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Biomedical subjects

F C Visser

Publications and source records attributed to F C Visser.

At least 73 records · Page 4Linked to original sources
PubMed1995

Relation between myocardial uptake of thallium-201 chloride and fluorine-18 fluorodeoxyglucose imaged with single-photon emission tomography in normal individuals.

Recently, we have demonstrated the feasibility of imaging myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) with single-photon emission tomography (SPET) using a specially designed collimator. Thallium-201 was used to determine distribution of perfusion for comparison with FDG uptake. However, regional 201Tl and FDG activities may be different, based on differences in tracer attenuation and the use of different collimators. To study the relation between tracer activities imaged with SPET, nine healthy individuals underwent resting 201Tl SPET and FDG SPET during a hyperinsulinaemic euglycaemic clamp. The SPET data were analysed semiquantitatively, using circumferential profiles. Mean profiles of midventricular short-axis slices showed no significant difference between 201Tl and FDG activity. Regional fluctuations were similar for FDG and 201Tl; the highest tracer activities were observed in the lateral wall and the lowest activities in the septum. Finally, pooled data (n = 1620 segmental activities) in nine individuals showed a linear correlation (P < 0.0001) between 201Tl and FDG activity: FDG = 0.76 201Tl + 0.23 (r = 0.70). These data demonstrate the absence of major differences between regional 201Tl and FDG activity in normal myocardium, suggesting that no separate 201Tl and FDG SPET reference values are needed for comparison with patient studies.

Adult↗
PubMed1995

Detection of viability after myocardial infarction: available techniques and clinical relevance--a review.

The differentiation of viable from nonviable myocardium in patients with myocardial infarction (MI) and left ventricular (LV) dysfunction is of important clinical relevance. It is now known that impaired LV function after infarction not always represents an irreversible process. LV ejection fraction is significantly reduced in many patients after infarction and, although abnormally contracting myocardial segments may result from irreversible scarring, numerous studies have shown that many asynergic zones have sustained metabolic activity. An accurate detection of myocardial viability aids in clinical decision making to select the appropriate therapy for patients with MI. Recently, cardiac imaging techniques that evaluate myocardial viability on the basis of myocardial perfusion, cell membrane integrity, metabolic activity and residual coronary reserve, have been developed with clinical success. These methods provide greater precision in the assessment of viable myocardium than can be achieved by analysis or coronary anatomy, regional function or the presence or absence of electrocardiographic Q waves, criteria that were used in the past. The clinical challenge is to predict which myocardial regions are viable and will improve systolic function after revascularization, thereby enhancing global LV function. In this review, the currently available imaging techniques for assessment of myocardial viability are discussed.

Cell Membrane↗
PubMed1995

Magnetic resonance imaging of the pulmonary venous flow pattern in mitral regurgitation. Independence of the investigated vein.

OBJECTIVES: The aim of the present study was two-fold: first, to quantify characteristic parameters of the pulmonary venous flow pattern in patients with mitral regurgitation by using magnetic resonance phase velocity mapping; second, to determine whether this pattern is dependent on the vein being investigated and the direction of the regurgitant jet. BACKGROUND: Echocardiographic findings threw doubt on whether the pulmonary venous flow pattern is independent of the vein being investigated and whether the flow velocities in the pulmonary veins have a linear relationship with the volume flow. SUBJECTS AND METHODS: Flow patterns were assessed in all four pulmonary veins by magnetic resonance velocity mapping in healthy volunteers and in 17 patients with echocardiographically mild and 13 patients with severe regurgitation. RESULTS: No differences were found between the use of velocity or volume flow for characterizing individual curves. The pulmonary venous flow pattern in controls was characterized by six points, a biphasic systolic wave (maximum systolic volume flow: 29 +/- 18 ml.s-1), and end-systolic descent (24 +/- 18 ml.s-1), a biphasic diastolic wave (maximum diastolic volume flow: 69 +/- 22 ml.s-1) and an end-diastolic reversed flow. Reversed end-systolic flow was a characteristic sign of severe regurgitation (-10 +/- 18 ml.s-1). The systolic-to-diastolic flow ratio was lower in severe regurgitation (0.5 +/- 0.6) than in mild regurgitation (1.4 +/- 0.9), P < 0.0001). In severe regurgitation, the normalized time intervals from Q wave to the highest systolic peak and end-systolic descent were of less prolonged duration than in mild regurgitation and controls (P < 0.01). Flow patterns between veins were similar and the median of the correlation coefficients between the curves was the same in patients with or without an eccentric jet, 0.80 and 0.81, respectively. CONCLUSION: Magnetic resonance velocity mapping is helpful in determining and understanding pulmonary venous flow characteristics. It is demonstrated that the pulmonary venous flow pattern is independent of the vein being investigated irrespective of the regurgitant jet direction, and that it is useful in grading mitral regurgitation.

