Isobel A. Muhiudeen

Estimation of mean left atrial pressure from transesophageal pulsed Doppler echocardiography of pulmonary venous flow.

To determine whether pulmonary venous flow and mitral inflow measured by transesophageal pulsed Doppler echocardiography can be used to estimate mean left atrial pressure (LAP), we prospectively studied 47 consecutive patients undergoing cardiovascular surgery. We correlated Doppler variables of pulmonary venous flow and mitral inflow with simultaneously obtained mean LAP and changes in pressure measured by left atrial or pulmonary artery catheters. Among the pulmonary venous flow variables, the systolic fraction (i.e., the systolic velocity-time integral expressed as a fraction of the sum of systolic and early diastolic velocity-time integrals) correlated most strongly with mean LAP (r = -0.88). Of the mitral inflow variables, the ratio of peak early diastolic to peak late diastolic mitral flow velocity correlated most strongly with mean LAP (r = 0.43), but this correlation was not as strong as that with the systolic fraction of pulmonary venous flow. Similarly, changes in the systolic fraction correlated more strongly with changes in mean LAP (r = -0.78) than did changes in the ratio of peak early diastolic to peak late diastolic mitral inflow velocity (r = 0.68). We conclude that in the surgical setting observed, pulmonary venous flow from transesophageal pulsed Doppler echocardiography can be used to estimate mean LAP. This technique may provide a rapid, simple, and relatively noninvasive means of gauging this variable in patients undergoing intraoperative transesophageal echocardiography.

Pulmonary venous flow patterns by transesophageal pulsed Doppler echocardiography: Relation to parameters of left ventricular systolic and diastolic function

We have previously shown that the systolic and diastolic pulmonary venous flow (PVF) distribution is predictive of left atrial pressure. This study was designed to define the confounding influences of left atrial expansion, descent of the mitral anulus, and left ventricular contractile function on that relationship; to define normal PVF patterns; and to document the interaction of PVF with mitral inflow. Therefore we studied 27 consecutive intraoperative patients with coronary artery disease (22 men and 5 women, ages 35 to 78 years) using transesophageal echocardiography. A group of 12 normal subjects served as a control. Doppler and two-dimensional echocardiographic parameters were obtained simultaneously with monitoring pulmonary capillary wedge pressure (PCWP). We found that neither left atrial expansion nor the descent of the mitral anulus influenced the relationship between PVF and PCWP, but that left ventricular fractional shortening confounded this relationship. In normal subjects PVF was dominant in systole, whereas PVF in patients with elevated PCWP was dominant in diastole (systolic fraction of 68 +/- 6% [SD] in normals versus 42 +/- 15% in patients with PCWP greater than or equal to 15 mm Hg). PVF velocities interacted with transmitral flow velocities. Peak early diastolic mitral inflow velocities increased linearly with peak early diastolic PVF velocities (r = 0.62). We conclude that systolic and diastolic PVF distribution is mainly determined by the level of PCWP and to a lesser extent by left ventricular contraction, but not by left atrial expansion or by mitral anulus descent. Transesophageal pulsed Doppler echocardiography of PVF provides useful clinical information about the level of PCWP in intraoperative patients with coronary artery disease.

Intraoperative estimation of cardiac output by transesophageal pulsed doppler echocardiography

To determine whether transesophageal echocardiography could be used to estimate intraoperative cardiac output, the authors studied 35 consecutive patients undergoing cardiovascular surgery (coronary artery disease [n = 22], aortic valve disease [n = 5], mitral valve stenosis [n = 5], peripheral vascular disease [n = 3]). Two-dimensional echocardiographic and pulsed-wave Doppler signals of the pulmonary artery and mitral valve flow velocity were obtained simultaneously with thermodilution measurements of cardiac output. Cardiac output derived from pulsed Doppler imaging of pulmonary artery systolic flow velocity modestly correlated with the thermodilution-derived cardiac output (r = 0.65), but output determined from the mitral valve diastolic flow velocity did not (r = 0.24). Transesophageal echocardiography of pulmonary artery systolic flow satisfactorily detected intraoperative increases in cardiac output greater than 15% (sensitivity, 71%; specificity, 82%) but not decreases (sensitivity, 54%; specificity, 90%). Although this technique identifies increases in cardiac output greater than 15%, it does not detect decreases as accurately as those detected by thermodilution measurements. At this time, therefore, transesophageal Doppler echocardiography has significant limitations as an off-line monitor of cardiac output.

