Characterizing the normal heart using quantitative three-dimensional echocardiography.

We present normative data on cardiac volume, geometry and shape derived using three-dimensional echocardiography (3-DE). Three-dimensional reconstructions were created using the piecewise smooth surface subdivision (PSSS) reconstruction technique of the left and right ventricular (LV and RV) endocardium and the mitral and tricuspid annuli (MA and TA) of 67 normal subjects. We derived LV end-diastolic (ED) and end-systolic (ES) volume indices (VI) of 76.5 +/- 16.8 ml m(-2) and 35.3 +/- 14.1 ml m(-2), LV ejection fraction (EF) of 56.1 +/- 9.93%, RV EDVI and ESVI of 93.2 +/- 20.0 ml m(-2) and 49.9 +/- 13.5 ml m(-2) and RVEF of 47.3 +/- 7.69%, along with data on the geometry and shape of the MA, TA, LV and RV. There was no pattern of consistent understatement or overstatement of volumes or dimensions compared with other imaging modalities, and observed variance in data can largely be accounted for through examination of the physics or protocol of each modality.

Three dimensional ultrasound analysis of fascicle orientation in human tibialis anterior muscle enables analysis of macroscopic torque at the cellular level.

The purpose of this study was to test the hypothesis that the internal structure of the bipennate human tibialis anterior muscle is sufficiently homogenous throughout the muscle that the cellular stresses could be interpreted correctly from measurable anatomic properties and torque in the limb. This result is needed for facile comparison of extrinsic mechanical data and intrinsic energetic fluxes. Three-dimensional imaging of the fascicles of the human tibialis anterior muscle was made by capturing a series of ultrasound images while registering their location in space. Subsequent tracing of hundreds of structures in the ultrasound images with the use of custom software identified muscle boundaries, tendon surfaces, and fascicles as anatomic elements in 3-D space. The tendon was reconstructed as a mesh through the tracings identified as a component of the tendon. The angle of insertion of each identified fascicle at the tendon was calculated against the nearest normal in the mesh of the tendon. In three subjects the average angle of insertion of the fascicles onto the internal tendon was 11 degrees (coefficient of variation 40%). The angle decreased along the length of the muscle from approximately 15 degrees near the belly of the muscle to 6 degrees near the ankle in fascicles superior and inferior to the central tendon. The angle increased by several degrees during a voluntary contraction. Despite the differences in angles of insertion that can be measured, these distinctions have little significance for the distribution of forces along cellular axes within the muscle: the angles, their distribution within the muscle and change with contraction are small. For this bipennate muscle the cosine of the angle of insertion of the cellular bundles is always close to unity. Thus measurements of whole muscle mechanical data are simply related to mechanical stress of its cells.

Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease.

BACKGROUND: Both lipid-modifying therapy and antioxidant vitamins are thought to have benefit in patients with coronary disease. We studied simvastatin-niacin and antioxidant-vitamin therapy, alone and together, for cardiovascular protection in patients with coronary disease and low plasma levels of HDL. METHODS: In a three-year, double-blind trial, 160 patients with coronary disease, low HDL cholesterol levels and normal LDL cholesterol levels were randomly assigned to receive one of four regimens: simvastatin plus niacin, vitamins, simvastatin-niacin plus antioxidants; or placebos. The end points were arteriographic evidence of a change in coronary stenosis and the occurrence of a first cardiovascular event (death, myocardial infarction, stroke, or revascularization). RESULTS: The mean levels of LDL and HDL cholesterol were unaltered in the antioxidant group and the placebo group; these levels changed substantially (by -42 percent and +26 percent, respectively) in the simvastatin-niacin group. The protective increase in HDL2 with simvastatin plus niacin was attenuated by concurrent therapy with antioxidants. The average stenosis progressed by 3.9 percent with placebos, 1.8 percent with antioxidants (P=0.16 for the comparison with the placebo group), and 0.7 percent with simvastatin-niacin plus antioxidants (P=0.004) and regressed by 0.4 percent with simvastatin-niacin alone (P<0.001). The frequency of the clinical end point was 24 percent with placebos; 3 percent with simvastatin-niacin alone; 21 percent in the antioxidant-therapy group; and 14 percent in the simvastatin-niacin-plus-antioxidants group. CONCLUSIONS: Simvastatin plus niacin provides marked clinical and angiographically measurable benefits in patients with coronary disease and low HDL levels. The use of antioxidant vitamins in this setting must be questioned.