Adult↗
PubMed1995

Myocardial F-18 fluorodeoxyglucose imaging by SPECT.

F-18 fluorodeoxyglucose (FDG) in combination with positron emission tomography (PET) is used in patients with coronary artery disease to detect viable myocardium. It was shown that FDG PET is highly accurate in predicting reversibility of cardiac function after revascularization when viable tissue is present. Because PET centers are not widely available, the clinical use of FDG is limited. The authors have shown in another study that imaging 511 keV with planar scintigraphy and a special collimator is feasible. Furthermore, they have studied myocardial FDG uptake in normal volunteers and in patients with coronary artery disease using SPECT. Recently, they have studied the value of FDG SPECT to predict recovery of contractile function before revascularization in patients undergoing bypass surgery. It appears that the FDG SPECT approach is feasible and can predict reversibility of wall motion abnormalities. Further studies are needed to compare FDG SPECT with other techniques for the detection of viable myocardium.

Coronary Disease↗
PubMed1995

Feasibility of planar fluorine-18-FDG imaging after recent myocardial infarction to assess myocardial viability.

UNLABELLED: The aim of this study was to define the clinical feasibility of planar myocardial 18F-fluorodeoxyglucose (FDG) imaging and to assess the relation between 201Tl, FDG and left ventricular function early after myocardial infarction. METHODS: Fifty-one patients were studied 5 +/- 2 days after infarction. Scintigraphic images were visually and quantitatively analyzed using a circumferential profiles technique. FDG uptake was normalized to the area with maximal 201Tl uptake. Scintigraphic data were compared with left ventricular wall motion as assessed by ventriculography in 22 patients. Relative regional 201Tl uptake was categorized as normal (> or = 75% of peak activity), moderately reduced (50%-75%) or severely reduced (< 50%). These tracer defects were considered viable if FDG uptake exceeded 201Tl uptake by > or = 20% and/or if FDG uptake was normal (> or = 75%). All regions with FDG uptake 20% less than 201Tl uptake were considered nonviable. RESULTS: Four hundred forty-one myocardial regions were analyzed; 200 showed normal 201Tl uptake, 241 had reduced uptake, 191 had moderately reduced 201Tl uptake and 50 regions had severely reduced uptake. Viability for moderately and severely reduced regions was observed in 62% and 48%, respectively. A concordance between flow and metabolism was observed in 38% and 52%, respectively. CONCLUSION: Myocardial FDG imaging is feasible with standard gamma camera systems and enables the identification of regions with preserved glucose metabolism in patients shortly after infarction.

Coronary Angiography↗
PubMed1993

Value and limitations of exercise stress testing to predict the functional results of coronary artery bypass grafting.

