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PubMed1995

Quantitation of cardiac output with velocity-encoded, phase-difference magnetic resonance imaging.

Velocity-encoded, phase-difference magnetic resonance imaging (MRI) previously has been used to measure flow in the aorta, as well as in the pulmonary, carotid, and renal arteries, but these measurements have not been validated against currently accepted invasive techniques. To determine the accuracy of velocity-encoded, phase-difference MRI measurements of cardiac output, 23 subjects (11 men and 12 women, aged 15 to 72 years) underwent velocity-encoded, phase-difference MRI measurements of cardiac output in the proximal aorta, followed immediately by cardiac catheterization, with measurement of cardiac output by the Fick principle and by thermodilution. For MRI, Fick, and thermodilution measurements, stroke volume was calculated by dividing cardiac output by heart rate. The magnetic resonance images were acquired in 1 to 3 minutes. For all patients, the agreement between measurements of stroke volume was 3 +/- 9 ml for MRI and Fick, -3 +/- 11 ml for MRI and thermodilution, and 0 +/- 8 ml for MRI and the average of Fick and thermodilution. Compared with standard invasive measurements, velocity-encoded, phase-difference MRI can accurately and rapidly determine cardiac output.

Adolescent↗
PubMed1997

[Measurement of cardiac output with continuous thermodilution. b1 Clinical experience with the Intellicath-Vigilans system].

BACKGROUND: Thermodilution cardiac output measurements are commonly obtained by a manual bolus technique with a pulmonary artery catheter. METHODS: A new thermodilution catheter has been developed which utilizes an integral thermal filament and provides semicontinuous online cardiac output. The response of this new device in 25 patients undergoing coronary artery bypass grafting was examined. A total of 250 data pairs was obtained; the cardiac outputs ranged from 2.2 to 11.9 lts.min. RESULTS: The linear regression is represented by the following equation: continuous thermodilution = 0.7196 bolus thermodilution +1.038. The correlation coefficient was 0.75; the mean bias was 0.493 +/- 1.034. CONCLUSIONS: The new technique provides acceptable accuracy in many clinical situations except when sudden haemodynamic changes occur.

Cardiac Output↗
PubMed1976

Cardiac output measurement by thermal dilution: reproducibility and comparison with the dye-dilution technique.

Cardiac output estimates by the principle of thermodilution (COth) was compared with dye-dilution estimates (COdye) in pigs. For COth estimates a Swan-Ganz 7 F floating thermodilution catheter and a 9500 Edwards Computer, were used. The COdye estimates were obtained by the apparatus constructed by Zijlstra and Mook. The effect of the thermistor position in the pulmonary artery on the COth estimates was also investigated. The reproducibility of COth was examined by duplicate determinations. Based on 101 simultaneous estimates of COth and COdye the correlation was found COth = 1.020 COdye + 0.2378, r = 0.971 for cardiac outputs between 0.65 l/min and 11 l/min. For 111 duplicate determinations of COth between 2 and 9 l/min the coefficient of variation was 4.74%. The thermistor position in the pulmonary artery had no influence on the COth estimates provided an undamped pressure curve could be monitored from the tip of the catheter. Cardiac output can thus be measured rapidly with good accuracy also for low values by means of a blindly inserted thermistor catheter positioned without x-ray control and a computer with digital display.

Animals↗
PubMed1991

Thermodilution cardiac output measurement with a large left-to-right shunt.

Cardiac output was measured by the thermodilution method in a patient with a left-to-right shunt undergoing cardiac catheterization. It appeared that the thermodilution method measured systemic rather than pulmonary blood flow. This occurred because of the slow injection of injectate in the presence of a large left-to-right shunt. Theoretical thermodilution cardiac output curves are provided to illustrate the interaction of these two factors when three different durations of injection and four different shunt sizes are used.

Adult↗
PubMed1998

Clinical evaluation of the Abbott Qvue-OptiQ continuous cardiac output system in critically ill medical patients.

