Measurement of cardiac output by transoesophageal echocardiography: a comparison of two Doppler methods with thermodilution

This study assessed the agreement between three methods of cardiac output (CO) measurement, thermodilution, the current clinical standard, and two transoesophageal echocardiographic techniques. Measurements were performed in 37 patients using thermodilution, continuous wave Doppler across the aortic valve and pulsed wave Doppler positioned in the left ventricular outflow tract. The aortic valve area was measured by direct planimetry, and the left ventricular outflow tract area was calculated from its diameter. Weighted least products regression analysis was employed to detect bias, and standard deviation of the difference (SDdiff) was calculated. There was no fixed bias but there was proportional bias between continuous wave Doppler and thermodilution methods (SDdiff 0.92 l/min). There was fixed bias but not proportional bias between pulsed wave and thermodilution methods (SDdiff 1.1 l/min). There was neither fixed nor proportional bias between pulsed wave and continuous wave Doppler methods (SDdiff 1.1 l/min). The transoesophageal Doppler methods described can be clinical alternatives to thermodilution cardiac output measurement.     

Automated cardiac output measurement by transesophageal color Doppler echocardiography

Automated cardiac output measurement (ACOM), which integrates digital color Doppler velocities in space and in time, has been validated using transthoracic echocardiography but has not been tested using transesophageal echocardiography (TEE). Therefore, we determined the feasibility of the ACOM method by TEE in 36 patients undergoing cardiovascular surgery. Regions of interest for ACOM were placed within a color sector across the main pulmonary artery (PA), the mitral annulus, and the left ventricular outflow tract. Cardiac output was determined from the PA flow, the mitral flow, and the left ventricular ejection flow at each view using the ACOM method. We compared measurements of cardiac output derived from the ACOM method with measurements simultaneously obtained by thermodilution (TD). In the mitral flow analysis, the values derived from ACOM correlated well with those from TD (R(2) = 0.85; mean difference = 0.01 +/- 0.58 L/min in the 2-chamber view; R(2) = 0.78; mean difference = -0.10 +/- 0.68 L/min in the 4-chamber view). In the PA flow analysis, the values derived from ACOM did not correlate with those from TD (R(2) = 0.30). In the left ventricular outflow tract analysis, it was very difficult to obtain the optimal view (44%) in which color Doppler flow signals adequately appeared. Using the ACOM method, we obtained good correlation and agreement for cardiac output measurements in the mitral flow analysis compared with TD. The ACOM method is a practical and rapid method to measure cardiac output by TEE analysis of mitral flow. IMPLICATIONS: Automated cardiac output measurement by transesophageal color Doppler echocardiography is a practical and rapid method to measure cardiac output. This technique is a promising new approach to echocardiographic quantification in the intraoperative setting.     

Comparison of thermodilution bolus cardiac output and Doppler cardiac output in the early post-cardiopulmonary bypass period

OBJECTIVE: To evaluate the accuracy of measuring cardiac output (CO) in the early post-cardiopulmonary bypass (CPB) period by comparing thermodilution with Doppler methods. DESIGN: Prospective and blinded human trial. SETTING: Academic medical center. PARTICIPANTS: Thirty adult patients undergoing elective coronary artery bypass graft surgery. MEASUREMENTS AND MAIN RESULTS: Thermodilution CO (TCO) was obtained in triplicate. Doppler CO (DCO) in triplicate was obtained at the left ventricular outflow tract (LVOT), aortic valve (AV), and right ventricular outflow tract (RVOT). CO measurements were made (1). before CPB (baseline), (2). immediately after CPB, (3).15 minutes after CPB, and (4). 30 minutes after CPB. Before CPB, the DCO at LVOT, RVOT, and AV showed good correlations (r = 0.87, r = 0.88, and r = 0.84, respectively) with TCO. Bias analysis showed no significant difference among TCO and 3 DCOs (p > 0.05 each). Correlation between DCO and TCO decreased but remained significant after CPB (r between 0.57 and 0.85, p < 0.001). The bias among TCO and each of the DCOs at the LVOT, RVOT, and AV increased immediately after CPB (p < 0.01, p < 0.01, and p < 0.05, respectively) and remained significant at 15 minutes and 30 minutes post-CPB except for DCO at the AV. TCO exceeded DCO by 0.44 to 0.72 L/min immediately after CPB. The CO measured by both thermodilution and Doppler methods gradually decreased over time post-CPB. The decrease in CO was significant at 30 minutes post-CPB (p < 0.01). CONCLUSION: This study adds further support that DCO is a clinically acceptable method to accurately assess the CO in patients even during periods of uneven regional body temperatures as may occur in the early post-CPB period.     

