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Biomedical subjects

H De Geest

Publications and source records attributed to H De Geest.

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

Geometrical variations of the canine superior vena cava: relationship between diameter, segment length and transmural venous pressure.

The dimensional variations of the superior vena cava throughout the cardiac cycle were investigated by means of angiographic and ultrasonic techniques. Results obtained by both methods were largely in agreement. In frontal direction the diameter curve resembled the transmural pressure variations, the sagittal diameter curve was not related to the venous pressure variations during certain phases of the cardiac cycle and compressional and/or stretching forces exerted by respectively the distending aorta and/or pulmonary artery and the contracting heart may have been responsible. Also segment length variations occurred: during atrial contraction, ventricular systole and early diastole the vein elongated, indicating the varying longitudinal traction forces, possibly exerted by the rotational movement of the contracting heart. Assuming elliptical symmetry the vena caval cross-section could be reconstructed, and the cross-sectional area, perimeter and segmental volume could be calculated throughout the cardiac cycle. Despite the high venous distensibility, no extreme collapse of the vein was observed during the cardiac cycle at low transmural pressures.

Animals↗
PubMed1987

LILLY--a linear least squares curve fitting program for one independent variable.

A program was written to perform a linear least squares curve fitting on data. It includes facilities to report the usual statistics and digital plotter output. Seven types of curves are available for fitting the data. Other features of LILLY include provision of facilities for the selection of subsets in different symbols and separate curve fitting for these subsets. The program also provides a confidence region about the fitted line and the prediction interval for data points. Examples of the use of the program are described.

Mathematical Computing↗
PubMed1987

Sensing and pacing with floating electrodes in the right atrium and right atrial appendage.

Unipolar and bipolar floating atrial electrograms from 58 pacemaker patients were recorded and compared. Twenty-four floating unipolar electrodes and 29 floating bipolar electrodes were used at mid-right atrial level and five orthogonal atrial J leads within the right atrial appendage. Each signal was analyzed in the time domain: peak to peak deflection of P wave and QRS complex, duration of P wave and QRS complex and slew rate; and in the frequency domain: maximum of the energy spectrum and frequency at which a decrease of 3 dB from the maximal amplitude occurred. Atrial P (1.31 +/- 0.94 mV, mean +/- SD) and QRS (1.0 +/- 0.56 mV) waves from unipolar floating electrodes were comparable, whereas they were significantly different from bipolar floating electrodes (1.15 +/- 0.77 mV and 0.25 +/- 0.39 mV). Amplitudes of P waves from orthogonal J leads were largest (3.1 +/- 2.6 mV) and QRS complexes (0.21 +/- 0.13 mV) smallest. The P waves had the highest frequency content (17.1 +/- 19.4 Hz). It is concluded that atrial electrograms from orthogonal electrodes (bipolar or orthogonal J) offer superior sensing characteristics because of the large amplitude P wave and discriminating power between P and QRS waves (P/QRS voltage 15:1). An orthogonal J lead can thus be used for P synchronous pacing at the atrial level, whereas an orthogonal ventricular lead can be used for rate-response pacing systems.

Atrial Function↗
PubMed1987

Treatment of prosthetic tricuspid valve thrombosis with recombinant tissue-type plasminogen activator.

Recombinant tissue-type plasminogen activator (rt-PA) was administered intravenously to a 64-years old female with thrombotic malfunction of a Björk-Shiley prosthetic tricuspid valve. 150 mg of single-chain rt-PA was infused over 8 hours followed by an additional dose of 50 mg over the next 8 hours. At the end of the first infusion, restoration of normal valve function was demonstrated by fluoroscopic and echo-Doppler examinations. Mild systemic activation of the fibrinolytic system occurred, with a decrease of fibrinogen and alpha 2-antiplasmin to 53% and 33%, respectively, of the preinfusion value at the nadir.

Female↗
PubMed1987

Determination of areal densities of blood vessel wall components in histological sections by means of image analysis.