PURPOSE: The aim of this study was to evaluate the reliability of a new continuous cardiac output (CCO) monitoring device (Qvue/OptiQ system; Abbott Critical Care Systems, Mountain View, CA) based on the pulsed warm thermodilution technique in critically ill medical patients. METHODS: Nineteen patients with cardiogenic or septic shock were included in the study. Pairs of CCO and intermittent bolus cardiac output (ICO) were noted at least every 6 hours for determination of bias, precision, and limits of agreement. Simultaneously, blood samples were collected, and arterial-venous oxygen content difference (C[a-v]O2) was determined. A multiple stepwise logistic regression was used to identify situations associated with a CCO-ICO difference exceeded 20%. A multiple linear regression was performed to analyze the respective accuracy of CCO and ICO to predict the variations of C[a-v]O2. RESULTS: A total of 203 pairs of cardiac output measurements was obtained. The bias was 0.12 L/min (1.2% of pairs mean) and the precision 1.0 L/min (13%). The 95% limits of agreement were between -1.7 L/min (-25%) and 1.9 L/min (+26%). Low blood temperatures and heart rates above 120 beats/min were significantly associated with a ICO-CCO difference higher than 20%. In a multiple linear regression, CCO was significantly correlated with C[a-v]O2, an independent reflection of the patient's cardiac output; by contrast, ICO did not. CONCLUSION: These results suggest that ICO and CCO measurement by the Qvue/OptiQ system are interchangeable, except for temperature or heart rate extreme values.

Cardiac Output↗
PubMed1976

Distribution of fetal cardiac output: importance of pacemaker location.

Important questions exist about the relative roles of changes in heart rate versus extent of myocardial shortening in regulating fetal cardiac output, because increases in heart rate created by left atrial pacing have been shown to increase right ventricular output and decrease left ventricular output. Since the pacemaker site could importantly influence foramen ovale flow and, hence, each ventricle's output, changes in individual ventricular outputs were examined when both the right and left atria were paced at a rate of 270 beats/min in five acute and in eight chronically instrumented fetal lamb studies. With pacing of either atrium, total cardiac output was unchanged compared to control values. However, the right ventricle contributed more to total cardiac output with left atrial pacing (73% acute, 65% chronic) than with right atrial pacing (51% acute, 57% chronic). Converse changes were observed in left atrial pacing (27% acute, 35% chronic) as compared to right atrial pacing (49% acute, 43% chronic). Thus the disparity that exists normally in the contributions of the right and left ventricles to total cardiac output is accentuated with left atrial pacing and minimized with right atrial pacing. Pressure measurements demonstrated changes in the atrial pressure relations that would be expected to alter flow across the foramen ovale depending on the chamber initially activated. Previous experimental differences can, therefore, be attributed to changes in the magnitude of shunting across the foramen ovale and depend on pacemaker location.

Animals↗
PubMed1994

Utility and limitations of biplane transesophageal echocardiographic automated border detection for estimation of left ventricular stroke volume and cardiac output.

Recent echocardiographic ABD algorithms can estimate LV volume on-line from a single long-axis plane. The objective of this study was to assess the capability and limitations of transesophageal ABD to estimate stroke volume and cardiac output in patients before and after coronary artery bypass surgery by correlating these data with simultaneous thermodilution measurements. ABD data were acquired on-line from the transverse-plane four-chamber view and the longitudinal-plane two-chamber view and calculated by automated area-length and Simpson's rule formulas for volume. Thirty-three studies were attempted in 18 patients. Technically adequate ABD data were available in all patients from at least one view. Twenty-two (67%) of 33 studies from the four-chamber view and 27 (82%) of 33 studies from the two-chamber view were technically adequate. Cardiac output by all ABD methods was significantly correlated with thermodilution values (r range 0.72 to 0.89; SEE range 0.48 to 0.55 L/min). The two-chamber view underestimated cardiac output slightly, by an average of 0.4 L/min, whereas the four-chamber view consistently underestimated cardiac output by an average of 1.9 L/min. The area-length and Simpson's rule algorithms produced similar results. Biplane transesophageal ABD is an alternative method for estimating cardiac output; the two-chamber view in particular has potential for on-line volume determination.

Adult↗
PubMed1976

Absolute determination of cardiac output in intra-aortic balloon pumped patients using the radial arterial pressure trace.

We describe a new method for the absolute determination of cardiac output in intra-aortic balloon pumped (IABP) patients. The method uses the known pumping volume of the IABP balloon and the radial arterial pressure trace, which is commonly used to monitor IABP patients, to determine the cardiac output. Two pressure excursions denoted by P1-P0 and P2-P0, characterizing IABP balloon deflation, and ventricular ejection, respectively, are extracted from the radial trace. The cardiac output (CO) is then determined by the simple relation: CO = (BV) x (P2-P0)/(P1-P0) x HR where HR is the heart rate, and the value for pumped balloon volume (BV) is corrected for the effect of the pressure in the patient's aorta. Comparison with dye dilution and thermal dilution procedures as carried out on a routine basis in a clinical setting produced a good correlation (r = .928). When fit to a straight line through zero output, the data yielded a constant of proportionality of 0.973 between the above formula and the clinical procedures. The procedure does not disturb the patient in any way, and enables continuous monitoring of cardiac output. This has been implemented using a real-time, miniaturized computer and allows much more information to be obtained than in usual single measurements.