Transesophageal echocardiographic evaluation of native aortic valve area: utility of the double-envelope technique.

OBJECTIVE: To assess the accuracy of aortic valve area (AVA) calculations using the continuity equation with data obtained from the double envelope (DE) (simultaneously obtained left ventricular outflow tract [V1]) and aortic valve [V2] velocities) during intraoperative transesophageal echocardiography (TEE). DESIGN: Prospective study; measurements were performed on-line. SETTING: University hospital. PARTICIPANTS: Cardiac and noncardiac surgical patients (n = 75) with recent aortic valve assessment (<3 months) undergoing general anesthesia or endotracheal intubation. INTERVENTIONS: Intraoperative AVA was measured by the continuity equation using the DE technique (DE/TEE) and by planimetry (PL/TEE). Left ventricular outflow tract diameter was obtained from midesophageal views, whereas subvalvular (V1) and valvular (V2) velocities were obtained simultaneously using continuous-wave Doppler from transgastric views. V1 was also obtained using pulsed-wave Doppler. Measurements were compared with AVA obtained preoperatively by the Gorlin equation during cardiac catheterization (G/CATH) or by transthoracic echocardiography using the traditional continuity equation (C/TTE) (nonsimultaneously obtained V1 and V2). MEASUREMENTS AND MAIN RESULTS: A DE was obtained in 73 of 75 patients (97%). Four patients had atrial fibrillation at the time of the examination, whereas the rest were in sinus rhythm. PL/TEE was performed in 54 of 71 patients with sinus rhythm (76%). Agreement was good between DE/TEE and G/CATH (mean bias, 0.02 cm(2) [SD, 0.24 cm(2)]), and C/TTE (mean bias, -0.05 cm(2) [SD, 0.16 cm(2)]). Agreement was not as good between PL/TEE and G/CATH (mean bias, -0.07 cm(2) [SD, 0.28 cm(2)]) and C/TTE (mean bias, -0.13 cm(2) [SD, 0.30 cm(2)]). V1 obtained by pulsed-wave Doppler and with DE closely agreed (mean bias, 0.01 m/sec [SD, 0.05 m/sec]). CONCLUSION: TEE evaluation of native AVA using the DE technique is feasible and in good agreement with that obtained by C/TTE and G/CATH. Compared with DE/TEE, PL/TEE did not agree as well. Use of DE/TEE should simplify the continuity equation and may minimize errors resulting from beat-to-beat variability in stroke volume.     

Low-dose dobutamine stress and left ventricular wall motion monitored with transesophageal echocardiography versus hemodynamic data derived from pulmonary artery catheterization in patients scheduled for CABG

BACKGROUND: The clinical acceptance of transesophageal echocardiography (TEE) as a monitoring technique for left ventricular function in open-heart surgery is now widely recognized. This technique's accurate imaging capabilities have been found to improve the information obtained by the pulmonary catheter (PAC) and thermodilution. TEE is also a less invasive technique than PAC. However, because it is costly, further comparisons between the techniques are worthwhile. This study compares hemodynamic data obtained with PAC and how these correspond to echocardiography data using TEE. METHODS: Twenty-four anesthetized patients undergoing elective coronary artery bypass grafting (CABG) were studied. They were monitored with PAC and TEE. A low-dose dobutamine protocol for viability was used with doses of 5 and 10 microg x kg(-1) x min(-1). Endpoints for this stimulation included on-line visual change in left ventricle wall motion (LVWM), increased arterial blood pressure more than 40 mmHg, a heart rate (HR) increase of more than 20%, or ST depression on ECG exceeding 0.2 mV. Visual assessment of LVWM using the transgastric short-axis view was made off line by a blinded observer. Six segments were used and a wall motion score was made at each level of dobutamine stimulation. RESULTS & CONCLUSION: Two patients reached the endpoint for elevated blood pressure with a dobutamine dose of 5 microg x kg(-1) x min(-1), and twenty-two patients were stimulated to 10 microg x kg(-1) x min(-1). There were significant increases in cardiac output (CO), stroke volume (SV), systolic arterial pressure (SAP), mean arterial pressure (MAP), diastolic arterial pressure (DAP), pulmonary capillary wedge pressure (PCWP) and left ventricle stroke work index (LVSWI), but not in HR and systemic vascular resistance (SVR). Moreover, the LVWM increased significantly, but not fractional area change (FAC). The main finding, however, was the increase in SV with an accompanying improvement in LVWM, suggesting that visual assessment of improved wall motion could substitute PAC and thermodilution monitoring in clinical settings which demand a quick estimate of left ventricular performance.     

