Automatic Cardiac Output Measurement (ACOM): Clinical applications of a new noninvasive tool

This study sought to validate a new noninvasive method to measure cardiac output, in the clinical setting, using color Doppler flow integration. This method, the automatic cardiac output measurement (ACOM), using color Doppler was recently developed and validated in vitro. ACOM was performed at the aortic valve and in the left ventricular outflow tract in 106 subjects (60 men, mean age 52 ± 18) and compared with the echocardiographic pulsed-wave Doppler and a 2-D volume method. In 14 patients the noninvasive methods were correlated with the thermodilution technique. ACOM was feasible in 101 subjects (95%). The correlation factor between the values obtained with ACOM in the apical 5-chamber view and apical long-axis view was 0.75 at the aortic valve and 0.74 in the left ventricular outflow tract. Interoperator variability for ACOM in the apical 5-chamber and apical long-axis views were 0.93 and 0.75, respectively. The best comparison of ACOM with the pulsed-wave echo-Doppler technique occurred in the apical long-axis view (n = 79, r = 0.62), whereas the correlation with the 2-D volume method was poor. The most favorable comparison of ACOM with the thermodilution technique (n = 14) was also obtained in the apical long-axis view (5.408 ± 1.72 vs. 3.356 ± l.281/min. [mean ± SD], r = 0.71). Assuming the thermodilution technique as ‘gold standard’, the pulsed-wave echo-Doppler technique showed a better correlation (5.408 ± 1.72 vs. 4.664 ± l.281/min., r = 0.84). ACOM is a useful, reproducible, noninvasive tool for rapid automated measurements of cardiac output. There is, however, an underestimation when compared with the pulsed-wave Doppler echocardiography and the thermodilution techniques. Good 2-D echocardiographic images, adequate color filling of the outflow tract and high frame rates are prerequisites for accurate values. Further refinements of this new technique are needed to enhance its clinical value in the future.     

Continuous measurement of cardiac output by the Fick principle: clinical validation in intensive care.

OBJECTIVE: To compare continuous measurement of cardiac output by the Fick principle with the thermodilution cardiac output technique in hemodynamically unstable patients. DESIGN: An open comparison of two methods. SETTING: Multidisciplinary ICU in a university hospital. PATIENTS: Eight patients after coronary bypass surgery and 13 patients with hyperdynamic septic shock. All patients were mechanically ventilated. MEASUREMENTS AND MAIN RESULTS: The continuous Fick cardiac output technique was compared with the thermodilution cardiac output using both warm and cold injection in the coronary artery bypass surgery patients and using warm injection only in the patients with hyperdynamic septic shock. The mean difference between the continuous cardiac output technique and all thermodilution measurements (n = 201) was 0.6 +/- 19%. There was a good correlation between the continuous cardiac output and the warm thermodilution technique (n = 125, r2 = .79; p less than .001). When consecutive measurements with warm and cold thermodilution were compared with the respective Fick-derived values (n = 76), the mean differences between the Fick-derived and the warm and cold thermodilution cardiac output values were 0.2 +/- 1.0 L/min and 0.3 +/- 1.0 L/min, respectively. The relationship between Fick-derived and both methods of thermodilution-derived cardiac output was relatively constant during different modes of ventilatory support. The correlation between the thermodilution measurements with cold and room temperature injectate was weak (r2 = .36; p less than .001), whereas a good correlation was observed between the respective Fick-derived values (r2 = .73; p less than .001). The mean difference between the warm and cold thermodilution cardiac output measurements was 0.1 +/- 1.1 L/min and between the corresponding Fick-derived measurements was 0.01 +/- 0.7 L/min. CONCLUSIONS: Continuous measurement of cardiac output by the Fick principle offers a convenient, reproducible method for hemodynamic monitoring of unstable patients. The variation between the two tested thermodilution techniques is likely to reflect relatively rapid dynamic variation of cardiac output, which is filtered in the 1-min average of cardiac output obtained by the continuous Fick technique.     

Triphasic mitral inflow velocity with middiastolic filling: clinical implications and associated echocardiographic findings.

