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Biomedical subjects

G Motte

Publications and source records attributed to G Motte.

At least 37 records · Page 2Linked to original sources
PubMed1984

Aortic input impedance in heart failure: comparison with normal subjects and its changes during vasodilator therapy.

This study was aimed at the evaluation of aortic impedance in patients with congestive heart failure. Aortic impedance (simultaneous measurements of aortic pressure and blood flow), mean (Wm) and pulsatile (Wp) powers were compared in 11 normal subjects and in 12 patients with heart failure. Pulse wave velocity (C: modified Moëns-Korteweg equation, simultaneous measurements of aortic pressure and radius) was determined under control conditions in all normal subjects and in 7 patients with heart failure. Impedance curves in patients with heart failure were characterized by increased values of the impedance modulus at 0 Hz (peripheral resistance) and at low frequencies. The characteristic impedance, C, and phase were not different from normal subjects. In six patients with heart failure, impedance curves were studied during nitroprusside infusion. During the infusion of the vasodilator, the impedance modulus at 0 Hz and at low frequencies decreased. The characteristic impedance was unchanged. The zero intercept of the phase was shifted towards lower frequencies. These results show that the changes in impedance curves in patients with heart failure are due to greater peripheral resistance and wave reflection. During nitroprusside infusion the stroke volume increased and the aortic blood flow became more pulsatile (greater values of low frequency components). This modification accounts for the increased values of Wm and Wp, and is related to decreased peripheral resistance and wave reflection.

Adult↗
PubMed1984

[Cardiotoxicity of anthracyclines].

The cardiotoxicity of the anthracyclines, of which doxorubicin is the leading drug, manifests itself in two ways: acutely, giving rise to temporary and usually benign phenomena, and chronically, giving rise to cardiac failure which is often irreversible. The risk of cardiomyopathy is related to the total dose of anthracycline administrated. The main risk factors are, age, previous cardiac disease and mediastinal radiotherapy. The prevention of cardiomyopathy is based on the respect of empirical guide lines (interruption of anthracyclines at "threshold" cumulative doses) and on methods of detection of infra-clinical disease. Myocardial angioscintigraphy which is easier to perform than myocardial biopsy and more sensitive and specific than echocardiography seems to be the investigation of choice. The main lines of research are aimed at improving our understanding of the mechanism of the cardiomyopathy, the institution of clinical trials to detect the first signs of toxicity of continuous infusions, the improvement of the standardisation and specificity of methods of detection, better definition of alarm thresholds and the development of new, less cardiotoxic, anthracyclines and cardioprotective agents.

Acute Disease↗
PubMed1983

Forward and backward waves in the arterial system, their relationship to pressure waves form.

The purpose of this work was to analyze, in human subjects, the shape of the aortic pressure wave from its forward and backward components calculated by use of Westerhof's model. Twenty-nine patients were studied: 11 normal subjects, 11 hypertensive patients and 7 patients with congestive heart failure. The following measurements and calculations were performed both under control conditions and during either angiotensin infusion in 5 normal subjects or nitroprusside infusion in 6 hypertensive patients: cardiac output, aortic blood pressure (catheter tip micromanometer), blood flow velocity (electromagnetic catheter-tip velocity transducer) in the ascending aorta, aortic impedance and reflection coefficients allowing the calculation of the aortic forward and backward pressure waves. The results show that the shape of aortic pressure wave in hypertensive patients is related to increased arterial wall stiffness which determines greater values and overlap of the forward and backward waves. This result is corroborated by the changes observed during angiotensin infusion in normal subjects. The shape of pressure wave in heart failure patients is dicrotic. This shape is related to smaller values and overlap of forward and backward waves. This appears related to a reduced stroke volume. During peripheral vasodilation the shape of pressure wave in hypertensive patients becomes dicrotic. However, this was mainly related to later backward waves. These results confirm that the shape of pressure waves depends both on the arterial wall stiffness and on the left ventricular performance: mainly on the stroke volume. The calculation of forward and backward waves allows a quantitative analysis of pressure waves.

