Intraoperative assessment of right ventricular volume and function

Objective: Right ventricular function is an important aspect of global cardiac performance which affects patients' outcome after cardiac surgery. Due to its geometrical complexity, the assessment of right ventricular function is still a very difficult task. Aim of this study was to investigate the value of a new technique for intraoperative assessment of right ventricle based on transesophageal 3D-echocardiography, and to compare it to volumetric thermodilution by using a new generation of fast response thermistor pulmonary artery catheters. Methods: Twenty-five patients with coronary artery disease underwent 68 intraoperative measurements by 3D-echocardiography and thermodilution simultaneously. Following parameters were analysed: right ventricular end-diastolic volume (RVEDV), end-systolic volume (RVESV) and ejection fraction (RVEF). Pulmonary, systemic and central venous pressures were simultaneously recorded. Segmentation of right ventricular volumes were obtained by the ‘Coons-Patches’ technique, which was implemented into the EchoAnalyzer^®, a multitask system developed at our institution for three-dimensional functional and structural measurements. Results: Right ventricular volumes obtained by 3D-echocardiography did not show significant correlations to those obtained by thermodilution. Volumetric thermodilution systematically overestimates right ventricular volumes. Significant correlations were found between RVEF measured by 3D-echocardiography and those obtained by thermodilution (r=0. 93; y=0.2+0.80x; SEE=0.03; P<0.01). Bland–Altmann analysis showed that thermodilution systematically underestimates RVEF. The bias for measuring RVEF was +15.6% with a precision of ±4.3%. The patients were divided into two groups according to left ventricular function. The group of patients with impaired function showed significantly lower right ventricular ejection fraction (44.1±4.6 vs. 55.1±3.9%; P<0.01). Conclusions: Three-dimensional echocardiography provides a useful non-invasive tool for intraoperative and serial assessment of right ventricular function. This new technique, which overcomes the limitations of previous methods, may offer key insights into management and outcome of patients with severe impairment of cardiac function.     

Measurement of stroke volume with three-dimensional transesophageal ultrasonic scanning: comparison with thermodilution measurement

The accuracy of measuring cardiac stroke volume with a new transesophageal phased array ultrasonic probe was investigated in 10 dogs. The method involved scanning the heart to obtain serial images covering the entire left ventricular cavity at end-expiration. An off-line computer analysis of the images was used to form three-dimensional reconstructions of the left ventricular cavity at end-diastole and end-systole, from which stroke volume was determined. Comparison with stroke volume determined by thermodilution during a wide range of hemodynamic conditions gave the following results for least-squares regression on 57 determinations (with the 95% confidence limits in parentheses): slope 0.95 (0.842-1.06), ordinate intercept 2.1 (2.0-2.2) ml, standard error of the estimate 4.1 ml, and correlation coefficient of 0.92 (0.87-0.95). Histologic examination of sections of esophagus surrounding the tip of the probe in nine dogs demonstrated minimal trauma to the esophageal wall, with eight specimens described as normal and one showing mild inflammation. The authors conclude that three-dimensional reconstruction of the left ventricular cavity from multiple transesophageal images offers a safe and accurate, although presently tedious, method for determining stroke volume.     

Transesophageal echocardiographic assessment of right heart hemodynamics during high-frequency jet ventilation.

STUDY OBJECTIVE: To evaluate right ventricular dimensions and function by echocardiography in anesthetized patients during superimposed high-frequency jet ventilation (HFJV). DESIGN: Prospective clinical study. SETTING: University hospital operating room. PATIENTS: 20 ASA physical status I patients undergoing elective minor otorhinolaryngological surgery, and undergoing conventional mechanical ventilation with subsequent superimposed HFJV. INTERVENTIONS: Two-dimensional transesophageal echocardiography with a 5-MHz multiplane transducer to determine right ventricular dimensions and function from a mid-esophageal view. Insertion of a radial artery catheter for monitoring blood pressure and blood gases. MEASUREMENTS AND MAIN RESULTS: Heart rate, mean arterial blood pressure, and right ventricular end-diastolic and end-systolic volumes determined by echocardiography, stroke volume, and ejection fraction. Measurements were performed after 10 minutes of conventional positive pressure ventilation (control) and after 10 minutes of subsequent superimposed HFJV at similar peak and positive end-expiratory airway pressures. Right ventricular systolic and diastolic volumes, stroke volume, and ejection fraction did not reveal statistical significant differences after transition to HFJV. Interventricular septum did not show any abnormalities in motion. In contrast, interatrial septum demonstrated momentary mid-systolic bows toward the left atrium in 9 of 17 patients (53%) during conventional ventilation, but in 15 of 17 patients (88%) during jet ventilation. Heart rate and mean arterial blood pressure remained unchanged, but arterial oxygen tension values were higher and arterial carbon dioxide tension values lower during HFJV. CONCLUSION: Transesophageal echocardiographic evaluation of right heart hemodynamics did not show any significant difference after transition of ventilation to superimposed HFJV applying similar airway pressures. Furthermore, superimposed HFJV was safe and effective, it improved oxygenation, and it facilitated carbon dioxide elimination.     