A technique is described which allows quantification of specifically stained, intermingled vessel wall components in paraffin-embedded tissue. The dissociation of elastic, muscular and connective tissue and the determination of their areal densities in the superior vena cava and in the ascending aorta of the dog, was performed by automated image analysis. The percentages of elastic+connective tissue, determined by this technique, correlated significantly with the data derived from biochemical measurements. It was further found that the structure of the vena cava wall was a function of the distance from the right atrium.

Animals↗
PubMed1987

Unexplained chest pain with normal coronary arteriograms. A follow-up study.

One hundred and forty-two consecutive patients with unexplained chest pain and normal coronary arteries were followed up for a mean period of 49.3 +/- 13.1 months. No cardiac deaths and one myocardial infarction occurred. Half of the patients were pain-free at follow-up. A definite relationship between persistence of pain and duration of pain history and a positive response to nitroglycerin before coronary arteriography were found. Patients with persistent pain were more frequently hospitalized for noncardiac diseases, underwent more surgical interventions and took more often noncardiac medication. Rehospitalizations for acute chest pain were infrequent. Two thirds of the patients resumed their normal activities. Younger age, disappearance of pain, type of occupation, and a shorter duration of the pain history favored return to work. Nonactive patients presented more intercurrent noncardiac, medical and surgical pathology. The findings in patients with a previous myocardial infarction were similar to those of the group with only chest pain.

Activities of Daily Living↗
PubMed1987

Reduction in infarct size and enhanced recovery of systolic function after coronary thrombolysis with tissue-type plasminogen activator combined with beta-adrenergic blockade with metoprolol.

The effect of beta-adrenergic blockade on the salvage and functional recovery of reperfused myocardium was investigated in anesthetized dogs. Immediately after thrombotic occlusion of the left anterior descending coronary artery, the cardioselective beta-blocking agent metoprolol was given intravenously at a dose of 0.5 mg/kg infused over 10 min. One hour after the onset of occlusion, recanalization was initiated by intravenous infusion of recombinant human tissue-type plasminogen activator (rt-PA, 10 micrograms/kg/min for 30 min). Anatomic infarct size expressed as percent of the left ventricular mass (I/LV), global ejection fraction, and mean systolic shortening of the segmental radii (SS) of the infarcted area were measured either after 24 hr or 1 week in six groups of six dogs each: group I (rt-PA + metoprolol, evaluated at 24 hr), group II (rt-PA + metoprolol, evaluated at 1 week, group III (rt-PA alone, evaluated at 24 hr), group IV (rt-PA alone, evaluated at 1 week), group V (persistent occlusion, evaluated at 24 hr), and group VI (persistent occlusion, evaluated at 1 week). The smallest infarcts were found in reperfused dogs given metoprolol, but the differences from dogs receiving rt-PA alone were not statistically significant (I/LV, expressed as mean +/- SEM: 5.5 +/- 0.9% in group I, 6.7 +/- 1.9% in group II, 15.4 +/- 5.0% in group III, 11.4 +/- 3.5% in group IV, 23.6 +/- 2.5% in group V, and 26.9 +/- 2.3% in group VI).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of betaxolol on heart rate in patients with a recent transmural myocardial infarction.

A randomized double-blind trial was performed with betaxolol, a beta 1-selective and long-acting beta-blocker, in patients with a recent first uncomplicated acute myocardial infarction (AMI). Patients were treated between the 3rd and 14th day after the onset of AMI with either a single oral dosage of 20 mg betaxolol or placebo. The effects on heart rate, ventricular and supraventricular arrhythmias were studied by continuous 24 hours ECG recordings on the 7th and between the 9th to 12th after the onset of AMI and by a submaximal exercise test on the 12th day. Hourly mean, peak and minimal heart rate were during the whole day significantly lower in the active treatment group. In betaxolol treated patients diurnal variations in heart rate were definitely changed. No differences in the occurrence of ventricular arrhythmias were found between both groups; auricular fibrillation was more common in placebo treated patients. Heart rate and pressure rate product were significantly higher during exercise in the placebo group. During exercise ventricular arrhythmias were infrequent in both groups. The clinical tolerance of betaxolol was excellent.

