Prevalence of valvular regurgitation by Doppler echocardiography in patients with structurally normal hearts by two-dimensional echocardiography

The prevalence of valvular regurgitation in a large population with structurally normal hearts remains unknown. From the computer database of the echocardiography laboratory of the hospital, 7209 records containing results of both two-dimensional and Doppler echocardiographic examinations were identified, from which 867 (12%) with no structural abnormality on two-dimensional echocardiograms were obtained for analysis. Of these 867 records, 291 (34%) had evidence of regurgitation by Doppler technique in at least one cardiac valve. Mitral regurgitation was found in 167 (19%), tricuspid regurgitation in 151 (17%), pulmonic regurgitation in 45 (5%), and aortic regurgitation in 29 records (3%). Regurgitation of just one valve was the most common and occurred in 207 records (24%). This was followed by regurgitation of two valves (69 records, 8%), three valves (13 records, 2%), and four valves (two records, 0.2%). The prevalence of mitral, tricuspid, and aortic regurgitation was found to increase significantly with increasing age, as was the prevalence of regurgitation involving multiple valves. In 98% and 95% of mitral and tricuspid regurgitations, respectively, the jets were confined to the proximal one fourth of the atria, suggesting only trivial or mild regurgitation. Thus valvular regurgitation occurs not uncommonly in patients with structurally normal hearts referred for echocardiographic evaluation. These findings caution against the inappropriate diagnosis of clinical disease in the many patients who fall into this category. The increasing prevalence of valvular regurgitation with increasing age suggests that a wear-and-tear phenomenon rather than a congenital cause is involved in most instances.

Pressure recovery distal to a stenosis: potential cause of gradient "overestimation" by Doppler echocardiography

Doppler ultrasound is currently being widely applied to measure intracardiac pressure gradients noninvasively. In comparative invasive studies, it is generally assumed that pressure is effectively uniform distal to the stenosis. As the poststenotic jet expands, however, its velocity decreases, and pressure is recovered to the extent permitted by turbulence, so that the measured gradient will be lower if the distal catheter is positioned downstream from the vena contracta. This can lead to apparent Doppler "overestimation" of the pressure gradient because of this phenomenon of pressure recovery. This study demonstrates that pressure recovery can be important in a variety of clinical settings studied by in vitro models. Although most prominent in streamlined tunnels modeled after the obstruction in patients with hypertrophic cardiomyopathy, these effects are important even for central stenoses at physiologic flow rates. Because precise catheter position is not always known or controlled, these findings suggest an important advantage for Doppler gradient estimation, because it provides the maximal gradient at the vena contracta, which determines the load on the proximal chamber.

Follow-up of patients undergoing percutaneous mitral balloon valvotomy. Analysis of factors determining restenosis

This study reports the clinical follow-up (13 +/- 1 months) of 100 consecutive patients who underwent percutaneous mitral balloon valvotomy (PMV). Echocardiographic (n = 32) and cardiac catheterization (n = 37) data from this group are also included. Patients were divided into two groups by an echocardiographic score. PMV resulted in a good hemodynamic result (post-PMV mitral valve area, greater than or equal to 1.5 cm2) in 88% of patients with a score of 8 or less and 44% of patients with a score of more than 8. Eighty-eight percent of patients with a score of 8 or less (n = 57) were New York Heart Association (NYHA) functional Classes III and IV before PMV; at follow-up, 81% were NYHA Class I and 12% were NYHA Class II. There were no deaths; three patients underwent mitral valve replacement (MVR). Ninety-eight percent of patients with a score of more than 8 (n = 43) were NYHA Classes III and IV before PMV; at follow-up, 58% were NYHA Classes I and II. Seven patients who did not improve and were not surgical candidates died 3.8 +/- 1.2 months after PMV. Nine patients who were surgical candidates underwent elective MVR at 4 +/- 0.9 months after PMV. Repeat cardiac catheterization demonstrated restenosis in only one of 27 patients (4%) with a score of 8 or less. Mitral valve area after PMV was 1.9 +/- 0.1 cm2 and at follow-up was 2 +/- 0.1 cm2 (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of the temporal contraction sequence after acute experimental myocardial infarction

