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Biomedical subjects

A L van Gelder

Publications and source records attributed to A L van Gelder.

17 recordsLinked to original sources
PubMed1993

Gated blood pool SPECT and phase analysis to assess simulated Wolff-Parkinson-White syndrome in the baboon.

This study assesses the diagnostic potential of a tomographic technique with phase analysis to detect premature electroventricular contraction patterns simulated by pacing in the baboon. The data of gated SPECT were analysed by backprojection of the Fourier coefficients, followed by angulation and integration to thick slices of the entire ventricular mass yielding separate ventricular contraction patterns in three perpendicular views. Electrodes were implanted in each baboon: at the sinoatrial node; posterior, left ventricular; anterior left ventricular; on the left and the right lateral ventricular walls. The atrium was stimulated throughout at a fixed rate. Subsequent ventricular stimuli followed during the QRS complex, such to invoke the appearance of pre-excitation QRS morphology. The first points of activation (FPA) from this algorithm were correctly detected for the RV, for the anterior and posterior sites, although the latter two manifested first points in the RV. LV pacing manifested also as a FPA in the RV, but was followed by a true subsequent point in the LV.

Algorithms↗
PubMed1991

The effect of fluid resuscitation on cardiac function changes monitored by radionuclide ventriculography in the septic shock baboon model.

Dramatic cardiac volume losses accompanied by a drop in arterial pressure and in pulmonary capillary wedge pressure (PCWP) were found to characterise the baboon model in bacterial septic shock. Loss of vascular tone and a probable vascular fluid leak were regarded as contributing factors. To prove this hypothesis an experiment was planned with the baboon model in septic shock, and an added protocol for fluid administration whereby the pulmonary wedge pressure was kept at 7 +/- 2 mm Hg. The six baboons served as their own controls. Raising PCWP by means of fluid loading resulted in an attenuation of the drop in left ventricular volumes, to a smaller decrease in stroke volume (SV) and smaller increases in left ventricular ejection fraction. The drop in arterial pressure remained and left ventricular stroke work therefore reflected the decrease in SV. Compliance as by EDV/PCWP remained unchanged. Fluid loading therefore, although not normalising the haemodynamic parameters, led to smaller changes and an improvement in some measures of cardiac function.

Animals↗
PubMed1990

Are clinical differences between black and white stroke patients caused by variations in the atherosclerotic involvement of the arterial tree?

The differences in site and degree of atherosclerotic involvement of various vascular beds and their clinical significance are emphasised in a study of 304 black stroke patients. Detailed clinical examinations, computed tomography (CT), gated blood pool studies, echocardiography and ECG were performed and autopsy studies carried out. CT of the brain showed that non-haemorrhage, i.e. ischaemic lesions, accounted for 71.2% of strokes, a similar figure to that found in white stroke patients. However, carotid bruits (0.62%) and peripheral vascular disease (0.9%) followed by transient ischaemic attacks (1.9%) were found to be uncommon. Similarly, ischaemic heart disease (6.9%) appeared to be less common than the incidence in reported white stroke patients. In 30 patients who came to autopsy, the maximum degree of atherosclerotic stenosis of the extracranial carotid arteries was 21.7% of the lumen diameter. The differences in the site and degree of atherosclerosis in blacks not only give rise to differences in the clinical features of stroke patients but may have an important bearing on their investigation, management and prognosis.

Adolescent↗
PubMed1989

The cardiovascular status of the black stroke patient.

The cardiac status of 102 consecutive black stroke patients entered to the Medunsa Stroke Databank was determined. Cardiological examination, echocardiography and a gated blood pool scan revealed structural and/or functional cardiac abnormalities in 73.6% of patients. Rheumatic heart disease was diagnosed in 15.6%, mitral valve prolapse in 5.8% and mitral annulus calcification in 4.9% of cases. 'Possible' cardiac sources of cerebral embolism were detected in 22.5% and 'definite' sources in 23.5% of patients. Hypertensive heart disease was diagnosed in 35.2% and cardiomyopathy in 13.7% of the study population. Ischaemic heart disease was present in 6.86%. Ultrasonography revealed ventricular bands in 29.4% of patients. The high incidence of structural cardiac abnormalities detected by non-invasive means is in keeping with recent studies in white stroke patients.