Aortic valve area: measurement by transesophageal echocardiography and prediction by left ventricular outflow tract area.

We compared three techniques of aortic valve area (AVA) measurement using transesophageal echocardiography (TEE) and determined if AVA can be predicted from simple patient or echocardiographic measurements. AVA was simultaneously measured with direct planimetry, the continuity equation and with a novel technique combining stroke volume using thermodilution and continuous wave Doppler. Using planimetry as the reference in patients with normal valves, left ventricular outflow tract area (LVOTA), lean body mass (LBM), body surface area (BSA) and height were assessed as predictors of AVA. All three methods of AVA measurement showed close agreement and can be used interchangeably. Both LVOTA and LBM were predictors of AVA, but LVOTA was better. BSA and height were not acceptable as predictors of AVA. TEE can be used to measure AVA either with planimetry, the continuity equation, or in combination with thermodilution. LVOTA was the best predictor of AVA.     

Aortic regurgitation causd by the proximal dissecting flap invagintion to the left ventricle

A 68-year-old male with sudden back pain and cardiogenic shock status transferred to our ward. Transthoracic echocardiography revealed that the abnormal rond shape string was in the left ventricular outflow tract. The continuity from the string to the aortic valve was unclear. Intimal flap could not be detected at the level of the ascending aorta. Color Doppler flow imaging showed that the severe AR jet extended into the round string. TEE showed that the intimal tear and flap was seen just above the left subclavian artery. Preoperative diagnosis was acute Stanford type A dissection and acute severe AR due to the inversion of the proximal intimal flap to the left ventricular outflow tract through the aortic valve. At operation, the proximal intimal flap was dissected circumferentially and was cut all the way around 8 cm above the aortic valve ring and was inverted to the left ventricular outflow tract. The aortic valve was preserved because of its normal character after exclusion of the proximal intimal flap. Ascending and arch replacement was carried out. Postoperative TEE and TTE showed no findings of AR. The patient’s postoperative course was uneventful. To our knowledge, this is the first reported case that severe AR caused by the proximal intimal invagination to the left ventricle.     

术中食管超声测定心排血量的临床应用

目的 观察术中使用食管超声（TEE）进行心排血量测定的可行性及准确性。方法 14例心脏手术病人全身麻醉后，经食管置入TEE探头至胃底，取左心室横断图形，测定左心室收缩末期及左室舒张末期的内径，由计算机自动计算出心脏每搏血量。同期经Swan-Ganz导管温度稀释法测定排血量（CO），并将两者进行比较。结果 术中使用TEE进行心脏排血量的无创测定操作简单，与Swan-Ganz导管温度稀释法测定值相关性好（r=0.92）。结论 术中TEE监测具有不影响手术、无创和可连续测定等优点，适合于心血管手术的术中监护。     

Descending aortic pulsed wave Doppler can predict changes in cardiac output during off-pump coronary artery bypass surgery.