Aorta, Thoracic↗
PubMed1995

Assumed oxygen consumption based on calculation from dye dilution cardiac output: an improved formula.

This study was performed because of observed differences between dye dilution cardiac output and the Fick cardiac output, calculated from estimated oxygen consumption according to LaFarge and Miettinen, and to find a better formula for assumed oxygen consumption. In 250 patients who underwent left and right heart catheterization, the oxygen consumption VO2 (ml.min-1) was calculated using Fick's principle. Either pulmonary or systemic flow, as measured by dye dilution, was used in combination with the concordant arteriovenous oxygen concentration difference. In 130 patients, who matched the age of the LaFarge and Miettinen population, the obtained values of oxygen consumption VO2(dd) were compared with the estimated oxygen consumption values VO2(lfm), found using the LaFarge and Miettinen formulae. The VO2(lfm) was significantly lower than VO2(dd); -21.8 +/- 29.3 ml.min-1 (mean +/- SD), P < 0.001, 95% confidence interval (95% CI) -26.9 to -16.7, limits of agreement (LA) -80.4 to 36.9. A new regression formula for the assumed oxygen consumption VO2(ass) was derived in 250 patients by stepwise multiple regression analysis. The VO2(dd) was used as a dependent variable, and body surface area BSA (m2). Sex (0 for female, 1 for male), Age (years), Heart rate (min-1) and the presence of a left to right shunt as independent variables. The best fitting formula is expressed as: VO2(ass) = (157.3 x BSA + 10.0 x Sex - 10.5 x In Age + 4.8) ml.min-1, where ln Age = the natural logarithm of the age. This formula was validated prospectively in 60 patients. A non-significant difference between VO2(ass) and VO2(dd) was found; mean 2.0 +/- 23.4 ml.min-1, P = 0.771, 95% Cl = -4.0 to +8.0, LA -44.7 to +48.7. In conclusion, assumed oxygen consumption values, using our new formula, are in better agreement with the actual values than those found according to LaFarge and Miettinen's formulae.

Adolescent↗
PubMed1989

Underestimation of cardiac output by thermodilution in patients with tricuspid regurgitation.

INTRODUCTION: This study was done to assess the accuracy and reliability of the thermodilution technique in measuring cardiac output in patients with tricuspid regurgitation. PATIENTS AND METHODS: In 30 subjects (17 men, 13 women, aged 50 +/- 14 [mean +/- SD] years), cardiac output was measured in close temporal proximity by thermodilution as well as Fick or indocyanine green dye, after which the presence and severity of tricuspid regurgitation were assessed by contrast right ventriculography or pulsed Doppler echocardiography. RESULTS: In the 13 patients without tricuspid regurgitation, there was excellent agreement between the results of thermodilution and Fick or indocyanine green dye cardiac output determinations (4.95 +/- 1.19 liters/minute by thermodilution, 4.90 +/- 1.11 liters/minute by Fick or indocyanine green dye; NS). In contrast, in the 17 patients with tricuspid regurgitation, the results of thermodilution were consistently lower than those of Fick or indocyanine green dye (4.22 +/- 1.45 liters/minute by thermodilution, 4.99 +/- 1.67 liters/minute by Fick or indocyanine green dye; p less than 0.001). CONCLUSION: Thus, the thermodilution technique of measuring cardiac output is inaccurate in patients with tricuspid regurgitation, yielding results that are consistently lower than the actual outputs.

Adult↗
PubMedDate not supplied

Cardiac output regulation in the moving actuator total artificial heart without a compliance chamber.

A new cardiac output regulation method for the moving actuator total artificial heart (TAH) has been developed without using an extra compliance chamber or any transducer. The left and right ventricular sacs are alternately pumped by the pendulous moving actuator, with the left sac attached to the actuator and a free right ventricle. Preload sensitive cardiac output response is achieved by adjusting heart rate just below the level needed to generate atrial collapse, while maintaining full-fill and full-ejection conditions. The motor current waveform analysis detects mild atrial suction related to the amount of venous return. In addition, the structural characteristic of the pendulous moving actuator allows for manipulation of the left and right ventricular output difference by adjusting the asymmetry of stroke angle to either the left or right. In mock circulatory system tests, cardiac output increased from 5 to 9 L/min, with left atrial pressure (LAP) maintained at approximately 5 mmHg higher than right atrial pressure (RAP) over a physiologic range of preload (0-12 mmHg of RAP) and afterload [80-120 mmHg of aortic pressure (AoP)].

