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PubMed1981

Continuous stroke volume and cardiac output from intra-ventricular dimensions obtained with impedance catheter.

To improve assessment of ventricular function during cardiac catheterisation there should be available a continuous registration of stroke volume and cardiac output in addition to ventricular pressure. To obtain the desired volumetric quantities a catheter has been developed which measures changes in intraventricular dimensions by electrical impedance. For this purpose, the catheter is equipped with eight electrodes spaced over a distance equal to the long axis of the left ventricle into which it is introduced. A constant current is imposed between the outermost electrodes while the inner six are used to measure resistance of volume segments of the blood contained within the ventricular cavity. The difference in resistance at the beginning and end of ejection is proportional to the contribution of each segment to stroke volume, which follows from addition to the segmental terms. Calibration is obtained by measuring electrical conductivity of a blood sample. The catheter was tested over a tenfold range of cardiac output, both in vitro, using an artificial heart model, while performance in vivo was evaluated in 12 dogs. In the animals study, stroke volume and cardiac output from the catheter were compared with flows obtained with an electromagnetic flowmeter. In both studies, linear regression analysis showed excellent correlation of cardiac output (r = 0.99, n = 10 in vitro, r = 0.95, n = 126 in vivo) while the regression equations were close to those of identity. Very good correlation (r = 0.98, n = 28) was also obtained for stroke volumes on a beat to beat basis during arrhythmia. It is concluded that the catheter, which has great potential for application in man, fulfills its primary aim of continuously recording stroke volume and cardiac output.

Animals↗
PubMedDate not supplied

Simultaneous cardiac output and regional myocardial perfusion determination with PET and nitrogen 13 ammonia.

BACKGROUND: The purpose of this study was to evaluate the possibility of measuring cardiac output during positron emission tomography (PET) examination of myocardial perfusion with nitrogen 13 ammonia. METHODS AND RESULTS: In 7 patients undergoing right-sided cardiac catheterization for evaluation of heart failure and 6 patients who had undergone heart transplantation, a thermodilution catheter for continuous measurement of cardiac output was inserted. An N-13 ammonia scan of the heart was subsequently performed, and with use of factor analysis, the time-activity curve from the right ventricle was derived from the dynamic image sequence. The PET-derived cardiac output was subsequently obtained according to the Stewart-Hamilton principle as the amount of injected tracer divided by the area under the time-activity curve. PET-acquired cardiac output measurements correlated closely with the invasively determined values for a wide range of cardiac output values (P < .0001). The mean difference was 0.12 L/min, with an SD of 0.74 L/min. The interobserver variation was low, with a mean difference of 0.06 L/min and an SD of 0.46 L/min. CONCLUSIONS: Cardiac output determination with N-13 ammonia and PET appears to be both accurate and precise and can be performed simultaneously with measurement of myocardial perfusion.

Adult↗
PubMed2005

Cardiac output by PulseCO is not interchangeable with thermodilution in patients undergoing OPCAB.

PURPOSE: To investigate the reliability of cardiac output assessed by arterial pressure waveform (PulseCO) in comparison with bolus thermodilution measurements in patients undergoing off-pump coronary artery bypass grafting (OPCAB). METHODS: 23 patients who underwent OPCAB were enrolled in this study. After premedication with oral diazepam 10 mg, anesthesia was induced with midazolam, fentanyl and vecuronium. After induction, radial artery and pulmonary artery catheters were inserted. Cardiac output was measured simultaneously by the PulseCO and the bolus thermodilution method using the Vigilance monitor: 1) after sternotomy, 2) after opening the mediastinum, and 3) at the end of surgery. The PulseCO was calibrated initially with cardiac output determined by the thermodilution method after induction of anesthesia. RESULTS: The correlation coefficients between the two techniques at the three measurement periods were: 1) R2 = 0.49, 2) R2 = 0.52, 3) R2 = 0.55. The limits of agreement (bias +/- 2 SD of bias) were: 1) 0.71 +/- 2.66, 2) 0.30 +/- 1.97, 3) 0.76 +/- 3.85 L.min(-1). CONCLUSIONS: Cardiac output by PulseCO is not interchangeable with cardiac output measured by thermodilution in patients undergoing OPCAB.

Aged↗
PubMed1985

Accuracy of the impedance cardiogram in the measurement of cardiac output in the elderly.