Assessment of mitral regurgitant jets by three-dimensional color Doppler

BACKGROUND: Color Doppler echocardiography is a standard technique for assessing mitral regurgitation before and after mitral valvuloplasty. Mitral valve prolapse produces complex eccentric jet flows that cannot be visualized and measured by two-dimensional color Doppler echocardiography. The aim of this study was to evaluate the clinical impact of three-dimensional color Doppler echocardiography, a new technique developed at our institution, for assessing mitral regurgitation. METHODS: Forty-five patients with mitral regurgitation underwent intraoperative transesophageal echocardiography and three-dimensional Doppler data acquisition. The grade of mitral regurgitation was assessed by angiography. The jet areas were calculated by planimetry from conventional color Doppler; the jet volumes were obtained by three-dimensional Doppler data. RESULTS: New patterns of mitral regurgitant flows were recognized according to the origin, direction, and spatial spreading into the left atrium. Conventional jet areas failed to separate the groups of patients with different degrees of regurgitation, whereas the jet volumes were able to divide patients with different regurgitation grades. No significant correlation was found between jet area and angiographic grading (r = 0.63, p = NS). Jet volumes were significantly correlated to angiography (r = 0.89, p < 0.001). CONCLUSIONS: Three-dimensional color Doppler echocardiography revealed new patterns of regurgitant flow and allowed a more accurate semiquantitative assessment of complex asymmetrical regurgitant jets.     

Real-time three-dimensional transesophageal echocardiography is useful for the localization of a small mitral paravalvular leak

The use of multiplane transesophageal echocardiography (TEE) to reconstruct 3-dimensional (3D) images is limited by time-consuming, multiplane image acquisition and the need for offline processing. To overcome these limitations, a 3D fully sampled matrix array transducer was recently developed to allow real-time acquisition and online display of 3D images. In this case, real-time 3D transesophageal echocardiography produced clear image of a small paraprosthetic leak point. Although the surgical view from the left atrium was poor due to severe adhesions, we were able to perform optimal repair of the small leak after intraoperative confirmation of the location of the leak that was identified by preoperative real-time 3D transesophageal echocardiography.     

A three-dimensional echocardiographic comparison of a deep pericardial stitch versus an apical suction device for heart positioning during beating heart surgery.

BACKGROUND: Heart positioning during beating heart surgery produces significant haemodynamic compromise either when a deep pericardial stitch (DPS) or apical suction devices (ApSDs) are used. In this study the two techniques' haemodynamic performance and effect on intracardiac structures were compared through transoesophageal echocardiography (TEE) obtained volume measurements and three-dimensional ventricular and mitral valve computer reconstructions. METHODS: Sequential 0 degrees to 180 degrees TEE images of the left heart were obtained in 10 patients undergoing beating heart surgery. Measurements with both techniques in three different positions were obtained: at baseline, the heart elevated to access its inferior surface and the heart elevated and rotated to access its lateral surface. Three-dimensional computer reconstructions of the mitral valve and the left heart were generated. Ventricular volume measurements were used to calculate stroke volume, ejection fraction and differences from baseline. An analysis of variance between each technique in all three positions was performed. RESULTS: Central venous, left atrial and pulmonary artery pressures were significantly increased with either technique during positioning. Both techniques significantly affected left ventricular function decreasing stroke volume and ejection fraction. In the vertical and rotated position, the ApSD produced a significant decrease from baseline both in stroke volume (DPS: 32.8+/-18.7 vs ApSD: 55.46+/-21.7; p=0.02) and in ejection fraction (DPS: 19.3+/-10.5 vs ApSD: 40.9+/-24.6; p=0.02). The three-dimensional reconstructions demonstrated significant distortion of the atrioventricular geometry and the mitral valve, which was more pronounced with the DPS. CONCLUSION: Both techniques produce variable degrees of deformation with associated cardiac dysfunction and haemodynamic instability. Cardiac function is impeded more with an ApSD with the heart elevated and rotated.     