Retraction and stabilization of the heart can induce rapid and large changes in the hemodynamic state during off-pump coronary artery bypass graft surgery (OPCABG). We aimed to determine if Doppler measurement of flow in the descending artery with transesophageal echocardiography (TEE) can provide a beat-to-beat assessment of changes in cardiac output (CO) in 26 OPCABG patients. Simultaneous measurements were performed of CO using thermodilution, and descending aortic flow (FlowDA) with TEE, prior to grafting, and during grafting to the left anterior descending artery (LAD), circumflex (Cx) and right coronary artery (RCA) territories. CO decreased from baseline (SD) values of 6.2 (1.7), to 5.4 (1.8) L/min during grafting to the LAD, 4.4 (1.5) L/min to the Cx territory, and 4.4 (1.4) L/min to the RCA territory (P<0.001). There was poor correlation between CO and FlowDA between individuals. In a subgroup of 16 patients who had grafts to all territories, the changes in Flow(DA), occurred in the same direction and magnitude as changes in CO (P = 0.062, RM-ANOVA for factor*time interaction). Doppler assessment of flow in the descending aorta is able to track changes in CO during OPCABG. (Ann Thorac Cardiovasc Surg 2003; 9: 314-8)     

Transesophageal Echocardiographic Hemodynamic Monitoring during Preoperative Acute Normovolemic Hemodilution

Background: Preoperative acute normovolemic hemodilution may compromise oxygen transport. The aims of our study were to describe the hemodynamic effects of normovolemic hemodilution and to determine its effect on systolic and diastolic cardiac function by multiplane transesophageal echocardiography.

Methods: In eight anesthetized patients (aged 13-51 yr) without heart disease, hemoglobin was reduced in steps from 123 +/- 8 (mean +/- SD) to 98 +/- 3 and to 79 +/- 5 g/l. Hemodynamic measurements (intravascular pressures, thermodilution cardiac output, and echocardiographic recordings) were obtained during a stabilization period and at each level of hemodilution. Left ventricular wall motion was monitored continuously, and Doppler variables, annular motion, and changes in ejection fractional area were analyzed off-line.

Results: During hemodilution, cardiac output by thermodilution increased by 16 +/- 7% and 26 +/- 10%, corresponding well to the increase in cardiac output as measured by Doppler (difference, 0.32 +/- 1.2 l/min). Systemic vascular resistance fell 16 +/- 14% and 23 +/- 9% and pulmonary capillary wedge pressure increased slightly (2 +/- 2 mmHg), whereas other pressures, heart rate, wall motion, and diastolic Doppler variables remained unchanged. Ejection fractional area change increased from 44 +/- 7% to 54 +/- 10% and 60 +/- 9% as a result of reduced end-systolic and increased end-diastolic left ventricular areas.     

Dynamic left ventricular outflow tract obstruction complicating bilateral lung transplantation

Dynamic left ventricular outflow tract obstruction (DLVOTO) has been observed in a variety of clinical circumstances but not previously reported in the setting of orthotopic lung transplantation. Diagnosis and effective management of this adverse event were facilitated by transesophageal echocardiography (TEE). IMPLICATIONS: Dynamic left ventricular outflow tract obstruction is not an uncommon phenomenon, but it is often unrecognized. Its rapid recognition and effective treatment was only possible with transesophageal echocardiography (TEE). This contributes to the support for TEE being routinely available for assessment of hemodynamic instability.     

Cardiac output measurements during cross-clamping of the descending thoracic aorta in pigs. A comparison between transit-time ultrasound, thermodilution and pulsed Doppler ultrasound

BACKGROUND: Cross-clamping of the descending thoracic aorta (XC) induces an increase in cardiac output (CO). The intention of this study was to evaluate the high CO during XC by the use of clinically available methods (thermodilution and pulsed Doppler ultrasound) compared to transit-time ultrasound flowmetry of the ascending aorta as the gold standard. METHOD: Ten pigs were anaesthetised with ketamine and fentanyl. The descending thoracic aorta was cross-clamped for 30 min, and cardiac output was measured with pulmonary artery thermodilution technique, pulsed Doppler ultrasound on the aortic annulus and transit-time ultrasound flowmetry of the ascending aorta. RESULTS: At 15 min following XC, CO increased from 1.7 l/min to 4.6 l/min measured with transit-time ultrasound (P<0.05). With thermodilution technique, CO increased from 2.6ll/min to 5.7 l/min (P<0.05), and from 2.4 l/min to 6.0 l/min measured with Doppler ultrasound (P<0.05). There was an increase in mean arterial pressure of 81% and heart rate increased 76% (P<0.05). CONCLUSION: XC of the descending thoracic aorta induces an increase in CO of 171%. Thermodilution and pulsed Doppler ultrasound are reliable methods for detecting high cardiac output during thoracic aortic surgery.     

