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Biomedical subjects

F C Visser

Publications and source records attributed to F C Visser.

At least 91 records · Page 5Linked to original sources
PubMed1991

Analysis of time-activity curves related to myocardial metabolism. The case of 123I-heptadecanoic acid.

Time-activity curves are frequently used in the external assessment of the kinetics of radiolabelled non-esterified fatty acids. Analysis of time-activity curves is accomplished by fitting an analytical curve through the data points of the time-activity curve, resulting in two or more parameters of the curve fit. Before interpreting the results of curve fitting, the precision of each of the parameters has to be determined. In the present study the precision of the parameters of monoexponential plus constant curve fit of time-activity curves after administration of 123I-heptadecanoic acid was assessed for an acquisition time of 75 min. Two parameters were used, the T1/2 of the monoexponential and the ratio A/A+C, where A is the amplitude of the monoexponential and C the constant. A model study was used to assess the precision of the parameters of curve fitting. The precision of the parameters was calculated for wide ranges of the T1/2 (0-60 min), A/A+C (0-100%) and the noise content of the time-activity curve. The results are presented as the 10th and 90th percentiles.

Animals↗
PubMed1991

Congestive heart failure: pathophysiology and management with special reference to systemic hypertension.

The recognition and management of heart failure is based on the knowledge of the underlying disease and precipitating factors. The underlying causes are all cardiovascular whereas precipitating factors comprise both cardiac and a variety of noncardiac factors. The influence of hypertension on the development of heart failure is complex. Increased ventricular systolic pressure raises myocardial oxygen demand, resulting in ischemic heart syndromes and arrhythmias. Also, systemic hypertension leads to hypertrophy, resulting in systolic and diastolic function abnormalities. Generally, heart failure is controlled by treating the underlying cause, by removal of precipitating factors, and by treatment of failure itself. Heart failure therapy involves general measures, and pharmacological and surgical therapy. The pharmacological treatment involves the use of diuretics, vasodilators, and positive inotropic agents. In patients with heart failure and hypertension, arterial and mixed type vasodilators are the drugs of choice. Positive inotropic agents have to be used with care because of the potential induction or aggravation of myocardial ischemia. Interest in beta-adrenergic-blocking agents, especially those with ancillary properties similar to vasodilators, has recently surged and will continue to provoke more and more clinical research in an attempt to unravel the complexities of these cardiovascular diseases and their therapies.

Animals↗
PubMed1990

Value of gadolinium-diethylene-triamine pentaacetic acid dynamics in magnetic resonance imaging of acute myocardial infarction with occluded and reperfused coronary arteries after thrombolysis.

The use of the paramagnetic contrast agent gadolinium-diethylene-triamine pentaacetic acid (DTPA) was evaluated in magnetic resonance imaging (MRI) of 18 patients with an acute myocardial infarction after thrombolysis. The patency of the infarct-related vessel was assessed by coronary angiography. At 58 +/- 9 hours after infarction MRI was performed before and after bolus injection of 0.1 mmol/kg gadolinium-DTPA. Myocardial signal intensities were measured using a circumferential profile. Normal and infarcted myocardium showed a maximum signal intensity enhancement of 35 and 66%, respectively. Signal intensity of infarcted relative to normal myocardium (I/N) increased from 1.06 +/- 0.16 before to a maximum of 1.39 +/- 0.13 after gadolinium-DTPA (p less than 0.001), whereas the contrast between normal myocardium and a pseudo-infarct region in 2 healthy volunteers did not change. Between patients with reperfused infarct-related vessels and occluded vessels without collaterals, maximum I/N did not differ. However, observing I/N as a function of time after injection of gadolinium-DTPA, the reperfusion group differed from the occlusion group on images acquired directly after injection (1.29 +/- 0.10 vs 1.14 +/- 0.05, p less than 0.02). Thus, gadolinium-DTPA enhanced the visualization of acute myocardial infarction on relatively longitudinal (T1)-weighted MR images and its dynamics seem of potential value for the noninvasive assessment of coronary artery reperfusion after thrombolysis.

