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PubMed1987

In utero ventilation with oxygen augments left ventricular stroke volume in lambs.

1. In order to determine mechanisms for increased stroke volume at birth, left ventricular function was investigated in eight fetal lambs during in utero pulmonary ventilation. At surgery fetuses were prepared with a tracheal tube, aortic electromagnetic flow sensor, and carotid, jugular, pericardial and left atrial catheters. 2. After 8.3 +/- 1.5 (mean +/- S.D.) post-surgery days and at 137 +/- 3 days gestation, haemodynamic values were obtained before and during pulmonary ventilation in utero. 3. During ventilation, O2 content increased from 7.3 +/- 2.1 to 14.7 +/- 2.7 ml dl-1 (P less than 0.001), right atrial pressure from 3.0 +/- 1.3 to 4.5 +/- 1.6 mmHg (P less than 0.05), left atrial pressure from 2.5 +/- 1.2 to 10.2 +/- 3.7 mmHg (P less than 0.001), left ventricular stroke volume from 1.1 +/- 0.4 to 1.9 +/- 1.2 ml kg-1 (P less than 0.05), and heart rate from 160 +/- 21 to 183 +/- 11 beats min-1 (P less than 0.05). 4. During O2 ventilation, left ventricular function curves relating stroke volume to left atrial pressure were shifted upward. 5. O2 ventilation produced rapid, reversible increases in left ventricular stroke volume which approximate increases in stroke volume at birth.

Animals↗
PubMed1986

Echocardiographic measurement of left ventricular stroke volume in newborn infants: a correlative study with pulsed Doppler and M-mode echocardiography.

Noninvasive monitoring of stroke volume by pulsed Doppler echocardiography is an important recent advance in neonatal care. Using this technique, we assessed stroke volume in 112 healthy neonates (birth weight 780-5350 g, menstrual age 27-42 weeks). Stroke volume increased with advancing birth weight (r = +0.93) and gestational age (r = +0.90). Mean stroke volume per kilogram body weight (1.77 +/- 0.28 ml/kg) was constant throughout the study population. Doppler-derived stroke volumes correlated linearly with left ventricular dimensions in diastole and in systole. Stroke volumes calculated from left ventricular dimensions using the Feigenbaum and Teichholz equations correlated equally well with Doppler-derived stroke volume values (r = +0.76 and +0.77, respectively).

Birth Weight↗
PubMed1999

Stroke volume changes during dobutamine-atropine stress echocardiography: the influence of heart rate and ischaemia.

BACKGROUND: A decrease in stroke volume during dobutamine-atropine stress echocardiography heralds ischaemia and possible hypotension. Hypotension results from worsening of LV-function (as a result of ischaemia) left ventricular outflow tract obstruction or hypovolemia, while an increase of stroke volume indicates the preservation of myocardial contractile reserve. OBJECTIVE: To assess stroke volume changes during dobutamine stress echocardiography in relation to heart rate and occurrence of ischaemia and to validate a new automated cardiac output measurement device. METHODS: In fifty patients, the stroke volume was assessed using the echocardiographic biplane discs method during a stress echocardiography. These data were reference values for the validation of a new automated cardiac output measurement using the first method as a reference. RESULTS: Stroke volume measured by the biplane discs method and automated cardiac output device decreased from rest to peak stress, respectively, from 54+/-16 to 34+/-9 (63%) ml and 63+/-17 to 38+/-15 (60%) ml (p < 0.001). Stroke volume decreased with increased heart rate and stress-induced ischaemia when assessed by the biplane discs method, but with the automated device it decreased only with increased heart rate. CONCLUSIONS: Both increased heart rate and myocardial ischaemia during dobutamine stress echocardiography cause a reduction of stroke volume. However, the automated device did not detect the effects of stress-induced ischaemia on stroke volume. It appears that the biplane discs method is more sensitive for evaluating the effect of ischaemia.

Adrenergic beta-Agonists↗
PubMed1981

Two-dimensional echocardiographic assessment of left ventricular stroke volume: experimental correlation with thermodilution and cineangiography in normal and ischemic states.