Three-dimensional echocardiographic assessment of annular shape changes in the normal and regurgitant mitral valve.

OBJECTIVES: To compare mitral annular shape and motion throughout the cardiac cycle in patients with normal hearts versus those with functional mitral regurgitation (FMR). BACKGROUND: The causes of mitral regurgitation without valvular disease are unclear, but the condition is associated with changes in annular shape and dynamics. Three-dimensional (3D) imaging provides a more comprehensive view of annular structure and allows accurate reconstructions at high spatial and temporal resolution. METHODS: Nine normal subjects and 8 patients with FMR undergoing surgery underwent rotationally scanned transesophageal echocardiography. At every video frame of 1 sinus beat, the mitral annulus was manually traced and reconstructed in 3D by Fourier series. Annular projected area, nonplanarity, eccentricity, perimeter length, and interpeak and intervalley spans were determined at 10 time points in systole and 10 points in diastole. RESULTS: The mitral annulus in patients with FMR had a larger area, perimeter, and interpeak span than in normal subjects (P <.001 for all). At mid-systole in normal annuli, area and perimeter reach a minimum, nonplanarity is greatest, and projected shape is least circular. These cyclic variations were not significant in patients with FMR. Annular area change closely paralleled perimeter change in all patients (mean r = 0.96 +/- 0.07). CONCLUSIONS: FMR is associated with annular dilation and reduced cyclic variation in annular shape and area. Normal mitral valve function may depend on normal annular 3D shape and dimensions as well as annular plasticity. These observations may have implications for design and selection of mitral annular prostheses.

Applications of three dimensional echocardiography beyond the left ventricle: other chambers and structural detail.

The authors' system for quantitative three-dimensional echocardiography (3D echo) now enables analysis of all four heart chambers, valves and associated structures. After image acquisition using freehand scanning and a magnetic field tracking device, the borders of cardiac structures are manually traced. Chambers are reconstructed with a piecewise smooth subdivision surface. The mitral and tricuspid annuli are fitted using a 4 term Fourier series. Other valves and orifices are reconstructed as ellipses. Anatomic labeling enables identification of the chordae, coronary sinus, intervalvular fibrosa, septum, and right and left ventricular apex. The dimensions, shape, and function of cardiac components and the spatial relationships between them such as distance and angle can be determined. These methods provide capability and flexibility for clinical applications such as modeling heart motion, investigating the mechanism of functional mitral regurgitation, and tracking left ventricular remodeling.

Performance of a Fourier-based program for three-dimensional reconstruction of the mitral annulus on application to sparse, noisy data.

OBJECTIVES: We investigated the accuracy of mitral annular reconstruction from noisy, sparse data typical of three-dimensional (3D) transthoracic echocardiograms. BACKGROUND: Our Fourier-based method for reconstructing the annulus from dense, accurate 3D transesophageal echo (TEE) data has been validated in vitro with four harmonics in the x, y, and z coordinates (4,4,4). METHODS: Thirteen mitral annuli were reconstructed from 'complete' 3D TEE data using four harmonics (4,4,4) and used to measure area, eccentricity. height, perimeter, and interpeak and intervalley distances; these were the 'true values'. To simulate transthoracic echo data, the TEE data sets were reduced evenly and unevenly (randomly). The complete and reduced data sets were used to reconstruct the annuli using three sets of fitting parameters: (4,4,4), (1,1,3), and (1,1,4). The resulting size and shape measurements were compared with true values. RESULTS: Regardless of the fitting parameters used, area, 2D perimeter, and 3D perimeter measurements were more accurate using reconstructions from evenly-reduced than randomly-reduced data sets (p < 0.006), and depended significantly on both data density (p < 0.015 for all) and data distribution (p < 0.02 for all). Perimeter, height, and eccentricity of the reconstructed annuli were more accurately measured using four harmonics (4,4,4). CONCLUSIONS: Mitral annuli can be reconstructed from sparse, noisy data using the (4,4,4) fit if at least 25 points are obtained from evenly distributed imaging planes. These results suggest that detailed analysis of mitral annular size and shape can be made accurately from 3D transthoracic echocardiograms.