To assess the value of exercise stress testing to predict the functional result of revascularization, 90 patients were evaluated by coronary angiography and exercise testing pre and postoperatively. Patients were classified on the basis of the postoperative angiogram in a group with successful surgery and a group with unsuccessful surgery. The predictive accuracy positive of ST segment depression to detect unsuccessful surgery was 67% The predictive accuracy negative was 61%. The best predictor of unsuccessful surgery was residual angina pectoris after revascularization with predictive value positive and negative of 85% and 60%, respectively. Thus exercise stress testing has limited value to accurately predict the degree of revascularization.

Adult↗
PubMed1993

The prognostic value, clinical, and angiographic characteristics of patients with early postinfarction angina after a first myocardial infarction.

To evaluate the prognostic value of early postinfarction angina and its relationship to clinical and angiographic variables, 231 consecutive patients who had a first myocardial infarction were studied. All underwent cardiac catheterization within 10 weeks after admission to the hospital. There were no differences in basic characteristics or in ejection fraction, extent or severity of coronary artery disease, or collateral circulation between the patients with early postinfarction angina (n = 27) and those without early postinfarction angina (n = 204) except for the incidence of angina before myocardial infarction. Patients with early postinfarction angina had exercise-induced angina (42% vs 21%; p < 0.025) more frequently and shorter exercise duration (6.9 +/- 2.5 minutes vs 8.3 +/- 2.5 minutes; p = 0.007). Early postinfarction angina was associated with a significantly higher event rate (15% vs 4%; p < 0.025) and a significantly higher mortality rate (15% vs 3%; p < 0.005) in the first year after infarction but not during the subsequent 4-year follow-up. In patients with early postinfarction angina, stress test results had no predictive value for future cardiac events in contrast to patients without early postinfarction angina in whom ST-segment depression as observed on the stress test ECG and exercise duration had predictive value for future cardiac events. In patients with early postinfarction angina there was no relationship between the incidence of events and the number of diseased vessels in contrast to patients without early postinfarction angina who had a high incidence of events when three-vessel disease was present (16% vs 62%; p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Feasibility of assessing regional myocardial uptake of 18F-fluorodeoxyglucose using single photon emission computed tomography.

Differentiation between viable myocardium and scar tissue in segments with abnormal contraction has important consequences in the clinical management of patients with coronary artery disease. Positron emission tomography (PET) can identify viable tissue using 18F-fluorodeoxyglucose (FDG). However, application of PET for daily routine is limited. In this study, FDG uptake was visualized with single photon emission computed tomography (SPECT) and compared with regional perfusion assessed with thallium-201 (201Tl) SPECT. The scintigraphic findings were related to regional wall motion determined with two-dimensional echocardiography. Patients (n = 9) with wall motion abnormalities underwent FDG SPECT and resting 201Tl SPECT. To control the metabolic status patients were studied with a hyperinsulinaemic euglycemic clamp during FDG SPECT. Analysis of reconstructed data was performed visually and semiquantitatively using circumferential profiles. High-quality images were obtained. Eight 201Tl defects showed concordantly decreased FDG uptake (metabolism-perfusion matches) indicating scarred tissue, whereas six regions of hypoperfusion demonstrated a relatively increased FDG uptake (mismatches), suggesting viable myocardium. Semiquantitative analysis confirmed visual findings. Mean 201Tl and FDG activities were not significantly different in matching defects. In mismatches the mean FDG activity was 81 +/- 11% vs 64 +/- 9% mean 201Tl activity (P < 0.0001). In four of six segments with increased FDG uptake, two-dimensional echo revealed hypokinesia. Seven of eight regions with a matching defect in contrast were akinetic. Thus, in the areas with a mismatch contractility was preserved. We conclude that FDG uptake can be visualized with SPECT. Furthermore, our preliminary observations suggest that this approach can identify viable tissue.

Adult↗
PubMed1993

Comparison of uptake, oxidation and lipid distribution of 17-iodoheptadecanoic acid, 15-(p-iodophenyl)pentadecanoic acid and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid in normal canine myocardium.