The effect of infarct maturation on the temporal sequence of contraction within infarct zones has not previously been described. Accordingly, the time-varying pattern of contraction within ischemic/infarct zones was studied with use of cross-sectional echocardiography in 17 dogs at 10 min to 6 weeks after acute experimental myocardial infarction. Left ventricular short-axis images were digitized from end-diastole to end-systole and endocardial fractional radial change along 36 evenly spaced rays was calculated. The circumferential extent of dyskinesia and the number of rays that exhibited maximal dyskinesia were determined for each decile of the normalized contraction sequence. Between 10 min and 1 week after infarction, the greatest circumferential extent of dyskinesia occurred between the 3rd and 4th deciles of the normalized contraction sequence. However, as the infarct matured, the greatest spatial expanse of dyskinesia was noted to occur progressively earlier in the contraction sequence (second decile at 6 weeks), and the extent of mid- to late-systolic dyskinesia decreased markedly. Whereas end-systolic dyskinesia was present in 30% to 50% of ischemic/infarct zone rays from 10 min to 48 h, end-systolic dyskinesia was no longer observed at 6 weeks. Similarly, the maximal amplitude of dyskinesia was most commonly observed during midsystole from 10 min to 48 h, but occurred progressively earlier as the infarct matured, falling during the first decile at 6 weeks after infarction. These data suggest that maximal circumferential extent and amplitude of dyskinesia occur progressively earlier in the systolic contraction sequence as the infarct matures.(ABSTRACT TRUNCATED AT 250 WORDS)

Calculation of transmitral flow by Doppler echocardiography: a comparison of methods in a canine model

Although several Doppler echocardiographic methods for measuring transmitral flow have been described, the optimal method for calculation of flow remains unclear. Seven time/shape combinations were tested in an experimental preparation in which mitral flow could be precisely controlled and measured. Annular shape was considered to be either circular or elliptical, and the mitral orifice area was calculated from the anteroposterior and/or the mediolateral dimension(s) recorded at early and middiastole. In addition the orifice area was calculated from the maximal mitral leaflet area corrected for diastolic variation. Transmitral flow ranged between 0.4 and 4.6 L/min. Good correlations with measured transmitral flow (r = 0.83 to 0.92) were observed for all methods of calculating the mitral orifice area. Methods that assumed a circular geometry and used the mediolateral annular diameter overestimated flow. Conversely, flows calculated by means of the anteroposterior diameter with the assumption of a circular anulus underestimated flow. The best approximations of transmitral flow were obtained with the assumption of an elliptical configuration that used measurements made in early diastole (Y = 1.04x + 0.2) and with the Fisher method (y = 0.94x + 0.08). Thus in the canine model approximation of the mitral orifice as an ellipse provides the most accurate measurement of transmitral flow.

Fluid dynamics model of mitral valve flow: description with in vitro validation

A lumped variable fluid dynamics model of mitral valve blood flow is described that is applicable to both Doppler echocardiography and invasive hemodynamic measurement. Given left atrial and ventricular compliance, initial pressures and mitral valve impedance, the model predicts the time course of mitral flow and atrial and ventricular pressure. The predictions of this mathematic formulation have been tested in an in vitro analog of the left heart in which mitral valve area and atrial and ventricular compliance can be accurately controlled. For the situation of constant chamber compliance, transmitral gradient is predicted to decay as a parabolic curve, and this has been confirmed in the in vitro model with r greater than 0.99 in all cases for a range of orifice area from 0.3 to 3.0 cm2, initial pressure gradient from 2.4 to 14.2 mm Hg and net chamber compliance from 16 to 29 cc/mm Hg. This mathematic formulation of transmitral flow should help to unify the Doppler echocardiographic and catheterization assessment of mitral stenosis and left ventricular diastolic dysfunction.

Limits of normal left ventricular dimensions in growth and development: analysis of dimensions and variance in the two-dimensional echocardiograms of 268 normal healthy subjects

The majority of studies generating normal echocardiographic reference values for left ventricular dimensions have been based on blindly performed M-mode measurements, and there are no previous reports based on two-dimensional echocardiography that provide a comprehensive analysis of the two-dimensional measurements from infancy to old age. This report presents the results of analyzing the left ventricular internal dimensions from cross-sectional echocardiographic studies on 268 normal healthy subjects (none were hospitalized for any reason) whose ages ranged from 6 days to 76 years. The mean data are reported as functions of body surface area and, in addition, the variance is modeled as a function of body surface area to provide an accurate and clinically useful determination of normal limits and to model changes in the cardiac dimensions and in their variance representing normal growth and development. The data fit well to the exponential growth model (r values 0.85 to 0.95). Variance about the central values also depended significantly on body size; that relation is represented effectively by a quadratic function of body surface area (r values 0.82 to 0.98). The model parameters allow calculation of normal limits at any desired level of confidence. Areas determined by hand planimetry have significantly greater variance compared with variance of linear dimensions, and also compared with variance of cross-sectional area using ellipses generated from the anteroposterior and mediolateral dimensions. This implies that either biologic variations in the amount of infolding or errors in freehand planimetry constitute a significant source of variance; this may be remedied by filtering out high frequency oscillations of contour. There is no significant difference in midnormal values and confidence limits for corresponding dimensions measured from orthogonal views. Furthermore, the anteroposterior and mediolateral dimensions of the left ventricle superimpose at each body size, consistent with circular cross section for normal subjects throughout growth and development. The data presented should comprise a useful set of reference standards for interpretation of cross-sectional echocardiograms.