Adult↗
PubMed1981

Double Wenckebach phenomenon in atrioventricular node and His bundle. Electrophysiological demonstration in a case of atrial flutter.

In a case of atrial flutter with a 9:2 atrioventricular response, the only possible way to explain the conduction pattern was 3:1 block in the atrioventicular node (which is 3:2 Wenckebach sequence in the N zone and a 2:1 block at the junction of the node with the bundle of His) plus 3:2 Wenckebach sequence distal to the H deflection. The recording of the His bundle deflection confirmed this analysis.

Aged↗
PubMed1980

[Aortic pressure and velocity signals processing: application to human aorta characterization (author's transl)].

The input to and characteristic impedances of the ascending aorta and the mean, pulsatile and maximum hydraulic powers generated by the left ventricle have been determined in 16 patients by simultaneous measurements of aortic pressure (by miniature transducer), velocity (by electromagnetic probe) and diameter (by cineangiography). Eight patients had normal blood pressure and eight were hypertensive. Harmonics of pressure and flow were calculated by processing the signals for 40 cycles, taking into account the frequency response of the velocity probe (Figs. 1 and 2). 1. The invariance of input impedance with heart frequency confirms the linearity of the arterial system under resting conditions (Fig. 3). 2. The characteristic impedances calculated by averaging the input impedance modulus above 2 Hz (Fig. 5) and from cineangiography are in good agreement for normotensive patients but discrepancies arise for hypertensive patients (Fig. 4). 3. Comparison of input impedance spectra (Fig. 6) reveals that in hypertensive patients the point of minimum modulus and zero phase is shifted towards higher frequencies while the characteristic impedance is higher. 4. The hydraulic power generated by the left ventricle is higher for hypertensive patients (Table I) and the increase in pulsatile power is almost entirely due to the increase in pressure harmonics (Figs. 7 and 8). These results suggest that the aorta plays an important role in left ventricular performance and that it may be characterized by its input impedance spectrum.

Adult↗
PubMed1980

[Methodology of hemodynamic study of a vasodilator drug (author's transl)].

The mechanism of action of a vasodilator drug is complex and depends on its predominant site of action: arterial or venous system. it leads to a) complex alteration of ventricular load that changes cardiac output, b) alteration of myocardial energetic metabolism. To classify a vasodilator drug, it is useful to study: a) its mechanism of action on the peripheral vascular system, b) the left ventricular function, and c) the coronary blood flow and the myocardial metabolism. The peripheral action of the drug is assessed by simultaneous measurement of peripheral blood flow, arterial pressure and venous pressure. From these data, arterial resistance (AR) and venous tone (VT) are calculated. A change of AR and for VT permits to classify a vasodilator drug as arterial, venous or both arterial and venous. Changes of factors of ventricular load are appreciated by measurement of aortic pressure, left ventricular pressure and ventricular volumes. If no change of heart rate occures, modification of stroke volume and cardiac output is due to a reduction of end diastolic volume (venous vasodilator drug) or of end systolic volume (arterial vasodilator drug).

Cardiac Output↗
PubMed1979

Post-extrasystolic left ventricular peak pressure with and without left ventricular failure.

18 patients without valvular pathology, coronary artery disease, or idiopathic hypertrophic subaortic stenosis were haemodynamically and angiographically investigated in order to analyse the effects of a ventricular extrasystolic beat upon the post-extrasystolic left ventricular peak pressure. In eight normal patients (group I), the post-extrasystolic peak pressure (P.ES.P.P.) was lower than that of the pre-extrasystolic beat; in 10 patients with symptoms of left ventricular failure (group II) the P.ES.P.P. significantly increased. The reasons are: 1) cardiac origin: stroke volume increased more in group II; 2) arterial origin. a) aortic compliance was lower in group II (this is probably related to the older age of patients in group II), and by decrease in end-diastolic aortic pressure was smaller in group II. Part of this arterial effect (2b) may probably be explained from the fact that post-extrasystolic compensatory pauses are equal in both groups, but the decay time of arterial pressure during diastole (assuming an exponential decay) is larger in group II. At the same age and with the identical aortic compliance only the two factors 1 and 2b play a part in the changes in P.ES.P.P.

