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Biomedical subjects

A Lenaers

Publications and source records attributed to A Lenaers.

At least 37 records · Page 2Linked to original sources
PubMed1987

Cardiovascular effects of chronic high-dose atriopeptin III infusion in normotensive rats.

Seventy-eight Sprague-Dawley rats received continuous intravenous infusions of either atriopeptin III (APIII), 60 micrograms/kg/hr, or distilled water vehicle for a period of 7 days by means of osmotic minipumps. On Day 7 approximately one-half of the animals (20 vehicle-treated rats and 21 APIII-treated rats) were instrumented for evaluation of cardiac function and terminated for measurement of heart weight. The minipumps remained in place during the evaluation of cardiac function. Also on Day 7, the osmotic pumps were removed from the remaining animals and an additional 7 days were allowed to elapse before heart weight and cardiac function were evaluated. Mean arterial blood pressure (MAP) of rats receiving APIII for 7 days was significantly lower (-9%, p less than 0.05) than that of rats receiving vehicle for 7 days. In addition, reductions (p less than 0.05) of total ventricular weightdry (-7%), left ventricular weightdry (-8%), and right ventricular weightdry (-9%) were observed in the APIII-treated rats (all ventricular weights are normalized for body weight). Hematocrit (HCT) was significantly higher (13%, p less than 0.05) in the APIII-treated group. Chronic APIII infusion did not influence ventricular performance nor did it affect regional vascular resistances. Seven days after termination of the APIII infusion the differences in MAP and HCT between vehicle-treated and APIII-treated animals were no longer evident. Partial recovery of the effect on heart weights was apparent, with total ventricular weightdry and left ventricular weightdry remaining slightly reduced (-4 and -5%, respectively; p less than 0.05). No differences were found between the two recovery groups for any index of cardiac function. In separate experiments, it was demonstrated that APIII, 60 micrograms/kg/hr iv, caused a significant increase in urine volume (p less than 0.05 relative to vehicle) during the initial 24 hr of infusion. The results indicate that chronic infusion of a large diuretic dose of APIII exerts relatively little influence on overall cardiovascular function in normotensive rats.

Animals↗
PubMed1987

Arterial reactivity, blood pressure, and plasma levels of atrial natriuretic peptides in normotensive and hypertensive rats: effects of acute and chronic administration of atriopeptin III.

We compared acute and chronic effects of atriopeptin III in normotensive and spontaneously hypertensive rats. Atriopeptin III relaxed isolated aortae and intrarenal microarteries but not coronary and mesenteric microarteries of normotensive rats. Effects on arterial smooth muscle were comparable in hypertensive and normotensive rats and were not affected by long-term treatment of the animals with the peptide. Acute administration of atriopeptin III (4-400 nmol/kg, intravenously) reduced systolic blood pressure in conscious spontaneously hypertensive and renal hypertensive rats but not in normotensive rats. In spontaneously hypertensive rats, nephrectomy increased the sensitivity to and the duration of the acute antihypertensive effect. Renal subcellular fractions rapidly inactivated atriopeptin III in vitro. This atriopeptinase activity was comparable for normotensive and spontaneously hypertensive rats and was not affected by long-term treatment of the rats with the peptide. Continuous administration of low doses of atriopeptin III (0.4 and 4.0 nmol/kg/h, intravenously (i.v.) during 7 days) caused a progressive reduction in systolic blood pressure in spontaneously hypertensive but not in normotensive rats. It did not affect plasma levels of aldosterone or renin and resulted in less than a doubling of the plasma levels of atrial natriuretic peptides. These findings confirm that atrial natriuretic peptides preferentially relax the renal microvasculature. They demonstrate that although atriopeptin III comparably relaxes arterial smooth muscle of normotensive and spontaneously hypertensive rats, both acute and chronic administration of the peptide preferentially lower blood pressure in hypertensive rats. Rather than contributing to the effects on blood pressure, the kidneys modulate the duration of action of atrial natriuretic peptides.

Animals↗
PubMed1986

Predictors of early death after acute myocardial infarction: two months follow-up.

