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Biomedical subjects

F C Visser

Publications and source records attributed to F C Visser.

At least 109 records · Page 6Linked to original sources
PubMed1987

Analysis of myocardial time-activity curves of 123I-heptadecanoic acid. I. Curve fitting.

Myocardial time-activity curves can be described by two or more parameters. To establish the optimal curve fitting method 33 myocardial time-activity curves were analyzed with different curve fitting methods: monoexponential, biexponential and monoexponential plus constant. A background correction was not applied. Biexponential curve fitting resulted in redundancy of parameters. Optimal curve fitting was obtained with monoexponential plus constant. The constant represents the background activity together with the stored radiolabelled lipids and the half-time value represents the wash-out of radioiodide from the myocardium. A strong relation was found between the constant and the half-time value: small errors in the determination of the constant (background activity) resulted in considerable errors of the half-time value. It is concluded that optimal analysis of a myocardial time-activity curve can be performed with a monoexponential plus constant without earlier correction for background activity.

Coronary Disease↗
PubMed1987

Analysis of myocardial time-activity curves of 123I-heptadecanoic acid. II. The acquisition time.

Optimal fitting of a myocardial time-activity curve is accomplished with a monoexponential plus a constant, resulting in three parameters: amplitude and half-time of the monoexponential and the constant. The aim of this study was to estimate the precision of the calculated parameters. The variability of the parameter values as a function of the acquisition time was studied in 11 patients with cardiac complaints. Of the three parameters the half-time value varied most strongly with the acquisition time. An acquisition time of 80 min was needed to keep the standard deviation of the half-time value within +/- 10%. To estimate the standard deviation of the half-time value as a function of the parameter values, of the noise content of the time-activity curve and of the acquisition time, a model experiment was used. In most cases the SD decreased by 50% if the acquisition time was increased from 60 to 90 min. A low amplitude/constant ratio and a high half-time value result in a high SD of the half-time value. Tables are presented to estimate the SD in a particular case.

Coronary Disease↗
PubMed1987

Magnetic resonance imaging of cardiac anatomy. A standard procedure.

A standard procedure was developed allowing study of cardiac anatomy with electrocardiographically gated MRI, using alteration of a single gradient angle of the imaging plane combined with patient rotation. This resulted in projections of the heart through its anatomical axes. The obtained images allow correlation with 2D-echocardiography and left ventriculography.

Adult↗
PubMed1986

Radioiodinated free fatty acids; can we measure myocardial metabolism?

To investigate the feasibility of radioiodinated free fatty acids for 'metabolic imaging', the kinetics and distribution pattern of metabolites of 131I-heptadecanoic acid were studied in canine myocardium throughout metabolic interventions. In control dogs and in dogs during glucose/insulin and sodium lactate infusion, biopsy specimens were taken during a 90-min period after 131I-HDA administration and analyzed. Clearly distinct patterns of distribution and elimination were seen during the metabolic interventions, indicating the usefulness of iodinated fatty acids for metabolic studies.

Animals↗
PubMed1986

Prediction of spontaneous coronary reperfusion in myocardial infarction.

To investigate the possibility of predicting the occurrence of spontaneous coronary reperfusion in acute myocardial infarction we studied 91 patients in a randomized trial on the clinical efficacy of intracoronary streptokinase compared to conventional treatment. Of the 46 patients treated conventionally 40 had catheterization 6 weeks after the infarction. Spontaneous coronary reperfusion was found in 19 patients (48%). The time to peak CK-MB in these patients was considerably longer than in patients with streptokinase-induced coronary reperfusion and similar to the time in patients without spontaneous coronary reperfusion. Spontaneous coronary reperfusion was associated with a relative improvement of radionuclide ejection fraction from day 1 to day 14 after admission. There was no difference in the occurrence of ventricular arrhythmia or recurrent ischaemic events between the patients with and those without spontaneous coronary reperfusion. Thus, spontaneous coronary reperfusion is not uncommon in traditionally treated myocardial infarction, but its occurrence cannot be predicted by enzymatic or clinical parameters.