Adolescent↗
PubMed1989

Left ventricular volume and function changes during beta-blockade and accompanying atrial pacing.

Radionuclide ventriculography was performed at rest and during transoesophageal pacing on nine anaesthetized baboons (Papio ursinus), alternatively with and without administration of a beta-blocker. Left ventricular volumes, cardiac output, and ejection fraction were determined at each heart rate. A gradual decrease in end-diastolic, end-systolic, and stroke volume followed with increasing heart rate, significantly more pronounced under beta-blockade. Cardiac output and ejection fraction showed no significant changes, although tendencies to increase were observed without beta-blockade. Comparisons of these parameter changes were drawn to those previously observed during the first 5 h of septic shock (E. coli). We conclude that the tachycardia present during this phase of shock is not the only contributory factor to cardiac function changes but that other depressant influences prevail as the added effect of the beta-blocker seems to suggest.

Adrenergic beta-Antagonists↗
PubMed1989

Changes in phase analysis patterns of radionuclide ventriculograms obtained from baboons during atrial pacing, septic shock, and induced myocardial infarction.

Changes in intraventricular phase delays, phase angle histograms, amplitude images, and electrocardiograms (ECG) were investigated during oesophageal pacing with and without beta-blockade, after induced myocardial infarction, and during septic shock in the anaesthetized baboon model. Unavoidable triggering from the pacemaker spike and to a lesser extent increased heart rate were responsible for parameter changes during pacing. Myocardial infarction changed contraction patterns, which did not always correlate with conduction changes from the ECG's. Cardiac volume changes during septic shock could be responsible for the abnormal trends in phase angle spread and electrocardiographic data.

Animals↗
PubMed1988

The relevance of left ventricular bands.

Left ventricular bands (LVBs) were first described almost a century ago but were largely ignored until their 'rediscovery' by echocardiography. Renewed interest in LVBs and the demonstration of their association with clinical abnormalities have resulted in attempts to establish their causal relationship with various phenomena, especially the vibratory systolic murmur and premature ventricular contractions. Published articles on LVBs are reviewed with specific reference to nomenclature, embryological development, histological features, prevalence, demonstration in vivo and at autopsy, and alleged clinical importance. Current views on LVBs are evaluated and future research directions are suggested.

Adult↗
PubMed1988

Atrio-ventricular block in a baboon (Papio ursinus).

Atrio-ventricular (A-V) block occurring in an anesthetized chacma baboon (Papio ursinus) is analysed. Hemodynamic, 12-lead electrocardiographical (ECG), hematological and biochemical parameters were monitored and data before and after block are compared. Though biochemical and other abnormal values were encountered, no conclusive evidence of the cause of the block was found.

Anesthesia, General↗
PubMed1988

A positive wave at the J-point of electrocardiograms of anaesthetized baboons (Papio ursinus).

Electrocardiograms were performed on 50 anaesthetized baboons (Papio ursinus). A positive deflection, referred to by us as the H-wave, consistently occurs at the junction between the QRS complex and the S-T segment. The significance of this deflection at the J-point, as the junction is known, is still to be established; however, characterization of the H-wave regarding amplitude and position with respect to the R-wave is done.

Animals↗
PubMed1983

Blood volume, heart rate, and left ventricular ejection fraction changes in dogs before and after exercise during endurance training.

In Beagles (n = 5) after 7 weeks' endurance training, resting blood volume increased by an average of 13.1%. Resting heart rates were not significantly affected, but heart rates measured 2 minutes after exercise were significantly lower after the endurance training than before. Left ventricular ejection fractions determined by radionuclide angiography from 2 minutes after exercise showed no significant changes in response to a single exercise period or over the 50 days' training.