Clinical variables and the results of non-invasive tests (exercise test, echocardiogram, gated equilibrium radionuclide ventriculography and 24 h ECG) were recorded in a series of 202 patients who left the hospital alive after an acute myocardial infarction. The short term (two months) predictive value of all these data was prospectively assessed by uni- and multi-variate analysis. The best correlation with early death was observed with the variables related to the extent of infarction and left ventricular dysfunction, namely: early clinical signs of heart failure, high peak CK-MB level, complete bundle branch block, increased cardiothoracic ratio on chest X-Ray, number of Mets reached during the stress test, echocardiographic dyskinesia index, and decreased left ventricular ejection fraction as measured by radionuclide ventriculography. Using multi-variate stepwise discriminant analysis, the following independent prognostic factors appeared by order of entry: early clinical signs of heart failure, peak CK-MB level and cardiothoracic ratio on chest X-Ray. These results highlight the short-term predictive value of the data related to left ventricular dysfunction and especially of simple clinical data for patients surviving an acute myocardial infarction.

Acute Disease↗
PubMed1986

Discrepancy between thermodilution and radionuclide right ventricular ejection fraction measurements: the importance of tricuspid regurgitation.

Measurement of right ventricular ejection fraction (RVEF) by the thermodilution technique has become routinely available at the bedside of the critically ill. We describe 2 patients with tricuspid regurgitation in whom RVEF values were considerably lower by thermodilution than by radionuclide techniques. Discrepancies could be due to the regurgitation of the thermodilution signal and possibly to the different nature of the two measurements (forward stroke volume with the thermodilution technique and total stroke volume with the radionuclide technique). We suggest that lower RVEF measurement by the thermodilution technique could be related to unrecognized tricuspid regurgitation. Measurement of an unexpectedly low RVEF by the thermodilution technique should suggest the presence of tricuspid regurgitation.

Heart↗
PubMed1986

[Early exercise test after myocardial infarction].

Exercise tests of coronary function at the tenth day of an uncomplicated myocardial infarction offer objective evaluation of short-term benefits of an early accelerated physical retraining program. They also allow better individual adaptation of exercises prescribed at the start of convalescence at home. Exercise test results show significant correlation with clinical data and bicycle ergometer tests carried out two months after infarction, with respect to physical aptitude, reasons for discontinuation of test and lethality risk two months after infarction. This suggests that exercise tests performed after the acute phase of myocardial infarction are of diagnostic and prognostic value.

Aged↗
PubMed1985

Amplitude distribution in the right ventricle.

Amplitude distribution in the right ventricle obtained from ECG-gated ventriculography has been reviewed and six amplitude distribution patterns were identified. Homogeneous distribution was rarely observed even in patients without any cardiac or pulmonary diseases. Furthermore, there was no difference in frequency distribution of the amplitude distribution patterns between the control group, patients with coronary diseases, and those with recent inferior myocardial infarction. It was concluded that amplitude distribution could not be used to detect hypokinetic areas in the right ventricle.

Angina Pectoris↗
PubMed1985

Measurement of left-ventricular volumes using an internal standard.

When performing equilibrium radionuclide angiocardiography with two successive acquisition views, absolute left-ventricular volumes can be calculated using an 'internal standard' generated by a computer in the left-ventricular cavity. The method is based on the computed ratio of maximum to global activity in the 40 degree-left-anterior-oblique view after background correction and on the measured depth of the left ventricle in almost-orthogonal, 30 degree-left-posterior-oblique Fourier first-harmonic images. The method does not require blood sampling or correction for self attenuation. The intra- and interobserver reproducibility is excellent, even in patients with severe impairment of the ventricular-contractility pattern. When compared with a classical method requiring venous-blood counting and an attenuation correction factor, the accuracy of the internal-standard method was fairly good, with a regression coefficient of 0.90.

Adult↗
PubMed1985

Influence of age on functional recovery after myocardial infarction.

Two age-groups of patients, of 45-59 and 65-69 years respectively, were investigated 10 days and 2 months after myocardial infarction. Left ventricular performance at rest was evaluated by radionuclide ventriculography, working capacity by submaximal heart rate-limited stress testing at discharge from the coronary care unit and maximal testing 2 months after the coronary attack. Resting ejection fraction remained unchanged while exercise tolerance increased in both age groups between the first and second examination but remained systematically lower in the elderly. The author conclude that although functional recovery after myocardial infarction is independent of age, physical capacity is lower in older patients during the acute phase as well as after early convalescence; resting ejection fraction remains, however, unchanged.