The cardiac output has been determined by radionuclide angiocardiography and by impedance cardiography in 93 elderly patients. The agreement between the two methods was excellent in patients in sinus rhythm, without regurgitant valvular lesions, and without severe airways obstruction or right bundle branch block. In atrial fibrillation the lack of correlation may be due to differences in heart rate during the two measurements, in regurgitant valvular lesions to the fact that impedance cardiography measures stroke output, whether forward or backward, in airways obstruction to high values for the basal thoracic impedance, and in right bundle branch block perhaps to the abnormal impedance wave-form often present.

Age Factors↗
PubMed1991

Relation of cardiac output at rest and during exercise to age in essential hypertension.

It has been suggested that the decline of cardiac output with age is due to increased prevalence of disease, particularly occult coronary artery disease. Therefore, the relation of cardiac output (direct oxygen Fick method) to age was analyzed in 110 sixteen- to 64-year-old men with World Health Organization stage I or II essential hypertension at the time of the hemodynamic study, who were alive and free of cardiovascular complications 7 years later. At supine and seated rest, during upright bicycle exercise at 50 W and and at peak work load, cardiac output was inversely (p less than 0.01) related to age. These relations were independent of weight and mean intraarterial pressure. Stroke volume decreased with advancing age at supine rest, but not at rest and during exercise in the seated position. Heart rate was not affected by age in the supine position, but was slower in older patients during upright rest and at peak exercise. In conclusion, in patients with essential hypertension who remained free of cardiovascular complications for 7 years, cardiac output was independently and inversely related to age at various levels of activity. These findings suggest that occult cardiovascular disease does not explain the decline in cardiac output with age in patients with essential hypertension.

Adolescent↗
PubMed1986

Angiotensin II infusion during beta-adrenergic stimulation by isoproterenol. Effects on hepatic, splenic and cardiac blood volumes and on the magnitude and distribution of cardiac output in the dog.

The cardiac and peripheral vascular adjustments to angiotensin II (0.1-0.2 microgram kg-1 min-1 i.v.) during high beta-adrenergic activity by a continuous isoproterenol infusion (0.2-0.3 microgram kg-1 min-1 i.v.) were examined in anaesthetized, atropinized dogs. Hepatic, splenic and left ventricular (LV) volume changes were estimated by an ultrasonic technique, and the blood flow distribution was measured by injecting radioactive microspheres and by electromagnetic flowmetry on the caval veins, the hepatic artery and the portal vein. During isoproterenol infusion, angiotensin II increased the systolic LV pressure by 45 +/- 3 mmHg and the stroke volume by 17 +/- 6%. Concomitantly, the hepatic and splenic blood volumes declined by 29 +/- 4 and 14 +/- 6 ml, respectively, and the LV end-diastolic segment length increased by 3 +/- 1%. The flow through the inferior caval vein increased by 39 +/- 9%, whereas the superior vena caval flow remained unchanged. The hepatic arterial flow more than doubled. Thus, at high inotropy by isoproterenol infusion, angiotensin II relocates blood from the liver and the spleen towards the heart. By activating the Frank-Starling mechanism, cardiac output is increased and conducted through the lower body, especially through the hepatic artery, because of the poor autoregulation of flow through this vessel.

Adrenergic beta-Agonists↗
PubMed2001

Flow dependency of error in thermodilution measurement of cardiac output during acute tricuspid regurgitation.

OBJECTIVE: To evaluate the effect of variable degrees of tricuspid regurgitation on thermodilution cardiac output measurements during changes in venous return. DESIGN: Prospective, controlled animal study. SETTING: University laboratory. PARTICIPANTS: Eight anesthetized mongrel dogs instrumented for simultaneous measurement of cardiac output by thermodilution and ascending aortic electromagnetometry. INTERVENTIONS: Data were collected before and after induction of moderate and severe tricuspid regurgitation. Under each condition, measurements were obtained at baseline and after opening 2 peripheral arteriovenous shunts to increase venous return. MEASUREMENTS AND MAIN RESULTS: Baseline electromagnetic flow ranged from 1.74 to 3.62 L/min (median 2.73 L/min). Moderate and severe regurgitation reduced median electromagnetic flow values by 31% and 51%. Applying generalized estimating equations to model thermodilution cardiac output as a function of electromagnetic flow, arteriovenous shunt, and severity of tricuspid regurgitation revealed that (1) moderate and severe regurgitation changed the slope and intercept of the thermodilution/electromagnetic regression, but the differences between them were not significant, and (2) arteriovenous shunt alone had no effect under any condition. A simplified model independent of shunt and containing just 2 levels of tricuspid regurgitation (none or present) crossed with electromagnetic flow was applied. This analysis showed that regurgitation caused thermodilution to significantly underestimate electromagnetic flow at cardiac outputs > 2.27 L/min (99 mL/kg/min) and overestimate it at flows < 1.02 L/min (44 mL/kg/min). CONCLUSIONS: These data show that acute tricuspid regurgitation may produce underestimation of cardiac output by thermodilution when flow is relatively high, produce overestimation when flow is relatively low, or have minimal effect when flow is in the midrange.