Adult↗
PubMed1990

Usefulness of two-dimensional echocardiography for immediate detection of myocardial ischemia in the emergency room.

Inappropriate discharge from the emergency room of patients with acute chest pain may have serious consequences. Regional asynergy is one of the first signs of myocardial ischemia and can be detected with 2-dimensional echocardiography (2-DE). This study determines the value of 2-DE in the emergency room for immediate detection of myocardial ischemia causing acute chest pain at the time the electrocardiogram was nondiagnostic. Forty-three patients (32 men and 11 women) with a normal or nondiagnostic electrocardiogram during acute chest pain were studied with 2-DE. Only patients without a previous myocardial infarction and without known coronary artery disease (CAD) were studied. The entire left ventricular wall was examined for presence of regional asynergy. Coronary angiography was performed within 3 weeks. Cardiac enzyme levels were measured serially to establish or rule out an acute myocardial infarction. Sensitivity of 2-DE for detection of myocardial ischemia was 88% (22 of 25), specificity 78% (14 of 18), negative predictive accuracy 82% (14 of 17) and positive predictive accuracy 85% (22 of 26). Sensitivity of 2-DE for detection of acute myocardial infarction was 92% (12 of 13), specificity 53% (16 of 30) and negative predictive accuracy 94% (16 of 17). Thus, 2-DE during pain and a nondiagnostic electrocardiogram can readily identify patients with CAD in the emergency room, and it can accurately rule out an acute myocardial infarction.

Chest Pain↗
PubMed1990

Silent versus symptomatic myocardial ischemia during exercise testing: a comparison with coronary angiographic findings.

Two-hundred-and-eighty individuals with anginal complaints, without prior myocardial infarction and with a positive exercise stress test were divided into a group (n = 67) with exercise-induced silent myocardial ischemia and another group (n = 213) with exercise-induced angina pectoris. Both underwent coronary angiography and were compared with each other with respect to various exercise and angiographic parameters. Patients with exercise-induced silent ischemia attained a longer mean exercise duration (P less than 0.001), a higher peak exercise heart rate (P less than 0.0001) and a higher peak exercise rate pressure product (P less than 0.001) than patients with exercise-induced angina pectoris. In the latter group, more patients showed exercise-induced ST-segment depression greater than 2 mm (P less than 0.05). The group of patients with silent ischemia encompassed more individuals with normal coronary arteries (P less than 0.0001). More patients with exercise-induced angina pectoris had three-vessel disease (P less than 0.0001). The exclusion of patients with normal coronary arteries (23% in those with silent ischemia group and 6% in those with exercise-induced angina had no influence on the level of significance for peak heart rate, mean exercise duration and exercise duration greater than 10 min. Thus, in this population, exercise-induced silent myocardial ischemia is associated with better exercise performance and less extensive coronary arterial pathology than in exercise-induced angina pectoris.

Adult↗
PubMed1990

Clinical value of studies with radioiodinated heptadecanoic acid in patients with coronary artery disease.

The results described in the literature of myocardial scintigraphy with radioiodinated heptadecanoic acid (IHDA) to detect coronary stenoses are contradictory. In the present study, IHDA scintigraphy was performed in nine control subjects and 67 patients with coronary artery disease. The acquisition time was 75 min and background correction was not applied. The time-activity curves of regions of interest were analyzed by curve fitting with a monoexponential plus constant. Two parameters were used: the halftime value of the monoexponential (T1/2 in min) and the ratio of the amplitude (A) of the monoexponential and the total activity at time t = 0 (amplitude + constant = A + C): A/A + C as a percentage. Based on the control group, a region of normal T1/2 values and A/A + C ratios was defined, for each calculated T1/2-A/A + C pair the probability of originating from a normal region was calculated. The value of the IHDA test, using the index of merit (sensitivity + specificity-100%), increased in the patient group without MI with the severity of the stenosis (21%, 24% and 47% for stenoses greater than or equal to 75%, greater than or equal to 90% and greater than or equal to 99%). In patients with MI, only small positive values in regions of non-infarct-related vessels were found (-1%-16%). It is concluded that the value of the IHDA test to detect stenoses of coronary arteries is too low to apply this test in clinical practice. However, a new type of analysis is offered, based on curve fitting of individual pixels.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1990

The fate of 131I-17-iodoheptadecanoic acid during lactate loading: its oxidation is strongly inhibited in favor of its esterification. A radiochemical study in the canine heart.