To explore underlying mechanisms and clinical implications of middiastolic filling, we measured early and late mitral inflow velocities, deceleration time of early mitral inflow velocity, and early diastolic mitral annular velocity (E') recorded by pulsed wave Doppler echocardiography in 3 cardiac cycles of 35 patients with prominent mitral inflow (middiastolic flow velocity > or = 0.2 m/s). E' was measured at the septal corner of the mitral annulus by Doppler tissue echocardiography from the apical 4-chamber view and was found to be reduced (E' < 0.1 m/s) in all patients; early mitral inflow velocity/E' ratio was > 10 in all but 1 patient. Valsalva maneuver unmasked delayed relaxation in 15 (88%) of 17 patients and abolished middiastolic filling in 10 (59%). Triphasic mitral inflow with middiastolic flow is related to elevated filling pressure, delayed myocardial relaxation, and slow heart rate, indicating advanced diastolic dysfunction.     

Noninvasive measurement of cardiac output by continuous-wave Doppler echocardiography: initial experience and review of the literature

Doppler echocardiographic measurement of the velocity of blood flow in the ascending aorta is a noninvasive method for determining cardiac output in the critically ill patient. Fifty-four patients in the medical intensive care unit (35 men and 19 women, age range 41 to 91 years) in whom a Swan-Ganz catheter had been inserted underwent measurement of cardiac output with use of a commercially available continuous-wave Doppler echocardiographic instrument. The aortic root diameter was measured by A-mode echocardiography. An additional 26 patients (17 men and 9 women, age range 20 to 83 years) who had undergone an open-heart surgical procedure and had hemodynamic monitoring in the postoperative period also underwent Doppler measurement of cardiac output. In these patients, the aortic root diameter was measured directly intraoperatively. Cardiac output was also determined by thermodilution in both groups. An adequate A-mode study was possible in 83% of the medical patients but only 27% of the surgical patients. Doppler signals were adequate in 84% of the medical patients and 92% of the surgical patients. The correlation between thermodilution and Doppler-derived cardiac output was good in both the medical (r = 0.94, SEE = 0.78, P less than 0.001) and the surgical (r = 0.85, SEE = 0.78, P less than 0.001) group. Doppler echocardiography is a promising noninvasive method for determining cardiac output in critically ill patients.     

Transgastric,pulsed doppler echocardiographic determination of cardiac output

Objective The aim of this study was to evaluate the accuracy of cardiac output measurement with transesophageal echocardiography (TEE) using a transgastric, pulsed Doppler method in acutely ill patients.Design Cardiac output was simultaneously measured by thermodilution (TD) and a transgastric, pulsed Doppler method.Setting The study was carried out in a surgical intensive care unit as part of the management protocol of the patients.Patients Thirty consecutive acutely ill patients with a Swan-Ganz catheter, mechanically ventilated, sedated and with a stable hemodynamic condition were included.Measurements Pulsed Doppler TEE was performed using a transgastric approach in order to obtain a long axis view of the left ventricle. Cardiac output was calculated from the left ventricular outflow tract diameter, the velocity time integral of the blood flow profile and heart rate.Results One patient was excluded because of the presence of aortic regurgitation and another, because of the impossibility of obtaining a transgastric view. Twenty-eight simultaneous measurements were performed in 28 patients. A clinically acceptable correlation and agreement were found between the two methods (Doppler cardiac output=0.889 thermodilution cardiac output +0.74l/min,r=0.975,p<0.0001).Conclusion Transgastric pulsed Doppler measurement across the left ventricular outflow tract with TEE is a very feasible and clinically acceptable method for cardiac output measurement in acutely ill patients.     