Clinical Trials as Topic↗
PubMed1985

The myocardial elimination rate of radioiodinated heptadecanoic acid.

To clarify the mechanism of the elimination of radioactivity after administration of radioiodinated heptadecanoic acid, dogs with and without coronary occlusion were studied. In myocardial tissue samples of normal and ischemic myocardium, the proportions of free radioiodide, radioiodinated heptadecanoic acid, and radioiodinated lipids were determined. Five minutes after intravenous injection of heptadecanoic acid 69% of the radioactivity was present as free iodine, 7% as unaltered heptadecanoic acid, and 24% as lipids. Even in ischemic myocardium 41% was free iodine and 47% lipids. After 2 h free iodine decreased to 48% and lipids increased to 44%. These results indicate that beta-oxidation is not the rate-limiting step in the elimination rate of heptadecanoic acid.

Animals↗
PubMed1985

The elimination rate of 123I-heptadecanoic acid after intracoronary and intravenous administration.

When calculating the elimination rate of radioactivity after the administration of radioiodinated heptadecanoic acid (123I-HDA), background correction is necessary due to the high level of background activity. In the present study, the subtraction method of Freundlieb et al. was investigated on validity. This was done by comparing the half-time values of the elimination rate after intravenous (i.v.) and intracoronary (i.c.) injection. In the latter case, no background correction was necessary. Six patients undergoing cardiac catheterization were studied. Scintigraphy was performed after the injection of 123I-HDA into the left coronary artery and after i.v. injection. Half-time values were calculated from regions of interest drawn over myocardium perfused by the left-anterior descending branch (LAD) and the left circumflex artery (LCX). In the LAD region, the mean half-time value in the i.c. study was 22 min, while in the corrected i.v. study, the mean value was 27 min. In the LCX region, the half-time values were 24 and 33 min, respectively. The background-subtraction procedure proposed by Freundlieb et al. for i.v.-injected 123I-HDA is incomplete, as it resulted in half-time values that were higher than those of the i.c. study.

Arteries↗
PubMed1985

A computer program for the analysis of serial electrocardiograms from patients who suffered a myocardial infarction.

A program is described, which compares serial ECG recordings of patients, who suffered a myocardial infarction. The comparison of the ECGs is based on the measurements, delivered by the Modular ECG/VCG Interpretation System. The two most recent ECGs are compared and a trend analysis based on all ECG recordings of the patient is performed. The criteria in the comparison program are based, among others, on data obtained from a combined cardiological and respiratory survey in The Netherlands in 1973 and 1976.

Computers↗
PubMed1985

Myocardial uptake of radioactively labelled free fatty acids.

Structural variations in the carbon chain of free fatty acids influence the uptake of free fatty acids in the myocardium. To enable the use of free fatty acids in nuclear cardiology, various methods of introducing gamma-emitting isotopes have been evaluated. The uptake of various free fatty acids is described and structure-activity relationships deduced.

Animals↗
PubMed1985

Evaluation of background correction methods.

After intravenous injection of radioiodinated heptadecanoic acid a high background activity disturbs direct determination of myocardial elimination rates. Several correction procedures for background activity are used. After intracoronary administration a much lower background activity is found. To validate the background subtraction procedures we compared in this study the results of the correction procedures with the results after intracoronary injection of the fatty acid, in which no background subtraction was performed. In ten patients myocardial elimination rates after intracoronary and after intravenous injection were determined. A modified bi-exponential curve fitting procedure, assuming a constant background activity, showed the best results compared with the intracoronary study.

Background Radiation↗
PubMed1985

Kinetics of radioiodinated heptadecanoic acid and metabolites in the normal and ischaemic canine heart.