Left ventricular stroke volumes derived by two-dimensional echocardiography (2D echo) were compared with thermodilution and cineangiography measurements in closed-chest dogs before andone hour after proximal LAD occlusion. Stroke volume was calculated from end-diastolic and end-systolic volumes reconstructed by two models: 1) Simpson's rule employing left ventricular length and five short-axis cross-sectional areas; 2) a simplified volume formula (V = 5/6 area . length), utilizing a single short-axis area at either the mitral valve or midpapillary muscle level. The comprehensive Simpson reconstruction yielded a good correlation of 2D echo stroke volume against thermodilution (r = 0.89) over a range of normal (N = 14) and ischemic (N = 8) states. The simplified formula provided a satisfactory correlation (r = .90, N = 22) when using the midpapillary cross-section, which encompassed the induced ischemic dys-synergy. In contrast, when using the mitral valve level cross-section above the site of ventricular asymmetry, there was no significant statistical correlation. Comparison of cineangiography with 2D echo volume reconstruction based on the simplified formula with the midpapillary muscle level section yielded good correlations for stroke volume (r = 0.87) and ejection fraction (r = 0.97). Intraobserver and interobserver variability of duplicate echo stroke volume measurements was 8% and 10%, respectively. We conclude that 2D echocardiography in dogs permits quantitation of left ventricular stroke volume in normal and ischemic states.

Animals↗
PubMed1990

Left ventricular stroke volume and output in healthy term infants.

Left ventricular output, left ventricular stroke volume, and systemic vascular resistance were measured noninvasively in 16 healthy term infants at 6 predefined time intervals from less than 15 minutes to 72 hours after birth. The blood flow velocity in the ascending aorta was measured by range-gated Doppler technique and multiplied by the cross-sectional area, measured by 2-dimensional and M-mode echocardiography to yield left ventricular output. Stroke volume was calculated by dividing left ventricular output by heart rate. Mean arterial blood pressure was measured by oscillometric technique and used for calculation of systemic vascular resistance. A poor association between heart rate and left ventricular output was found, whereas there was a very close relationship between stroke volume and left ventricular output. There was also a reciprocal relationship between systemic vascular resistance and stroke volume. This suggests that stroke volume and not heart rate is the main determinant of neonatal left ventricular output and that the low postnatal afterload might strengthen this relationship.

Cardiac Output↗
PubMed2005

A review of the stroke volume response to upright exercise in healthy subjects.

Traditionally, it has been accepted that, during incremental exercise, stroke volume plateaus at 40% of Vo(2)max. However, recent research has documented that stroke volume progressively increases to Vo(2)max in both trained and untrained subjects. The stroke volume response to incremental exercise to Vo(2)max may be influenced by training status, age, and sex. For endurance trained subjects, the proposed mechanisms for the progressive increase in stroke volume to Vo(2)max are enhanced diastolic filling, enhanced contractility, larger blood volume, and decreased cardiac afterload. For untrained subjects, it has been proposed that continued increases in stroke volume may result from a naturally occurring high blood volume. However, additional research is needed to evaluate the importance of blood volume, or other mechanisms, that influence the stroke volume response to exercise in untrained subjects.

Adolescent↗
PubMed1996

On-line estimation of left ventricular stroke volume using transoesophageal echocardiography and acoustic quantification.

We have examined the usefulness of transoesophageal echocardiography (TOE) and automated endocardium detection for on-line calculation of left ventricular stroke volume. In 12 of 15 patients undergoing abdominal surgery, stroke volume was derived continuously from the multiple discs (MD) and area-length (AL) methods and compared with stroke volume calculated by thermodilution. In 10 patients (80%), more than three manipulations of the ultrasound transducer were required before measurements. Linear regression analysis of automated TOE methods and thermodilution revealed weak correlations (r < 0.75) for stroke volume (114 matched pairs) and its changes (105 matched pairs). Correlation of percentage changes in stroke volume calculated by thermodilution with those derived from MD (r = 0.85) and AL (r = 0.79) was better. Changes in MD (AL) derived stroke volume by more than 20% identified changes in thermodilution-derived stroke volume greater than 20% (n = 57) with a sensitivity of 74% (70%) and a specificity of 82% (79%). Signal instability, lack of accuracy and only a moderate trend capability currently limit the intraoperative usefulness of automated TOE techniques for continuous estimation of stroke volume from a single long-axis plane.

Abdomen↗
PubMed1986

Maternal heart rate and stroke volume in the pygmy goat: effects of exercise and cardiac autonomic blockade.

To determine the normal maternal heart rate and stroke volume response to exercise and the role of the autonomic nervous system in this response, pregnant and non-pregnant pygmy goats were studied at rest, during and following treadmill exercise, and after autonomic blockade. Resting heart rates, stroke volumes and cardiac outputs were 10%, 60%, and 76% higher in pregnant compared to non-pregnant animals (P less than 0.05, 0.001, and 0.001 respectively). During exercise, heart rate and stroke volume rose in both pregnant and non-pregnant animals by similar amounts. Immediately post-exercise, stroke volume in pregnant animals dropped precipitously below resting levels by 15% (P less than 0.005) but cardiac output was preserved by heart rate. This fall in stroke volume was not seen in control animals. Autonomic blockade lowered resting and exercise heart rates in both groups without changing stroke volume. The elevations in heart rate and stroke volume in pregnancy are not primarily mediated via the autonomic nervous system. Although the maternal cardiac output response to exercise appears normal, the post-exercise fall in stroke volume, presumed secondary to a reduction in preload, could potentially be harmful to both mother and fetus.