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.     

Three-dimensional color Doppler for assessing mitral regurgitation during valvuloplasty.

OBJECTIVE: Transesophageal color Doppler (or 2D Doppler) is the most widely used technique for intraoperative assessment of mitral valve repair. However, the most severe mitral regurgitations produce eccentric jet flows which cannot be assessed by 2D imaging. Up to now the indications for surgical intervention and intraoperative decisions after valve repair have been based on 2D Doppler examinations. Aim of this study was to compare conventional 2D Doppler to three-dimensional (3D) Doppler for assessing residual regurgitation in patients after mitral valvuloplasty. METHODS: Twenty-four patients were referred to surgery for mitral valve repair. They underwent transesophageal echocardiography and 3D data acquisition during mitral valve reconstruction. Conventional assessment of mitral valve regurgitation, measured by color Doppler jet area, was compared to the volume of regurgitant jets obtained by 3D Doppler. Regurgitant volume and fraction were measured by pulsed Doppler and two-dimensional echocardiography. The 3D reconstructions of color Doppler data were accomplished by means of the 'Heidelberg Raytracing Algorithm' developed at our institution. RESULTS: The jet areas did not show any significant correlation to the regurgitant fraction (r = 45; P = NS) or regurgitant volumes (r = 0.40; P = NS). In contrast the jet volumes correlated significantly to regurgitant fraction (r = 0.71; P < 0.01) and regurgitant volume (r = 0.85; P < 0.01). The reproducibility analysis of repeated jet volume and jet area measurements also showed that the parameter jet volume has a lower variability and higher agreement of repeated measurements than jet area. CONCLUSIONS: Three-dimensional color Doppler flow imaging revealed the complex geometry of eccentric regurgitant jets and showed that the assessment of mitral regurgitation, based on conventional 2D Doppler, can be misleading. This new technique has a great potential for becoming a reference method for assessing mitral valve repair.     

Three-Dimensional Stereoscopic Volume Rendering of Malignant Pleural Mesothelioma

Our objective was to investigate the application of three-dimensional (3D) stereoscopic volume rendering with perceptual colorization on preoperative imaging for malignant pleural mesothelioma. At present, we have prospectively enrolled 6 patients being considered for resection of malignant pleural mesothelioma that have undergone a multidetector-row computed tomography (CT) scan of the chest. The CT data sets were volume rendered without preprocessing. The resultant 3D rendering was displayed stereoscopically and used to provide information regarding tumor extent, morphology, and anatomic involvement. To demonstrate this technique, this information was compared with the corresponding two-dimensional CT grayscale axial images from two of these patients. Three-dimensional stereoscopic reconstructions of the CT data sets provided detailed information regarding the local extent of tumor that could be used for preoperative surgical planning. Three-dimensional stereoscopic volume rendering for malignant pleural mesothelioma is a novel approach. Combined with our innovative perceptual colorization algorithm, stereoscopic volumetric analysis potentially allows for the accurate determination of the extent of pleural mesothelioma with results difficult to duplicate using grayscale, multiplanar CT images.     

Intraoperative Determination of Cardiac Output Using Multiplane Transesophageal Echocardiography: A Comparison to Thermodilution

Background: Limitations in the imaging views that can be obtained with transesophageal echocardiography (TEE) have hindered development of a widely adopted Doppler method for cardiac output (CO) monitoring. The authors evaluated a CO technique that combines steerable continuous-wave Doppler with the imaging capabilities of two-dimensional multiplane TEE.

Methods: From the transverse plane transgastric, short-axis view of the left ventricle, the imaging array was rotated to view the left ventricular outflow tract (LVOT) and ascending aorta. Steerable continuous-wave Doppler was subsequently used to measure aortic blood flow velocities. Aortic valve area was determined using a triangular orifice model. Matched thermodilution and Doppler CO measurements were obtained serially during surgery.