This study was undertaken to elucidate if the myocardial elimination rate of the radioactivity after administration of radioiodinated heptadecanoic acid was related to beta-oxidation of the fatty acid or related to washout of free radioiodide. In samples of normal and ischaemic myocardium the distribution of the radioactivity over free radioiodide, heptadecanoic acid and lipids was determined. In normal myocardium the major component was free radioiodide, only a small percentage being heptadecanoic acid. In ischaemic myocardium more radiolabelled lipids were present and less free iodide when compared with normal myocardium. The percentage heptadecanoic acid was slightly increased. It is concluded that radioiodinated heptadecanoic acid behaves like the natural analogues regarding uptake and distribution. However, washout of free radioiodide determines the elimination rate as observed during a scintigraphic study.

Animals↗
PubMed1985

Thallium-201 exercise testing in patients 6-8 weeks after myocardial infarction: limited value for the detection of multivessel disease.

In a clinical study, the value of exercise electrocardiography and thallium-201 scintigraphy was determined for the detection of multivessel disease in 176 patients 6-8 weeks after a first myocardial infarction. In all patients coronary arteriography was performed within 3 days after the non-invasive procedure. Of the 176 patients, 77 patients had multivessel disease (prevalence 44%). The exercise electrocardiogram was positive in 49 of these 77 patients (sensitivity 64%), while the thallium scintigram was positive in only 24 patients (sensitivity 31%). When the results of both procedures were added, a moderate sensitivity of 66% and a similar specificity of 62% was found; the positive and negative predictive values were 57% and 70%, respectively, and were considered too low for the adequate clinical diagnosis of multivessel disease after myocardial infarction. Based on our results, it is concluded that qualitative assessment of thallium exercise scintigraphy, alone or combined with electrocardiography, should not be used to predict the absence or presence of multivessel disease in patients after previous myocardial infarction.

Aged↗
PubMed1985

Free fatty acid scintigraphy in patients with successful thrombolysis after acute myocardial infarction.

Twenty-three patients with successful intracoronary thrombolytic therapy in the acute stage of infarction underwent scintigraphy with radioiodinated heptadecanoic acid two weeks after myocardial infarction and three to 12 months later. In patients with normal or slow elimination rates in the infarct area, ejection fractions were significantly higher than in patients with fast elimination (70 +/- 6% vs 47 +/- 13%, P less than 0.05). Consequently, left ventricular damage score was lower in patients with normal and slow elimination rates (1.7 +/- 1.6 vs 4.9 +/- 2.4, P less than 0.05). Repeated scintigraphy showed normalization of the elimination rates in patients with previously slow elimination, except in one patient in whom the elimination rate remained slow, patients with fast elimination rates remained unaltered. It is concluded that scintigraphy with radioiodinated heptadecanoic acid is an appropriate method to assess myocardial viability in patients with successful thrombolytic therapy.

Adult↗
PubMed1985

Metabolic fate of radioiodinated heptadecanoic acid in the normal canine heart.

To clarify the metabolic fate of radioiodinated heptadecanoic acid in myocardium, the time course and distribution of the radioactivity over 131I-heptadecanoic acid, free radioiodide, and various lipids (with incorporated iodoheptadecanoic acid) were determined in normal canine myocardium. In 10 dogs seven biopsy specimens were taken over 30 min after injection of 131I-heptadecanoic acid. The radioactivity in the specimens increased until the fifth minute and decreased thereafter, with a half-time of 36 min. In the fifth minute, 61% of the radioactivity was free iodide, and its curve paralleled the curve of the total radioactivity. As early as the first minute 131I-heptadecanoic acid activity was reduced to 14% and decreased further. Activity of radioiodinated phospholipids, (mono, di, tri)-glycerides, and cholesterol-esters remained constant after an initial increase. These results indicate that immediately after uptake, 131I-heptadecanoic acid is either metabolized, liberating the radioiodide, or stored in lipids. Because the activity of radiolabeled lipids remained constant during the study period and because iodide activity paralleled the total activity in biopsy specimens, it is concluded that in normal myocardium, washout of free radioiodide determines the elimination rate as observed during a scintigraphic study. Thus the elimination rate cannot be related to the beta-oxidation rate as previously supposed.

Animals↗
PubMed1984

Metabolic consequences of beta-adrenergic receptor blockade for the acutely ischemic dog myocardium.