The kinetics of 17-[123I]iodoheptadecanoic acid (IHDA), 15-(p-[125I]iodophenyl)pentadecanoic acid (pIPPA) and 15-(p-[131I]iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) were investigated in normal canine myocardium. After simultaneous intravenous injection, myocardial biopsy specimens and samples of arterial blood were taken over 80 min. IHDA showed the highest myocardial uptake (995 +/- 248 dpm/mg.mCi versus pIPPA: 785 +/- 197 dpm/mg.mCi, ns) and the largest size of oxidation (74% +/- 4% versus pIPPA: 65% +/- 5%, p < 0.05). Myocardial activity of IHDA decreased with a half-time value of 11.2 min (pIPPA: 13.2 min). Phospholipids were the main lipid fraction into which IHDA was incorporated, whereas pIPPA was predominantly incorporated into triacylglycerols. DMIPPA myocardial activity remained constant during the assay period and instead of being oxidized, DMIPPA was mainly incorporated into triacylglycerols (55% +/- 12%). The myocardium-to-blood ratios of DMIPPA were greater than 10:1. The ratios at peak for IHDA and pIPPA were 4.1:1 and 3.9:1, respectively (both p < 0.0001 versus DMIPPA). In conclusion, differences have been found in the myocardial uptake, oxidation and lipid distribution of IHDA, pIPPA and DMIPPA. DMIPPA is a promising tracer for fatty acid uptake studies with single-photon emission computerized tomography because of its prolonged retention and high myocardium-to-blood ratios.

Animals↗
PubMed1992

Incorporation of radioiodinated fatty acids into cardiac phospholipids of normoxic canine myocardium.

The aim of this study was to assess the phospholipid distribution of radioiodinated 17-iodoheptadecanoic acid (IHDA), 15-(p-iodophenyl)pentadecanoic acid (p-IPPA) and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) under normoxic conditions and to compare these data with the fatty acid composition of the phospholipid classes. After simultaneous i.v. injection of the radioiodinated fatty acids (I-123-IHDA; I-131-p-IPPA; I-125-DMIPPA) in open-chest dogs seven myocardial biopsies were taken over 40 min (n = 26). After lipid extraction of the biopsies the organic phase was analyzed for both neutral and polar lipids by two different TLC systems. The following polar lipid fractions were analyzed: lysophosphatidylcholine (LPC), sphingomyelin (SPH), phosphatidylcholine (PC; lecithin), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG; cardiolipin) and neutral lipids. Fractions were counted in a gamma well counter and corrected for cross-over and recovery. Results of the polar phospholipids analysis showed that IHDA has the highest incorporation into the phospholipids. The IHDA was mainly incorporated into PI (45.6%) followed by PC (30.9%), PE (14.0%) and PS (5.6%). The p-IPPA was predominantly incorporated incorporated into PC (37.2%), followed by PS (20.1%) and PE (13.7%). In contrast to IHDA, incorporation of p-IPPA into PI was small (6.4%). The DMIPPA analogue was incorporated into phospholipids to only a very small degree, compared to IHDA and p-IPPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Performance characteristics of a 511-keV collimator for imaging positron emitters with a standard gamma-camera.

Line-source experiments were conducted to assess the performance of a gamma-camera equipped with a specially designed 511-keV collimator for the planar imaging of positron emitters. The results were compared with the camera performance with routinely used collimators and radionuclides (thallium-201, technetium-99m and gallium-67). With positron emitters, scatter contributed less to the widening of the line spread function than with radionuclides emitting lower photon energies. These observations can be explained by the relative deterioration in the discrimination power of the gamma-camera to reject scattered radiation at low energies. Planar 511-keV imaging may provide relevant clinical information, as we showed by fluorodeoxyglucose studies in a patient with a myocardial infarction and in a patient with a malignant lymphoma. It is concluded that positron emitters can be effectively applied for planar imaging with the generally available gamma-cameras. This study implies that radiotracers developed for positron emission tomography may find a place in the practice of conventional nuclear medicine.