Adrenergic beta-Antagonists↗
PubMed1987

Hypertrophic cardiomyopathy caused by hyperparathyroidism. Report of a case and review of the literature.

Hyperparathyroidism is a rare, recently recognized cause of hypertrophic cardiomyopathy. Elevated serum levels of parathyroid hormone, rather than a rise in the extracellular calcium concentration, appear to be associated with left ventricular hypertrophy. This report describes the history of a patient who developed left ventricular hypertrophy during a 17 years lasting period of recurrent nephrocalcinosis, prior to the diagnosis of hyperparathyroidism. Cardiac function tests remained unchanged fifteen years after parathyroidectomy, suggesting that the latter intervention did not reverse the pathological process but only prevented further cardiac deterioration.

Cardiomyopathy, Hypertrophic↗
PubMed1987

Complete occlusion of the main left coronary artery. A clinical study.

Between 1975 and 1985, 12 patients with complete occlusion of the main left coronary artery (MLCA) were seen. The historical, clinical, biochemical, radiological, electrocardiographic, angiographical, surgical and follow-up findings were analyzed. Eight of the 12 patients presented on admission an unstable clinical situation. A normal ECG at rest was found in only 3 patients. Exercise testing elicited definite electrocardiographic changes in 5 of 6 cases. Coronary atherosclerosis was the cause of occlusion in 11 patients; in 1 patient the underlying disease process remained unclear. Significant lesions of the right coronary artery (RCA) were found in 9 and of the left anterior descending (LAD) or circonflex (CFLX) artery in 6 patients. Global and/or regional left ventricular dysfunction at rest was present in 10 patients. Angiographically visible collateral circulation was found in all patients but its extent was variable. All patients underwent bypass surgery. There were 1 operative and 2 late deaths.

Adult↗
PubMed1987

Acute myocardial infarction in the very elderly. A comparison with younger age groups.

In a consecutive series of 2312 patients with acute myocardial infarction (AMI) admitted from 1973 till 1979, 188 were 80 years or older (group III). They were compared with 1167 patients younger than 65 years (group I) and 957 aged 65 to 79 years (group II). The sex ratio (males/females) fell from 5.46 in group I to 0.9 in group III. Group III patients had more frequently a history of previous heart failure and more often atypical or no chest pain before admission. Less group III patients were admitted within 4 hours after onset of symptoms, but the incidence of heart failure, pulmonary edema and cardiogenic shock on admission and during CCU stay was definitely higher than in younger patients. Atrial arrhythmias, 2nd and 3rd degree atrioventricular block, complete bundle branch block and intraventricular conduction disturbances occurred more frequently in group III. The electrocardiographic extent and location of the infarction and peak enzyme levels were similar in the three groups. Mortality in group III was 43.6% at the 28th day and 76.6% at one year after AMI. At different intervals after the onset of AMI mortality increased progressively from group I to III. Age by itself, probably on the basis of definite structural changes of the heart and of other organs occurring during aging, leads to higher early and late mortality in very elderly people.

Aged↗
PubMed1987

An unexpected Q fever endocarditis. Report of a case.

A man with blood culture negative endocarditis since 1983 received in October 1984 a mitral valve bioprosthesis. Reintervention in April 1985 was performed because of a paravalvular leak. In September 1985, mitral insufficiency reappeared and high-titer phase II Q fever antibody was detected, which has since then persisted with concomitant high-titers of phase I antibody. In serum from 1983, phase II antibody was detected on reexamination in September 1985. For unexplained reasons this antibody had not been detected in 1983. The patient has since September 1985 been successfully treated with doxycycline. The current literature is reviewed. Q fever endocarditis should be considered also in Belgium in culture negative endocarditis even in persons with no previous history of valvular disease and no known exposure to animals or unpasteurized dairy products. Quality of viral reagents and diagnosis present sometimes a challenge.