Results: The left ventricular outflow tract was imaged in 32 of 33 patients (97%). Data analysis reveal a mean difference between techniques of - 0.01 l/min, and a standard deviation of the differences of 0.56 l/min. Multiple regression showed a correlation of r = 0.98 between intrasubject changes in CO. Multiplane TEE correctly tracked the direction of 37 of 38 serial changes in thermodilution CO but with a modest 14% underestimation of the magnitude of these changes.     

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.     

Right and left ventricular performance during and after abdominal aortic aneurysm repair.

To evaluate the effect of aortic occlusion and limb reperfusion on global and regional function of the right and left ventricle during infrarenal abdominal aortic aneurysm repair, 23 patients underwent five intraoperative first-pass radionuclide angiocardiograms: 1) before the skin incision, 2) at aortic cross-clamp, 3) 20 minutes after aortic occlusion, 4) at unclamping, and 5) after skin closure. A subset of twelve patients had simultaneous transesophageal echocardiography to evaluate left ventricular wall stress. Parameters measured included the electrocardiogram (ECG), heart rate, blood pressure, pulmonary artery pressure, the cardiac output, the left and right ventricular ejection fractions, left ventricular volumes, and left ventricular wall stress. Significant changes (p less than 0.01) were observed at aortic clamping in the left ventricular ejection fraction (from 0.56 to 0.48), end-diastolic volume (from 171 to 225 ml), end-systolic volume (from 85 to 127 ml), mean blood pressure (from 82 to 91 mmHg), and meridional end-systolic wall stress (from 53 to 67 10(3) dyne/cm2). Once the clamp was removed, significant variations were seen in the left ventricular ejection fraction (from 0.51 to 0.58), end-diastolic volume (from 205 to 187 ml), end-systolic volume (from 105 to 94 ml), mean blood pressure (from 84 to 69 mmHg), and meridional end-systolic wall stress (from 67 to 46 10(3) dyne/cm2). No differences were observed between the two aortic occlusion studies, and the baseline level of function was recovered in all parameters during the last study. These data quantify the changes in heart function that occur during abdominal aortic aneurysm operation and demonstrate that the majority of the adaptations that occurred were due to a variation in afterload.     

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.     

Beat-to-beat Augmentation of Left Ventricular Function by Intraaortic Counterpulsation

Background: Measuring the effects of intraaortic balloon counterpulsation (IABP) in single cardiac beats may permit an improved understanding of the physiologic mechanisms by which IABP improves the circulation. The objective of the study was to use transesophageal echocardiography in combination with hemodynamic measurements to test the hypothesis that IABP improves global left ventricular systolic function selectively in the IABP-augmented cardiac beats by acutely decreasing left ventricular afterload.

Methods: Twenty-seven studies in which the IABP-to-R wave trigger ratio was serially changed from 1:1, 1:2, 1:4, 0:1 (IABP off) and back to 1:1 were performed in 20 anesthetized cardiac surgical patients during IABP support. Left ventricular short-axis end-diastolic cross-sectional area, end-systolic area, mean end-systolic wall thickness, and ejection time were measured by transesophageal echocardiography at the midpapillary muscle level. Aortic pressure was measured simultaneously from the central lumen of the intraaortic balloon catheter. These measurements were used to calculate the fractional area change, end-systolic meridional wall stress, and heart rate-corrected velocity of circumferential fiber shortening. The echocardiographic and hemodynamic parameters of left ventricular preload, afterload, and systolic function immediately after balloon deflation (IABP-augmented cardiac beats) were compared to the parameters measured during nonaugmented cardiac beats to determine the beat-to-beat effects of IABP on left ventricular function.

Results: IABP-augmented cardiac beats had a decreased systolic arterial pressure and end-systolic meridional wall stress and increased diastolic blood pressure, fractional area change, and velocity of circumferential fiber shortening compared to the nonaugmented cardiac beats. IABP did not cause significant beat-to-beat changes in heart rate, pulmonary artery diastolic pressure, or central venous pressure. The improvement in left ventricular systolic function associated with IABP-augmented cardiac beats correlated with the decrease in end-systolic meridional wall stress for that cardiac beat.     