Animals↗
PubMed1983

The influence of cycle length on the radionuclide left ventricular volume curve acquired with a scintillation camera and ECG-triggered data processor.

This study was designed to evaluate the effect of cycle length on the parameters of left ventricular function such as left ventricular ejection fraction (LVEF), ejection rates and ejection times. Radionuclide (in vivo 99mTc-labelled red blood cells) volume curves were obtained from ten chacma baboons. Transoesophageal atrial pacing of the baboon hearts was controlled by a microcomputer. A sequence of four beats was generated during arrhythmic pacing, consisting of two beats of equal cycle lengths, followed by a beat 15% shorter and a subsequent beat after a compensatory pause. Triggering impulses were sent to the data processor coincident with one of these beats until sufficient counts were obtained, before advancing to the next beat. Global LVEFs were found to be influenced by the preceding cycle length, increasing on a previous long cycle and decreasing on a previous short cycle and were even found to be influenced one normal beat on from the unrepresentative cycle. Similar trends were found for ejection times and rates. Discarding specific unrepresentative cycle lengths in order to correct for arrhythmia without attention to the previous cycle and even to the following cycle is therefore inappropriate.

Animals↗
PubMed1979

Prognostic significance of ventricular ectopic beats in chronic ischaemic heart disease.

Holter studies were performed periodically over a period of up to 7 years (mean 33 months) in 175 post-myocardial infarction patients. According to the number of ventricular ectopic beats (VEBs), the patients were classified into two main groups: those with few VEBs, i.e. less than 8 per hour, and those with many, i.e. 8 or more per hour. By comparing the number of ectopic beats during the different monitoring sessions, it was found that individual patients tended to remain in their originally allocated groups. Patients with frequent VEBs were more likely to die suddenly, the difference being significant (P < 0,001). No association could be demonstrated between recurrent non-fatal myocardial infarction and ectopic beat frequency (P > 0,10).

Adult↗
PubMed1976

Ventricular ectopic activity in chronic ischaemic heart disease.

Ventricular ectopic activity in 116 consecutive postmyocardial infarction patients was studied. The study extended over a period of 5 years and 700 periodic 6-7-hour Holter tape recordings were perfomred. A classification of ectopic activity is presented and it is suggested that patients be classified into group I with few, i.e. less than 8, and group II with multiple, i.e. 8 or more, ectopic beats per hour. It was found that the frequency of ventricular ectopic activity tends to remain constant over prolonged periods of time, and that repetitive firing as well as multiformity are functions of the absolute number of ventricular ectopic beats (VEB) present. A 6-7-hour sample of ventricular ectopic activity gives only marginally more information than a 1-hour recording, and the presence of VEB on a resting ECG correlates well with a frequency of more than 8 VEB per hour (group II) on extended monitoring.

Adult↗
PubMedDate not supplied

Cardiac function and Fourier phase data from simulated Wolff-Parkinson-White syndrome in a baboon model.

The diagnostic value of Fourier phase analysis and planar scintigraphy in Wolff-Parkinson-White (WPW) syndrome has been suspect. This study investigates phase analytical data from planar radionuclide ventriculography of six baboons with simulated WPW syndrome by means of implanted electrodes. An electrode in the atrium controlled the heart rate and a subsequent stimulation was delivered by electrodes placed at different sites on the ventricles, delayed to cause the characteristic delta wave of the WPW syndrome. Sensitivity for accurately-localizing variously-situated first points of activation (FPAs) from the Fourier phase images was found highest for premature right ventricular (RV) activation, and for atrioventricular (AV) delays around 125 msec. Other sites were subject to artifacts. Changes in cardiac function, phase delay, and histogram parameters were not statistically meaningful.

Animals↗