Edmond Lee

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.

Noninvasive evaluation of pulmonary artery pressure during exercise by saline-enhanced Doppler echocardiography in chronic pulmonary disease.

To determine the feasibility of noninvasive determination of right ventricular systolic pressure (RVSP) during a graded-exercise protocol, saline contrast-enhanced Doppler echocardiography of tricuspid insufficiency was performed in 36 patients with chronic lung disease and 12 normal controls. In the patients with chronic pulmonary disease, symptom-limited, incremental supine bicycle exercise and pulse oximetry were performed on and off high-flow oxygen. Technically adequate Doppler studies were initially obtained in 20 patients (56%) at rest and 14 (39%) on exercise; these numbers increased to 33 (92%) and 32 (89%), respectively, after enhancement with agitated saline (both p less than 0.001). In 10 patients with chronic lung disease who had simultaneous hemodynamic monitoring during exercise, the correlation between Doppler and catheter measurements of pulmonary artery systolic pressure was close (r = 0.98). Among controls, RVSP increased from 22 +/- 4 at rest (mean +/- SD) to 31 +/- 7 mm Hg at peak exercise. In patients with chronic lung disease, RVSP increased from 46 +/- 20 to 83 +/- 30 mm Hg (both p less than 0.001 vs. controls). Despite normal resting values for RVSP in 28% of study patients, nearly all showed abnormal increases in RVSP during supine bicycle exercise. Increases in RVSP during exercise were greatest in patients who showed oxyhemoglobin desaturation. The short-term administration of oxygen significantly blunted the increase in RVSP during exercise. Saline contrast-enhanced Doppler evaluation of tricuspid insufficiency seems a potentially valuable noninvasive method of determining the exercise response of RVSP in patients with chronic pulmonary disease.

Quantitation of the Motion of the Cardiac Base in Normal Subjects by Doppler Echocardiography

Because the motion of the base of the heart plays a central role in its filling and emptying, we developed an original method to characterize the base motion dynamics throughout each cycle by use of pulsed Doppler echocardiography. A 100 Hz wall filter and low gain settings were used to record the low-frequency, high-energy Doppler signals generated by the motion of the base. From the apical four-chamber view, the sample volume was placed at the lateral margin and at the common septal margin of the tricuspid and mitral annuli. These signals were differentiated from left and right atrioventricular flows by their opposite direction, higher energy, timing, and unique audio signal. The dynamics of the cardiac base were quantitated in 17 normal subjects (31 +/- 13 years). The time relationship between transvalvular flows and the motion of the base was studied in nine normal subjects by matching recordings at the same RR interval. The Doppler signal of the motion of the cardiac base showed a succession of positive (apically directed) and negative (atrially directed) velocity waves. Differences in the dynamics of the cardiac base were demonstrated between its left and right components, probably related to different loading conditions and different myocardial mechanical properties. The relationship between the motion of the base and mitral flow as shown in this study suggests that Doppler-measured mitral flow velocity underestimates relative left ventricular inflow velocity with respect to the atrium by about 17% at peak early flow and by 20% at peak late flow. The method reported in the present study allows a more informative noninvasive quantitation of the cardiac base motion derived from measurements of its velocity, excursion, and acceleration. This new method may provide unique information on the left ventricular and right ventricular performance in the meridional direction.

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.

Septal Bounce, Vena Cava Plethora, and Pericardial Adhesion: Informative Two-Dimensional Echocardiographic Signs in the Diagnosis of Pericardial Constriction

To assess the diagnostic value of three different two-dimensional echocardiographic signs of pericardial constriction (early diastolic septal bounce, plethora of the inferior vena cava with blunted respiratory response, and pericardial adhesion), two independent observers retrospectively evaluated echocardiograms in 100 patients, 39 of whom had pericardial constriction, 15 had hemodynamically insignificant pericardial thickening, 16 had restrictive cardiomyopathy, and 30 had normal hearts. Causes of pericardial disease included cardiac surgery, malignancy, and uremia. Sensitivity and specificity of the three signs for constriction were 62% and 93% for septal bounce, 79% and 80% for vena cava plethora, and 79% and 90% for pericardial adhesion, respectively. The presence of either vena cava plethora or pericardial adhesion increased sensitivity, whereas the presence of both plethora and adhesion increased specificity. Between the two readers, septal bounce was the most consistent and pericardial adhesion the least consistent sign. False positive results included right ventricular pacing or left bundle branch block (septal bounce), postpericardiotomy (pericardial adhesion), and right heart failure (vena cava plethora). False negative results were often caused by technical problems with imaging. We conclude that these three two-dimensional echocardiographic signs are useful in differentiating pericardial constriction from hemodynamically insignificant pericardial thickening or restrictive cardiomyopathy.