Clinical validation of an edge detection algorithm for two-dimensional echocardiographic short-axis images

The purpose of this study was to validate an edge detection algorithm for short-axis two-dimensional echocardiographic studies in a protocol that stimulated its implementation at multiple clinical laboratories. Six short-axis two-dimensional echocardiographic studies were solicited from each of five clinical laboratories. A single cardiac cycle from each of the resulting 30 studies was entered into the computer system. Five expert observers came to the laboratory on separate occasions and traced endocardial borders from the short-axis studies on 2 separate days. The computer algorithm generated borders on each frame of the cardiac cycles on the basis of regions of search defined by the observers. Of the 30 original studies, five were considered excellent, seven were good, nine were poor, and nine were technically inadequate by consensus of the five observers. The correlation coefficient for computer-defined borders with manually defined borders in the excellent quality studies was 0.985. Interobserver variability was expressed as the mean percent area difference for all possible pairings of observers. The mean percent area differences were decreased from +/- 9.8% to +/- 5.3%, +/- 12.5% to +/- 8.4%, and +/- 17.4% to +/- 15.6% when comparing observer with computer-generated borders in the excellent, good, and poor quality studies, respectively. Intraobserver variability was expressed as decrease in mean percent area difference on corresponding frames between days 1 and 2. Intraobserver variability was decreased from +/- 6.5% to +/- 4.5%, +/- 10.8% to +/- 7.0%, and +/- 14.0% to +/- 11.9%, respectively. All reductions in variability were statistically significant at p less than 0.01. Observer acceptance of computer-defined borders was estimated at 94%, 93%, and 97% for excellent, good, and poor quality studies, respectively. Once the observer defined a region of search, computer process time to generate all borders in the cardiac cycle was approximately 4 minutes. The conclusion is that the algorithm produces accurate, reliable, and acceptable borders.

Percutaneous balloon dilatation of the mitral valve: an analysis of echocardiographic variables related to outcome and the mechanism of dilatation

Twenty two patients (four men, 18 women, mean age 56 years, range 21 to 88 years) with a history of rheumatic mitral stenosis were studied by cross sectional echocardiography before and after balloon dilatation of the mitral valve. The appearance of the mitral valve on the pre-dilatation echocardiogram was scored for leaflet mobility, leaflet thickening, subvalvar thickening, and calcification. Mitral valve area, left atrial volume, transmitral pressure difference, pulmonary artery pressure, cardiac output, cardiac rhythm, New York Heart Association functional class, age, and sex were also studied. Because there was some increase in valve area in almost all patients the results were classified as optimal or suboptimal (final valve area less than 1.0 cm2, final left atrial pressure greater than 10 mm Hg, or final valve area less than 25% greater than the initial area). The best multiple logistic regression fit was found with the total echocardiographic score alone. A high score (advanced leaflet deformity) was associated with a suboptimal outcome while a low score (a mobile valve with limited thickening) was associated with an optimal outcome. No other haemodynamic or clinical variables emerged as predictors of outcome in this analysis. Examination of pre-dilatation and post-dilatation echocardiograms showed that balloon dilatation reliably resulted in cleavage of the commissural plane and thus an increase in valve area.