Intraoperative echocardiography for evaluation of congenital heart defects in infants and children.

To determine the accuracy, utility, and limitations of intraoperative transesophageal echocardiography (TEE) in infants and children, we performed prebypass and postbypass TEE in 90 children undergoing surgical repair of congenital heart lesions, comparing the results to those obtained using intraoperative epicardial echocardiography and pre- and postoperative precordial echocardiography. Patients ranged in age from 4 days to 21 yr (mean 4.1 yr) and in weight from 3 to 68 kg (mean 15.4 kg). Prebypass, we obtained high-quality, two-dimensional TEE images in 86 patients, with correction of the preoperative precordial diagnosis in 3 and confirmation of the preoperative diagnosis in the rest. Adequate epicardial images were obtained in 78 patients, with confirmation of the preoperative diagnosis in all. Shunt lesions that were well delineated prebypass by both TEE and epicardial imaging included interatrial, interventricular, and atrioventricular septal defect lesions. TEE failed to detect the exact size and location of lesions involving the right ventricular outflow tract, i.e., doubly committed subarterial (supracristal) ventricular septal defects. Regurgitant lesions (n = 30) were identified and their severity evaluated in all patients by both TEE and epicardial imaging. Obstructive lesions (n = 33), excluding those involving the right ventricular outflow tract, were well defined by both echocardiographic approaches. Postbypass, we obtained high-quality, two-dimensional, color and Doppler TEE images in 86 patients and epicardial images in 78 patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Importance of atrial systole to ventricular filling predicted by transesophageal echocardiography

This study documented mitral flow velocity patterns in anesthetized patients with ischemic heart disease and left ventricular dysfunction and investigated the relationship between transmitral flow velocity measurements and the hemodynamic response to ventricular pacing. Twenty-four patients in sinus rhythm without evidence of mitral valve disease undergoing elective myocardial revascularization were studied. Anesthesia consisted of a high-dose opioid-muscle relaxant-oxygen technique. After endotracheal intubation a 3.5-MHz phased-array transesophageal echocardiographic probe was inserted and positioned to obtain a long-axis view of the left atrium and left ventricle. The Doppler sample volume was placed at the mitral annulus with minimal cursor angulation, and the biphasic velocity tracing of transmitral blood flow was recorded. A hemodynamic profile was obtained, and cardiac output was measured in triplicate by thermodilution. Ventricular pacing was then instituted and the hemodynamic and thermodilution measurements were repeated. The peak early filling (E) velocity was 0.34 +/- 0.11 m/s, and the peak atrial (A) velocity was 0.38 +/- 0.09 m/s. The mean E:A ratio was 0.91 +/- 0.3, and the median value was 0.88. In sinus rhythm the cardiac index of those patients with an E:A greater than 0.88 (group 1) was 1.97 +/- 0.32 l/min and those with an E:A less than 0.88 (group 2) was 1.76 +/- 0.50 (NS). During ventricular pacing the patients in group 1 (1.56 +/- 0.32 l/min) had significantly higher cardiac indices than those in group 2 (1.21 +/- 0.31 l/min) (P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of transesophageal echocardiographic and scintigraphic estimates of left ventricular end-diastolic volume index and ejection fraction in patients following coronary artery bypass grafting

Transesophageal echocardiography (TEE) has become a commonly used monitor of left ventricular (LV) function and filling during cardiac surgery. Its use is based on the assumption that changes in LV short-axis ID reflect changes in LV volume. To study the ability of TEE to estimate LV volume and ejection immediately following CABG, 10 patients were studied using blood pool scintigraphy, TEE, and thermodilution cardiac output (CO). A single TEE short-axis cross-sectional image of the LV at the midpapillary muscle level was used for area analysis. Between 1 and 5 h postoperatively, simultaneous data sets (scintigraphy, TEE, and CO) were obtained three to five times in each patient. End-diastolic (EDa) and end-systolic (ESa) areas were measured by light pen. Ejection fraction area (EFa) was calculated (EFa = (EDa - ESa)/EDa). When EFa was compared with EF by scintigraphy, correlation was good (r = 0.82 SEE = 0.07). EDa was taken as an indicator of LV volume and compared with LVEDVI which was derived from EF by scintigraphy and CO. Correlation between EDa and LVEDVI was fair (r = 0.74 SEE = 3.75). The authors conclude that immediately following CABG, a single cross-sectional TEE image provides a reasonable estimate of EF but not LVEDVI.     

