Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cardiac Output”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed2002

Effect of the degree of tricuspid regurgitation on cardiac output measurements by thermodilution.

OBJECTIVE: To determine the relationship between the degree of tricuspid regurgitation (TR) and accuracy of cardiac output measurement by thermodilution in mechanically ventilated patients. DESIGN AND SETTING. Prospective observational study in a 20-bed general intensive care unit in the university hospital. PATIENTS: We examined 27 patients (not undergoing cardiac surgery): 8 with no or 1st degree TR, 9 with 2nd degree, and 10 with 3rd degree TR. INTERVENTIONS: All patients were measured twice using simultaneously transesophageal echocardiography and pulmonary artery catheter for cardiac output. MEASUREMENTS AND RESULTS: Continuous Doppler measurements were taken in the left ventricular outflow tract at the level of the aortic valve. Cardiac output was calculated by multiplying the velocity-time integral by aortic valve area and heart rate. Simultaneous pulmonary artery catheter measurements were taken averaging the results of the three 10-cc boluses of iced saline. The difference between the methods was 0.5+/-1.1 l/min (mean +/-2 SD) in patients with no or 1st degree TR (r=0.96), 0.8+/-2.0 l/min in those with 2nd degree TR (r=0.92), and 1.9+/-2.3 l/min in those with 3rd degree TR (r=0.69). CONCLUSIONS: A high degree of TR is associated with underestimation of cardiac output measured by thermodilution.

Cardiac Output↗
PubMed1980

A new technique for repeated measurement of cardiac output during cardiopulmonary resuscitation.

The authors have developed a method for measurement of cardiac output during CPR with ventricular fibrillation. The method avoids the problems encountered when conventional techniques are used under the conditions of very low cardiac output. The method consists of injecting 5% saline as the indicator into the left ventricular and detecting its appearance in the descending aorta by withdrawing aortic blood through an electrically calibrated conductivity cell. The adequacy of indicator mixing has been verified by obtaining dilutions curves simultaneously from the brachial and femoral arteries. Cardiac output can be determined even when output is as low as 7 ml/min . kg during CPR with ventricular fibrillation. Repeated determinations can be made as often as every min. This method offers promise as a practical research tool which can also be used with dye indicators.

Cardiac Output↗
PubMed1985

Cardiac output distribution and uteroplacental blood flow in the pregnant rabbit: a comparative study.

This study presents data on cardiac output distribution and uterine and placental blood flows in pregnant rabbits under chronic steady-state conditions. Ten liters and 67 fetuses were studied at 29 days of gestation, by means of radioactive microspheres. Five nonpregnant female animals were also studied for comparison. Mean cardiac outputs were 747.16 +/- 55.7 and 613.80 +/- 63.76 ml/min in the pregnant and nonpregnant states, respectively. In the pregnant animals, uterine and mammary blood flows were 6.7% +/- 0.7% and 5.1% +/- 0.5% of cardiac output, respectively. Within litters, the highest placental blood flows occurred at the ovarian and vaginal ends of the uterine horn. Placental blood flow per gram of fetus was 0.106 +/- 0.008 ml X min-1 X gm-1. A comparison with analogous data in the guinea pig and sheep demonstrates that toward the end of pregnancy placental blood flow per gram of fetus is approximately 2.5-times higher in sheep than in rabbits and guinea pigs. Expressed as a percentage of cardiac output, near-term uterine blood flow is significantly less in rabbits than in guinea pigs and sheep, whereas mammary blood flow is significantly higher. These interspecies differences are related to differences in placental structure, fetal/maternal mass ratio, and maturity at birth.

Animals↗
PubMed2005

[Non-invasive determination of cardiac output by continuous wave Doppler in air rescue service].