Influence of echocardiographic scan plane location and number on the accuracy of three-dimensional left ventricular volume and shape determination.

Quantitative 3-dimensional (3-D) echocardiography provides accurate assessment of left ventricular (LV) volume, shape, and function, but depends on manual endocardial border tracing. This study determined the minimal number of borders that need to be traced to obtain an accurate analysis of not only the volume of the left ventricle but also its shape, using the integrated methods for quantitative 3-D echocardiography developed by our laboratory. Transthoracic 3-D echocardiographic studies were obtained in 9 normal subjects and 6 patients with heart disease by freehand scanning. The LV endocardium was manually traced in 17 +/- 5 imaging planes and reconstructed in 3 dimensions. The volume and shape of each reconstruction were compared with values measured from surfaces reconstructed from 8 subsets containing 2 to 7 borders; each subset was acquired from different combinations of spatially distributed parasternal and apical views. Accurate measurements were obtained from data sets having > or = 5 borders, regardless of whether the image planes were predominantly apical or parasternal views. In conclusion, the LV border should be traced in > or = 5 imaging planes to obtain accurate measurements of volume and shape. The piece-wise smooth reconstruction method and freehand scanning using a magnetic field tracing system allow the borders to be acquired from whatever combination of acoustic windows and views provides optimal image quality.

Left ventricular shape analysis from three-dimensional echocardiograms.

The objective of this study was to develop and validate a three-dimensional technique of left ventricular shape analysis. Geometric phantoms and left ventricles of excised calf hearts, normal human subjects, and one subject each with aortic stenosis and dilated cardiomyopathy were reconstructed from three-dimensional echocardiograms. The fit between the reconstructions and true surfaces of the geometric phantoms and excised ventricles was determined. To evaluate in vivo left ventricular shape, a center axis was constructed from the centroid of the mitral annulus to the furthest endocardial point. Regional shape was evaluated as the relative distances of 16 separate myocardial segments from the center axis compared with a population-derived mean value. Global shape was evaluated as the average standard deviation from the normal value over the 16 segments. The system precisely reproduced the shapes of the phantoms and excised left ventricles (root-mean-square error between true and reconstructed surface 1.0 0.2 mm and 1.2 0.8 mm, respectively). The in vivo shape analysis differentiated the pathological from normal left ventricles.

System for quantitative three-dimensional echocardiography of the left ventricle based on a magnetic-field position and orientation sensing system.

Accurate measurement of left-ventricular (LV) volume and function are important to monitor disease progression and assess prognosis in patients with heart disease. Existing methods of three-dimensional (3-D) imaging of the heart using ultrasound have shown the potential of this modality, but each suffers from inherent restrictions which limit its applicability to the full range of clinical situations. We have developed a technique for image acquisition using a magnetic-field system to track the 3-D echocardiographic imaging planes and 3-D image analysis software including the piecewise smooth subdivision method for surface reconstruction. The technique offers several advantages over existing methods of 3-D echocardiography. The results of validation using in vitro LV's show that the technique allows accurate measurement of LV volume and anatomically accurate 3-D reconstruction of LV shape and is, therefore, suitable for analysis of regional as well as global function.

Estimation of the human liver volume and configuration using three-dimensional ultrasonography: effect of a high-caloric liquid meal.