In an experimental study in 50 dogs the myocardial uptake of free fatty acids (FFAs) after beta-blockade was determined using radioiodinated heptadecanoic acid as a metabolic tracer. All 4 beta-blockers used (metoprolol, timolol, propranolol and pindolol) lowered the uptake of FFAs in the normal canine heart. Uptake of FFAs was also diminished after coronary artery occlusion per se, but administration of beta-blockers exerted little additional influence on the uptake of FFAs. This observation was qualitatively paralleled by the uptake of 201Tl in concomitant experiments. Plasma FFA levels were increased by pindolol (non-selective with intrinsic sympathomimetic activity), not changed by metoprolol (a cardioselective beta-blocking agent) and lowered by timolol and propranolol (both non-selective compounds). The extent of ischemic tissue, as reflected by uptake of iodoheptadecanoic acid and 201Tl, was diminished by metoprolol but not by other beta-blockers. Regional distribution of both tracers, as shown in the endo-epicardial uptake ratios, was hardly influenced by beta-blockade, except for a small increase of 201Tl uptake in non-occluded endocardium. Uptake of 201Tl as well as of iodoheptadecanoic acid in the ischemic area was increased by metoprolol, timolol and propranolol and decreased by pindolol. We conclude that beta-blocking agents confer different effects on myocardial uptake and metabolism of FFAs which might possibly be related to their different inherent properties.

Acute Disease↗
PubMed1984

Determination of myocardial FFA elimination rates by functional images of uncorrected half-time values.

This paper presents an alternative method of demarcating regions of interest over the myocardium after administration of 123I-heptadecanoic acid to patients with coronary artery disease. In a matrix of 32 X 32 pixels the elimination rates of the radioactivity, which are not corrected for background activity, are visualized per pixel in a functional image. The functional image showed areas in the myocardium with high values of uncorrected elimination rates. These areas corresponded with the tracer defects on the scintigram. Corrected elimination rates obtained from regions of interest of functional images were comparable with those of scintigrams. Thus based on functional images of uncorrected elimination rates a reliable, objective determination of regions of interest over normal and abnormal myocardium can be made.

Adult↗
PubMed1984

Myocardial uptake of iodinated free fatty acids and 201Tl in experimental ischemia.

In an experimental study, we evaluated the uptake of (131I)-17-iodo heptadecanoic acid (131I-HDA), (125I)-15-4 (4-iodophenyl) pentadecanoic acid (125I-PPA) and thallium-201 (201Tl) in the dog heart. Twenty dogs were studied and divided into 3 groups: in group A, 10 dogs (4 normal, 6 with coronary artery occlusion) were studied with 131I-HDA and 201Tl; in group B, 5 dogs (with occlusion) received 125I-PPA and 201Tl; and in group C, 5 dogs (with occlusion) were studied with 125I-PPA and 131I-HDA. Two min after administration of the compounds the hearts were excised and stored in formaldehyde. After sectioning of the left ventricle, total uptake was counted and expressed in percentage of injected dose. Uptake in the normal myocardium (group A) was 4.2 +/- 0.6% for 131I-HDA and 4.6 +/- 0.7% for 201Tl; in the occluded dog hearts (group A) we measured values of 2.6 +/- 0.4% for 131I-HDA (p less than 0.001) and 3.4 +/- 0.6% for 201Tl (p less than 0.01). Uptake of 131I-HDA, 125I-PPA and 201Tl in groups B and C was not significantly different: group B, 125I-PPA 2.8 +/- 0.8% and 201Tl 2.5 +/- 0.5%; group C, 125I-PPA 1.9 +/- 0.7% and 131I-HDA 1.6 +/- 0.6%. Moreover, regional distribution of both iodinated fatty acids was quite comparable with the distribution of 201Tl. We conclude that 131I-HDA and 125I-PPA show similar uptake as 201Tl and are distributed according to coronary artery perfusion, which underscores their value as myocardial imaging agents.

Animals↗