Animals↗
PubMed1987

Measurement of cardiac output and exercise factor by pulsed Doppler echocardiography during supine bicycle ergometry in normal young adolescent boys.

The purposes of this study were to determine the ability of pulsed Doppler echocardiography to consistently and accurately measure cardiac output during exercise, and to measure the exercise factor by Doppler methodology when oxygen consumption was simultaneously measured. Thirty-four healthy young adolescent male volunteers (mean age 13 years) were recruited. Submaximal exercise was performed by supine bicycle ergometry. Cardiac output was calculated as mean velocity X cross-sectional area. Successful rest and exercise determinations of cardiac output were obtained in 81% (n = 52) of the studies. Mean cardiac output increased from 4.6 to 8.9 liters/min (p less than 0.001) during exercise and mean oxygen consumption increased from 212 to 899 ml/min (p less than 0.001). Doppler-estimated rest and exercise cardiac outputs correlated well with simultaneously measured oxygen consumption (r = 0.89, SEE = 1.2 liters/min; y = 0.006 X 3.2 liters/min). Mean exercise factor was 6.4 (1.2 SD). Twenty-six pairs of rest and exercise cardiac output determinations by Doppler technique and indirect Fick method were simultaneously compared in a subset population (r = 0.86, SEE = 1.4 liters/min; slope = 0.93, y intercept = 1.4 liters/min). Results of this study demonstrate that cardiac output and exercise factor can be estimated by pulsed Doppler echocardiography during exercise.

Adolescent↗
PubMed1988

Doppler-derived cardiac output in healthy newborn infants in relation to physiological patency of the ductus arteriosus.

Noninvasive Doppler-derived cardiac output was measured with the pulsed Doppler method in 22 healthy newborns during their first four days of life. Maximal blood flow velocity in the aorta was measured with the Doppler ultrasound method. The mean Doppler-derived cardiac output was 273 +/- 59 ml/min/kg. Ductal left-to-right shunting was also determined and then graded according to the flow in the main pulmonary artery. The mean Doppler-derived cardiac output was 301 +/- 61 ml/min/kg when there was a moderate ductal left-to-right shunt, 266 +/- 59 ml/min/kg when the shunting was mild, and 260 +/- 53 ml/min/kg when there was no shunting ductus. The Doppler-derived cardiac output was significantly higher when there was a moderate left-to-right shunt than without such shunting. This method seems to be a useful approach in monitoring the cardiac function of newborns without unduly disturbing their condition. Normal values on Doppler-derived cardiac output have to be judged in relation to the magnitude of ductal left-to-right shunt.

Cardiac Output↗
PubMed2000

[Non-invasive evaluation of the hemodynamic profile in patients with heart failure: estimation of cardiac output].

In patients with chronic heart failure the estimation of cardiac output represents a valuable tool in assessing both prognosis and therapy. The thermodilution method during right heart catheterization remains the standard method, even if some echo-Doppler methods have been demonstrated to be feasible and accurate in determining cardiac output. Using echo-Doppler it is also possible to determine right atrial pressure (evaluating respiratory changes in the diameter of the inferior vena cava), the right ventricular-atrial pressure gradient (using the continuous wave Doppler of the tricuspid regurgitant jet) and, consequently, systolic pulmonary artery pressure. Diastolic pulmonary artery pressure can be calculated from the continuous wave Doppler of the pulmonary regurgitant jet, so mean pulmonary artery pressure can be calculated. Pulmonary capillary wedge pressure can be calculated by echo-Doppler using a few methods proposed in the literature. All these parameters allow for the calculation of the transpulmonary gradient and (with determination of cardiac output) of pulmonary vascular resistance. The main purpose is the assessment of prognosis after heart transplantation. Due to the fact that chronic heart failure patients need serial evaluations when awaiting for transplantation, echocardiography could became an alternative, safe and feasible procedure in these cases.