Animals↗
PubMedDate not supplied

An experimental evaluation of impedance cardiographic and electromagnetic measurements of stroke volumes.

The reliability of impedance cardiography for absolute and relative measurements of stroke volumes is assessed by comparing data with electromagnetic flowmeter measurements in 14 anaesthetized mongrel dogs. Cardiac output was altered in each dog (as much as possible) by a variety of physical and pharmacological interventions. Impedance cardiography does not provide absolute values for stroke volumes, although relative changes may be calculated with reasonable reliability if a correction factor ('CIMP') is employed. 'CIMP' is around 0 . 8 in subjects breathing spontaneously or when alternative pressure ventilation is applied. However, this factor can only be used in an intermediate range of stroke volumes (10-30 ml in the dog). At lower and higher cardiac output levels other correction factors must be observed accordingly. Intermittent positive pressure ventilation increases the sensitivity of relative stroke volume measurements by transthoracic impedance, leading to an average 'CIMP' of 1 . 5. For calculation of relative stroke volume changes by impedance cardiography, the simple formula: (formula; see text) is satisfactory instead of the more complicated Kubicek formula.

Animals↗
PubMed1983

Measurement of cardiac stroke volume during cesarean section: a comparison between impedance cardiography and the dye dilution technique.

Simultaneous determination of cardiac stroke volume by impedance cardiography and the dye dilution technique was compared in ten women undergoing elective cesarean section performed under general or epidural anesthesia. The influence of delivery and the anesthetic procedures used on stroke volume determination by the two methods was evaluated and compared. The correlation coefficients for measurements performed before and during anesthesia showed little variation and were largely unchanged after delivery of the child (r = 0.90-0.97). Mean stroke volume determined by impedance cardiography was significantly (P less than 0.001) lower than mean stroke volume calculated from the dye dilution technique. However, there was no significant difference between the mean change in stroke volume determined by the two techniques during serial measurements. Impedance cardiography was found to be a safe, reliable, non-invasive technique for the measurement of changes in stroke volume during cesarean section. The ability of the impedance method to determine changes in stroke volume was unaffected by the anesthetic procedures employed or by delivery of the child.

Anesthesia, Epidural↗
PubMed1991

Stroke volume increases by similar mechanisms during upright exercise in normal men and women.

To define the effects of gender on stroke volume control during upright exercise in normal subjects, we examined central hemodynamics in 34 men and 27 women during staged bicycle ergometry. Central hemodynamics were assessed by right-sided cardiac catheterization and simultaneous radionuclide angiography. Left ventricular end-diastolic and end-systolic volumes were calculated from the stroke volume (by direct Fick) and the corresponding left ventricular ejection fraction. Men were larger than women (1.85 +/- 0.11 vs 1.65 +/- 0.13 m2, p less than 0.001) but groups were matched for age (39 +/- 12 vs 36 +/- 9 years, p = 0.27). Oxygen consumption at peak exercise was higher in men than in women (2.51 +/- 0.50 vs 1.74 +/- 0.30 liters/min, p less than 0.001) but was not different when adjusted for body weight (31.5 +/- 8.1 vs 28.4 +/- 6.4 ml/kg/min, p = 0.14), indicating similar levels of overall fitness in the 2 groups. At rest and during submaximal and maximal exercise, stroke volume and left ventricular end-diastolic and end-systolic volumes were higher in men than in women, but there were no intergroup differences in stroke volume index, left ventricular ejection fraction, and left ventricular end-diastolic or end-systolic volume indexes. Comparison of derived regression equations of cardiac index, stroke volume index and left ventricular end-diastolic and end-systolic volume indexes revealed no differences in the time course or magnitude of changes with respect to oxygen consumption, expressed as percentage of peak oxygen consumption, in the 2 groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Simultaneous measurement of blood volume in the arteries of the neck and stroke volume].

The work describes a method of using a home tetrapolar two-channel rheograph RPG-2-02 for a one-step registration of differential rheogram (DRG) of the chest and neck-head. The stroke volume of the heart and the systolic blood volume in the cervical arteries were calculated by the corresponding DRG and the Kublicek formula. The clinical approbation of the method gave similar results of the capacitance blood flow with the literature data and with the rheographic method of determination of the cerebral blood flow.

Adult↗
PubMedDate not supplied

Impedance cardiography the reproducibility of stroke volume measurements under conditions of mass examination.