The flail mitral valve: Echocardiographic findings by precordial and transesophageal imaging and doppler color flow mapping

To determine the echocardiographic and Doppler characteristics of mitral regurgitation associated with a flail mitral valve, precordial and transesophageal echocardiography with pulsed wave and Doppler color flow mapping was performed in 17 patients with a flail mitral valve leaflet due to ruptured chordae tendineae (Group I) and 22 patients with moderate or severe mitral regurgitation due to other causes (Group II). Echocardiograms were performed before or during cardiac surgery; cardiac catheterization was also performed in 28 patients (72%). Mitral valve disease was confirmed at cardiac surgery in all patients. By echocardiography, the presence of a flail mitral valve leaflet was defined by the presence of abnormal mitral leaflet coaptation or ruptured chordae. Using these criteria, transesophageal imaging showed a trend toward greater sensitivity and specificity than precordial imaging in the diagnosis of flail mitral valve leaflet. By Doppler color flow mapping, a flail mitral valve leaflet was also characterized by an eccentric, peripheral, circular mitral regurgitant jet that closely adhered to the walls of the left atrium. The direction of flow of the eccentric jet in the left atrium distinguished a flail anterior from a flail posterior leaflet. By transesophageal echocardiography with Doppler color flow mapping, the ratio of mitral regurgitant jet arc length to radius of curvature was significantly higher in Group I than Group II patients (5.0 +/- 2.3 versus 0.7 +/- 0.6, p less than 0.001); all of the Group I patients and none of the Group II patients had a ratio greater than 2.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative Assessment of Left Ventricular Function and Wall Motion by Transesophageal Echocardiography

Over the last decade, transesophageal echocardiography has evolved as an important intraoperative clinical tool for assessment of left ventricular function in high-risk cardiac patients. Such patients include those with advanced age, pre-existing coronary artery disease, depressed left ventricular function, or associated peripheral vascular disease. Alterations in left ventricular function in these patients may result from (1) the development of intraoperative ischemia, (2) induction of unfavorable loading conditions, or (3) direct myocardial depressant effects of anesthetic agents. Because of the unique ability of transesophageal echocardiography to provide instantaneous online assessment, the technique offers an ideal method for prompt recognition of changes in left ventricular function and also provides an early opportunity for mitigating intervention. This review will summarize the experience with intraoperative transesophageal echocardiography over the last 10 years. Three areas of investigation will be emphasized

Doppler echocardiography and ultrafast cine computed tomography during dynamic exercise in chronic parenchymal pulmonary disease

In an effort to better understand the cardiac contribution to exercise limitation in chronic lung disease, 21 patients with advanced chronic pulmonary parenchymal disease and 10 normal control subjects were evaluated for changes in right ventricular (RV) pressure, volume and function during incremental, symptom-limited supine bicycle exercise. Patients underwent sequential exercise tests with Doppler echocardiography and ultrafast cine computed tomography (CT). RV systolic pressure during exercise was determined by saline-enhanced Doppler of tricuspid regurgitation. RV ejection fraction, end-diastolic volume, stroke volume and cardiac index were obtained by CT at rest and peak exercise. Sixteen of the 21 study patients also exercised on high-flow oxygen. In the control subjects RV systolic pressure increased from 21 +/- 6 mm Hg (mean +/- standard deviation) at rest to 32 +/- 8 mm Hg at peak exercise, whereas in patients with lung disease, RV systolic pressure increased from 42 +/- 17 to 81 +/- 26 mm Hg (both p less than 0.01). Compared with the control subjects, the patients with lung disease had significantly lower mean values for RV ejection fraction at rest (47 +/- 7 vs 55 +/- 7%) and at peak exercise (47 +/- 9 vs 57 +/- 3%, respectively, both p less than 0.05). The patients who demonstrated oxyhemoglobin desaturation during exercise showed the most abnormal cardiac responses, with marked increases in mean RV systolic pressure, decreases in mean RV ejection fraction and blunted increases in cardiac index and RV stroke volume. Although acute oxygen supplementation was associated with a slight decrease in RV systolic pressure at peak exercise and a longer duration of exercise, there was no significant improvement in RV function. Doppler echocardiography and CT provide complementary and potentially useful information about right-sided heart pressures and RV ejection fraction during exercise in patients with advanced chronic lung disease. Oxyhemoglobin desaturation during exercise is a marker for the most abnormal pulmonary vascular reserve, as indicated by RV contractile dysfunction and limited ability to increase cardiac index.