The aim of this study was to investigate whether or not a magnetic position sensing system for free-hand acquisition of 3-D ultrasound images could be used to estimate liver volumes, and to study the effect of a high-caloric meal on these volumes in healthy subjects. In vitro accuracy was evaluated by scanning porcine and rabbit livers. Ten healthy subjects were examined fasting and 30 min after ingesting a high-caloric liquid meal. Portal and hepatic vein blood flow were measured by 2-D duplex sonography. The 3-D system yielded a strong correlation (r = 0.99) between true and estimated volumes in vitro. No significant increase in liver volume in response to the meal was seen. However, portal and hepatic vein flow volume increased significantly. Experience in human subjects suggests that a complete 3-D study of liver volumes can be obtained from multiple acoustic windows. In healthy subjects, no significant increase in liver volume was seen in response to ingestion of a high-caloric liquid meal.

Quantitative three-dimensional echocardiography by rapid imaging from multiple transthoracic windows: in vitro validation and initial in vivo studies.

Three-dimensional echocardiography has demonstrated superiority over two-dimensional techniques in the determination of left ventricular mass and volumes. We describe a technique based on a magnetic tracking system which provides rapid three-dimensional image acquisition from multiple acoustic windows. Interactive three-dimensional border tracking and reconstruction with a piecewise smooth subdivision model accurately reproduced phantom volume (calculated volume = 1.00 true volume - 0.6 ml, r = 1.000, standard error of the estimate = 1.3 ml), in vitro heart volume (calculated volume = 1.02 true volume - 1.3 ml, r = 1.000, standard error of the estimate = 0.4 ml), in vitro heart mass (calculated mass = 0.98 true mass + 1.4 gm, r = 0.998, standard error of the estimate = 2.5 gm), and in vivo stroke volume (calculated stroke volume = 1.18 Doppler stroke volume - 17.9 ml, r = 0.990, standard error of the estimate = 2.8 ml). The three-dimensional in vivo data sets, which include views from three acoustic windows, were acquired in less than 90 seconds. We conclude that this method of three-dimensional echocardiographic data acquisition and analysis overcomes limitations inherent in currently available systems.

Variability in frame by frame analysis of left ventricular wall motion from contrast angiograms.

BACKGROUND: Measurement of the timing of left ventricular (LV) wall motion, of asynchrony, and of diastolic function from contrast angiograms requires delineation of the endocardial border frame by frame through the cardiac cycle. This study was performed to determine the magnitude of intraobserver and interobserver variability in manual border tracing, and to measure the impact of this variability on the derived functional parameters. METHODS: The contrast ventriculograms of 25 patients with coronary artery disease (CAD) or with normal coronary arteries were analyzed frame by frame, by two observers or twice by the same observer. Motion was measured using the centerline method at each twelfth of systole and of diastole. Variability was calculated as the absolute difference between repeated measurements of: wall motion, asynchrony, and the time at which each region of the LV reached 10%, 50%, and 100% of peak contraction, and 50% of filling. RESULTS: Intraobserver and interobserver variability in wall motion were similar, and varied with time in the cycle, and with location on the LV contour. Variability was highest at end systole, when it averaged 8% of the normal mean for wall motion. Variability in timing was highest at peak contraction; however, the variability in measuring asynchrony averaged only 18 msec. CONCLUSION: Analysis of the magnitude and synchrony of regional LV wall motion through the cardiac cycle from contrast ventriculograms can be performed with reproducibility comparable to that at end systole.

How positionally stable is a transesophageal echocardiographic probe? Implications for three-dimensional reconstruction.