Continuous cardiac output monitoring with an uncalibrated pulse contour method in patients supported with mechanical pulsatile assist device

We evaluated the accuracy of an uncalibrated pulse contour method called Pressure Recording Analytical Method (PRAM) compared with continuous thermodilution for cardiac output (CO) monitoring in patients implanted with a pulsatile left ventricular assist device (LVAD). Twelve adult patients implanted with the HeartMate I-XVE device were studied. CO was simultaneously evaluated by PRAM and by continuous thermodilution. Blood flow values displayed by the LVAD's console were also used for the comparison. Bland-Altman and linear regression analyses were applied. A total of 72 CO measurements (range 3.8-6.7 l/min) were obtained. Mean CO was 5.23±0.70 l/min for the 'hot' pulmonary thermodilution (ThD-CCO) method, 5.28±0.63 l/min for PRAM and 4.83±0.67 l/min for LVAD-CO. A high correlation (r=0.90), a good agreement (mean bias -0.04 l/min, precision ±0.38 l/min) and a low percentage of error (7.3%) were observed between PRAM-CO and ThD-CCO. A good correlation was found between LVAD-CO and either ThD-CCO (r=0.88) or PRAM-CO (r=0.86), but an overestimation of 10% was observed for both PRAM-CO (mean bias -0.44 l/min) and ThD-CCO (mean bias -0.40 l/min). Our results demonstrated good agreements between PRAM-CO, ThD-CCO and LVAD-CO. PRAM derives CO from a peripheral artery without calibration and may be a complementary tool in the hemodynamic assessment of patients supported with a VAD.     

Transesophageal echocardiographic hemodynamic monitoring during preoperative acute normovolemic hemodilution

BACKGROUND: Preoperative acute normovolemic hemodilution may compromise oxygen transport. The aims of our study were to describe the hemodynamic effects of normovolemic hemodilution and to determine its effect on systolic and diastolic cardiac function by multiplane transesophageal echocardiography. METHODS: In eight anesthetized patients (aged 13-51 yr) without heart disease, hemoglobin was reduced in steps from 123 +/- 8 (mean +/- SD) to 98 +/- 3 and to 79 +/- 5 g/l. Hemodynamic measurements (intravascular pressures, thermodilution cardiac output, and echocardiographic recordings) were obtained during a stabilization period and at each level of hemodilution. Left ventricular wall motion was monitored continuously, and Doppler variables, annular motion, and changes in ejection fractional area were analyzed off-line. RESULTS: During hemodilution, cardiac output by thermodilution increased by 16 +/- 7% and 26 +/- 10%, corresponding well to the increase in cardiac output as measured by Doppler (difference, 0.32 +/- 1.2 l/min). Systemic vascular resistance fell 16 +/- 14% and 23 +/- 9% and pulmonary capillary wedge pressure increased slightly (2 +/- 2 mmHg), whereas other pressures, heart rate, wall motion, and diastolic Doppler variables remained unchanged. Ejection fractional area change increased from 44 +/- 7% to 54 +/- 10% and 60 +/- 9% as a result of reduced end-systolic and increased end-diastolic left ventricular areas. CONCLUSIONS: A reduction in hemoglobin to 80 g/l during acute normovolemic hemodilution does not normally compromise systolic or diastolic myocardial function as determined by transesophageal echocardiography. Preload, left ventricular ejection fraction, and cardiac output increase with a concomitant fall in systemic vascular resistance.     

Intraoperative cardiac assessment with transesophageal echocardiography for decision-making in cardiac anesthesia