Algorithms↗
PubMed2003

Decreased cardiac output in humans during laparoscopic antireflux surgery: direct measurements.

OBJECTIVE: In a porcine model, we demonstrated that laparoscopic Nissen fundoplication causes a significant drop in cardiac output (30%) because it exposes both the peritoneal cavity and the mediastinum to CO(2) under pressure. To determine if this occurs in humans, we examined cardiovascular physiology during laparoscopic Nissen fundoplication. Because of invasiveness required in this pilot trial, only six patients were studied. METHODS: The arterial blood pressure (via radial arterial catheter) and the pulmonary artery diastolic pressure and cardiac index (via pulmonary artery thermodilution catheter) were measured at seven points in time during each laparoscopic Nissen fundoplication. RESULTS: The systolic blood pressure decreased in all patients, and the cardiac index decreased in all but one patient. The exception was a patient with Huntington disease, in whom the cardiac output did not decrease. In four of the five patients, the cardiac output was lowest during hiatal dissection, and in the fifth, it was lowest after reverse Trendelenburg positioning. No significant change in the pulmonary artery diastolic pressure was noted. All patients received adequate intravenous fluid replacement (average, 58 +/- 16 mL/kg) to support blood pressure. In one patient, with a particularly large paraesophageal hernia, profound hypotension (40/25 mm Hg) developed during the mediastinal phase of the procedure, and this patient required alpha-adrenergic support followed by laparotomy to eliminate a surgical cause (none found). CONCLUSIONS: Although it is a tremendous advance for patients, laparoscopic Nissen fundoplication can be associated with a significant reduction in cardiac output and blood pressure. Surgeons and anesthesiologists must be alert to changes reflecting these decreases during procedures, which violate both the peritoneal cavity and the mediastinum. We propose careful hemodynamic monitoring during these procedures, especially in patients with coronary artery disease or significant left ventricular dysfunction.

Aged↗
PubMed1987

Combined Doppler and echocardiographic measurement of cardiac output: theory and application in pregnancy.

A non-invasive technique for the measurement of cardiac output in pregnancy by combined cross-sectional and Doppler echocardiography at three intracardiac sites is described. The validity of the technique for use during pregnancy is reviewed. Comparison with cardiac output determined simultaneously by the direct Fick technique in 15 non-pregnant subjects showed close agreement for all three measurement sites. Acceptable measurements were obtained from the aortic and pulmonary valves in all pregnant subjects and from the mitral valve in 84% of pregnant subjects. The within-patient intra-observer and hour-to-hour variabilities of cardiac output in pregnant and non-pregnant subjects were less than 5% of the mean for all three valves studied. Flow measurements at each of the three intracardiac sites correlated closely. The advantages and limitations of the technique for use during pregnancy are discussed.

Adolescent↗
PubMed1986

Effect of prolonged infusion of ritodrine on uteroplacental blood flow and cardiac output distribution in unanesthetized pregnant guinea pigs.

The effects of ritodrine, 15 micrograms X min-1 X kg-1 administered intravenously, on the maternal circulation and uteroplacental blood flow were investigated in eight chronically catheterized pregnant guinea pigs near term. Cardiac output and its distribution were measured by means of the radionuclide-labelled microsphere technique before, and after 2 and 6 h of infusion of ritodrine. Ritodrine produced a sustained elevation of cardiac output to 135 and 137% of the control value after 2 and 6 h, respectively. The carcass and gastrointestinal tract together accounted for the greatest portion of the extra blood flow, 77 and 84% at the times of the two flow measurements during treatment. After 2 h of ritodrine, mean placental blood flow was reduced to 85% of the control level (n.s.), uteroplacental vascular resistance was 127% of its initial value (n.s.), and the placental fraction of cardiac output had decreased from 18 to 12% (P less than 0.02). Continuation of the infusion to 6 h resulted in an increase in mean placental blood flow to 107% of the control value and return of uteroplacental vascular resistance to its initial level. The placental fraction of cardiac output increased to 14%, significantly (P less than 0.05) different from both the initial and the 2-h values. Blood flow to the skin, lungs, spleen and mammary glands decreased between the 2- and 6-h flow measurements. These observations are compatible with the hypothesis that the changes in uteroplacental blood flow during administration of ritodrine are passive, resulting from the balance between the increase in cardiac output and vasodilatation in extrauterine vascular beds.