Algorithms↗
PubMed1993

Prenatal ultrasonographic diagnosis of intracranial teratoma and massive craniomegaly with associated high-output cardiac failure.

Congenital intracranial teratomas are rare and usually fatal. We present prenatal diagnosis of such a case associated with scalp, facial, and body skin edema, hepatomegaly, extramedullary hematopoiesis, polyhydramnios, and a hydropic placenta. These manifestations of high-output cardiac failure were thought to be the result of the large cardiac output required by massive intracranial tumor arteriovenous shunting.

Adult↗
PubMed1997

Low-intensity exercise training decreases cardiac output and hypertension in spontaneously hypertensive rats.

The decrease in cardiac sympathetic tone and heart rate after low-intensity exercise training may have hemodynamic consequences in spontaneously hypertensive rats (SHR). The effects of exercise training of low and high intensity on resting blood pressure, cardiac output, and total peripheral resistance were studied in sedentary (n = 17), low- (n = 17), and high-intensity exercise-trained (n = 17) SHR. Exercise training was performed on a treadmill for 60 min, 5 times per week for 18 weeks, at 55% or 85% maximum oxygen uptake. Blood pressure was evaluated by a cannula inserted into the carotid artery, and cardiac output was evaluated by a microprobe placed around the ascending aorta. Low-intensity exercise-trained rats had a significantly lower mean blood pressure than sedentary and high-intensity exercise-trained rats (160 +/- 4 vs. 175 +/- 3 and 173 +/- 2 mmHg, respectively). Cardiac index (20 +/- 1 vs. 24 +/- 1 and 24 +/- 1 ml.min-1 x 100 g-1, respectively) and heart rate (332 +/- 6 vs. 372 +/- 14 and 345 +/- 9 beats/min, respectively) were significantly lower in low-intensity exercise-trained rats than in sedentary and high-intensity exercise-trained rats. No significant difference was observed in stroke volume index and total peripheral resistance index in all groups studied. In conclusion, low-intensity, but not high-intensity, exercise training decreases heart rate and cardiac output and, consequently, attenuates hypertension in SHR.

Animals↗
PubMedDate not supplied

Continuous registration of cardiac output with a new computer system designed for hot-film anemometry: an in vitro study.

We have developed and improved a method for the continuous on-line registration of cardiac output. By measuring blood velocity with a hot-film anemometer probe in the pulmonary artery, cardiac output can be estimated by gated systolic integration of the velocity signals. The integrated value for a certain period can be converted to a cardiac output proportional value. A thermistor placed next to the velocity probe enables thermodilution measurement of cardiac output, which serves as in vivo and in situ calibration. In this paper an in vitro study of the method applied to pulsatile flow is presented. A good correlation was found between real flow and both the velocity method and the thermodilution method. Fluid temperature and changing stroke volume and/or pulse frequency had minimal influence on accuracy, whereas altered probe position required recalibration for the velocity method but not for the thermodilution method. The advantages of the velocity method for the measurement of cardiac output are: The continuous on-line monitoring of cardiac output. The need for the injection of only very small volumes of cold saline, as the frequency of thermodilution measurements is reduced.

Cardiac Output↗
PubMed1985

Patient selection for iced versus room temperature injectate for thermodilution cardiac output determinations.

In 42 patients who required hemodynamic monitoring there was no statistically significant difference between mean cardiac output determined with iced vs. room temperature injectate. There was also no statistical difference in mean cardiac output values using iced vs. room temperature injectate when data were grouped according to body temperature, mean arterial pressure, and cardiac output. These results suggest that when cardiac output is measured by the methods described, the use of iced injectate is unnecessary in many critically ill patients.

Blood Pressure↗
PubMed1979

[Adrenalin and cardiac output in pregnancy (author's transl)].

The heart rate performance, cardiac output and catecholamine excretion were observed at rest in the ergometer test (40 min at 50 watts) in a group of 8 pregnant women whose case history and clinical record did not reveal any abnormal findings, during the course of pregnancy (20th, 28th and 36th weeks of pregnancy) as well as 2 and 12 weeks post partum. It was found that the cardiac output increased, dependent upon the heart rate, the stroke volume remaining approximately constant (max. + 60%) during pregnancy, compared with the controls post partum. There is a close linear correlation (r = 0.983) between the measured heart rates and the corresponding excretion of epinephrine (adrenalin) with the urine at rest and under load. It may be assumed that there is a causative link between the increase in secretion of catecholamine by the mother and the well-known change in cardiac output during pregnancy.