Intraoperative measurement of cardiac output by transesophageal echocardiography of transmitral flow

INTRODUCTION: Intraoperative transesophageal echocardiography is used to study cardiac structure and function. Cardiac output is measured by calculating the velocity with which a volume of blood travels a predetermined area. Output can be assessed at the mitral valve by parallel alignment of the Doppler transducer to measure flow velocity. OBJECTIVE: To compare cardiac output measurements from transesophageal echocardiography with measurements performed by the standard clinical technique of thermodilution. PATIENTS AND METHODS: Cardiac output measurements obtained by thermodilution and by echocardiography at the mitral valve were compared in a prospective study during 34 cardiac surgery procedures. RESULTS: Cardiac output measurements ranged from 2.3 L min(-1) to 7.8 L min(-1) (mean 4.27 +/- 0.125 L min(-1) for measurements made by Doppler echocardiography and from 1.9 L min(-1) to 8.1 L min(-1) (mean 4.36 +/- 0.124 L min(-1)) for measurements made by thermodilution. The correlation between the methods was high (r = 0.926, p = 0.00001). CONCLUSION: Intraoperative measurement of cardiac output by transesophageal Doppler echocardiography at the mitral valve is easy and correlates highly with the clinical method of thermodilution used at present. Use of the technique will widen the spectrum of information provided by echocardiography, which is a safe, minimally invasive technique.     

数字化与虚拟现实技术在皮瓣移植中的应用

目的研究数字化与虚拟现实技术在股前外侧皮瓣解剖设计与可视化中的应用。方法①应用“虚拟中国人”男性3号数据集,在薄层断面图像上观察旋股外侧动脉的主要解剖结构,应用Amira 3．1 (TGS)软件对股前外侧皮瓣结构进行计算机三维重建并立体显示。②明胶一氧化铅混悬液灌注的新鲜成人下肢标本1具,行连续螺旋CT扫描,观测旋股外侧动脉分布及彼此间的吻合情况,应用Amira 3．1软件对股前外侧皮瓣结构进行计算机三维重建并立体显示。结果重建的数字化模型可准确反映股前外侧皮瓣的解剖学结构特点。结论重建的图像可以提供正常股前外侧皮瓣三维动态解剖,为临床教学术前皮瓣设计提供了直观的数字化解剖依据；同时可为下一步虚拟手术的设计奠定良好的基础。     

Increased aortic compliance maintains left ventricular performance at lower energetic cost.

OBJECTIVE: The aim of this study was to investigate left ventricular contractility and energetic cost of cardiac ejection under conditions of acute increase in aortic compliance. METHODS: In six anaesthetized pigs, ascending aortic compliance was increased by adding a volume chamber in parallel to the ascending aorta. Systemic vascular parameters, including characteristic impedance, peripheral resistance, total vascular compliance, and inertance, were estimated with a four-element windkessel model. Arterial elastance was derived from these parameters. Left ventricular systolic function was assessed by end-systolic pressure-volume relationship (end-systolic elastance), and stroke work. Pressure-volume area was used as a measure of myocardial oxygen consumption. Heart rate remained constant during the experimentation. RESULTS: Adding the aortic volume chamber significantly increased vascular compliance from 0. 95+/-0.08 to 1.17+/-0.06 ml/mmHg (P<0.01), while inductance, characteristic impedance, peripheral resistance, and arterial elastance remained statistically at basal values, respectively 0. 0020+/-0.0003 mmHg.s(2)/ml, 0.105+/-0.009 mmHg.s/ml, 1.27+/-0.12 mmHg.s/ml, and 2.43+/-0.21 mmHg/ml. During the same interval, stroke work and pressure-volume area decreased respectively from 2700+/-242 to 2256+/-75 mmHg.ml (P<0.01), and from 3806+/-427 to 3179+/-167 mmHg.ml (P<0.01). Stroke work and pressure-volume area decreased at matched end-diastolic volumes. In contrast, end-systolic elastance, ejection fraction, and stroke volume remained statistically unchanged, respectively at 2.29+/-0.14 mmHg/ml, 48.1+/-2.1 %, and 32. 4+/-1.7 ml. CONCLUSIONS: These data suggest that, when facing an increased aortic compliance, the left ventricle displays unchanged contractility, but the energetic cost of cardiac ejection is significantly decreased. These data may be of clinical importance when choosing an artificial prosthesis for ascending aortic replacement.     