Animals↗
PubMed1999

Does bronchial thermodilution allow estimation of cardiac output?

OBJECTIVE: Transcapillary heat transfer after injections of cold saline into the right atrium generates bronchial thermodilution curves resembling those observed in the aorta. Under the assumption that no indicator is lost or gained within the pulmonary capillary bed and changes in blood temperature are instantaneously recorded in the bronchial system, we tested the hypothesis that flow rates calculated from bronchial temperature-time curves are similar to those from aortic curves. DESIGN: Comparative study of two cardiac output estimates in five dogs. SETTING: Research laboratory for Experimental Anaesthesiology. INTERVENTIONS: Cardiac output was decreased (repeated withdrawal of blood) and increased (infusion of colloids or dobutamine) in order to study a wide range of cardiac outputs. MEASUREMENTS AND RESULTS: Thermistors were placed in a bronchiole (wedge position) and in the ascending aorta of anaesthetized dogs. Bronchial and aortic thermodilution curves were recorded after injection of 5 ml ice-cold saline into the right atrium. We found that bronchial thermodilution yields flow estimates similar to those from aortic curves. Correlation between the two flow estimates was acceptable (r = 0.84) with a mean difference between the two of less than 2%. CONCLUSION: We conclude that the Stewart-Hamilton equation may be extended to bronchial temperature-time curves for estimations of cardiac output. At this time, however, we do not advocate bronchial thermistors as suitable and less invasive alternatives to pulmonary arterial catheters for routine cardiac output measurements in patients.

Animals↗
PubMed1981

Non-invasive measurement of cardiac output during anaesthesia. An evaluation of the soluble gas uptake method.

A technique for measuring cardiac output which depends on the uptake of an inert soluble gas from the lungs has been evaluated during anesthesia. A respiratory mass spectrometer has been used to follow the concentrations of argon and freon-22 during passive rebreathing in anaesthetized patients before cardiopulmonary bypass. Values for cardiac output obtained with this technique are reproducible, but lower than those recorded using the direct Fick technique before and after the rebreathing manoeuvre. A reduction in cardiac output caused by vigorous rebreathing is the most likely explanation for the discrepancy and, although serial measurements of oxygen consumption may permit application of a correction factor, a method of measurement which causes significant haemodynamic disturbance cannot be recommended for widespread use.

Adult↗
PubMed1983

Regurgitation of prosthetic heart valves: dependence on heart rate and cardiac output.

Prosthetic heart valves exhibit closure and leakage backflow; however, no well-controlled study to evaluate the influence of factors such as cardiac output and heart rate on backflow has been reported to date. Four clinically used prosthetic aortic valves (size 27 mm)--St. Jude Medical, Björk-Shiley Spherical Disc, Björk-Shiley Convexo Concave, and Starr-Edwards model 1260--were studied in the aortic chamber of a pulse duplication system at heart rates of 50, 80, 110, and 140 beats/min, cardiac output of 2, 4, 6, and 8 liters/min, and mean aortic pressure of 100 mm Hg. Regurgitation was calculated in percentage and found to vary directly with heart rate and inversely with cardiac output. The range of values obtained were 5.5% for the Starr-Edwards model 1260 valve at 110 beats/min and 8 liters/min, to 37.5% for the Björk-Shiley Convexo Concave valve at 140 beats/min and 2 liters/min. Regurgitation was also calculated in milliliters/stroke and ranged from 3.4 ml/stroke for the Starr-Edwards model 1260 valve at 140 beats/min and 2 liters/min, to 17.3 ml/stroke for the Björk-Shiley spherical disc valve at 50 beats/min and 2 liters/min. Regurgitation associated with prosthetic heart valves may present a problem clinically, particularly under conditions of low cardiac output and tachycardia.

Cardiac Output↗
PubMed1996

Redistribution of cardiac output in response to heat exposure in the pony.

Radioactive microspheres were used to measure cardiac output and blood flow to most major tissues in 4 ponies at rest in thermoneutral (16 degrees C/60% RH) and mildly hot (41 degrees C/34% RH) environments. In response to heat stress there were increases in cardiac output (2-fold), respiratory frequency (5-fold), blood flow to the skin of the body (3-fold), and limbs (50%), respiratory muscles (2-fold) and the upper respiratory tract (3-fold). Ponies were able to maintain body temperature in the hot environment by increasing blood flow to the tissues involved in heat dissipation, while blood flow to all other tissues remained stable. This was achieved by increasing the cardiac output without need for reduction of blood flow to other tissues.

Animals↗