Adult↗
PubMed2004

Equivalence of the bioimpedance and thermodilution methods in measuring cardiac output in hospitalized patients with advanced, decompensated chronic heart failure.

BACKGROUND: An accurate and reliable noninvasive method for determining cardiac output/cardiac index would be valuable for patients with acutely decompensated advanced systolic heart failure. OBJECTIVES: To determine whether a correlation exists for cardiac output and index determined by using bioimpedance and thermodilution in patients with acutely decompensated complex heart failure and if differences between results with the 2 methods could be explained by the patients' advanced condition. METHODS: Cardiac output and index were determined by using bioimpedance and thermodilution in 33 patients. Echocardiographic and electrocardiographic data were assessed to determine if differences between results with the 2 methods could be explained by the patients' advanced condition. Concordance correlation coefficients and Bland-Altman agreement between methods were calculated. RESULTS: Four patients were excluded from analysis because reliable measurements could not be obtained; the remaining 29 patients constituted the study population. Mean cardiac outputs determined by thermodilution and bioimpedance were 5.48 and 5.40 L/min, respectively (rhoc = 0.89, P < .001), and mean cardiac indexes were 2.67 and 2.65 (rhoc = 0.82, P < .001). Mean bias (limits of agreement) between data pairs was 0.08 (-0.18 to 0.35) L/min (P = .52) for cardiac output and 0.03 (-0.097 to 0.16; P = .61) for cardiac index. Six data pairs (21%) had an absolute percent difference greater than 15%. Of these, 50% had a higher thermodilution value. CONCLUSION: Determinations of cardiac output and index by both methods were significantly correlated. Mean bias between the 2 methods was small, suggesting clinical utility for bioimpedance in patients with complex decompensated heart failure.

Atrial Fibrillation↗
PubMed1994

Effect of injectate temperature and thermistor position on reproducibility of thermodilution cardiac output determinations.

STUDY OBJECTIVE: The purpose of this study was to evaluate the effect of thermistor position with varying injectate temperatures on the reproducibility of thermodilution cardiac output determination. The key hypothesis to be tested was that the positioning of the proximal thermistor at the right atrial port would improve the reproducibility of thermodilution cardiac output determination, independent of injectate temperature. DESIGN: Prospective randomized trial. SETTING: The study was performed in the cardiac catheterization laboratory of the West Haven Veterans Affairs Medical Center. PARTICIPANTS: Twenty consecutive patients undergoing right and left heart catheterizations were enrolled in the study. INTERVENTIONS: Each patient underwent triplicate determination of thermodilution cardiac output measurements under four experimental conditions: (1) ambient or room temperature injectate using an external thermistor in the injectate reservoir; (2) iced injectate using an external thermistor; (3) room temperature injectate using an internal right atrium (RA) thermistor; and (4) iced injectate using an RA thermistor. Reproducibility was assessed by the coefficient of variation (CV) and standard error of the mean percent (SEM%), of the triplicate measurements. MEASUREMENTS AND RESULTS: Using an internal RA thermistor improved the reproducibility of cardiac output determinations independent of injectate temperature. Using room temperature injectate, the CV was 12.8 percent using an external thermistor and 7.9 percent using an internal RA thermistor (p < 0.05). Using iced injectate, the CV was 10.2 percent using an external thermistor and 5.5 percent using an internal RA thermistor (p < 0.05). CONCLUSIONS: Reproducibility of thermodilution cardiac output determinations is improved when injectate temperature is measured internally, at the RA, as opposed to externally in the reservoir. This has clinical implications for determining significant changes in serial cardiac output determinations.

Analysis of Variance↗
PubMed1983

[Mechanisms of regulation of high cardiac output in patients with hypertension (angiocardiographic study)].

To identify mechanism conditioning high cardiac output, an angiocardiographic study was conducted in 39 patients with essential hypertension. Increased stroke and cardiac output was found to be due to increased venous inflow, with inotropic condition of the hypertrophic myocardium being reduced in spite of enhanced general pumping function of the left ventricle. As arterial hypertension tended to stabilize and cardiac output declined, total peripheral resistance assumed the principal responsibility for its regulation, whereas at earlier stages of the disease it shows either normal, or even reduced levels, and venous inflow is the principal factor controlling cardiac and stroke output.

Adult↗