Adult↗
PubMed1992

Reproducibility of symptom-limited exercise-stress testing performed 2 and 6 weeks after myocardial infarction.

To assess the reproducibility of variables with prognostic value from exercise testing, two symptom-limited treadmill exercise tests were performed in 76 consecutive patients at 2 weeks (predischarge) and 6 weeks after myocardial infarction. In addition, cardiac catheterization was performed at 6 weeks. Exercise duration showed a moderate increase from 7.9 +/- 4.4 min to 8.8 +/- 3.0 min (NS). The rate-pressure product increased from 22,377 +/- 5491 to 24,832 +/- 7261 (P less than 0.001). Reproducibility of ST-segment depression was dependent on the initial response: among the group of 25 patients with ST-segment depression at 2 weeks, only 13 (52%) patients had a reproducible result, whereas among the group of 51 patients without initial ST-segment depression, 40 (78%) patients showed reproducibility. There was no difference in coronary anatomy or ejection fraction between the groups with and without reproducibility results. Among the 30 patients with initial ST-segment elevation, 15 (50%) patients showed reproducibility, while among the 46 patients without initial ST-segment elevation, 42 (91%) patients showed reproducibility: the ejection fraction was significantly higher in the latter group than in the group of patients with lower reproducibility. Thus predischarge exercise testing in postinfarction patients identifies a different group of patients at risk compared to exercise testing after 6 weeks, due to considerable variation between the two tests.

Adult↗
PubMed1992

Global left ventricular perfusion: noninvasive measurement with cine MR imaging and phase velocity mapping of coronary venous outflow.

Velocity and volumetric flow of left ventricular venous outflow in the distal coronary sinus were measured with magnetic resonance (MR) velocity mapping techniques in 24 healthy men. A total of 16-21 velocity maps were acquired throughout the cardiac cycle. To determine the accuracy of the MR velocity-mapping pulse sequence, measurements were obtained with a flow phantom. Mean blood flow was 144 mL/min +/- 62 (standard deviation); mean velocity, 2.1 cm/sec +/- 1.0; and mean cross-sectional area, 1.2 cm2. Phasic measurements revealed a biphasic flow pattern in the coronary sinus, with a first peak in systole (257 mL/min +/- 174) and a second peak in early diastole (1,090 mL/min +/- 487). The cross-sectional area varied between 0.5 cm2 +/- 0.2 at end diastole and 1.9 cm2 +/- 0.6 in systole, a finding that suggests a capacitance function for venous outflow. Mean blood flow measurements were in agreement with measurements obtained invasively in previous studies. It is concluded that MR velocity mapping can enable noninvasive measurement of coronary venous outflow and global left ventricular perfusion and may become clinically useful in assessment of coronary blood flow reserve.

Adult↗
PubMed1992

Prognostic value of thallium-201 exercise scintigraphy in low-risk patients after Q-wave myocardial infarction: comparison with exercise testing and catheterization.

In a prospective study of 100 consecutive patients discharged after a Q-wave myocardial infarction, the value of reversible ischemia on thallium-201 scintigraphy to assess the risk of cardiac events (death or reinfarction) during 4 years was compared with variables from exercise testing and cardiac catheterization. Patients with markedly impaired left ventricular function [ejection fraction (EF) < or = 0.30] were excluded. During follow-up there were 20 cardiac events (10 cardiac deaths and 10 reinfarctions). Thallium-201 scintigraphy was significantly better than all exercise test variables and better than an EF < 0.40, with good sensitivity and specificity (75 and 51%, respectively). Exercise-induced reversible ischemia on scintigraphy yielded the same information as the presence of multivessel disease. Exercise test variables were of limited value to assess prognosis. Thus, thallium-201 scintigraphy can be used as the only tool to predict future cardiac events in low-risk patients after a Q-wave myocardial infarction.

Adult↗
PubMed1991

Effects of nisoldipine on systolic and diastolic function in postinfarction patients with reduced left ventricular function: a randomized, double-blind, placebo controlled study.

