. Biplane transoesophageal echocardiography allowed an optimal preoperative assessment. In the longitudinal plane, a discrete calcified membrane was imaged. Consequently, a pulmonary arteriotomy was chosen for the relief of the malformation.

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↗
PubMed1990

[Exercise hypertension in children after surgical repair of treated ventricular and atrial septal defects].

The blood pressure profile during exercise of children who have undergone surgery for left-to-right intracardiac shunt is not well documented. The aim of this study was to measure the peak blood pressure during dynamic exercise stress testing in children operated on for atrial or ventricular septal defects and to compare the results with those of normal children and children operated on for tetralogy of Fallot. Forty eight cases of atrial septal defect, 53 cases of ventricular septal defect and 33 cases of tetralogy of Fallot aged 5 to 14 years underwent maximal exercise stress testing on a treadmill using a modified Bruce protocol, one to ten years after the surgical repair. The heart rate, blood pressure and electrocardiogram were recorded. The duration of the test was used to judge effort tolerance. In order to compare children of different ages and sizes, the relative values were calculated using the following formula: patient value minus the mean value of the control group of the same age divided by the standard deviation of this group. At rest before exercise, there was no difference between the blood pressure of patients operated on for a left-to-right shunt and of the control group of normal children. However, the maximum systolic blood pressure during exercise was higher in patients who had undergone surgery for a left-to-right shunt than in the controls. The differences were only 0.42 standard deviations in ventricular septal defects and 0.61 standard deviations in atrial septal defects, but they were statistically significant (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Delayed elimination of digoxin antidotum determined by radioimmunoassay.

An observation of a treatment with digitalis antibodies (Fab-fragments) in a young child is presented. The elimination of this antidotum proved to be much slower than normally expected. In the patient's history, the disappearance of the Fab-fragments out of the blood lasted 142 days with a half-life of 15.6 days, whereas an elimination with a T1/2 of 28 hours is accepted. Probably there has been intracellular penetration of the antibodies into the liver, caused by concomitant diseases (Hepatitis A and B infections). An "in vitro" experiment is reported. It demonstrates the equimolar binding of the Fab-fragments for digoxin and shows that the elimination of the Fab-fragments can be established by a routine radioimmunoassay of digoxin, in an indirect way.

Antibodies↗