Inaccuracy of mitral pressure half-time immediately after percutaneous mitral valvotomy. Dependence on transmitral gradient and left atrial and ventricular compliance

Mitral pressure half-time (T1/2) is widely used as an independent measure of mitral valve area in patients undergoing percutaneous mitral valvotomy. However, fluid dynamics theory predicts T1/2 to be strongly dependent on chamber compliance and the peak transmitral gradient, which are variables that change dramatically with valvotomy. These theoretical predictions were tested in an in vitro model of the left heart where valve area, chamber compliance, and initial gradient were independently adjusted. Measured T1/2 was observed to vary inversely with orifice area and directly with net chamber compliance and the square root of the initial pressure gradient. Theoretical predictions of T1/2 agreed with observed values with r = 0.998. To test this theory in vivo, the hemodynamic tracings of 18 patients undergoing mitral valvotomy were reviewed. Predictions were made for T1/2 assuming dependence only on valve area; these showed some correlations before valvotomy (r = 0.48-0.64, p less than 0.05) but none after valvotomy (r = 0.05-0.28, p = NS). Predictions for T1/2 based on the theoretical derivation (and thus including compliance and pressure in their calculation) were much better: before valvotomy, r = 0.93-0.96, p less than 0.0001; after valvotomy, r = 0.52-0.66, p less than 0.05. These data indicate that T1/2 is not an independent inverse measure of mitral valve area but is also directly proportional to net chamber compliance and the square root of the initial transmitral gradient. These other factors render T1/2 an unreliable measure of mitral valve area in the setting of acute mitral valvotomy.

The problem of echocardiographic detection of mitral valve prolapse and determination of its true prevalence

The prevalence of mitral valve prolapse and the frequency of associated complications is currently still not known with certainty. In post-mortem studies, myxomatous changes of the mitral valve are found in less than 5%. The relationship between characteristic auscultatory findings, detectable in 6 to 18% of young asymptomatic subjects, and angiographic criteria for mitral valve prolapse, observed in up to 30% and more of those undergoing routine cardiac catheterization, is similarly unclear. Establishing the diagnosis based on M-mode echocardiographic criteria has yielded problems, in particular, a frequency too high for apparently healthy subjects. By means of two-dimensional echocardiography, displacement of a mitral leaflet could be detected more frequently in the four-chamber view than in the parasternal long-axis view, a finding which renders both the diagnostic comparability and the assumption of a planar mitral annulus questionable. Accordingly, a saddle-shaped mitral annulus has been postulated. The hypothesis of the saddle-shaped form has been repeatedly tested and confirmed: on a valve model, in patients without mitral valve disease by means of two-dimensional echocardiography as well as by means of three-dimensional reconstruction of two-dimensional echocardiographic images and, lastly, in animal experiments with surgical implantation of radioopaque markers with fluoroscopic observation. Patients can be divided into one of three categories according to the position of the leaflet with respect to the highest or lowest point of the mitral annulus: level of coaptation of the leaflets beneath, completely within or above the highest and lowest points of the annulus. A subgroup of patients in the latter category can be regarded as abnormal.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined influence of ventricular loading and relaxation on the transmitral flow velocity profile in dogs measured by Doppler echocardiography

The relation of the Doppler transmitral flow velocity profile to left ventricular loading conditions and diastolic properties remains poorly described. We studied seven adult mongrel dogs with an open-chest right heart bypass model in which left atrial pressure, representing preload, was varied by controlling blood flow into the pulmonary artery and left ventricular systolic pressure, representing afterload, was controlled independently by pumping blood into or from the femoral arteries. Heart rate was kept constant by crushing the sinus node and pacing the right atrium. Mitral inflow velocity profiles were measured by pulsed-wave Doppler echocardiography at multiple left atrial and left ventricular systolic pressures. In individual dogs, the peak E-wave velocity increased linearly with increasing left atrial V-wave pressure at constant left ventricular systolic pressure and decreased with increasing left ventricular systolic pressure at constant left atrial pressure. Stepwise multiple linear regression analysis of data pooled from all experimental stages in all dogs identified left atrial V-wave pressure, the time constant of relaxation (TL), and left ventricular systolic pressure, in order of decreasing significance, as predictors of the peak E-wave velocity (n = 82, multiple r = 0.87, p less than 0.0001). Multivariate analysis with the same three factors in individual dogs yielded higher r values (mean r = 0.89; range, 0.85-0.97), suggesting the presence of important interdog differences that were not accounted for by these three factors alone. When the values of codeterminant hemodynamic factors were kept within narrower limits, correlations between peak E-wave velocity and left atrial V-wave pressure (n = 35, multiple r = 0.83, p less than 0.0001), TL (n = 76, multiple r = -0.54, p less than 0.0001) and left ventricular systolic pressure (n = 20, multiple r = -0.59, p less than 0.005) improved substantially. In the pooled data, the relation of the peak E-wave velocity to left atrial V-wave pressure was shifted downward by an increase in TL (reduced relaxation rate), and the relation of the peak E-wave velocity to TL was shifted upward by an increase in left atrial V-wave pressure. Multivariate analysis also selected left atrial V-wave pressure and TL as the two most significant correlates of the velocity-time integral and deceleration rate of the E wave.(ABSTRACT TRUNCATED AT 400 WORDS)

