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Biomedical subjects

D L Clement

Publications and source records attributed to D L Clement.

At least 163 records · Page 9Linked to original sources
PubMed1985

Adrenergic and vagal influences on blood pressure variability.

The present paper reviews our recent studies set up to define the role of sympathetic and vagal nervous influences on blood pressure variability. Blood pressure and its variability was measured in men by Arteriosonde or by Portometer (the latter recording 12 hours ambulatory blood pressure) and in the dog by intraarterial recordings. It was shown that sympathetic nerves do not influence variability as no change was seen with drugs acting on either beta (atenolol, metoprolol, propranolol) or alpha adrenergic receptors (prazosin, phentolamine, guanfacine). Also no correlation was found with plasma catecholamines or sympathetic function tests. By contrast, clear inhibition was demonstrated with atropine indicating an important role of vagal nerves on variability. However, in men, inhibition was not complete with atropine; thus, also other mechanisms play a role but these are, at present, largely unknown.

Adrenergic beta-Antagonists↗
PubMed1984

The prevention of pacemaker mediated tachycardias in double-chamber pacing.

In 32 consecutive patients selected for physiological pacing assessment of ventriculo-atrial conduction (VAC) was performed, with incremental pacing and ventricular extrastimulation. This is easily done intraoperatively; VA conduction was present in 13 patients. When sinus node disease accompanied antegrade block retrograde conduction never occurred. The mean VA time was 241 +/- 42 ms (Mean +/- standard deviation). One patient developed pacemaker mediated tachycardia while negative findings were present; it was induced by coupled ventricular premature beats. Two patients of the group with VAC had to be reprogrammed in DVI because of disabling symptoms. Pacemaker tachycardia usually develops within the first hours after implantation. The mechanisms and the ways to prevent the tachycardia are discussed.

Arrhythmias, Cardiac↗
PubMed1984

Influence of vagal nervous activity on blood pressure variability.

In our previous studies, it was shown that blood pressure variability was largely independent from the adrenergic nervous system. In the present work, vagal nervous influence on blood pressure variability was analysed both in dogs and in men. In eight chronically instrumented conscious dogs, striking fluctuations of blood pressure were observed when quietly resting; these fluctuations correlate well with fluctuation of heart rate. Atropine abolished all variations both of heart rate and of pressure. Reflex stimulation of vagal tone by neosynephrine increased variability of both parameters. Thus, in dogs, blood pressure variability is related to variability of heart rate which is largely influenced by vagal tone. The same question was approached in seven male volunteers; blood pressure and heart rate were measured automatically every 2 min, during 1 h, before and after atropine. In control conditions, no correlation between variability of heart rate and of blood pressure was observed. Atropine clearly decreased variability of heart rate and of diastolic blood pressure. These data confirm the animal results; however, the influence of vagal nerves on variability is less pronounced in man than in dogs.

Adult↗
PubMed1983

Prevalence of left ventricular hypertrophy in middle-aged men according to various ECG-VCG techniques.

The prevalence rates of left ventricular hypertrophy (LVH) were studied in a middle-aged male working population using the Minnesota code, an automated processing of the orthogonal leads, and the Pipberger program. These various methods resulted in significant differences in prevalence rates. The odds ratios and relative differences were calculated for each method in subgroups according to the presence or absence of personal antecedents of arterial hypertension. For detecting LVH, the orthogonal criteria are superior to the other methods. The concordances between methods are low overall, leaving the question open as to the independent prognostic value of each method.

Adult↗
PubMed1983

Lack of influence of propranolol and metoprolol on walking distance in patients with chronic intermittent claudication.

Ten patients with chronic intermittent claudication were included in a double-blind, randomized cross-over study of placebo, propranolol 80 mg b.i.d. and metoprolol 100 mg b.i.d., each given for two months. At the end of each treatment period, the patients were tested on a treadmill and the time to first claudication pain and to intolerable claudication pain was noted. There was no decrease in time to first claudication pain or to intolerable pain with either propranolol or metoprolol as compared to placebo.

Chronic Disease↗
PubMed1982

Effect of spironolactone on systemic blood pressure, limb blood flow and response to sympathetic stimulation in hypertensive patients.

Since there is only scanty, indirect information about the mechanism of the hypotensive effect of spironolactone, 9 patients with essential hypertension were studied according to a randomised double-blind, cross-over protocol. Spironolactone 100mg b.i.d. and placebo were each given for one month and the following parameters were studied: blood pressure, heart rate, response to cold pressure and handgrip tests, as well as blood flow in the calf and finger vessels. Flow in the calf and fingers representing muscle and skin arteries, respectively, was measured semicontinuously with an ECG-triggered venous occlusion plethysmograph. After spironolactone there was a significant decrease in the systolic and diastolic blood pressures in the supine, sitting and standing positions; the sitting systolic and diastolic blood pressure decreased by (mean +/- SE) 27 +/- 4mm Hg (p less than 0.001) and 11 +/- 4mm Hg (p less than 0.02), respectively. No orthostatic response was observed. Heart rate remained unchanged. Blood flow through muscle and skin vessels increased in 6 out of 9 patients, and in these patients calculated vascular resistance in these areas decreased. Spironolactone did not significantly change the response of systemic blood pressure to the handgrip and cold pressure tests. The present data confirm the hypotensive properties of spironolactone and show that this effect is associated with dilatation of muscle and skin arteries in many but not in all the patients. The data do not support the hypothesis that spironolactone decreases the responsiveness of systemic blood pressure to orthosympathetic stimulation.