An alternative thermodilution method to measure cardiac output in a rat model of stagnant hypoxia

Rats are often used to study hemodynamics in animal research. We have established an alternative method to measure cardiac output in a conscious rat using a thermodilution technique via a left ventricular injection. The validity of this method was evaluated in conscious rats and compared with the results obtained using the radiolabeled microspheres (reference sample method). Using 20 male Sprague-Dawley rats, a baseline cardiac index was measured by thermodilution to determine the baseline cardiac index and to evaluate between animal variability. The baseline cardiac index was compared to the reference sample method with 6 rats. Following baseline measurements, an intra-atrial balloon was inflated in a stepwise manner to create 2 to 3 different cardiac outputs, and the cardiac index was computed. For each measurement, the cardiac index was first measured by thermodilution and immediately followed by the reference sample method. A total of 21 measurements were obtained, and the results were analyzed by a Bland-Altman plot and the correlation coefficient was calculated. Although the agreement between the two methods was poor, both methods had a good correlation (r2 = 0.59). With the thermodilution technique, we demonstrated a small coefficient of variation in each measurement, with a low intra-animal and inter-animal variability. As there is no gold standard method to measure cardiac output in rats, we believe that left ventricular thermodilution is a reliable method, and overcomes several technical difficulties such as heat loss, one of the significant limitations of the conventional thermodilution method (via right atrial injection). This new thermodilution technique (via the left ventricle) is therefore an attractive alternative method to measure cardiac output in rats.     

二维及三维彩色我普勒超声心动图在心搏出量计算方面的实验性研究

目的比较二维超声及三维彩色多普勒超声在心搏出量计算方面的准确性。方法运用M超Teichholtz公式法、双平面Simpson公式法、主动脉血流频谱积分与瓣口面积相乘法以及彩色三维多普勒超声计算10只犬在静息状态及结扎左冠状动脉前降支后通过主动脉瓣口的流量变化,并与热稀释法测定的数值比较。结果冠脉结扎前后彩色三维超声计算的犬每搏量与生理仪热稀释法测得相应的数值相关显著,其中静息状态下r＝0.85,结扎冠脉后r＝0.92,t检验无显著性差异;二维超声计算的心搏出量在基态时与生理仪热稀释法测值相关较好,Teichholtz公式法、Simpson法、Doppler频谱法与热稀释法测值的相关系数分别为0.96、0.85、0.95;t检验示Teichholtz公式法及Simpson法的测值与热稀释法测值无显著性差异,Doppler频谱法的测值与热稀释法测值相差显著(P＜0.01)。冠脉结扎后Teichholtz公式法的测值与热稀释法数值无显著相关,r＝0.68;Simpson法及Doppler频谱法测值的相关系数分别为0.86和0.91;t检验示Simpson法测值与热稀释法测值无显著性差异,其余两组数值与热稀释法相差显著(P＜0.01)。结论彩色三维多普勒超声在理论上不存在几何学方面的假设,可不受节段性室壁异常运动的影响,准确地计算心搏出量的变化。     

应用多普勒组织成像评价单纯性风湿性二尖瓣狭窄患者的左室长轴收缩功能

目的探讨应用多普勒组织成像(DTI)评价单纯性风湿性二尖瓣狭窄患者左室长轴收缩功能的意义。方法23例单纯性风湿性二尖瓣狭窄患者与26例健康志愿者行常规超声心动图及DTI检查。DTI测定二尖瓣环的室间隔、侧壁、下壁、前壁、前间隔、后壁处各位点的收缩期峰值运动速度(Vs)。结果两组间左室射血分数(LVEF)差异无显著性意义。与对照组相比,患者组各节段Vs及平均Vs(AVs)显著降低。患者组AVs与LVEF呈高度正相关,与二尖瓣口面积无显著相关。患者组侧壁、前壁、后壁Vs与AVs的相关性较好。结论患者组虽然左室整体收缩功能正常,但其左室长轴收缩功能显著受损,其受损与风湿性二尖瓣狭窄的程度无关。AVs可定量评价患者左室长轴收缩功能,二尖瓣环侧壁、前壁、后壁均是定量评价左室长轴收缩功能的较好节段。     

Mitral annulus velocity in the evaluation of left ventricular diastolic function in atrial fibrillation.