Antibodies, Bacterial↗
PubMed1986

Coronary thrombolysis with recombinant tissue-type plasminogen activator: patency rate and regional wall motion after 3 months.

In a double-blind, placebo-controlled, randomized trial the long-term (+/- 3 months) effects of intravenous administration of recombinant tissue-type plasminogen activator (rt-PA) versus placebo were compared in relation to left ventricular function, coronary patency rate and antigenicity in 28 patients with a first myocardial infarction. Patency rate of the infarct-related coronary artery at the end of the rt-PA/placebo infusion and after 3 months of medical treatment (including oral anticoagulant agents) was 86 and 71%, respectively, in the rt-PA group, and 21 and 58%, respectively, in the placebo group. Regional wall motion of the infarct-related area was quantitated with digital subtraction angiography. Intrapatient comparisons revealed significant improvement in regional wall motion after 3 months in both the rt-PA and placebo groups. The improvement in the rt-PA group was not significantly greater than that in the placebo group. Thirteen patients (10 with rt-PA and 3 with placebo) with persistent patency (both early and late) of the infarct-related coronary artery showed a significant improvement of both global and regional left ventricular function, while 8 patients (2 with rt-PA and 6 with placebo) with persistent occlusion showed no changes. Antibodies against rt-PA were not detected in serum 2 weeks after the infusion, which is indicative of the lack of antigenicity of rt-PA and allows for its repeated administration.

Angiography↗
PubMed1986

Axial pressure gradient in the canine superior vena cava.

In the superior vena cava of anaesthetised open chest dogs the axial pressure gradient was measured simultaneously with the blood flow velocity under different preload conditions. Both pressure gradient and velocity curves showed distinct systolic and diastolic waves. Peak pressure gradient ranged between 26 and 93 Pa X cm-1 (0.2-0.7 mm Hg X cm-1) and velocity varied between 0.095 and 0.19 m X s-1. Peak systolic pressure gradient, but not peak diastolic pressure gradient, was significantly linearly correlated to peak systolic velocity and peak diastolic velocity respectively. The shape of the two curves corresponded fairly well, but variations in pressure gradient preceded the variations in velocity. Both the correspondence in shape and the phase lag between pressure gradient and velocity waves were evaluated by the normalised cross correlation technique. During volume expansion the shape correspondence improved and the phase lag decreased. It is concluded that the transient vena caval blood velocity variations are directly related to the pulsatile axial pressure gradient.

Animals↗
PubMed1986

Coronary artery fistulas in an adult population.

A consecutive series of 14 708 coronary arteriograms, performed between 1 April 1975 and 1 August 1983 was examined for the presence of coronary artery fistulas. The incidence was 0.13. There was 1 traumatic and 19 congenital cases. All fistulas were small and of little haemodynamic significance. No symptoms or complications could be ascribed to these fistulas. In the large majority no continuous or other murmurs suggested their presence. The large majority arose from the proximal anterior descending artery and emptied in the pulmonary artery. Surgical treatment for these fistulas is not indicated.

Adult↗
PubMed1986

Sensing characteristics of unipolar and bipolar orthogonal floating atrial electrodes: morphology and spectral analysis.

We investigated wave morphology and spectral energy distributions of signals picked up by floating atrial unipolar and bipolar orthogonal sensing electrodes. Our data show that atrial P and QRS waves from unipolar floating electrodes are comparable. On the other hand, atrial P and QRS waves from bipolar orthogonal floating electrodes are significantly different. Even at high and mid right atrial locations, QRS waves are either absent or much smaller in amplitude and lower in frequency content than P waves. We conclude that the bipolar orthogonal floating atrial electrode is superior to the unipolar one for sensing due to its P to QRS wave discriminating power, which makes complex input filters or algorithms unnecessary. Our data support the idea that physiologic pacing with a VDD or VAT pacemaker is possible using a single pass lead.

Electrocardiography↗