The influence of lactate loading on fatty acid metabolism (pH = 7.4) by the normal canine heart was investigated radiochemically using the radioiodinated fatty acid 131I-17-iodoheptadecanoic acid (131I-17-HDA). Fatty acid metabolism was studied during control conditions (n = 8) and after lactate loading (n = 7). In the canine heart total myocardial 131I-17-HDA radioactivity (uptake) was not changed during the lactate intervention. The oxidation decreased fivefold (measured as free 131I-iodide ion) from 70% to 14% (p less than 0.0001, Student's t-test). Thin-layer chromatography of cardiac lipids demonstrated that the non-oxidized 131I-17-HDA was mainly stored in the triglycerides and phosphoglycerides. These results suggest that lactate inhibits cardiac 131I-HDA oxidation.

Animals↗
PubMed1990

The influence of lactate and dipyridamole on myocardial fatty acid metabolism in man, traced with 123I-17-iodoheptadecanoic acid.

Changes in myocardial metabolism can be detected externally by registration of time-activity curves after administration of radioiodinated fatty acids. In this scintigraphic study the influence of lactate on fatty acid metabolism was investigated in the normal human myocardium, traced with 123I-17-iodoheptadecanoic acid (123I-17-HDA). In patients (paired, n = 7) lactate loading decreased the uptake of 123I-17-HDA significantly from 27 (control: 22-36) to 20 counts/min/pixel (16-31; p less than 0.05 Wilcoxon). The half-time value increased to more than 60 min (n = 5), oxidation decreased from 61 to 42%. Coronary vasodilatation, a well-known side effect of lactate loading, was studied separately in a dipyridamole study (paired, n = 6). Coronary vasodilatation did not influence the parameters of the time-activity curve. These results suggest that changes in plasma lactate level as occurring, among other effects, during exercise will influence the parameters of dynamic 123I-17-HDA scintigraphy of the heart.

Aged↗
PubMed1989

Short-term and long-term prognosis after myocardial infarction: prognostic value of coronary anatomy and left ventriculography.

To assess prospectively short-term (1 year) and long-term (4 years) prognostic variables from heart catheterization, 325 consecutive patients of 65 years or less who survived a myocardial infarction were studied. In all coronary angiography and left ventriculography was performed 4-6 weeks after infarction. First year mortality rate was significantly higher in patients with an ejection fraction less than 0.30 (20%) than in patients with an ejection fraction greater than or equal to 0.30 (2%, P less than 0.001). During 4-year follow-up cumulative mortality was 44% in patients with an ejection fraction less than 0.30 vs 11% in patients with an ejection fraction greater than or equal to 0.30 (P less than 0.001). In patients who survived the first year after infarction, however, a low ejection fraction less than 0.30 was not associated with higher mortality rate during the subsequent 3 years. Mortality in patients with one-, two- or three-vessel disease was equally distributed in the first year. After 4 years patients with three-vessel disease had a significant higher mortality (32%) than patients with two- or one-vessel disease (12 and 11%, respectively; P less than 0.05). Reinfarction rate was higher in patients with an ejection fraction less than 0.30 (14%) than in patients with an ejection fraction greater than or equal to 0.30 (3%, P less than 0.05) in the first year. During 4-year follow-up reinfarction rate was 38% in patients with an ejection fraction less than 0.30 vs. 13% in patients with an ejection fraction greater than or equal to 0.30 (P less than 0.05). Again, in patients who survived the first year without reinfarction, an ejection fraction less than 0.30 had no prognostic value for recurrent myocardial infarction during the subsequent three years. Three-vessel disease had no higher reinfarction rate in the first year of follow-up: during 4 years, patients with three-vessel disease had a reinfarction rate (32%) compared to patients with two- and one-vessel disease (14 and 11%, respectively; P less than 0.05). It is concluded that an ejection fraction less than 0.30 is a major risk factor for cardiac death and reinfarction only in the first year after myocardial infarction. Beyond the first year, a subgroup of patients with three-vessel disease is at risk for both cardiac death and reinfarction during the three subsequent years.