The long-term effects of oral nisoldipine or placebo on clinical variables, exercise test results and echo Doppler-determined systolic and diastolic functions were studied in 30 consecutive patients with reduced left ventricular function (predischarge echocardiographic wall motion score greater than or equal to 8) following myocardial infarction. Groups were comparable in clinical variables, exercise results, echo Doppler measurements and coronary anatomy. During 6 months follow-up, death, reinfarction and bypass surgery or balloon angioplasty were equally distributed. A significant increase in exercise duration and time to onset of ST-depression was found in the nisoldipine treatment group, compared to the placebo group after 3 and 6 months. Time to onset of angina was not significantly different. Echocardiographic indices of left ventricular systolic function (ejection fraction and wall motion score) were unaltered; however, the time-velocity integral of the early diastolic filling phase and the early vs late diastolic flow velocity ratio were significantly increased while the atrial time-velocity integral vs total time-velocity integral was significantly decreased in the nisoldipine treatment group after 3 and 6 months of follow-up. In conclusion, nisoldipine reduced exercise-induced ischaemia, improved exercise capacity and diastolic left ventricular function in postinfarction patients with reduced left ventricular function.

Cardiac Catheterization↗
PubMed1991

Independent prognostic value of supraventricular arrhythmias on 24-h ambulatory monitoring following myocardial infarction.

To determine the prognostic value of supraventricular arrhythmias, in addition to ventricular arrhythmias and clinical variables after myocardial infarction, 99 consecutive patients had 24-h ambulatory monitoring within 2 weeks of discharge. All patients completed at least 4-year follow-up (mean 56 +/- 6 months). During follow-up there were 29 cardiac events (13 cardiac deaths and 16 reinfarctions). The highest risk was associated with ventricular tachycardia (positive predictive accuracy 100%, negative predictive accuracy 75%, risk ratio 4.0) and supraventricular tachycardia i.e. paroxysmal tachycardia or AV nodal tachycardia (positive predictive accuracy 86%, negative predictive accuracy 80%, risk ratio 4.2). By multivariate analysis, supraventricular tachycardia proved to be an independent predictive variable, in addition to ventricular tachycardia, premature ventricular depolarisations greater than or equal to 10 h-1 and the presence of Killip class greater than or equal to II while in the coronary care unit for future cardiac events. These data suggest that supraventricular tachycardias detected on 24-h ambulatory monitoring shortly after discharge carry a poor prognosis and may indicate a different pathophysiology as compared to ventricular tachycardias.

Aged↗
PubMed1991

An in vivo validation of quantitative blood flow imaging in arteries and veins using magnetic resonance phase-shift techniques.

Magnetic resonance (MR) techniques have recently been introduced, allowing quantitative measurement of blood flow with high spatial and temporal resolutions. These techniques are based on the phase of the MR signal rather than on the amplitude, and are referred to as MR phase or velocity mapping. Clinical validation is still lacking. We therefore performed an in vivo validation of such a technique in 17 healthy volunteers. Velocity maps were acquired at 50 ms intervals over the cardiac cycle in the aorta, superior and inferior vena cava. Plots were made of flow velocity and volume flow vs time and used for calculation of left ventricular stroke volume (SV), cardiac output (CO) and venous return. Comparison with Doppler ultrasound (x) yielded y = -7.5 + 1.1x (r = 0.76) for SV measurements (ml), and y = 0.3 + 0.9x (r = 0.86) for CO calculations (1 min-1). Comparison between MR SV (x) and MR determination of venous return (y), obtained by summation of the flow volumes per cardiac cycle in the superior and inferior vena cava, was close to identity, y = 1.3 + 1.0x (r = 0.91). Also, preliminary applications are presented in patients with aortic diseases. The findings of this study show that magnetic resonance velocity imaging can be accurately applied in vivo as a non-invasive means of measuring flow.

Aortic Dissection↗