Three-dimensional (3D) reconstruction from a single esophageal scanning position requires a stable relationship between the probe and the heart. The purpose of this study was to examine the movement of a transesophageal echocardiographic probe during 3D image acquisition. A new dual-axis multiplane probe was used that includes a miniature (6 x 6 x 9 mm) magnetic sensor in the tip. The sensor identifies the probe's 3D position and 3D orientation in space with respect to the location of a magnetic field generator placed beneath the subject. In vivo 3D scanning was performed in five anesthetized, ventilated dogs, with positional determinations acquired every 66 msec. Probe movement was estimated by computing the deviations of each x, y, and z position and orientation determination, compared with the average values during each 3D scan or cardiac cycle. Ten 3D scans were analyzed, involving 263 cardiac cycles and 2328 determinations. The range and SD of the translational movement of the transducer were 2.3 and 0.8 mm, 1.7 and 0.5 mm, and 2.4 and 0.7 mm in x, y, and z directions, respectively, during 3D scanning. Translational movement was more dominant than was rotational movement. Misregistration of three-dimensional reconstructions may be due to subtle probe movement. The ability to monitor probe movement may be helpful in optimizing 3D data sets.

Lumen diameter of normal human coronary arteries. Influence of age, sex, anatomic variation, and left ventricular hypertrophy or dilation.

BACKGROUND: Precise knowledge of the expected "normal" lumen diameter at a given coronary anatomic location is a first step toward developing a quantitative estimate of coronary disease severity that could be more useful than the traditional "percent stenosis." METHODS AND RESULTS: Eighty-three arteriograms were carefully selected from among 9,160 consecutive studies for their smooth lumen borders indicating freedom from atherosclerotic disease. Of these, 60 men and 10 women had no abnormalities of cardiac function, seven men had idiopathic dilated cardiomyopathy, and six men had left ventricular hypertrophy associated with significant aortic stenosis. Lumen diameter was measured at 96 points in 32 defined coronary segments or major branches. Measurements were scaled to the catheter, corrected for imaging distortion, and had a mean repeat measurement error of 0.12 mm. When sex, anatomic dominance, and branch length were accounted for, normal lumen diameter at each of the standard anatomic points could usually be specified with a population variance of +/- 0.6 mm or less (SD) and coefficient of variation of less than 0.25 (SD/mean). For example, the left main artery measured 4.5 +/- 0.5 mm, the proximal left anterior descending coronary artery (LAD) 3.7 +/- 0.4 mm, and the distal LAD 1.9 +/- 0.4 mm. For the LAD, lumen diameter was not affected by anatomic dominance (right versus left), but for the right coronary artery, proximal diameter varied between 3.9 +/- 0.6 and 2.8 +/- 0.5 mm (p less than 0.01) and for the left circumflex, between 3.4 +/- 0.5 and 4.2 +/- 0.6 mm (p less than 0.01). Women had smaller epicardial arterial diameter than men (-9%; p less than 0.001), even after normalization for body surface area (p less than 0.01). Branch artery caliber was unaffected by the anatomic dominance but increased with branch length, expressed as a fraction of the origin-to-apex distance (p less than 0.001). Lumen diameter was not affected by age or by vessel tortuosity but was significantly increased among men with left ventricular hypertrophy (+ 17%; p less than 0.001) or dilated cardiomyopathy (+ 12%; p less than 0.001). CONCLUSIONS: This is a reference normal data set against which to compare lumen dimensions in various pathological states. It should be of particular value in the investigation of diffuse atherosclerotic disease.

Quantitative analysis of regional wall thickening by transesophageal echocardiography.

To develop a method for quantitative analysis of regional left ventricular function from transesophageal two-dimensional echocardiograms, we conducted studies 10 and 20 minutes after induction of anesthesia in 16 patients with normal hearts who were undergoing minor orthopedic operations. Wall thickening was measured with the centerwall method along 100 chords drawn perpendicular to a line constructed around the center of the ventricular wall, midway between the endocardial and epicardial contours. Thickening, either normalized by the length of the end-diastolic perimeter or expressed as a percentage of the end-diastolic wall thickness at each chord, was compared with measurements of endocardial motion. Wall motion was relatively diminished in the anteroseptal region and enhanced on the contralateral wall, but wall thickening was homogeneous throughout the contour. Normalized wall thickening was significantly less variable (standard deviation/mean, 0.47 +/- 0.13) in the normal population than were either percent wall thickening (0.53 +/- 0.012) or wall motion (0.51 +/- 0.09) (p less than 0.005 for both comparisons). There was no significant change in regional or global function between 10 minutes and 20 minutes after the induction of anesthesia. In summary, normalized wall thickening as a parameter of regional left ventricular function is more homogeneous and less variable in subjects with normal hearts than is endocardial motion because wall thickening measurements are not subject to cardiac translocation artifacts. This low variability suggests that normalized wall thickening measured by the centerwall method may prove particularly useful for intraoperative and postoperative monitoring of regional left ventricular function by transesophageal echocardiography in patients undergoing both cardiac and noncardiac surgical procedures.