BACKGROUND: Determination of cardiac output (CO) enables to assess the hemodynamic situation as well as to administer optimal catecholamine therapy especially in critically compromised patients with hemodynamic instability. Invasive determination of CO is possible via a Swan-Ganz-catheter with its associated risk of implantation in the hospital. Using the Doppler technique, we evaluated the feasibility of the USCOM-system for non-invasive CO determination in preclinical emergency medicine in air rescue service. METHODS: In 32 patients (17 months to 92-years-old) cardiac output was determined non-invasively (USCOM) at the scene and during the helicopter transport at Christoph 4, based at Hannover Medical School. Simultaneously, blood pressure, ECG and oxygen saturation were determined. Non-invasive CO was assessed by a suprasternal access aiming at the aorta ascendens. 19 patients were unconscious due to cardial and non-cardial reasons, and 13 were conscious (sepsis, status epilepticus, anaphylactic reaction). 7 patients were hemodynamically unstable. In three patients the monitor was used during interhospital transfer by helicopter. RESULTS: Non-invasively determined CO via the USCOM system was 4.8 +/- 0.7 l/min with a cardiac index of 2.4 +/- 0.3 l/m (2). Highest CO values were determined in a patient with sepsis and during a grand-mal-status in epilepsy (CO 8.2 l/min). All examinations were done by the same emergency physician of the emergency helicopter Christoph 4 immediately after arrival at the scene. The examination took on average 25 seconds. During the helicopter transport, several consecutive CO measurements were performed to assess volume and catecholamine therapy with increase of stroke volume after volume load with colloidal fluids. CONCLUSIONS: Using the USCOM system it is possible to determine the beat-to-beat cardiac output in air rescue service non-invasively. The emergency physician gains additional crucial hemodynamic information to diagnose and treat adequately by administration of volume load and catecholamines at the scene and during flight conditions. Further preclinical prospective trials are mandatory to elucidate the value of this novel device in emergency medicine.

Adolescent↗
PubMed1986

Measurement of cardiac output without right heart catheterization: reliability, advantages, and limitations of a left-sided indicator dilution technique.

This study was done to determine the accuracy and reliability of cardiac output measurements by the injection of indocyanine green into the left ventricle, with simultaneous sampling from a systemic artery. In 40 patients (18 men, 22 women, aged 34 to 74 years), cardiac output was measured in close temporal proximity by (a) standard indicator dilution (right atrium-to-pulmonary artery thermodilution in 11, pulmonary artery-to-systemic artery indocyanine green in 29) and (b) left ventricle-to-systemic artery indocyanine green. There was excellent agreement between the two techniques (r = 0.98, SEE = 0.12 liters/minute). In 28 of the patients, cardiac output also was measured by ascending aorta-to-systemic artery indocyanine green. In these individuals, this technique yielded results that were disparate from those obtained by standard indicator dilution (difference between standard indicator dilution and left ventricle-to-systemic artery indocyanine green = 0.18 +/- 0.13 [mean +/- SD] liters/minute; difference between standard indicator dilution and ascending aorta-to-systemic artery indocyanine green = 0.72 +/- 0.55 liters/minute; p less than 0.001), and in 22 of the 28, the ascending aorta-to-systemic artery indocyanine green cardiac outputs were greater than those obtained by standard indicator dilution. Thus, cardiac output can be measured accurately by injecting indocyanine green into the left ventricle, with simultaneous sampling from a systemic artery, but it cannot be quantified reliably by introducing indicator into the ascending aorta. The left ventricle-to-systemic artery indocyanine green technique can be used in patients undergoing only left heart catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Effect of angiotensin-converting enzyme inhibition by captopril on cardiac output, coronary blood flow, and systemic arterial blood pressure in the intact and in the bilaterally nephrectomized rabbit.

The purpose of this study was to investigate the hemodynamic responses, mainly cardiac output and regional blood flow, to converting enzyme inhibition by captopril in the intact and nephrectomized rabbit. Twenty-one New Zealand white rabbits anesthetized with pentobarbital has systemic arterial blood pressures measured and cardiac output and regional blood flow determined by the microsphere method. Captopril (1--3 mg/kg) significantly reduced cardiac output in the intact but not in nephrectomized rabbits. In both the intact and nephrectomized animals, captopril was associated with small but not significant decreases in blood pressure and no significant change in total peripheral vascular resistance or heart rate. Regional blood flow was reduced, but the fractional distribution of cardiac output to the myocardial, lung (bronchial), hepatic, and splanchnic (small intestine) circulations was unchanged after captopril. These data suggest that the reduction in cardiac output induced by converting enzyme inhibition may be attributed to a fall in venous return that in turn may be dependent on renal factors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Cardiac output distribution in response to hypoxia in the chick embryo in the second half of the incubation time.