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)

Intraoperative echocardiography in infants and children with congenital cardiac shunt lesions: Transesophageal versus epicardial echocardiography

To determine the utility and limitations of intraoperative transesophageal echocardiography in infants and children with congenital intracardiac shunts, intraoperative transesophageal (n = 50) and epicardial (n = 49) echocardiograms were performed before and after cardiopulmonary bypass in children from 4 days to 16 years old and 3 to 45 kg in body weight. A miniaturized transesophageal probe (6.9 mm maximal diameter) was used in 36 patients weighting less than or equal to 20 kg. Epicardial imaging was performed with a 5 MHz precordial probe. The intraoperative transesophageal echocardiographic findings before and after cardiopulmonary bypass were correct and complete in 94% of patients. Transesophageal echocardiography correctly identified atrial septal defects, most types of ventricular septal defects, anomalous pulmonary veins, atrioventricular septal defects, tetralogy of Fallot, truncus arteriosus and double inlet ventricles. It failed to provide a correct diagnosis in only three patients, all of whom had doubly committed subarterial ventricular septal defects. Epicardial echocardiography identified all cases that had a doubly committed subarterial ventricular septal defect. A correct and complete intraoperative diagnosis was obtained with the use of epicardial imaging in 92% before and after cardiopulmonary bypass, but this technique required interruption of surgery and could not be completed in three patients because of induced arrhythmias and hypotension. These results demonstrated that intraoperative transesophageal echocardiography consistently defined important morphologic, color and pulsed Doppler ultrasound features of most congenital shunt lesions. Lesions that involved the right ventricular outflow tract are sometimes difficult to image with uniplane transesophageal echocardiography. There were no complications in any of the 50 subjects.

Response of the interatrial septum to transatrial pressure gradients and its potential for predicting pulmonary capillary wedge pressure: An intraoperative study using transesophageal echocardiography in patients during mechanical ventilation☆☆☆

OBJECTIVES We hypothesized that the directional movement of the interatrial septum and its curvature may reflect the pressure relations between the left and right atria. BACKGROUND Interventricular septal shape is primarily dependent on the pressure gradient between the left and the right ventricle. No analogous study has carefully evaluated the determinants of interatrial septum shape and motion. METHODS Patients (n = 52) undergoing cardiac or vascular surgery were studied intraoperatively at multiple intervals with transesophageal echocardiography and simultaneous measurement of central venous pressure, pulmonary capillary wedge pressure and airway pressure. RESULTS Overall interatrial septum shape, which usually curved toward the right atrium, changed concordantly with the interatrial pressure gradient (pulmonary capillary wedge pressure-central venous pressure difference). The degree of interatrial septum curvature was also primarily dependent on the interatrial pressure gradient and, to a lesser extent, was affected by changes in left atrial size (F = 130.4 vs. F = 14.1). During passive mechanical expiration, the interatrial pressure gradient, usually positive, often reverses transiently and the interatrial septum momentarily bows toward the left atrium. Midsystolic reversal was seen in 64 of 72 episodes when the pulmonary capillary wedge pressure was < or = 15 mm Hg but in only 2 of 40 episodes when it was > 15 mm Hg (sensitivity = 0.89, specificity = 0.95, positive predictive value = 0.97). CONCLUSIONS These findings suggest that overall interatrial septum shape depends on the pressure gradient between the left and right atria. Midsystolic reversal of the interatrial septum, which probably reflects the increased venous return in the right relative to the left atrium during mechanical expiration, may be a useful indicator of the pulmonary capillary wedge pressure.