Adult↗
PubMed1989

Reperfused and nonreperfused myocardial infarction: diagnostic potential of Gd-DTPA--enhanced MR imaging.

Forty-five patients with suspected acute myocardial infarction were examined with magnetic resonance (MR) imaging before and serially up to 30 minutes after intravenous injection of gadolinium diethylenetriaminepentaacetic acid (DTPA), 0.1 mmol/kg of body weight. Coronary angiography after thrombolytic therapy was performed in all patients to assess reperfusion. Intensity ratios between both reperfused and nonreperfused infarcted areas and normal myocardium increased significantly up to 15-20 minutes after administration of Gd-DTPA and were still elevated 30 minutes after injection (P less than .0001). In accordance with the findings in experimental studies, four distribution patterns of infarct enhancement were observed. The overlap in enhancement patterns and similar maximal intensity ratios after Gd-DTPA administration for both reperfused and nonreperfused infarcts preclude a reliable differentiation on the basis of these factors alone. Significant enhancement of both reperfused and nonreperfused infarcts allows adequate infarct imaging up to at least 30 minutes after administration of Gd-DTPA.

Adult↗
PubMed1988

Evaluation of magnetic resonance imaging for determination of left ventricular ejection fraction and comparison with angiography.

Left ventricular ejection fraction was measured by magnetic resonance imaging (MRI) and compared with standard monoplane left ventriculography in 46 patients with various cardiac diseases. Two different MRI strategies were used. In 28 patients (group 1), ejection fraction was determined using a single slice comparable with the right anterior oblique projection of the ventriculogram. Comparison of left ventricular ejection fraction yielded a poor correlation between single slice MRI (y) and ventriculography (x) (y = 28.7 + 0.47 x, r = 0.65). In 18 patients (group 2), a multiple contiguous slice MRI technique was used to allow ejection fraction and stroke volume determination by summing up the volumes of ventricular cavity intersections. Regression analysis showed a high correlation between multiple slice MRI (y) and ventriculography (x) (y = 7.2 + 0.88 x, r = 0.98). Also, correlation between MRI right (y) and left (x) ventricular stroke volumes was satisfactory, (y = -12.8 + 1.09 x, r = 0.83). It is concluded that the multiple slice imaging technique in MRI provides an accurate noninvasive means for quantification of left ventricular ejection fraction that can be extended to the determination of left ventricular volume.

Angiocardiography↗
PubMed1988

Magnetic resonance imaging of the heart for determination of ejection fraction.

In 28 patients with various cardiac diseases we compared ejection fractions obtained by magnetic resonance imaging in a single oblique slice with monoplane ventriculography in the right anterior oblique projection, the latter serving as the standard. Also, results were evaluated for clinical relevance and relation to image quality. The correlation between the two techniques was moderate (r = 0.65). According to our standardized limits for clinical relevance, insufficiently correlating ejection fractions were obtained in 14 patients. In 8 of these patients this was attributed to poor endocardial edge detection. Edge detection problems were more frequently encountered by imaging with echo-time 20 msec than with echo-time 32 msec. Other causes for mismatching of the obtained ejection fractions are discussed. It is concluded that determination of ejection fraction by single slice magnetic resonance imaging should not be used for clinical application. Improvement can be expected by using a contiguous slicing technique, a longer echo-time in the spin-echo pulse sequence, or in due course by application of newly developed fast-imaging pulse sequences.