Echocardiographic evaluation of mitral valve structure and function in patients followed for at least 6 months after percutaneous balloon mitral valvuloplasty

Although beneficial results have been reported immediately after percutaneous mitral balloon valvuloplasty, little information is available concerning the longer-term outcome of this procedure. The anatomic and functional results of percutaneous mitral valvuloplasty were assessed in 20 patients, in whom two-dimensional and Doppler echocardiographic examination could be obtained both immediately and 6 to 11 months (mean 7.5 +/- 2.0) after balloon dilation. Mean valve area measured by planimetry decreased slightly but significantly from 1.90 +/- 0.59 cm2 immediately after valvuloplasty to 1.62 +/- 0.55 cm2 (p less than 0.001) at follow-up. Individual changes in valve area were variable, and in four patients valve area decreased by greater than 25%. Echocardiographic scores of valvular morphology were obtained by assigning scores of 0 to 4 (with increasing abnormality) to each of four morphologic characteristics of the valve, namely, leaflet mobility, thickening, calcification and subvalvular thickening. This score was higher in the four patients with a decrease in valve area greater than 25% at follow-up than in the other patients (11 +/- 2 versus 7 +/- 2, p less than 0.002). Multiple regression analysis of several hemodynamic and echocardiographic factors identify first the echocardiographic score and second the valve area postvalvuloplasty as the only significant predictors of the percent decrease in valve area (r = 0.70, p less than 0.006). Mitral regurgitation graded by pulsed Doppler ultrasound decreased from 1.9 +/- 1.2 immediately after valvuloplasty to 1.0 +/- 0.9 (p less than 0.003) at follow-up, whereas there was no change in mean transmitral pressure gradient by Doppler echocardiography (5 +/- 2 versus 6 +/- 3 mm Hg, p = NS) and left atrial volume (74 +/- 34 versus 72 +/- 27 cm3, p = NS). Thus, 6 to 11 months after balloon mitral valvuloplasty, mean mitral valve area decreases slightly. Individual changes in valve area, however, are variable. Valvular morphology assessed by two-dimensional echocardiography may be useful for identifying those patients who have an increased likelihood of developing valvular restenosis.

Percutaneous balloon mitral valvotomy for patients with mitral stenosis. Analysis of factors influencing early results

Percutaneous balloon mitral valvotomy has recently been developed as an alternative to surgical commissurotomy for patients with rheumatic mitral stenosis. We analyzed our initial experience with 60 consecutive procedures performed in 49 patients over 1 1/2 years and identified factors influencing the immediate hemodynamic results. For the total patient population, the mitral valve area increased after percutaneous mitral valvotomy from 0.8 +/- 0.04 to 1.6 +/- 0.11 cm2 (p less than 0.001). Mean diastolic mitral gradient fell from 18 +/- 1 to 7 +/- 0.4 mm Hg (p less than 0.001), and cardiac output increased from 3.8 +/- 0.2 to 4.5 +/- 0.2 L/min (p less than 0.01). Although percutaneous mitral valvotomy resulted in an increase in mitral valve area in each patient, a suboptimal result, as defined by a postprocedure mitral valve area of 1.0 cm2 or less, an increase in area of 25% or less, or a final mitral gradient of 10 mm Hg or more occurred in 21 of the 60 procedures (35%). Multivariate analysis of 16 variables was performed to determine which factors might predict this result. Patients with a suboptimal result were more likely to have severe valve leaflet thickening or immobility and an extreme degree of subvalvular thickening and calcification on echocardiogram. Other factors that predicted a suboptimal result were a smaller effective balloon dilating area and the presence of atrial fibrillation. Thus optimal immediate hemodynamic results can be obtained in the majority of patients undergoing percutaneous mitral valvotomy. Optimal results may be expected in patients in normal sinus rhythm, with pliable mitral leaflets, and with no severe subvalvular disease identified by echocardiography, who undergo dilation with large effective balloon dilating areas.