1. The fetus develops cardiovascular adaptations to protect vital organs in situations such as hypoxia and asphyxia. These include bradycardia, increased systemic blood pressure and redistribution of the cardiac output. The extent to which they involve maternal or placenta influences is not known. The objective of the present work was to study the cardiac output distribution in response to hypoxia in the chick embryo, which is independent of the mother. 2. Fertilized eggs were studied at three incubation times (10-13 days, 14-16 days and 17-19 days of a normal incubation time of 21 days). Eggs were placed in a Plexiglass box in which the oxygen concentration could be changed. Eggs were opened at the air cell and a chorioallantoic vein was catheterized. Cardiac output distribution was measured with 15 micron fluorescent microspheres injected during normoxia, during the last minute of a 5 min period of hypoxia and after 5 min of subsequent reoxygenation. 3. Hypoxia caused a redistribution of the cardiac output in favour of heart (+17 to +160 % of baseline) and brain (+21 to +57 % of baseline) at the expense of liver (-3 to -65 % of baseline), yolk-sac (-46 to -77 % of baseline) and carcass (-6 to -33 % of baseline). 4. The magnitude of the changes in cardiac output distribution to the heart, brain, liver and carcass in response to hypoxia increased with advancing incubation time. 5. The data demonstrate the development of a protective redistribution of the cardiac output in response to hypoxia in the chick embryo from day 10 of incubation.

Animals↗
PubMed2002

Comparison of cardiac output and circulatory blood volumes by transpulmonary thermo-dye dilution and transcutaneous indocyanine green measurement in critically ill patients.

OBJECTIVE: We prospectively studied the agreement between transpulmonary aortic fiberoptic-based and pulse dye densitometry (PDD) measurements of cardiac output and circulatory blood volumes. DESIGN: Prospective clinical study. SETTING: Operative ICU of a university hospital. PATIENTS: Sixteen critically ill, deeply sedated patients receiving mechanical ventilation with ARDS (n = 8), sepsis/septic shock (n = 6), subarachnoid hemorrhage (n = 1), and severe head injury (n = 1). MEASUREMENTS AND RESULTS: Each patient received a 4F aortic catheter with an integrated fiberoptic and thermistor that was connected to a computer system for automatic calculation of the transpulmonary indicator dilution (TPID) technique for the measurement of cardiac output (COTPID), intrathoracic blood volume (ITBV), and total blood volume measured by TPID technique (TBVTPID). In each patient, an indocyanine green sensor was attached to one nasal wing and connected to an analyzer for the PDD measurement of cardiac output (COPDD), central blood volume (CBV), and TBV measured by PDD (TBVPDD). For all first measurements, linear regression analysis between COTPID and COPDD revealed that COPDD = 0.63 x COTPID + 3.69 (L/min) [r = 0.64, p = 0.008]. Mean bias between both techniques was - 0.8 L/min (SD, 1.7 L/min). Correlations between ITBV/CBV (r = 0.52) and TBVTPID/TBVPDD were only moderate: TBVPDD = 0.74 x TBVTPID + 2,362 (mL) [r = 0.60, p = 0.015; mean bias, - 999 mL; SD, 1,353 mL]. Over all 55 measurements, TPID measurements were on average 11.5% (cardiac output) and 17.6% (TBV) higher than PDD measurements. The differences between both measurements ranged from - 58 to 81% (cardiac output) and from - 47 to 82% (TBV; 95% reference ranges). The main source of variation were the intraindividual differences, resulting in different peaks and trends in the patients time courses depending on which measurement method was used. CONCLUSION: PDD measurement of cardiac output and circulatory blood volumes agrees moderately with transpulmonary thermo-dye dilution technique in critically ill patients.

Adolescent↗
PubMed1993

Organ blood flow and distribution of cardiac output in dopexamine- or dobutamine-treated endotoxemic rats.