Transesophageal echocardiography is an invaluable hemodynamic monitoring modality. Extended and anatomically based evaluation of cardiac function with transesophageal echocardiography is essential to prompt and accurate decision-making in anesthetic management during cardiac surgery. Fractional shortening and fractional area changes are indices widely used to assess the global systolic performance of the left ventricle. Monitoring regional function using semi-quantitative scoring has been demonstrated to be a more sensitive indicator of myocardial ischemia. Assessment of left ventricular diastolic function should be performed in a systematic way, measuring transmitral flow, pulmonary venous flow, transmitral color M-mode flow propagation velocity, and mitral annulus tissue Doppler imaging. The unique anatomical features of the right ventricle make echocardiographic evaluation complicated and therefore less frequently employed. Right ventricular fractional area change, tricuspid annular plane systolic excursion, maximal systolic tricuspid annular velocity with tissue Doppler imaging, and myocardial performance index are indices successfully incorporated into intraoperative right ventricular assessment. Left ventricular outflow tract obstruction with systolic anterior motion of the mitral valve may develop after cardiac procedures. Transesophageal echocardiography plays a central role in prevention as well as diagnosis of systolic anterior motion. Transesophageal echocardiography is extremely useful not only for detecting and locating intracardiac air, but also for guiding and evaluating the procedures to remove air. Air is likely to persist in the right and left superior pulmonary vein, left ventricular apex, left atrium, right coronary sinus of Valsalva, and ascending aorta. Accurate evaluation of cardiac function depends on performing TEE examination properly and obtaining optimal images.     

Transesophageal echocardiographic area and Doppler flow velocity measurements: comparison with hemodynamic changes in coronary artery bypass surgery

OBJECTIVE: Changes in transesophageal echocardiography (TEE)-derived Doppler flow velocities through the mitral valve and pulmonary veins occur after cardiopulmonary bypass and are believed to reflect left ventricular (LV) diastolic functional impairment. The aim of this study was to determine the time-coincidence between these Doppler flow velocity parameters, LV two-dimensional (2D) short-axis area measurements, and hemodynamic parameters in patients after coronary artery bypass grafting. DESIGN: Prospective clinical study. SETTING: University hospital. PARTICIPANTS: Twenty patients with normal ejection fraction undergoing elective cardiac surgery. INTERVENTIONS: At multiple intervals during surgery and 6 hours postoperatively, mitral inflow velocity and pulmonary venous flow velocity were measured with pulsed Doppler TEE. LV short-axis area by echocardiography and cardiac output by thermodilution were simultaneously obtained. MEASUREMENTS AND MAIN RESULTS: Time-coincidence was found in the immediate postbypass period between a decreased E/A ratio from 1.16 (95% confidence interval, 1.0 to 1.31) to 0.64 (95% confidence interval, 0.47 to 0.81, p < 0.01), a decreased E-wave deceleration time, and a significantly increased heart rate (HR) and cardiac index. End-diastolic area (EDA) and stroke volume index (SVI) decreased after sternal closure. HR, E-wave deceleration time, and SVI remained altered until 6 hours postoperatively. No change was found in pulmonary venous flow velocity parameters and systolic LV function. CONCLUSION: In patients with normal systolic ventricular function and no inotropic support, Doppler flow velocity patterns alone did not sufficiently reflect hemodynamic changes, whereas 2D LV area, especially EDA measurements, provided useful information about hemodynamically significant LV filling impairment.     

A comparison of transoesophageal echocardiographic Doppler across the aortic valve and the thermodilution technique for estimating cardiac output

This study was undertaken in order to elucidate the differences between various planes of measurement and Doppler techniques (pulsed- vs. continuous-wave Doppler) across the aortic valve to estimate cardiac output. In 45 coronary artery bypass patients, cardiac output was measured each time using four different Doppler techniques (transverse and longitudinal plane, pulsed- and continuous-wave Doppler) and compared with the thermodilution technique. Measurements were performed after induction of anaesthesia and shortly after arrival in the intensive care unit. Optimal imaging was obtained in 91% of the patients, in whom a total of 82 measurements of cardiac output were performed. The respective mean (SD) areas of the aortic valve were 3.77 (0.71) cm2 in the transverse plane and 3.86 (0.89) cm2 in the longitudinal plane. A correlation of 0.87 was found between pulsed-wave Doppler cardiac output and the thermodilution technique in either transverse or longitudinal plane. Correlation coefficients of 0.82 and 0.84 were found between thermodilution cardiac output and transverse and longitudinal continuous-wave Doppler cardiac output, respectively. Although thermodilution cardiac output is a widely accepted clinical standard, transoesophageal Doppler echocardiography across the aortic valve offers adequate estimations of cardiac output. In particular, pulsed-wave Doppler cardiac output in both the transverse and longitudinal plane provides useful data.