Reconsideration of echocardiographic standards for mitral valve prolapse: lack of association between leaflet displacement isolated to the apical four chamber view and independent echocardiographic evidence of abnormality

Mitral valve prolapse by current echocardiographic criteria can be diagnosed with surprising frequency in the general population, even when preselected normal subjects are examined. In most of these individuals, however, prolapse is present in the apical four chamber view and absent in roughly perpendicular long-axis views. Previous studies have shown that systolic annular nonplanarity can cause apparent prolapse in the four chamber view without actual leaflet displacement above the most superior points of the anulus, and there is evidence for such nonplanarity in vivo. It is then reasonable to ask whether superior leaflet displacement limited to the four chamber view has any pathologic significance or complications. The purpose of this study, therefore, was to address the following hypothesis: that patients with superior leaflet displacement confined to the four chamber view have no higher frequency of associated echocardiographic abnormalities than do patients without displacement in any view. Such abnormalities, which would provide independent evidence of mitral valve pathology or dysfunction, include leaflet thickening, left atrial enlargement and mitral regurgitation. Leaflet displacement was measured in the parasternal long-axis and apical four chamber views in 312 patients who were studied retrospectively and selected for the absence of forms of heart disease other than mitral valve prolapse. Leaflet thickness and left atrial size were measured and mitral regurgitation was graded. Patients with leaflet displacement limited to the four chamber view were no more likely to have associated abnormalities than were patients without displacement in any view (0 to 2% prevalence, p greater than 0.5). In contrast, patients with leaflet displacement in the long-axis view were significantly more likely to have associated abnormalities (12 to 24%, p less than 0.005), the frequency of which increased with the extent of leaflet displacement in that view (p less than 0.0001). These results suggest that displacement limited to the apical four chamber view is, in general, a normal geometric finding unassociated with echocardiographic evidence of pathologic significance.

Correlation between echocardiographic endocardial surface mapping of abnormal wall motion and pathologic infarct size in autopsied hearts

We previously developed a cross-sectional echocardiographic technique for quantitatively mapping the endocardial surface of the left ventricle and on which regions of abnormal wall motion can be superimposed in their correct spatial distribution. This endocardial mapping technique (EMT) provides a measure of the left ventricular endocardial surface area (ESA in cm2), the area of abnormal wall motion (AWM in cm2), and the overall percent dysfunction (%AWM) as a measure of the functional "infarct size." To test this approach, we compared the EMT measurements with the actual endocardial surface area (in cm2) and pathologic infarct size (both percent infarct by volume and percent endocardial surface overlying infarct) measured at later autopsy in 20 adults (14 men, six women) ranging in age from 47 to 76 years (mean 64 +/- 9.6 years). The median interval from echocardiographic study to death was 19 days (range 1 to 269 days). Patients were divided into two groups based on the age of their infarcts at the time of death: (1) recent (infarct age less than 14 days; mean age 5.3 +/- 4.6 days) and (2) old (infarct age greater than 6 months; mean age 3.6 +/- 3 years). When the left ventricular endocardial surface area at autopsy was compared with the EMT-derived ESA, a close correlation was found (EMT area = 1.17 X autopsy area + 20.4; r = .94, p = .0001), with the systematic difference in the measurements accounted for by systolic arrest, loss of distending pressure, and specimen shrinkage. The echocardiographic measure of infarct size (%AWM) correlated well with the autopsy percent infarction by volume (%AWM = 1.1 X infarct volume + 5.5; r = .82, p = .0001). Similarly, a good correlation was found for the percent abnormal wall motion and the autopsy percent endocardial surface area overlying infarction (%AWM = 0.89 X infarct area - 0.9; r = .89, p = .0001). When the data were examined in relation to the age of the myocardial infarct, the echocardiographic %AWM appeared to overestimate the autopsy infarct size (by percent infarct volume) in the recent infarct group (n = 6), and underestimate the extent in the old infarct group (n = 13). The findings suggest that the EMT will provide a useful quantitative measure of left ventricular endocardial surface area and the extent of ischemic/infarct-related dysfunction.

Early natural history of regional left ventricular dysfunction after experimental myocardial infarction

Existing studies provide conflicting information concerning the natural history of regional dysfunction after subacute myocardial infarction. The purpose of this study was to use quantitative computer-assisted two-dimensional echocardiography to define the natural history of abnormal wall motion in a subacute canine infarct model within individual short-axis echocardiographic planes, and in the entire ventricle as well. Serial short-axis echocardiograms were obtained from 10 closed-chest dogs before occlusion and at 0.5, 6, 24, 48, and 72 hours after ligation of the circumflex (six dogs) or left anterior descending (four dogs) coronary artery. The circumferential extent of abnormal wall motion was quantified by two different computer-assisted methods: the first, a derived correlation method, examined wall motion throughout the systolic contraction sequence; the second method examined the fractional radial change in endocardial ray length from end-diastole to end-systole. The study shows that for individual planes there is a slight but not statistically significant increase in the circumferential extent of abnormal wall motion from 0.5 to 72 hours after coronary artery occlusion; however, when the total extent of left ventricular asynergy was used to define a global functional infarct size, we observed a small (3.6% to 5.4%) but significant increase in the circumferential extent of abnormal wall motion.

