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Biomedical subjects

L Tjon-A-Meeuw

Publications and source records attributed to L Tjon-A-Meeuw.

7 recordsLinked to original sources
PubMed1993

Regional diastolic dysfunction in postischaemic myocardium in calf: effect of nisoldipine.

OBJECTIVE: The aim was to assess the effect of nisoldipine on left ventricular systolic and diastolic function during prolonged myocardial ischaemia. METHODS: The left circumflex coronary artery was ligated for 2 h and reperfused for 4 h in 12 calves. The animals were randomised to a control group (n = 6) or to treatment with 1.25 mg.h-1 intravenous nisoldipine (n = 6) during 2 h of ischaemia. Circulatory support by a ventricular assist device was performed throughout the experiment except for the time of haemodynamic measurements. Regional wall thickening of a normal and an ischaemic left ventricular region was determined using pairs of ultrasonic crystals. Left ventricular pressure was measured by micromanometry. Left ventricular wall thickness and regional wall stiffness at a common preload of 10 mm Hg were calculated using an elastic model with shifting asymptote. RESULTS: Ten animals survived after 6 h. No difference was observed in systolic function between controls and nisoldipine treated animals. Systolic thickening of the ischaemic wall remained depressed 4 h after reperfusion and showed some recovery after dopamine infusion. Ischaemic wall stiffness at a common preload was lower after nisoldipine during ischaemia and reperfusion than in controls. Control wall stiffness remained unchanged during the whole experiment with and without nisoldipine. Diastolic thinning of the ischaemic wall was prevented by nisoldipine during ischaemia and after reperfusion. CONCLUSIONS: Prolonged myocardial ischaemia is associated with increased myocardial stiffness of the ischaemic wall. Mechanical unloading can help to bridge the acute phase but cannot prevent postischaemic diastolic dysfunction of the ischaemic wall. Nisoldipine has a beneficial effect on regional diastolic function during ischaemia and reperfusion by decreasing regional wall stiffness and preventing diastolic thinning of the ischaemic wall.

Animals↗
PubMed1992

[Cor triatriatum in adulthood: Doppler echocardiographic diagnosis. Case report of an asymptomatic adult].

Cor triatriatum is a rare cardiac malformation occurring in about 0.1% of all congenital heart disease. As symptoms are usually present soon after birth, diagnosis in adulthood is extremely rare. We describe a case of a 33-year-old asymptomatic woman who was referred for echocardiographic examination because of a postural variable systolic click. The anatomy of the malformation and the hemodynamics of the left atrium were accurately assessed by means of conventional transthoracic Doppler echocardiography. The antero-inferior course of the intraatrial membrane inserting proximal to the left atrial appendage was documented in multiple perpendicular planes of examination. All pulmonary veins drained correctly into the proximal compartment of the left atrium. Additionally, a small atrial septal defect communicated between the distal compartment of the left atrium and the right atrium. Using pulsed wave Doppler, no site of pressure gradient could be detected between the two compartments of the left atrium. Thus, conventional transthoracic Doppler echocardiography represents an adequate tool for assessing cor triatriatum in adults. The patient refused transesophageal echocardiography.

Adult↗
PubMed1992

Preservation of myocardial function by mechanical circulatory support during prolonged ischaemia.

The effect of mechanical circulatory support on left ventricular (LV) function was evaluated during prolonged myocardial ischaemia. Regional wall thickening of a normal and an ischaemic LV region were determined in eight calves (mean body weight 76 kg) using pairs of ultrasonic crystals. LV end-diastolic (mmHg) and peak systolic (mmHg) pressure as well as maximum dP/dt (mmHg s-1) were calculated from LV high-fidelity pressure tracings. The left circumflex coronary artery was ligated proximally for 6 h and reperfused for 18 h. Circulatory support by the assist device was performed from the beginning of ischaemia to the end of the experiment. After a mean time of 4 h all animals showed ventricular fibrillation, which was converted successfully in six animals after a mean time interval of 5 h. Five animals survived after 24 h. The non-surviving animals had larger infarcts, greater creatine kinase release and a larger drop in cardiac output during ischaemia. Haemodynamic measurements were carried out after turning off the assist device. Inotropic stimulation with 0.68 mg.min-1 dopamine i.v. was performed at the end of the study. LV regional function showed systolic bulging during myocardial ischaemia. After 18 h of reperfusion, the ischaemic wall recovered and showed normal systolic wall thickening in the presence of an increased LV preload. LV relaxation was prolonged after reperfusion, suggesting diastolic dysfunction. It is concluded that mechanical circulatory support is effective in protecting myocardial function during prolonged ischaemia in approximately two-thirds of the animals, despite severe ischaemic ventricular dysfunction and intermittent ventricular fibrillation.