Cardiomyopathy, Hypertrophic↗
PubMed1988

Comparison of 17-iodine-131 heptadecanoic acid kinetics from externally measured time-activity curves and from serial myocardial biopsies in an open-chest canine model.

The relation between the externally measured myocardial time-activity curve and the radiochemically determined kinetics of iodine-131(131I) heptadecanoic acid was studied in an open-chest canine model under different metabolic interventions. Kinetics were assessed by analysis of 12 biopsies taken in an assay period of 90 min. Time-activity curves were fitted with a monoexponential plus constant. The halftime value of the exponential of the external curve corresponded well with the elimination rate of 131I from the myocardium: 14.6 +/- 4.5 min vs. 14.6 +/- 5.3 min. The constant was build up of three components: free 131I in cardiac tissue, the almost constant activity of the radiolabeled free fatty acid (FFA) in the myocardial lipid pool, and the radioactivity of blood and noncardiac tissues. The contribution of blood and noncardiac tissue to the constant amounted to a mean value of 77%. These findings support the analysis of externally measured time-activity curves with a monoexponential plus constant curve fit, in which background correction is not necessary. In cases where lipid storage is predominantly present, high T1/2 values, both internally and externally, were found, which were fitted with a monoexponential curve. It can be concluded that externally measured time-activity curves reflect satisfactorily the kinetics of radioiodinated heptadecanoic acid.

Animals↗
PubMed1988

Pacing and the non-invasive evaluation of myocardial fatty acid metabolism by means of 17-123I-heptadecanoic acid scintigraphy.

The extent of myocardial non-esterified fatty acid (NEFA) oxidation depends among other things on exogeneous NEFA supply and energy demand. In 6 patients with a multi-programmable pacemaker scintigraphy with 17-123Iodo-heptadecanoic acid (17-123I-HDA) was performed to investigate NEFA metabolism at two levels: at a control level (basal heart rate 69 +/- 6) and at increased pace frequency (104 +/- 5). In both situations the derived time-activity curves, measured during a period of 75 min, were fitted with a monoexponential plus a constant curve: A(t) = A(0).exp (-t In2/T1/2) + C. The half-time value, the uptake measured as the peak activity and the relative size of the oxidation pool were determined. The median of the half-time value did not change: 24 min (range 19-31) in the control heart rate study and 22 min (19-27) during the increased pace frequency study. The median of the uptake increased significantly from 33 cpm/pixel/2 mCi/100 kg (23-34) to 40 cpm/pixel/2 mCi/100 kg (35-42; p less than 0.05 Wilcoxon). The median of the relative size of the oxidation pool increased from 57% (52-62) to 69% (63-71; p less than 0.05). We conclude that during pacing the augmented need for NEFA resulted in a demonstrable increase in uptake and oxidation of 17-123I-HDA. This result suggests that radioiodinated NEFA may be a valuable tool to quantify noninvasively the level of the myocardial NEFA metabolism in the human heart.

Fatty Acids↗
PubMed1987

The influence of glucose on the myocardial time-activity curve during 17-iodo-123 heptadecanoic acid scintigraphy.

The lipid pools of the heart (i.e. the triglyceride and phospholipid pool) participate in the free fatty acid metabolism. The degree of involvement, for instance will be determined by the available substrate in the blood. Scintigraphy with 17-iodo-123 heptadecanoic acid was performed to study free fatty acid kinetics in the normal human myocardium during control and glucose infusion (n = 9). In both situations the derived time-activity curves, measured during a period of 75 min, obeyed a monoexponential plus a constant curve fitting [A(t) = A(o)exp(-tln2/T1/2)+C]. During glucose infusion the half-time values did not change but the lipid storage increased in favour of the oxidation pool. In the three protocols used, hypoglycaemic responses were observed, therefore these protocols cannot be advocated.

Fatty Acids↗