Mitral regurgitation after percutaneous balloon mitral valvuloplasty in adults: evaluation by pulsed Doppler echocardiography

Percutaneous balloon mitral valvuloplasty is a new technique used in the treatment of adult patients with mitral stenosis. To evaluate the occurrence and severity of mitral regurgitation after balloon valvuloplasty, 24 patients (20 women and 4 men, mean age 57 years) were studied using two-dimensional and Doppler echocardiography before and less than 24 h after this procedure. Mitral valve area increased after valvuloplasty in all patients, from 0.89 +/- 0.07 to 1.61 +/- 0.09 cm2 (p less than 0.001). Before valvuloplasty, 10 patients had no mitral regurgitation, 4 had 1+, 4 had 2+ and 6 had 3+ mitral regurgitation. After valvuloplasty, new mitral regurgitation occurred in six patients. Regurgitation grade did not change in 13 patients (54%), increased by one grade in 8 patients (33%) and by two grades in 3 patients (13%). Left atrial volume decreased in all except one patient from 100 +/- 12 to 83 +/- 12 cm3 (p less than 0.001). Neither age, sex, cardiac rhythm, initial mitral valve area, increase in mitral valve area, morphologic characteristics of the valvular and subvalvular apparatus, previous mitral commissurotomy nor effective balloon dilating area discriminated between those patients with and without an increase in mitral regurgitation after valvuloplasty. Thus, mitral balloon valvuloplasty is frequently associated with an increase in mitral regurgitation. However, in this series, no patient developed severe mitral regurgitation, and left atrial volume decreased in nearly all patients. An increase in mitral regurgitation could not be predicted from any features of the valve or subvalvular apparatus, clinical characteristics of the patients or technical aspects of the procedure.

Improved accuracy of echocardiographic endocardial borders by spatiotemporal filtered Fourier reconstruction: description of the method and optimization of filter cutoffs

The usefulness of digitized echocardiographic borders in quantitative regional left ventricular function analysis has been limited by the wide reported range for normal wall motion with this technique. We postulated that random error in endocardial border positioning is a major cause of this limitation. To test this hypothesis, we traced the endocardial borders field by field from 17 complete echocardiographic cycles in six dogs. These cycles showed a great deal of random movement, with each endocardial point reversing its motion an average of 18.5 times per cardiac cycle. Spatiotemporal Fourier analysis of these sequences demonstrated that most of the valid information on endocardial motion was contained in the first four temporal harmonics and the first seven spatial harmonics and that beyond these points the Fourier transform has the spectral characteristics of noise. Reconstruction of these 17 cycles eliminating all Fourier components above the sixth temporal and eighth spatial harmonics reduced the mean number of endocardial reversals per cycle to 2.3 (p less than .00001). To derive the optimal temporal and spatial cutoffs, we compared reconstructions of each of the 17 cycles with three M mode echocardiograms obtained simultaneously with the cross-sectional images. Fourier cutoffs were varied between two and 20 harmonics and demonstrated that the optimal temporal cutoff was 5.5 harmonics and optimal spatial cutoff 6.9. With optimal filtering, the correlation between ventricular diameter derived from the M mode and from the cross-sectional images was r = .965, compared with .877 for the M mode vs unfiltered cross-sectional data (p less than .0001). We conclude that two-dimensional filtered Fourier reconstruction significantly improves the accuracy of traced echocardiographic borders. This technique should be useful in the postprocessing of endocardial borders extracted by automated edge detection schemes and should also be applicable to cardiac images derived from modalities other than echocardiography.

Doppler mitral pressure half-time: a clinical tool in search of theoretical justification

The Doppler determination of the mitral pressure half-time has gained widespread acceptance as a reliable estimate for mitral valve area, despite little theoretical basis for its "independence" of other hemodynamic variables. A simple model of the left atrium and mitral valve has been developed and a governing equation derived from fluid dynamics fundamentals. Solution of this equation indicates that the pressure half-time should vary inversely with mitral valve area, but also proportionally to net left atrial and ventricular compliance and to the square root of the peak transmitral gradient. This complex relation is apparently masked in the typical clinical situation because pressure and compliance tend to change in opposite directions, thereby partly offsetting each other. In several clinical settings, such as balloon mitral valvotomy, left ventricular hypertrophy and aortic regurgitation, changes in initial pressure and compliance may be large enough to alter the relation between mitral area and pressure half-time. This study reviews the development of the pressure half-time concept, presents an overall method for studying mitral valve flow using mathematical modeling and describes the effects of factors other than mitral valve area on pressure half-time.