Blood Pressure↗
PubMed1982

The orthogonal Frank electrocardiogram in 70 well-trained athletes.

Interpretation of the vectorcardiogram in athletes requires normal values based on quantitatively analyzed data obtained in large groups of athletes. Frank electrocardiograms of extensively trained white athletes aged 23 +/- 5 years were analyzed by computer. Different sport disciplines were included. Tables are provided describing the results for the complete group of 70 athletes (A), respectively indicating the difference between 27 footballers (F) and 16 endurance athletes (E). A critical comparison with two control groups is also discussed, as for other purposes, vectorcardiograms had been collected in healthy non-trained young men, respectively 68 medical students (MS) and 63 nurse students (NS). The following figures may serve as an example to illustrate the difficulty of constituting and using similar normal limits in athletes: mean QRS spatial maximal amplitude (mV.) was respectively 1.82 (MS), 2.03 (NS), 2.17 (A), 1.97 (E), 2.29 (F). It can often be hazardous to attribute certain deviations of electrocardiological measurements to training effects in the athlete.

Adult↗
PubMed1981

Non-invasive evaluation of cardiac function in professional cyclists.

Cardiac dimensions and left ventricular function were investigated at rest with non-invasive methods in 14 professional road race cyclists and in 11 age-matched sedentary control subjects. The electrocardiographic findings were in agreement with previous studies in endurance athletes and the vectocardiographic data showed anterior displacement of the electrical forces. Echocardiographic dimensions at end-diastole showed higher values in the cyclists for left ventricular internal diameter, left ventricular posterior wall thickness, and interventricular septal thickness. Derived values for left ventricular volume and left ventricular mass were also much larger in the cyclists and there was excellent agreement between total heart volume measured with radiology and total measured by echocardiography. There was a significant correlation between maximal oxygen consumption and end-diastolic left ventricular diameter.

Adult↗
PubMed1981

The orthogonal Frank electrocardiogram in 257 nurse students.

It has clinically well been recognized that the vectorcardiogram in younger patients often shows characteristics that are largely different from the figures obtained in general adult populations. Well documented information on VCG parameters in younger subjects is scarce; the present paper deals with a report on 194 white females and 63 white males, aged 18-25 years. Data were analyzed using the Pipberger program 3.6, and also statistically compared to the classical Pipberger standards. Some parameters (e.g. QRS duration) show different values typically in females, as well in our group of young females as in the reference Pipberger group; other measurements (e.g. Q/Rz amplitude ratio) are specifically deviated in the young population and a pronounced anterior displacement of QRS is regularly observed here. It appears remarkable that QRS amplitude in the young age groups is significantly higher than in the general Pipberger groups only when examined in the inferior direction. The 96% range limits found in this study resp. in young males, and in young females, for the QRS spatial maximal vector (3.08 resp. 2.61 mV) and for RX + RZ (3.22 resp. 2.45 mV) can be taken into account for considering LVH in youngsters.

Adolescent↗
PubMed1980

Blood-pressure response to swimming in ice-cold water.

The cardiovascular responses to cold were studied in a group of 28 subjects who enjoyed swimming in ice-cold water in winter ("ice-bears"). History and clinical examination had revealed no abnormalities except hypertension (180/105 mm Hg) in 1, while 3 other subjects had a diastolic value of 95 mm Hg. Systolic blood-pressure increased significantly while the subjects were waiting undressed in cold air in the cabin by the pond. Neither immersion nor swimming in the ice-cold water caused further increase in systolic blood-pressure, and diastolic blood-pressure showed only a modest rise. 4 min later, blood-pressure had returned to control values. Electro and vector cardiographic signs remained unchanged. Although very high pressures were recorded in several subjects, no signs of left ventricular hypertrophy or of cardiovascular of cerebrovascular damage could be detected.

Blood Pressure↗
PubMed1980

Cardiac output distribution during induced static muscular contractions in the dog.

Previous experiments in the dog have shown that static contractions of the muscles of one limb elicit a reflex increase of resistance in the vessels of the opposite limb, along with an increase of systemic blood pressure. The aim of the present experiments was to examine whether this reflex can cause a redistribution of cardiac output from the resting areas, in favor of the working parts. In 17 anesthetized and ventilated dogs, static contraction of the muscles of the right thigh was elicited with electrodes inserted into these muscles. The carotid sinuses were kept at constant pressure and the vagi cut. During static contractions systemic blood pressure and cardiac output increased by 17.7 +/- 3.1 and 24.2 +/- 5.5%, respectively. The blood flow measured with an electromagnetic flowmeter decreased by 21.9 +/- 5.3% in the femoral artery of the resting limb and increased by 101 +/- 21% in the femoral artery of the "active limb". Data obtained in six dogs with injection of radioactive microspheres during stimulations show that blood flow decreased not only in the muscles of the rising limb (34 +/- 10%), but also in several other resting areas, such as skin (38 +/- 8%), kidney (24 +/- 8%), gut (38 +/- 6%), and tongue (23 +/- 3%). The results show that the reflex under study causes a redistribution of the cardiac output during static muscular contractions.

Animals↗