This study assessed the clinical utility of mitral annulus velocity in the evaluation of left ventricular diastolic function in patients with atrial fibrillation. Atrial fibrillation is the most common sustained arrhythmia encountered in clinical practice. The clinical usefulness of conventional Doppler indexes is limited in atrial fibrillation because of the altered left atrial pressure and loss of synchronized atrial contraction. Mitral inflow and mitral annulus velocities were measured simultaneously with tau in 27 patients with nonrheumatic atrial fibrillation at the cardiac catheterization laboratory. Among deceleration time of mitral inflow, peak mitral inflow velocity (E), and peak diastolic mitral annulus velocity (E), only E correlated with tau (r = 0.51, P =.007). Prolonged tau (>/=50 ms) could be predicted by E <8 cm/s with a sensitivity of 73% (16 of 22) and a specificity of 100% (5 of 5). The E/E ratio correlated with left ventricular filling pressure (r = 0.79, P <.001). The E/E ratio of >/=11 could predict elevated left ventricular filling pressure (>/=15 mm Hg) with a sensitivity of 75% (9 of 12) and a specificity of 93% (14 of 15). Mitral annulus velocity is useful in the detection of impaired left ventricular relaxation and estimation of filling pressure even in patients with atrial fibrillation.     

Abnormal septal motion affects early diastolic velocities at the septal and lateral mitral annulus, and impacts on estimation of the pulmonary capillary wedge pressure.

Abnormal motion of the interventricular septum (ASM), seen post cardiac operation, with left bundle branch block or right ventricular pacing, may affect septal mitral annular motion and correlation of the ratio between the velocity of early diastolic mitral inflow and the early diastolic mitral annular velocity (E/Ea) with pulmonary capillary wedge pressure (PCWP). We examined the effect of ASM on the relationship between E/Ea and E/Vp (propagation velocity of mitral inflow) ratios and PCWP in adult patients in the intensive care unit (14 with normal septal motion [NSM], 36 with ASM) undergoing echocardiography and pulmonary artery catheterization. E/Ea correlated well with PCWP during NSM ( r = 0.86 lateral annulus, r = 0.75 septal annulus), but poorly during ASM ( r = 0.36 lateral annulus, r = 0.39 septal annulus). E/Vp correlated poorly with PCWP ( r = 0.05 NSM, r = 0.17 ASM). For patients who are critically ill, E/Vp ratios poorly estimate PCWP. During NSM, E/Ea ratios measured at the lateral or septal annulus correlate well with PCWP. ASM affects E/Ea ratios at both the septal and lateral annulus, making E/Ea ratios unreliable for estimating PCWP in this group.     

Relationship of bioimpedance to thermodilution and echocardiographic measurements of cardiac function

Bioimpedance cardiography has been suggested as a noninvasive means to monitor cardiac function. However, this method has not been compared to more conventional techniques such as echocardiography. This study compared simultaneously obtained thermodilution cardiac output and right ventricular ejection fraction (RVEF), and echocardiographic left ventricular fractional shortening (LVFS), to bioimpedance cardiac output and the maximum first derivative of the bioimpedance signal (dZ/dtmax) during positive inotropic stimulation and preload reduction. Eight pigs were instrumented with a rapid response thermistor (positioned in the pulmonary artery) and bioimpedance electrodes. Simultaneous thermodilution, echocardiographic, and bioimpedance measurements were performed at baseline and after 5, 10, and 15 min of isoproterenol infusion (0.5 microgram/kg.min). In six pigs, measurements were also performed after balloon occlusion of the inferior vena cava. A significant correlation was observed between LVFS and dZ/dtmax (r = .88, n = 35) over all time points. Thermodilution and bioimpedance cardiac output were in close agreement (r = .92, n = 35). However, bioimpedance overestimated cardiac output in the very low and high output states. The mean difference between thermodilution and bioimpedance cardiac outputs was -0.02 +/- 0.37 L/min. There was a positive relationship between RVEF and dZ/dtmax (r = .54, n = 35). In summary, bioimpedance was significantly correlated with thermodilution cardiac output over a wide hemodynamic range. The peak first derivative of the bioimpedance signal dZ/dtmax may provide a noninvasive index of ventricular pump performance. Further studies are required to evaluate the diagnostic value of bioimpedance cardiography in the clinical setting.     