Intraoperative transesophageal echocardiography of atrioventricular septal defect

To determine the accuracy and utility of single-plane transesophageal echocardiography in analyzing atrioventricular (AV) septal defect, intraoperative transesophageal echocardiography was performed before and after institution of cardiopulmonary bypass in 16 patients (age 24 days to 14 years, weight 3 to 47 kg). Prebypass transesophageal echocardiography (including two-dimensional echocardiography, Doppler color flow mapping and pulsed wave Doppler ultrasound) correctly diagnosed divided AV valve, common AV valve and unbalanced AV valve, as well as atrial or ventricular septal defect, or both, in all cases. It correctly analyzed AV valve regurgitation in all 10 patients with right and all 14 with left AV valve regurgitation and correctly analyzed 30 of 33 additional cardiac anomalies. Transesophageal echocardiography was able to detect the absence of normal pulmonary venous connections but failed to demonstrate all of the complex anomalous pulmonary venous connections in three patients with atrial isomerism. Postbypass transesophageal echocardiography documented the absence of a significant residual shunt in 11 of 11 patients undergoing corrective surgery and verified residual AV valve regurgitation in 7 of 9 patients with tricuspid regurgitation and 11 of 13 with mitral regurgitation. Transesophageal echocardiographic information that altered or refined the surgical treatment was obtained in 5 (31%) of 16 patients. Epicardial and transesophageal echocardiography results were concordant in all 13 patients in whom both were performed. Transesophageal echocardiography provides useful and accurate imaging of the important two-dimensional, pulsed wave Doppler ultrasound and Doppler color flow mapping features in AV septal defect.

Transesophageal transgastric echocardiography in infants and children: The subcostal view equivalent

Transesophageal echocardiography has been limited in the assessment of congenital heart disease involving ventriculoarterial connections. These can be viewed with biplane imaging, but the angle of incidence does not permit assessment of gradients. To determine whether transgastric transesophageal imaging could provide this information, we examined 127 infants and children during cardiac surgery, ranging from 2.7 to 32 kg in weight and 1 day to 16 years in age. The additional information (if any) provided by the transgastric plane, the frequency with which views could be obtained, the value in examining different congenital heart lesions, and assessing reductions in pressure across the left and right ventricular outflow tracts were determined. Slices obtained from anatomic specimens substantiated the imaging planes and confirmed the anatomic features. Transgastric images were obtained successfully in 89% of patients. Doppler estimates of pressure drops across the ventricular outflow tracts were within good limits of agreement with estimates obtained by manometry. There were no major complications from this technique. We conclude that the transgastric viewing plane enhances the usefulness of intraoperative transesophageal echocardiography for diagnosis and evaluation of congenital heart lesions by permitting more complete echocardiographic examinations and detection of areas of residual obstruction across the ventricular outflow tracts.

Intraoperative Transesophageal Echocardiography of Ventricular Septal Defect

The accuracy and limitations of intraoperative two‐dimensional (2‐D) and color Doppler flow mapping transesophageal echocardiography (TEE) of ventricular septal defect (VSD), before and after cardiopulmonary bypass, were analyzed in 62 children. Twenty‐one patients had an isolated VSD, and 41 had a VSD plus additional cardiac anomalies. Two‐dimensional and color Doppler flow mapping TEE were performed with a miniaturized 5‐MHz single (transverse) plane transducer in the 51 of 62 patients weighing <20 kg. The remaining 11 were monitored using a single plane adult probe (n= 4) and a biplane (transverse plus longitudinal) probe (n= 7). Prebypass TEE provided a correct diagnosis in 57 of 62 cases (92%) and corrected an erroneous preoperative transthoracic echocardiographic diagnosis in three of 62 cases (5%). Single plane TEE diagnosis was erroneous in five patients: four with doubly‐committed subarterial VSD and one with multiple small apical muscular defects and pulmonary hypertension. Biplane TEE (transverse longitudinal) provided clear and complete imaging of the right ventricular outflow tract in all seven cases in whom it was used. Postbypass TEE showed absence of a hemodynamically significant residual VSD in 38 of 40 patients (95%) who underwent VSD patch closure, prospectively identified two of 40 with significant residual VSD, and accurately measured the color Doppler jet width of all residual VSDs. We conclude that hemodynamically significant VSDs can be identified immediately after cardiopulmonary bypass based on the width of the residual VSD color Doppler flow map jet. Therefore, 2‐D and color Doppler flow mapping TEE provide an accurate diagnosis in most cases of VSD but may miss doubly‐committed subarterial and apical muscular VSD unless biplane TEE is used. (ECHOCARDIOGRAPHY, Volume 8, November 1991)