The stroke volume at rest of 81 test subjects with no evident cardiac or circulatory dysfunction was determined by impedance cardiography and the measurements were repeated after 11 weeks. In order to attain comparable and reproducible conditions, 44 test subjects were chosen who showed heart rates at rest not higher than 83 beats per min, and whose changes in heart rate between the two tests were not greater than 11 beats per min. The stroke volumes determined by impedance cardiography are greater than those measured with the invasive methods reported by other authors. If the electrodes are removed between the tests sufficient reproducibility is not obtained. It is concluded that determinations of stroke volume by impedance cardiography as described in the literature are only suitable for detecting directional changes when the electrodes are left in place. It is impossible to obtain comparable data with electrodes once removed and replaced for the second measurement. Impedance cardiography is based on theoretical assumptions which do not permit estimation of errors affecting the measurement.

Cardiac Output↗
PubMed1978

[The reproducibility of stroke-volume measurements by impedance cardiography. A critical analysis (author's transl)].

40 determinations of the stroke volume were carried out by impedance cardiography in one and the same subject. The stroke volume varied between 136 and 209 ml (x, x = 169 ml, S.D. = 17.5 ml). The mean error was in the same range as obtained by the Fick principle or by dye-dilution technique as referred to the literature. However, analysing the factors affecting the variability of the determined stroke volumes we may infer, the Kubicek formula for stroke volume is neither theoretically nor empirically sufficiently proved. A quantitative determination of the stroke volume or of any other circulatory quantity by the impedance cardiography seems to be impossible by our present method of procedure.

Cardiac Output↗
PubMed1995

Influence of preload reserve on stroke volume response to exercise in patients with left ventricular systolic dysfunction: a Doppler echocardiographic study.

OBJECTIVES: This study evaluated the role of preload reserve in the stroke volume response to exercise in patients with left ventricular systolic dysfunction by assessing the relation between stroke volume and late left ventricular diastolic filling during exercise. BACKGROUND: In patients with left ventricular diastolic dysfunction, the absence of left ventricular distension is the fundamental mechanism explaining the nonaugmentation of stroke volume during exercise. METHODS: In 32 patients with left ventricular systolic dysfunction and 16 healthy control subjects, mitral and aortic velocities were recorded by Doppler echocardiography at rest and during submaximal supine bicycle exercise. Stroke volume, peak early (E) and late (A) mitral velocities, A/E ratio and end-diastolic filling were measured at rest and during exercise. RESULTS: Stroke volume increased significantly in control subjects but did not change in patients. Peak early mitral velocity increased significantly and to the same extent in both groups, whereas peak late mitral velocity and end-diastolic filling increased significantly in both groups but more so in control subjects; the A/E ratio increased significantly in control subjects but did not change in patients. In addition, stroke volume correlated significantly with peak late mitral velocity during exercise in patients (r = 0.72, p < 0.001). CONCLUSIONS: Compared with control subjects, patients with left ventricular systolic dysfunction exhibited limited increases in both stroke volume and late left ventricular filling during exercise. Furthermore, their stroke volume response correlated with the capacity of the left ventricle to increase late diastolic filling, that is, preload reserve.

Adolescent↗
PubMed1983

Evaluation of pulse contour methods in calculating stroke volume from pulmonary artery pressure curve (comparison with aortic pressure curve).

The reliability of five equations in assessing stroke volume from pulmonary artery pressure curves were critically evaluated in six dogs and in six patients. To alter stroke volume, isoproterenol, dobutamine, propranolol, lactate Ringer solution and artificial pacing were employed in the animal study and diltiazem (a calcium blocker) in the human study. A good correlation was found between the calculated and measured stroke volume (r = 0.80-0.86 in the animal study and r = 0.94-0.96 in the human study). The assessment of stroke volume from the pulmonary arterial pressure curves using equations was as good as that from the aortic pressure curves calculated simultaneously. These results suggest that the five equations may be clinically applicable for assessing stroke volume in critically ill patients. The employment of pulmonary arterial pressure curves in assessing stroke volume may be more useful clinically since its recording can be carried out more safely than recordings of aortic pressure curves.

Animals↗
PubMed2002

Changes in stroke volume in rat pups during adaptation to various regimens of motor activity.

Experiments on rat pups showed that regular exercise for 4 weeks starting from day 14 after birth considerably increased stroke volume. Similar dynamics of stroke volume was observed in subsequent period of restraint locomotion. Experimental hypokinesia starting from day 14 after birth significantly limited the age-dependent increase in SV. However, subsequent exercise training promoted the increase in stroke volume in these rats. In trained rats the regulation of stroke volume during hypokinesia remained unchanged, while in restrained rats subsequent training was associated with considerable reduction of sympathetic regulation of stroke volume.

Adaptation, Physiological↗