Comparison of pulsed Doppler and thermodilution methods for measuring cardiac output in critically ill patients

We obtained 145 consecutive cardiac output measurements in 38 critically ill patients, using the invasive thermodilution and the noninvasive pulsed Doppler methods. The mean thermodilution cardiac output (TDCO) was 5.7 +/- 1.87 L/min and the mean pulsed Doppler cardiac output (PDCO) was 5.16 +/- 1.66 L/min. The mean difference between the two measurements was 0.51 L/min with an SD greater than 1.6 L/min, reflecting the scattering of results. The overall correlation coefficient was .58. The intercepts were large and the regression equation some way from the line of equal values (TDCO = 2.28 + 0.66 PDCO). When the results were analyzed according to diagnosis or by group experience, there were some differences in the bias of the estimate; however, the SD of the difference between methods was greater than one liter/min in all groups. Thus, the pulsed Doppler method failed to estimate accurately TDCO in critically ill patients.     

Assessment of left ventricular function using mitral annular velocities in patients with congestive heart failure with or without the presence of significant mitral regurgitation.

Myocardial velocities in patients with congestive heart failure (CHF) were studied using pulsed wave Doppler tissue imaging. Velocities were recorded at the mitral and tricuspid annulus. Four sites at the mitral annuli were selected corresponding to the septal, lateral, inferior, and anterior walls of the left ventricle from apical 4- and 2-chamber views. A mean value from the above 4 sites was selected to describe the mitral annular velocities. Only one site of the tricuspid annulus was selected, corresponding to the right ventricular free wall. Three different annular velocities were recorded: the peak systolic, and the peak early and late diastolic velocities. A total of 96 patients were compared with 12 age-matched healthy participants. Patients with CHF had significantly decreased mitral and tricuspid systolic velocities compared with healthy participants (4.9 vs 9.3 cm/s, P <.001, for the mitral annulus and 10.4 vs 14.6 cm/s, P <.001, for the tricuspid annulus). The early diastolic velocity was also reduced in patients compared with healthy participants (5.9 vs 10.9 cm/s, P <.001, for the mitral annulus and 8.6 vs 12.9 cm/s, P <.001, for the tricuspid annulus). Patients with CHF had a severely depressed left ventricular ejection fraction (EF) (27%). The correlation the between systolic mitral annular velocity and EF was relatively good (r = 0.59 and P <.001). The patients with CHF were divided into 2 subgroups depending on the presence or absence of significant mitral regurgitation. There was a correlation between EF and the systolic mitral annular velocity both in patients with (r = 0.61, P <.001) and without (r = 0.59, P <.001) significant mitral regurgitation. In conclusion, compared with healthy participants, the mitral and tricuspid annular velocities are significantly decreased in patients with CHF. The correlation between EF and the systolic mitral annular velocity is relatively good irrespective of the presence or absence of significant mitral regurgitation. Measurements of annular velocities constitute a simple and useful method for evaluating patients with CHF.     

Determination of cardiac output during positive end-expiratory pressure--noninvasive electrical bioimpedance compared with standard thermodilution

Many investigators have demonstrated the accuracy and reliability of thoracic electrical bioimpedance (TEB) in spontaneously breathing patients and under mechanical intermittent positive-pressure ventilation. Most of these studies showed a good correlation between TEB and invasive methods, such as thermodilution (TD) or the Fick method. But during PEEP, contrary results occur when comparing TEB and TD. In six patients undergoing neurosurgical interventions, TEB cardiac output measurements were compared during zero end-expiratory pressure (ZEEP) and during PEEP at 8 cm H2O with a low respiratory rate. The data revealed a good correlation during ZEEP (r = .93) and during PEEP (r = .91). There was no significant statistical difference when measuring cardiac output by TEB during ventilation with PEEP. During normal or decreased cardiac output, TEB overestimated cardiac output compared with TD, whereas TEB underestimated cardiac output compared with TD during increased cardiac output, especially during PEEP.     