Adult↗
PubMed1979

Study of left ventricular pressure-volume relations during nitroprusside infusion in human subjects without coronary artery disease.

Studies were made on 21 patients, 8 without any symptoms of left ventricular failure, group 1, and 13 with clinical symptoms of heart failure, group 2. Cardiac output, mean aortic and left ventricular pressures (using catheter tip micromanometer), and ventricular volume (obtained from left ventricular cineangiograms) were measured before and during nitroprusside infusion. The heart rate did not change in either of the groups. Only in group 2 did cardiac index and stroke volume increase significantly. Mean aortic pressure and total systemic vascular resistance decreased significantly in both the groups. Left ventricular end-diastolic pressure decreased significantly in both the groups, but this decrease was greater in group 2 (9 mmHg compared with 3 mmHg for group 1). The decrease in the left ventricular end-diastolic volume was similar in both the groups. The decrease in left ventricular end-systolic pressure was greater in group 1, but the decrease in the left ventricular end-systolic volume was greater in group 2. These facts are explained by the differences in the active and passive left ventricular pressure-volume relations in the two groups.

Adult↗
PubMed1978

Evaluation of the elasticity and characteristic impedance of the ascending aorta in man.

In 30 patients, simultaneous measurements of ascending aortic pressure and diameter were performed, allowing one to evaluate: (1) the influence of age, the aortic diastolic pressure, and the radius on the aortic elasticity; (2) the correlations between characteristics impedance of the aorta (Zo), systemic arterial resistance, age and diastolic aortic pressure; and (3) the importance of Zo when comparing two indices of left ventricle performance; one during isovolumic phase ([dP/dt]/Pt)max and the other during the outflow phase (maximum acceleration of aortic blood flow).

Adult↗
PubMed1977

Acute digitoxin intoxication treated by intracardiac pacemaker: experience in sixty-eight patients.

Out of 124 patients who had taken massive doses of digitoxin in attempted suicide, emergency endocardial pacing was performed in the 68 with the worst prognosis. The mortality (13%) in the 124 patients compared favorably with the mortality (20%) in a previous series of 70 similar patients none of whom were paced. Sixteen (23%) of the 68 paced patients died. The causes of death were: asystole (two); cardiogenic shock (two); septicemia (one); and ventricular fibrillation (eleven). Ventricular fibrillation occurred during introduction of the pacing catheter in two patients, as a result of electrode displacement in these patients, because of premature withdrawal of the catheter in one patient, and for no detectable reason, during normally proceeding pacing, in five patients. Endocardial pacing has a place in the emergency treatment of massive digitoxin poisoning. Its chief hazards are mechanical, and one of the commonest is electrode displacement.

Adolescent↗
PubMed1976

[The ventricular pressure-volume ratio, an index of left ventricular performance in man].

The left ventricular systolic pressure-volume diagram has been established before and after infusion of Nitro-prusside, Angiotensin and over post-extrasystolic potentiation on 33 patients, by the simultaneous measure of the aortic pressure and the left ventricular volume. In every case left ventricular dp/dt max. and (dp/dt/Pt) max. have been measured before and during post-extrasystolic potentiation, and in 16 cases after vasomotor therapy. The end-systolic left ventricular pressure-volume ratio appears to be independent of loading modifications--more than dp/dt max. and (dp/dt/Pt) max.--and on the opposite to be a good index of inotropic state alterations.

Angiotensin II↗