Endotoxemia causes a decrease of blood flow to most organs. If this could be prevented, chances of survival might improve. In endotoxemic rats, we studied the effect of a therapeutic infusion of dopexamine (dopaminergic, beta 2-adrenergic) on blood flow and percentage of the cardiac output distributed to heart, brain, hepatic artery, stomach, intestines, spleen, pancreas, kidneys, adrenals, diaphragm, skeletal muscle, and skin. Dopexamine action was compared with that of dobutamine (beta 1-adrenergic). Endotoxin shock was induced in 28 rats with infusion of 8 mg/kg Escherichia coli O127:B8 endotoxin from 0 to 60 minutes; the rats were then divided into 3 groups, which received from 60 to 135 minutes of an infusion of saline (ES; n = 10), dopexamine hydrochloride (DX, 3 x 10(-8) mol/kg.min; n = 10) or dobutamine (DB, 10(-7) mol/kg.min; n = 8). A fourth group served as time-matched controls (C, saline from 0 to 135 minutes; n = 8). In the untreated endotexemic rats, cardiac output decreased and organ blood flow decreased except in the diaphragm, heart, and brain; the percentage of the cardiac output to those organs increased. Dopexamine and dobutamine similarly improved cardiac output in endotoxemic rats. All organs benefitted to the same extent from the increased cardiac output. Therapeutic infusion of dopexamine during endotoxemia did not favor flow to any particular organ; redistribution of cardiac output changed little after administration of dopexamine, and its effects were not significantly different from those of dobutamine.

Adrenergic Agonists↗
PubMed1989

Mechanism for decrease in cardiac output with atrial natriuretic peptide in dogs.

To examine the mechanism by which atrial natriuretic peptide (ANP) decreases cardiac output, we studied changes in the heart, peripheral circulation, and blood flow distribution in eight dogs. ANP was given as a bolus (3.0 micrograms/kg) followed by an infusion of 0.3 microgram.kg-1.min-1. ANP did not change heart rate, total peripheral vascular resistance, and the first derivative of left ventricular pressure but decreased mean aortic pressure from 91 +/- 4 to 76 +/- 3 mmHg (P less than 0.001) and cardiac output from 153 +/- 15 to 130 +/- 9 ml.kg-1.min-1 (P less than 0.02). Right atrial pressure and left ventricular end-diastolic pressure also decreased. Mean circulatory filling pressure decreased from 7.1 +/- 0.3 to 6.0 +/- 0.3 mmHg (P less than 0.001), but venous compliance and unstressed vascular volume did not change. Resistance to venous return increased from 0.056 +/- 0.008 to 0.063 +/- 0.010 mmHg.ml-1.kg.min (P less than 0.05). Arterial compliance increased from 0.060 +/- 0.003 to 0.072 +/- 0.004 ml.mmHg-1.kg-1 (P less than 0.02). Total blood volume and central blood volume decreased from 82.2 +/- 3.1 to 76.2 +/- 4.6 and from 19.8 +/- 0.8 to 17.6 +/- 0.6 ml/kg (P less than 0.02), respectively. Blood flow increased to the kidneys. We conclude that ANP decreases cardiac output by decreasing total blood volume. This results in a lower operating pressure and volume in the venous capacitance system with no significant venodilating effects. Cardiac factors and a redistribution of flow to the splanchnic organs are not important mechanisms to explain the decrease in cardiac output with ANP.

Animals↗
PubMed1982

Cardiac output and stroke volume in exercising ducks and pigeons.

The purpose of this study was to determine the relationship between oxygen consumption (VO2) and cardiac output, stroke volume, and arteriovenous O2 content differences in resting and exercising birds. Pigeons and ducks showed a linear relationship between oxygen consumption and cardiac output and appeared to have a greater cardiac output for a given oxygen consumption than do mammals of the same body mass. In these birds the arteriovenous O2 content difference was hyperbolically related to oxygen consumption. The cardiac output was relatively high, implying a smaller arteriovenous O2 content difference than found in mammals. Resting stroke volume, relative to body mass, was greater in these birds than in mammals. However, as birds have disproportionately larger hearts for their body mass, these birds showed almost the same stroke volume per gram of heart as do mammals.

Animals↗
PubMed1975

Responses to exogenous dibutyryl adenosine 3',5'-monophosphate of cardiac output and blood flow in the renal, superior mesenteric and carotid arteries in anesthetized dogs.