Comparison between ultrasonic and thermodilution cardiac output measurements in intensive care patients

The reliability of ultrasonic cardiac output measurement was assessed using a commercial device that combines A-mode aortic root diameter determination and continuous wave (CW) Doppler flow velocity measurement in the ascending aorta. We compared this method with thermodilution (TD) cardiac output in 41 intensive care patients. Aortic root diameter measurement with A-mode was not possible in four (10%) patients. Using strictly defined criteria based upon our initial experience, we could not obtain acceptable CW Doppler flow signals in nine (22%) patients. Thus, ultrasonic cardiac output measurement was possible in 28 (68%) patients in whom there was an excellent correlation with cardiac output (r = 0.97; p less than .001). This study demonstrates that the transcutaneous CW Doppler method for measuring cardiac output is accurate and reliable in a limited percentage of ICU patients. Combining the CW Doppler with B-mode echocardiogram increases the applicability when an A-mode measurement is not possible.     

Effects of first myocardial infarction on left ventricular systolic and diastolic function with the use of mitral annular velocity determined by pulsed wave doppler tissue imaging.

This study was undertaken to assess the effect of a first myocardial infarction (MI) on the systolic and diastolic velocity profiles of the mitral annulus determined by pulsed wave Doppler tissue imaging and thereby evaluate left ventricular (LV) function after MI. Seventy-eight patients with a first MI were examined before discharge. Peak systolic, peak early diastolic, and peak late diastolic velocities were recorded at 4 different sites on the mitral annulus corresponding to the septum, anterior, lateral, and inferior sites of the left ventricle. In addition, the amplitude of mitral annular motion at the 4 above LV sites, the ejection fraction, and conventional Doppler diastolic parameters were recorded. Nineteen age-matched healthy subjects served as controls. Compared with healthy subjects, the MI patients had a significantly reduced peak systolic velocity at the mitral annulus, especially at the infarction sites. A relatively good linear correlation was found between the ejection fraction and the mean systolic velocity from the 4 LV sites (r = 0.74, P <.001). The correlation was also good when the mean peak systolic mitral annular velocity was tested against the magnitude of the mean mitral annular motion (r = 0.77, P <.001). When the patients were divided into 2 different groups with respect to an ejection fraction > or =0.50 or <0.50, a cutoff point of mean systolic mitral annular velocity of > or =7.5 cm/s had a sensitivity of 79% and a specificity of 88% in predicting a preserved global LV systolic function. Similar to systolic velocities, the early diastolic velocity was also reduced, especially at the infarction sites. The peak mitral annular early diastolic velocity correlated well with both LV ejection fraction (r =.66, P <.001) and mean systolic mitral annular motion (r = 0.68, P <.001). However, no correlation existed between the early diastolic velocity and conventional diastolic Doppler parameters. The reduced peak systolic mitral annular velocity seems to be an expression of regionally reduced systolic function. The peak early diastolic velocity is also reduced, especially at the infarction sites, and reflects regional diastolic dysfunction. Thus, quantification of myocardial velocity by Doppler tissue imaging opens up a new possibility of assessing LV function along its long axis.     

A comparison of left atrial size by two-dimensional transthoracic echocardiography and magnetic endocardial catheter mapping

This study sought to validate the accuracy of magnetic electroanatomic mapping (MEAM) for determining cardiac chamber size in a clinically relevant situation. The authors chose to compare LA size measured by MEAM to that assessed by two-dimensional guided M-mode echocardiography. The study included 37 patients with drug refractory paroxysmal atrial fibrillation who underwent two-dimensional echocardiography and a detailed MEAM of the LA. The entire LA was mapped with a mean of 132 +/- 50 points with attention to identifying the mitral annulus and posterior wall of the LA. The MEAM measurement of LA size was taken as the distance from the anterior wall of the LA to the posterior wall in a plane parallel to the mitral valve annulus at atrial end-diastole. LA dimension determined by M-mode echocardiography was assessed in a plane parallel to the mitral valve annulus in the parasternal long-axis view during atrial end-diastole. LA size assessed by M-mode echocardiography was 41.2 +/- 5.0 versus 40.9 +/- 4.5 mm as assessed by MEAM, with good correlation (r = 0.87, P < 0.001). Only three patients had a difference in LA size that was > 0.3 cm between the two measurement techniques. Thus, it appears that LA anteroposterior dimension as determined by electroanatomic mapping is similar to that determined by two-dimensional guided M-mode echocardiography. MEAM appears to be an accurate method by which LA size can be assessed in patients with drug refractory atrial fibrillation undergoing left atrial ablation procedures.     