Early beneficial effect of streptokinase on left ventricular function in acute myocardial infarction.

The effect of intravenous streptokinase therapy on the time course of functional recovery was investigated in a controlled study of 64 patients randomized within 3 hours after the onset of acute myocardial infarction (AMI). Contrast ventriculography was performed 1 to 4 days after AMI and repeated 5 weeks later. Wall motion was analyzed by the centerline method in the central infarct, peripheral infarct and noninfarct regions. In patients with ventriculographic data at the early catheterization, streptokinase-treated patients had less severe hypokinesia in the central infarct region than control patients (-2.9 +/- 0.9 [n = 29] vs -3.4 +/- 0.7 standard deviations below normal [n = 21], p less than 0.05). The benefit of streptokinase was more marked in the peripheral infarct region (-1.5 +/- 0.7 vs -2.1 +/- 0.6, p less than 0.001). As a result, the ejection fraction was slightly higher in treated versus control groups (46 +/- 10 vs 43 +/- 7%, respectively; difference not significant). At 5 weeks, function in the streptokinase and control groups had diverged further because of continued improvement in the streptokinase-treated patients. This study shows that streptokinase benefits left ventricular (LV) function by 1 to 4 days after AMI, earlier than previously reported. The benefit was not limited to the peripheral infarct region, where ischemia might have been less severe, but was also seen in the central infarct region. The implication is that thrombolytic therapy can improve LV function during the period of myocardial stunning, while myocardial function is still recovering.

Influence of coronary arterial thrombus location on left ventricular function in acute myocardial infarction.

In 238 patients with acute myocardial infarction studied during intracoronary streptokinase therapy, the circumferential extent of left ventricular hypokinesis was measured by 5 methods and correlated with the location of the infarct-related coronary artery segment and with 1-year survival. Of the 5 methods, 1 focused only on the infarct region, and 4 varied in the complexity of the noise filter. Hypokinetic segment length measurements by all 5 methods correlated significantly with the location of occlusion along the left anterior descending coronary artery. No method yielded measurements that correlated with occlusion location along the right coronary artery. Measurements by all methods correlated significantly with survival, but the method that focused on the infarct region performed least well. Thus, the circumferential extent of hypokinesis in patients with acute myocardial infarction is greater for proximal than mid- or distal occlusions of the left anterior descending but not the right coronary artery. Survival is influenced by the function of periinfarct and noninfarct regions and by the function of the infarct region. Complex noise filters provide no advantage over simpler filters in measuring the extent of hypokinesis.

Intrathoracic spatial location of specified coronary segments on the normal human heart. Applications in quantitative arteriography, assessment of regional risk and contraction, and anatomic display.

