Patricia E. Assmann

Two-Dimensional Echocardiographic Analysis of the Dynamic Geometry of the Left Ventricle: The Basis for an Improved Model of Wall Motion

To establish an appropriate echocardiographic model for wall motion analysis we first determined the precise dynamic geometry of the left ventricle during systole, as visualized by two-dimensional echocardiography. With the epicardial apex and the aortic-ventricular and mitral-ventricular junctions as anatomic landmarks, we quantitatively analyzed apical long-axis views in 61 normal subjects, 41 patients with anterior myocardial infarction, and nine patients with posterior myocardial infarction. Thoracic impedance registration allowed exclusion of extracardiac motion from the measurements. In normal subjects the epicardial apex moved outwardly only 0.6 +/- 0.3 mm (mean +/- standard error). Examination of 15 hearts fixed in formalin revealed apical myocardial thickness of 1.5 +/- 0.2 mm. These data suggest that the observed inward motion of the endocardial apex (4.1 +/- 0.7 mm) resulted from obliteration of the apical cavity as a result of inward motion of the adjacent walls. Translation of the base was considerable in normal subjects (14.1 +/- 0.4 mm) and decreased in myocardial infarction (9.1 +/- 0.5 mm, p less than 0.0001). Unequal shortening of the adjacent walls in anterior and posterior myocardial infarction caused basal rotation in the opposite direction (-9.1 +/- 0.8 degrees and 9.7 +/- 1.4 degrees, respectively, p less than 0.0001 versus that of normal subjects, -3.4 +/- 0.7 degrees). Long-axis rotation was not clinically significant (less than 1 degree). We conclude that during ventricular contraction the apex serves as a stable point, whereas the base translates toward the apex because of shortening of the adjacent walls. We then propose a model for analyzing regional wall motion from two-dimensional echocardiograms on the basis of these observations.

Quantitative Echocardiographic Analysis of Global and Regional Left Ventricular Function: A Problem Revisited

We recorded two-dimensional echocardiograms simultaneously with the respiration measurements of 20 normal subjects and 20 patients with anterior myocardial infarction. The apical long-axis and four-chamber views were quantitatively analyzed. Measurement variability of global ejection fraction and regional ejection fraction of 100 regions was calculated during inspiration and at end-expiration for two observers. To minimize variability, the endocardial contour was redefined and traced with an improved computer-assisted tracing system. Variability (absolute mean difference) between two beats at end-expiration was significantly less than during inspiration (p less than 0.05): for ejection fraction the variability at end-expiration was 3.4% and the variability during inspiration was 6.4% (mean, 54%; SD, 7%); for regional ejection fraction the variability at end-expiration was 11.8% and the variability during inspiration was 21.5% (mean, 56%; SD, 15%). Intraobserver and interobserver variability values of one beat at end-expiration for ejection fraction were 3.1% and 3.8%, respectively, and 9.5% and 12.8%, respectively, for regional ejection fraction. Variability in patients with myocardial infarction was comparable. This method of recording respiration and analyzing left ventricular function at end-expiration, with a new contour definition and tracing system, provides a measurement variability that is considerably less than that reported in previous echocardiographic studies and that is comparable to angiographic methods.

Comparison of models for quantitative left ventricular wall motion analysis from two-dimensional echocardiograms during acute myocardial infarction

To develop quantitative analysis of regional left ventricular wall motion in the absence of a gold standard, an objective statistical measure to compare models of wall motion is described. This measure can be derived from wall motion analysis of subgroups of patients with different patterns of wall motion. A priori knowledge of the exact localization of wall motion abnormalities is not needed. Two-dimensional echocardiograms were analyzed from 79 patients with myocardial infarction. The following 4 models were compared: Model I was based on the descent of the base toward the stable apex during systole. Models II and III measured area reduction with fixed- and floating-reference systems, respectively. Model IV was the centerline model. Classification by the electrocardiogram of the myocardial infarction as anterior (n = 37), posterior (n = 17) and inferior (n = 25) provided the a priori probability for classification of myocardial infarction. The a posteriori probability for classification of myocardial infarction was derived from the detection of wall motion abnormalities by echocardiographic analysis. The mean difference between a posteriori and a priori probability is a measure for the diagnostic value of the model, and was measured for 200 regions/patient. Use of the described measure revealed model I to be the most informative model and model III the least informative. Thus, the described statistical measure contributes to the development of regional wall motion analysis.

Two-dimensional and Doppler echocardiography in acute myocardial infarction and its complications.

Two-dimensional echocardiography is an outstanding and unique bedside diagnostic and prognostic method for cardiologists facing the early diagnosis and complications of acute myocardial infarction. Its advantages are safety, rapidity, portability, and relatively low costs. It is suitable for evaluation of global and, more importantly, segmental myocardial function. Segmental wall motion analysis reliably detects, localizes, and estimates the extent of myocardial infarction in the first hours after onset of symptoms. In addition, it is the most sensitive method to diagnose right ventricular infarction and provides information predictive of early and late postinfarct complications. In postinfarct hemodynamic deterioration two-dimensional echocardiography allows one to distinguish primary pump failure from mechanical complications as: rupture of the free wall, of the ventricular septum or mitral valve dysfunction. In the subacute stage complications as ventricular (pseudo) aneurysm and thrombus may be diagnosed by two-dimensional echocardiography. Combined Doppler echocardiographic examination provides reliable information about the presence of insufficiency or shunting. Thus, echocardiography has become indispensable at the coronary care unit as it provides a complete picture of cardiac structure and function making it superior to most other methods in the clinical situation of an acute myocardial infarction with such a volatile and unpredictable course. This is an argument to house an echo/Doppler instrument in the coronary care unit.