Changes in the cardiac output and blood flow in the renal, superior mesenteric and carotid arteries in anesthetized dogs were observed, using the non-cannulating electromagnetic flow meter. Dibutyryl cyclic-AMP, 5 mg/kg body weight, was given intravenously and the following results were obtained: 1) Dibutyryl cyclic-AMP increased the stroke volume and the cardiac output, and slightly increased the heart rate. These effects appeared 3 to 5 min after administration of dibutyryl cyclic-AMP. 2) The mean systemic blood pressure as well as the central venous pressure fell slightly. 3) The renal and the superior mesenteric artery blood flow increased markedly, but the carotid artery blood flow did not change. 4) Distribution of the cardiac output to the renal and superior mesenteric arteries did not change but distribution to the carotid artery decreased. 5) Total peripheral resistance, renal artery vascular resistance and superior mesenteric artery vascular resistance decreased, and carotid artery vascular resistance decreased slightly. 6) The cardiac output and blood flow were enhanced by aminophylline (3 mg/kg), and were not blocked by propranolol (0.3 mg/kg).

Aminophylline↗
PubMed2004

Measurement of cardiac output by transpulmonary arterial thermodilution using a long radial artery catheter. A comparison with intermittent pulmonary artery thermodilution.

Cardiac output can be measured accurately by transpulmonary arterial thermodilution using the PiCCO (Pulsion Medical Systems, Munich, Germany) system with a femoral artery catheter. We have investigated the accuracy of a new 50 cm 4 French gauge radial artery catheter and the ability to use the system with a shorter radial catheter. We studied 18 patients who had undergone coronary artery surgery and made three simultaneous measurements of cardiac output by arterial thermodilution and with a pulmonary artery catheter. The radial catheter was withdrawn in 5 cm increments and the measurements were repeated. We found close agreement between arterial thermodilution and pulmonary artery thermodilution with a mean (SD) bias of 0.38 (0.77) l x min(-1). Arterial thermodilution became unreliable once the catheter had been withdrawn by more than 5 cm. We conclude that cardiac output measurement with arterial thermodilution with a radial catheter is interchangeable with that derived from a pulmonary artery catheter, and that a centrally sited arterial catheter is required for accurate determination of cardiac output by transpulmonary arterial thermodilution.

Aged↗
PubMed1995

Impedance cardiography in the measurement of cardiac output: studies in rabbits.

A thoracic electric bioimpedance device with improved signal processing was used to noninvasively measure cardiac output in eight New Zealand White rabbits (average wt = 4.7 kg). Prospective correlation was performed between aortic thermodilution and impedance cardiography in a closed chest model. Aortic thermodilution was compared to the electromagnetic flowmeter in an open chest model. In four rabbits, the change in the impedance signal (dZ/dt) was quantified after repeated mechanical occlusion of the aorta and pulmonary artery. The mean cardiac output as measured by the impedance device was 0.56 +/- 0.01 liter/min (range 0.29-1.16 liter/min) compared to 0.53 +/- 0.01 liter/min (range 0.25-0.83 liter/min) by aortic thermodilution. For the 116 data pairs, regression analysis revealed a statistically significant agreement (r = 0.82, P < 0.001) between the two techniques. The mean difference between the techniques (bias) was -0.03 liter/min and 81% of the impedance values were within 0.1 liter/min of the individual thermodilution measurements. A statistically significant decline in the mean magnitude of the dZ/dt signal tracing (1.6 +/- 0.10 V-pre, 0.31 +/- 0.4 V-post, P < 0.005, n = 21) was observed upon aortic arch occlusion. conversely, pulmonary artery occlusion did not have a statistical effect on the impedance signal (1.07 +/- 0.09-pre, 0.95 +/- 0.08-post, P > 0.05, n = 20). In conclusion, a significant correlation was observed between impedance cardiography and aortic thermodilution in measurement of cardiac output in sedated, anesthetized rabbits. This simple technique which involves application of skin electrodes may prove useful in measurement of cardiac output in surgical experimental small animal models.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

[Quantitative aortic flow and cardiac output volume determinations in rabbits using tetrapolar impedance plethysmography].

In 25 normal rabbits the transthoracic impedance changes were continually registered at rest and during pharmacological exercise by use of various types of electrodes. These changes were quantified by the formula of Kubicek for estimation of cardiac output. The obtained values were compared with the values of cardiac output and the flow in the aorta descendens measured by electromagnetic flowmetry in the aorta descendens. Linear regression analyses for several intervals of ejection and various types of electrodes showed a high and significant correlation between the values estimated by both methods (r greater than or equal to 0.96, p less than or equal to 0.001). The analyses of confidence intervals of the parameters of linear regression showed that the functional relations can be described by uniform parameters of regression. On this basis were estimated coefficients of correction which allow quantitative evaluation of the cardiac output and the flow in the aorta descendens in rabbits by use of tetrapolar impedance plethysmography. For cardiac output: (Formula: see text) for the flow in the aorta descendens: (Formula: see text) Tetrapolar impedance plethysmography is a noninvasive method, which allows quantitative and dynamic evaluation both of the cardiac output and the flow in the aorta descendens in rabbits.