Animals↗
PubMed1991

[Aneurysm of the abdominal aorta. Diagnosis and indications for therapy].

Atherosclerotic abdominal aortic aneurysms are found in about 4% of all men aged over 65 years. The most severe complication of the abdominal aortic aneurysm is rupture. The probability of rupture depends upon the diameter of the aneurysm. The chance of rupture is 30% within 2 years in aneurysms with a maximum diameter of more than 5 cm. Preoperative evaluation includes clinical examination and abdominal ultrasonography. Depending on the results, aortography and/or computed tomography are required. When the diameter is less than 5 cm in an asymptomatic patient, conservative management is indicated provided that clinical tests and ultrasonography are performed on a regular basis. The mean increase of diameter varies between 0.2 and 0.4 cm/year. All aneurysms with a diameter of more than 5 cm should be treated by implantation of a dacron graft. Symptomatic aneurysms should, independently of the diameter, be considered an emergency situation and resected immediately. Patients with ruptured aneurysms have a poor prognosis; only 40-60% of these patients reach the hospital and approximately 50% of them die despite immediate surgery. A special subgroup is the so called inflammatory abdominal aortic aneurysm. Characteristic findings of this entity are increased wall thickness and retroperitoneal fibrosis. The indications for resection are the same as for the atherosclerotic aneurysm. If management is conservative, treatment with corticosteroids is useful.

Adrenal Cortex Hormones↗
PubMed1990

[Comparison of enalapril and captopril in the treatment of chronic heart failure].

The long-term effect of enalapril (group 1) and captopril (group 2) on clinical symptomatology and left ventricular function was evaluated in 29 patients with severe congestive heart failure (13 ischemic and 12 dilated cardiomyopathy, four valvular heart disease). During the 6-month observation period, five patients died (two on enalapril and three on captopril therapy = 6-month mortality rate 18%). Nine patients showed no beneficial effect of enalapril or captopril on clinical and hemodynamic findings (= nonresponders). The initial findings on these nine patients were, however, not significantly different from the clinical and hemodynamic findings on the patients who improved. Enalapril had to be discontinued in two patients because of side effects (progressive renal failure and gastrointestinal symptoms, respectively). A total of 22 patients completed the study, 11 treated with enalapril (mean dosage 25 +/- 10 mg/day) and 11 treated with captopril (mean dosage 77 +/- 26 mg/day). After 6 months there was a significant improvement according to the New York Heart Association (NYHA) classification, from 2.4 to 1.9 in group 1 (p less than 0.01) and from 2.7 to 1.9 in group 2 (p less than 0.001). The cardio-thoracic ratio (chest x-ray) decreased significantly from 0.59 to 0.56 (p less than 0.001) in group 1 and from 0.56 to 0.53 (p less than 0.001) in group 2. Physical working capacity (bicycle ergometry) showed a significant increase in both groups from 61% to 81% in group 1 (p less than 0.01) and from 66% to 83% in group 2 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1988

Left ventricular volume determination in dogs: a comparison between conductance technique and angiocardiography.

Left ventricular (LV) volume was determined simultaneously by monoplane cineangiocardiography and conductivity using a multielectrode conductance catheter at rest and during pressure loading in seven mongrel dogs (mean body weight 22 kg). LV volumes were calculated frame-by-frame (75 frames s-1) by angiocardiography and matched with instantaneous volumes obtained by conductivity. There was an excellent correlation between the two techniques at rest (correlation coefficient, r = 0.96) and during pressure loading (r = 0.92) when the data of each dog were pooled. The standard error of estimate of the mean angiographic volume was 4%. The slope of the regression analysis showed a small but significant (P less than 0.01) decrease from 0.365 at rest to 0.289 during pressure loading, whereas the intercept remained unchanged (24 versus 26 ml). Since no calibration for parallel conductivity of the surrounding tissue was performed, LV end-systolic volume was significantly over- and LV ejection fraction significantly underestimated whereas LV end-diastolic volume was estimated correctly by the conductance technique. It is concluded that LV end-diastolic volume can be determined accurately by the conductance technique in dogs. However, LV end-systolic volume is significantly over- and ejection fraction significantly underestimated. Since there is a good correlation between angiocardiography and conductivity, exact determination of LV volumes and ejection fraction is feasible using a correction factor. The change in slope of the regression equation between angiocardiography and conductivity suggests a change in conductivity of the surrounding tissue during pressure loading which limits the application of the conductance catheter to stable haemodynamic situations or calls for repeated calibrations by an independent technique during acute interventions.

Angiocardiography↗