The clinically important coronary segmental anatomy has been described in a format useful for quantitative analysis and standardized display. We have determined the intrathoracic location and course of each of the 23 coronary artery segments and branches commonly used for clinical description of disease. Measurements were averaged from perpendicular angiographic view-pairs in 37 patients with normal-sized hearts. Each segment or branch is described by several points along its course; each point is specified in polar coordinates as the radial distance from the principal coronary ostium and by angles about the patient, corresponding to those describing rotation in c-arm radiographic systems. This computer-assisted measurement method is accurate to within +/- 0.2 cm (SD) and +/- 2 degrees in phantom studies. Coronary segment location among a group of normal-sized hearts can be specified to within +/- 1.0 cm (SD). For example, the left anterior descending coronary artery segment at the apex of the heart is 12.2 +/- 1.0 cm from the left coronary ostium, 32 +/- 4 degrees to the left of the anterioposterior axis, and at 46 +/- 7 degrees of caudal angulation. There are several clinically important applications of this new knowledge. First, this anatomic format provides the basis for estimating regional myocardial contraction and the relative size of the myocardial region at risk from a given arterial occlusion. Second, precise knowledge of "normal" segment location greatly simplifies the computation of dimensional correction factors for quantitative arteriography. Third, viewing angles most appropriate for videodensitometric assessment of lesion lumen area may be computed from these data. The theoretical basis and numerical values needed for most of the above estimates are provided. Finally, a computer program has been written to generate a three-dimensional tree-branch vascular model from these anatomic locations. This easily used interactive program aids in teaching coronary angiographic anatomy and, of importance, permits selection of viewing angles that "best" visualize the traditionally difficult parts of the coronary tree.

Early recovery of left ventricular function after thrombolytic therapy for acute myocardial infarction: an important determinant of survival.

Thrombolytic therapy for acute myocardial infarction reduces early mortality, but full recovery of left ventricular function after reperfusion is delayed. Therefore, the relations among reperfusion, survival and the time course of left ventricular functional recovery were examined in 226 patients treated with intracoronary streptokinase; 77% (134 patients) had sustained reperfusion and 31 patients had no reperfusion or had reocclusion by day 3. Wall motion was measured from contrast ventriculograms performed in the acute period and 3 days later in the central and peripheral infarct regions and the noninfarct region by the centerline method in 165 patients. Patients with reperfusion had better survival (p less than 0.05, mean follow-up 4.5 years) and a higher ejection fraction at 3 days (52 +/- 12 versus 46 +/- 10%, p less than 0.02) attributable to a significantly different change in peripheral infarct region function between the acute and 3 day studies (0.1 +/- 1.0 versus -0.3 +/- 0.9 SD, p less than 0.05). These early functional changes were significant in patients with anterior myocardial infarction and showed similar trends in those with inferior myocardial infarction. On Cox regression analysis, function measured at 3 days was more predictive of survival than was function measured acutely (chi square for acute ejection fraction = 11.48 versus 24.59 at 3 days). Although, as previously reported, greater than 45% of total recovery of left ventricular function occurs later, the ejection fraction achieved by day 3 is already predictive of survival. Thus, the mechanism by which successful thrombolytic therapy enhances survival is improvement of regional and global left ventricular function early after acute myocardial infarction.

Limitations in the interpretation of rest-exercise ejection fraction changes after early thrombolytic therapy during acute myocardial infarction.

The effect of exercise on left ventricular wall motion in the infarct and noninfarct regions, and their contribution to the global ejection fraction response to exercise was evaluated in 24 patients studied at least 2 weeks following thrombolytic therapy for acute myocardial infarction. To achieve this goal, a nonstandard protocol was used: contrast ventriculography was performed at rest and immediately following 3 minutes of supine bicycle exercise at 50 watts. Wall motion in the infarct and noninfarct regions was measured using the centerline method. The global ejection fraction response to exercise correlated poorly with the exercise response of motion in the infarct region (r = 0.38). In 15 of the 24 patients, the function of the infarct and noninfarct regions changed in opposing directions, and in only 8 (53%) of these did the global ejection fraction response follow the exercise response of motion in the infarct region. The motion of the noninfarct region was the predominant influence on the ejection fraction response in the other 7 patients. Subgroup analysis revealed that the global ejection fraction response was more dependent on the response of motion in the anterior wall (r = 0.71, p less than 0.001) than in the inferior wall (r = 0.16), regardless of infarct location. The regional wall motion response to exercise also better distinguished reperfused from nonreperfused patients than did the ejection fraction response. These results indicate that the global ejection fraction response to exercise may be an unreliable indicator of the functional status of the infarct region.(ABSTRACT TRUNCATED AT 250 WORDS)