Animals↗
PubMed1991

Comparison of estimates of cardiac output by indicator dilution and freon 22 uptake during gas mixing in dogs.

STUDY OBJECTIVE: The aim was to measure cardiac output while rebreathing tidal volumes, by correction of soluble gas uptake for gaseous mixing. DESIGN: Simultaneous measurements of cardiac output by indocyanin green and freon 22 uptake during rebreathing were made. Mixing for a hypothetical gas of identical gaseous diffusivity to freon 22 was calculated by interpolation between concentrations of two insoluble gases, helium and sulphur hexafluoride. Mixing efficiency was estimated by the number of breaths for helium to become 99% equilibrated with lung gas (n99-He). EXPERIMENTAL MATERIAL: Five anaesthetised dogs rebreathed at intervals with 300 ml of test gas. MEASUREMENTS AND MAIN RESULTS: 63 comparisons of cardiac output using indocyanin green and freon 22 uptake (over breaths 7-13 using the mean mixed volume of distribution), gave a mean (95% confidence interval) underestimation of 0.345 (0.093-0.597) litre.min-1 (14%). Exclusion of 12 points in which n99-He was greater than 15 resulted in a mean underestimation of 0.052(-0.163-0.267) litre.min-1 (2%). Without correction for gaseous mixing, freon 22 uptake for these data overestimated blood flow by a mean of 1.31 litre.min-1 (overestimation = 2.7 over breaths 5-11). Use of the equilibrium volume of distribution resulted in an overestimation of blood flow relative to green dye of 1.2 litre.min-1 (breaths 5-11) and 0.76 litre.min-1 (breaths 7-13). CONCLUSIONS: Estimates of cardiac output by soluble gas uptake are optimal when correction is made for mixing of gas of identical diffusivity. The mean mixed gas volume gives the best correlation with the reference method, implying a selective distribution of blood flow to the better ventilated areas.

Animals↗
PubMed1989

Linear cardiac output in borderline and sustained hypertension.

We assessed the relative contributions of raised cardiac output and increased peripheral resistance to elevation and lability of blood pressure in patients with borderline and sustained hypertension. Ninety-five untreated patients were admitted to hospital for assessment. Using Doppler ultrasound, linear cardiac output was measured as minute distance on the day of admission and 24 h later; blood pressure was measured at the same times, enabling calculation of linear resistance (analogous to peripheral vascular resistance). In sustained, but not borderline, hypertension linear resistance was increased at the first measurement (+ 36%, P less than 0.001), but mean minute distance did not differ significantly from normal in either group. Between the first and second measurements in borderline and sustained hypertension there were significant falls of mean blood pressure (-9%, P less than 0.001 and -4%, P less than 0.01). In borderline, but not sustained, hypertension there was an associated fall of linear resistance (-11%, P less than 0.05); in neither group was there a significant change of minute distance. Both elevation and lability of blood pressure in borderline and sustained hypertension are due more to changes of peripheral resistance than to changes of cardiac output.

Adolescent↗
PubMed1983

Changes in aortic blood pressure and cardiac output curves as induced by stenosis of the descending thoracic aorta.

In 9 anaesthetized open chest rabbits cardiac output and aortic blood pressure were recorded. Cardiac output was obtained by means of an electromagnetic blood flow transducer placed around the ascending aorta. When a 10 sec stenosis of the descending thoracic aorta was produced, an increase of mean, systolic, diastolic and pulse pressure was observed above the stenosis, with a remarkable delay of the peak systolic pressure with respect to the peak velocity of ventricular ejection. Moreover, it is note worthy that during the stenosis the deceleration phase of the ventricular ejection showed a slackening which was responsible for a longer ejection time. Owing to such a longer ejection time, in 4 experiments stroke volume and cardiac output increased above the control in spite of a high aortic impedance. It is probably that the changes observed in the contour of the ventricular ejection curve, depend on modifications of the gradient between left ventricle and aortic blood pressure as well as on the combined effects of the Starling's law and of the afterload.

Animals↗