Early identification of patients at risk for significant left ventricular dilation one year after myocardial infarction

We prospectively investigated criteria to identify patients in the early phase of acute myocardial infarction at risk for significant left ventricular (LV) dilation 1 year after myocardial infarction. In 54 patients receiving thrombolysis within 4 hours after onset of symptoms, the end-diastolic volume index (EDVI) and the end-systolic volume index were assessed by two-dimensional echocardiography initially (within 23 +/- 21 hours) and 1 year after myocardial infarction. After 1 year, LV dilation occurred in 51 patients (94%) and was significant (> mean normal value + 2 SDs) in 14 patients (26%). Significant univariate predictors (p < 0.05) for LV dilation were age, anterior myocardial infarction, initial EDVI and end-systolic volume index, enzymatic infarct size, LV end-diastolic pressure, and mitral regurgitation. No other variables obtained from clinical information, two-dimensional echocardiography, or angiography, including residual coronary perfusion or stenosis, had predictive value. The optimal multivariate predictive model was the combination of the initial EDVI and the enzymatic infarct size, which correctly predicted significant LV dilation in 12 of 14 patients and falsely in eight of 39 patients (sensitivity 86%; specificity 79%). Patients at risk for significant LV dilation 1 year after myocardial infarction were identified adequately 3 days after myocardial infarction by the combination of the initial echocardiographic assessment of EDVI and the enzymatic infarct size. Thus a simple method could facilitate the selection of patients for intervention after acute myocardial infarction.

Reference Systems in Echocardiographic Quantitative Wall Motion Analysis With Registration of Respiration

Registration of respiration allows analysis at the end-expiratory phase and may thus favor the use of the fixed-reference system versus the floating-reference system in echocardiographic quantitative wall motion analysis. Analysis is performed on two-dimensional echocardiograms of 44 normal subjects, 38 patients with anterior myocardial infarction, and 17 patients with posterior myocardial infarction. Two different models for wall motion analysis are applied, each using the fixed-reference system and the floating-reference system, respectively. In patients with anterior myocardial infarction, the fixed-reference system indicates severe wall motion abnormalities at the anterior, septal, and apical walls, whereas the floating-reference system indicates less severe wall motion abnormalities almost equally at every wall. In patients with posterior myocardial infarction, the fixed-reference system indicates severe wall motion abnormalities at the posterior wall, whereas the floating-reference system indicates less severe wall motion abnormalities almost equally at every wall. These findings indicate that the fixed-reference system is superior to the floating-reference system in quantification of wall motion of end-expiratory two-dimensional echocardiograms.

Analysis of left ventricular function in patients with myocardial infarction

Reduced left ventricular function is a major determinant of prognosis after myocardial infarction, so many acute interventions including thrombolysis are directed at preventing or reversing acute left ventricular damage. Assessment of the outcome of such therapies is necessary both for clinical decision making and for research, and requires accurate and reproducible methods of identifying or localising regions of abnormal function and of quantifying left ventricular function. Traditionally, the standard for such measurements has been biplane left ventricular cineangiography, but this is neither feasible in all patients in the acute phase after myocardial infarction nor applicable for repeated use during recovery and convalescence.

The Mechanical Complications of Acute Myocardial Infarction

Two-dimensional echocardiography allows the diagnosis of acute myocardial infarction and its rapid differentiation from other causes of severe chest pain such as dissecting aneurysm or pericarditis. It provides direct information about the localization and extent of the infarcted myocardium and the function of the noninfarcted myocardium. The advantages in such a situation are rapid and complete assessment, bedside application, safety, and serial follow-up examination. An echocardiogram made in the first hours after the acute event is often predictive for subsequent complications. Whenever clinical deterioration occurs in a patient with recent myocardial infarction, two-dimensional echocardiography should be performed since mechanical complications such as rupture of the free wall, the ventricular septum, or the papillary muscle are readily diagnosed and early diagnosis is important for successful surgical treatment.

The role of cardiac ultrasound in the diagnosis of the surgical complications of acute myocardial infarction

Two-dimensional echocardiography is a useful technique for the diagnosis of patients presenting with myocardial infarction. It can rapidly differentiate acute myocardial infarction from other causes of acute severe chest pain such as thoracic aortic dissection, pericarditis and aortic valve disease. The technique has also become a major diagnostic tool for the detection of the mechanical complications of myocardial infarction which in many cases can be corrected by surgical intervention. In addition Doppler echocardiography and more particularly color Doppler flow mapping help to assess the hemodynamic and blood flow abnormalities resulting from these complications so that their presence and severity can be readily evaluated at the bedside in the coronary care unit. The diagnostic potential of both methods may be extended by the transesophageal approach offering an alternative window to the heart when the precordial windows provide poor quality images. This is especially true in immobile, supine patients on ventilators or with an intra aortic counterpulsation in situ. However, at the present time, the reported experience with transesophageal echocardiography in the assessment of the acute complications of myocardial infarction is limited.