Lack of agreement between bioimpedance and continuous thermodilution measurement of cardiac output in intensive care unit patients

BACKGROUND: Bolus thermodilution is the standard bedside method of cardiac output measurement in the intensive care unit (ICU). The Baxter Vigilance monitor uses a modified thermodilution pulmonary artery catheter with a thermal filament to give a continuous read-out of cardiac output. This has been shown to correlate very well with both the 'gold standard' dye dilution method and the bolus thermodilution method. Bioimpedance cardiography using the Bomed NCCOM 3 offers a noninvasive means of continuous cardiac output measurement and has been shown to correlate with the bolus thermodilution method. We investigated the agreement between the continuous bioimpedance and continuous thermodilution methods, enabling acquisition of a large number of simultaneous measurements. RESULTS: A total of 2390 paired data points from seven patients were collected. There was no correlation (r2 = 0.01) between the methods. The precision (1.16 l/min/m2) of agreement between the Vigilance and the Bomed, assessed by the Bland-Altam method, was very poor although the bias (-0.16 l/min/m2) appeared fair. CONCLUSIONS: The Bomed NCCOM 3 bioimpedance monitor shows poor agreement with the Baxter Vigilance continuous thermodilution monitor in a group of general ICU patients and cannot be recommended for cardiac output monitoring in this situation.     

Age-related changes in diastolic atrioventricular annular velocity: Studies using pulsed Doppler tissue imaging

Age-related changes in the diastolic velocity of the mitral and tricuspid annuli were studied in 67 healthy subjects aged 15 to 79 years. Ventricular inflow velocities were recorded by pulsed Doppler echocardiography with sample volumes at the mitral and tricuspid orifices in the apical four-chamber view, and peak early (E) and late (A) diastolic velocities were measured. Atrioventricular annular velocities were recorded by Doppler tissue imaging with sample volume set on the lateral portion of each annulus in the same view, and peak early (Ea) and late (Aa) diastolic velocities were determined. E and Ea correlated inversely with age, while A and Aa correlated directly with age in both ventricles. E/A and Ea/Aa ratios correlated inversely with age in both ventricles. Coefficients of correlation of these variables with age were higher for annular velocity than for inflow velocity. The E/A ratio at the tricuspid orifice was higher than that at the mitral orifice in all decades. An E/A ratio of less than 1 was observed at the mitral orifice in the sixth decade, but at the tricuspid orifice in the seventh decade. The Ea/Aa ratio at the tricuspid annulus was lower than that at the mitral annulus in all decades. The Ea/Aa ratio was less than 1 at the mitral annulus in the fifth decade and at the tricuspid annulus in the fourth decade. Diastolic function of both ventricles thus deteriorates with age, and diastolic annular velocity reflects ventricular diastolic function more accurately than ventricular inflow velocity.     

Clinical evaluation of a diameter sensing Doppler cardiac output meter

A concentric beam Doppler ultrasonic flowmeter has been developed. This instrument has capacity for independent assessment of volumetric flow, as it determines flow cross-section area, stroke length, and pulse rate from the Doppler signals alone. The method is practically independent of the angle of interrogation. We used this device and obtained noninvasive estimates of cardiac output in 54 patients undergoing invasive assessment of cardiac output by thermodilution, Fick, or indicator dye methods (x). Correlations against pooled cardiac output reference standards ranged from r = .86 (y = .86x + 1.03) in 26 studies of high confidence to r = .45 (y = .30x + 2.62) in 17 studies under difficult conditions. The overall correlation was r = .68 (y = .63x + 1.49, n = 87). Noninvasive results of experienced and inexperienced operators were similar (r = .87). The instrument returned accurate assessments of heart rate (r = .83), but underestimated stroke length (r = .72) and appeared to be limited in the assessment of aortic diameters less than 28 or greater than 31 mm (r = .23). We conclude that stand-alone Doppler assessment of cardiac output is appealing and feasible, but difficult or impossible in many ICU scenarios. Further evolution of the concentric beam Doppler approach is needed and anticipated.