Intraoperative determination of heart time volume with transesophageal pulsed Doppler echocardiography

Stroke volume and cardiac output (CO) can be determined noninvasively by means of the pulsed Doppler technique to measure blood flow velocities in specified regions of the heart or neighboring great vessels along with 2D-echocardiographic imaging to measure the diameter of vessels or valve orifices. Disadvantages of the transthoracic approach, such as precordial inaccessibility and instability of the probe position, have prevented the continuous application of pulsed Doppler echocardiography during surgery. Recently, we presented a new technique using the transesophageal approach with combined pulsed Doppler measurements and 2D-echocardiographic imaging. This study was designed to assess the feasibility of transesophageal pulsed Doppler echocardiography (TDE) for CO measurements during surgery and to test the method for accuracy against the thermodilution technique (TD) as well as evaluate its ability to track dynamic CO changes during general anesthesia. Transmitral and pulmonary artery flow analysis using TDE was performed in 35 adult patients undergoing a variety of surgical procedures under general anesthesia. For the transesophageal approach we used the prototype of a new 5-MHz phased array transducer with 64 elements fixed at the distal end of a 9 mm gastroscope. The mitral valve flow methods combined the velocity of transmitral flow at the mitral anulus with the cross-sectional area of the anulus calculated from its diameter at middiastole, while the pulmonary flow method combined the velocity of pulmonary artery flow with the cross-sectional area of the vessel calculated from its diameter during early systole. High-resolution 2D-echocardiograms of the mitral valve allowed accurate diameter measurements of the mitral valve orifice in all patients. A fixed esophageal transducer position behind the left atrium enabled continuous transmitral Doppler recordings of invariably high quality to be made. Regression analysis of TDE-CO vs. TD-CO for 50 measurements in 27 patients yielded a good correlation (r = 0.95, y = 0.95x + 0.42, SEE = 0.34 l/min). Use of halothane in 8 further patients resulted in a 21.0 +/- 5.9% and 37.3 +/- 11.7% decrease of TDE-CO at 1.0 MAC and 1.5 MAC, respectively. Transesophageal images adequate to determine the cross-sectional area of the pulmonary artery could be obtained in 16 of 27 (59.3%) patients. CO determined by the TDE pulmonary flow method (28 measurements in 16 patients) correlated with the TD-CO, with an r value of 0.91 and SEE 0.49 l/min.(ABSTRACT TRUNCATED AT 400 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.     

Acute volume reduction with aortic valve replacement immediately improves ventricular mechanics in patients with aortic regurgitation

OBJECTIVES: Few data have been available regarding the immediate response in ventricular mechanics to acute volume reduction caused by aortic valve replacement for aortic regurgitation. METHODS: We studied 9 patients in the operating room immediately before and after the institution of cardiopulmonary bypass. Left ventricular pressure and cross-sectional area (a surrogate of left ventricular volume) were measured with a catheter-tip manometer and a transesophageal echocardiographic system equipped with automated border-detection technology. Left ventricular pressure-area loops were constructed, and the caval occlusion method was used to obtain the slope of the end-systolic pressure-area relationship and the end-systolic area associated with 100 mm Hg. From the steady-state beats, stroke area was obtained by subtracting the minimum area from the maximum area. Effective arterial elastance, a measure of ventricular afterload, was calculated from end-systolic pressure, and stroke area as follows: effective arterial elastance equals end-systolic pressure divided by stroke area. RESULTS: Reductions in maximum area (21.0 +/- 8.5 to 16.0 +/- 6.8 cm(2) [SD])and minimum area (15.3 +/- 8.4 to 12.0 +/- 6.1 m(2)) shifted the baseline pressure-area loops to the left. The slope of the end-systolic pressure-area relationship (11.6 +/- 4.8 to 16.0 +/- 7.5 mm Hg/cm(2)) and afterload (effective arterial elastance, 17.9 +/- 11.6 to 26.3 +/- 16.4 mm Hg/cm(2)) were increased, and the end-systolic area associated with 100 mm Hg was reduced (18.3 +/- 10.0 to 13.7 +/- 5.8 cm(2)). CONCLUSION: Correction of volume overload reduced preload (minimum area), shifted the end-systolic pressure-area relationship to the left (decreased end-systolic area), and improved ventricular contractility (increased slope of the end-systolic pressure-area relationship). The result indicated that acute volume reduction favorably influenced ventricular mechanical parameters immediately after the operation.