Age Factors↗
PubMed1984

Determination of sorbitol and galactitol at the nanogram level in biological samples by high-performance liquid chromatography.

Aldose reductase is an enzyme that plays an important role in diabetic complications such as cataract and neuropathy. The best way to estimate the enzymatic activity of this enzyme in vivo consists of measuring the accumulation of sorbitol or galactitol in various types of cells or tissues. A sensitive method to measure the polyols in biological samples by high-performance liquid chromatography has been developed. This method is based on the fact that polyols like sorbitol and galactitol react with phenylisocyanate to yield uv-absorbing derivatives at 240 nm. Applications to the separation and determination of polyols in biological samples of various origins, such as lenses, sciatic nerves, human skin fibroblasts, and red cells, are described and illustrated.

Animals↗
PubMed1983

The evaluation of right ventricular performance using krypton-81m.

The availability of krypton-81m suitable for intravenous injection provides an easy means for assessing right ventricular function. The superimposition of the other heart chambers does not constitute a problem. The activity in the left heart is negligible and the study can be performed in the right anterior oblique position to obtain optimal separation between the right atrium and the right ventricle. Lung activity is quite high and should be corrected before computing the right ventricular ejection fraction. This correction can be accomplished by performing Tc-99m MAA perfusion scintigraphy. The measurement of the right ventricular ejection fraction appears to be reproducible with very small inter-and intraobserver variability. Good quality phase and amplitude images can be obtained with such high count rates.

Cardiac Output↗
PubMed1981

Radionuclide quantitation of left-to right cardiac shunts using deconvolution analysis: concise communication.

Quantitative radionuclide angiocardiography (QRAC) was performed with and without deconvolution analysis (DA) in 87 children with various heart disorders. QRAC shunt quantitation was possible without DA in 70% of the cases and with DA in 95%. Among 21 patients with prolonged bolus injections, quantitation of the shunt was possible in 52% of the cases without DA an in all cases with DA. Correlation between oximetry and QRAC with DA was better than between oximetry and QRAC without DA. It is concluded that QRAC with DA is a more reliable, noninvasive means for detection and quantitation of left-to-right cardiac shunts than QRAC without DA.

Adolescent↗
PubMed1979

Postinfarction exercise capacity after lidoflazine treatment or physical training.

44 male postinfarction volunteers were divided into 4 groups and submitted to performance tests. Groups I and II consisted of 24 patients, 12 of whom followed a 2-month physical training program, while the other 12 served as controls. Groups III and IV (10 patients each) were included in a 10-month double-blind crossover study with lidoflazine 240 mg/day vs. placebo. The cardiovascular adaptation of the patients treated for 5 months with lidoflazine had two features in common with that observed after 2 months of physical training, namely an increase in maximal exercise capacity and, during submaximal exercise tests, a decrease in heart rate compensated for by an increase in stroke volume. In contrast to physical training, treatment with lidoflazine did not improve the peripheral oxygen consumption by the muscles.

Blood Pressure↗
PubMed1978

Radioactive isotopes in the diagnosis of heart disease.

Since the first application of radionuclides in cardiology, fifty years ago, a lot of invasive and noninvasive techniques have been developed. Invasive methods, performed in the catheterization room, have increased our comprehension of physiopathological mechanisms in congestive heart failure and coronary insuffiency. Noninvasive methods have allowed assessment of regional left ventricular wall motion and ejection fraction, of myocardial perfusion at rest and after exercise and of intracardiac shunts, in ambulatory patients. Most of these methods have been developed in the last two decades, and particularly in the last few years. Technical improvements, like scintillation cameras, computers and shortlived tracers, have considerably improved their possibilities. New techniques, like positron imaging with three-dimensional reconstruction, current use of ultra-short life indicators and further refinements in radio-immunoassays, will undoubtly increase our fundamental and clinical knowledge of congenital and acquired heart diseases.

Blood Volume↗