Preload dependence of Doppler-derived indexes of left ventricular diastolic function in humans

To determine the effect of filling pressure on the pattern of left ventricular filling in humans, the mitral flow velocity profile was measured by pulsed wave Doppler echocardiography during right and left heart catheterization in 11 patients before and during nitroglycerin infusion. Nitroglycerin reduced mean arterial pressure from 90 +/- 9 to 80 +/- 11 mm Hg (p less than 0.001) and mean pulmonary capillary wedge pressure from 9 +/- 4 to 4 +/- 2 mm Hg (p less than 0.001). Cardiac output fell from 6.6 +/- 1.5 to 5.5 +/- 1.4 liters/min (p less than 0.001) and heart rate increased from 60 +/- 13 to 65 +/- 14 beats/min (p less than 0.002). The time constant of isovolumic relaxation (TI.) decreased from 51 +/- 9 to 46 +/- 8 ms (p less than 0.01), indicating faster left ventricular relaxation. Nitroglycerin altered the Doppler characteristics of the early filling (E) wave but not those of the atrial contraction (A) wave. Peak velocity of the E wave decreased from 56 +/- 14 to 44 +/- 9 cm/s (p less than 0.001), peak velocity of the A wave did not change and the ratio of peak velocities of the E and A waves decreased from 0.97 +/- 0.33 to 0.77 +/- 0.20 (p less than 0.02). The deceleration of the E wave decreased from 289 +/- 138 to 186 +/- 71 cm/s2 (p less than 0.02). The ratio of velocity-time integral of the A wave to total velocity-time integral (that is, contribution of atrial contraction to total filling) increased from 0.31 +/- 0.09 to 0.36 +/- 0.08 (p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of selectively altering collateral driving pressure on regional perfusion and function in occluded coronary bed in the dog

To determine whether selectively altering the coronary perfusion pressure in the adjacent nonoccluded vessel has any influence on the occluded bed, the effects of alterations in the perfusion pressure of the left anterior descending coronary artery on the perfusion and function of the acutely occluded left circumflex coronary (LC) arterial bed were studied in 10 anesthetized open-chest dogs. Radiolabelled microsphere-assessed regional myocardial perfusion and endocardial excursion determined by two-dimensional echocardiography were measured during control conditions prior to mid-LC occlusion with left anterior descending coronary arterial pressure (LADP) equal to aortic pressure (AoP) (Stage 0) and to 3 randomly performed postocclusion stages. At each postocclusion stage, the perfusion territory of the occluded LC bed (area at risk) was measured in vivo using myocardial contrast two-dimensional echocardiography. During Stage 1 (LADP = AoP), area at risk was 5.1 +/- 0.9 cm2 (x +/- 1 SD) and transmural blood flow to the LC arterial bed decreased from 0.96 +/- 0.50 ml/min/g (Stage 0) to 0.16 +/- 0.12 ml/min/g (p less than 0.01), while endocardial excursion decreased from 28.0 +/- 9.0% to 2.0 +/- 10.0% (p less than 0.01). During Stage 2 (LADP greater than AoP), area at risk decreased to 4.4 +/- 1.0 cm2 compared with Stage 1 (p less than 0.01), and transmural blood flow, endocardial:epicardial blood flow ratio, and endocardial excursion increased to 0.51 +/- 0.39 ml/min/g, 0.64 +/- 0.20, and 14 +/- 6%, respectively (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The importance of defining left ventricular area at risk in vivo during acute myocardial infarction: an experimental evaluation with myocardial contrast two-dimensional echocardiography

Because the left ventricular "area at risk" is the most important determinant of ultimate infarct size, it would be useful to know the size of the area at risk during acute myocardial infarction to make therapeutic decisions. We therefore performed a series of experiments in four groups of dogs. In group I dogs (n = 15) we attempted to determine whether current methods of assessing left ventricular function during acute myocardial infarction reflect the true size of the area at risk. At each of two to five sequential stages, a more proximal coronary occlusion was performed to produce a larger area at risk until cardiovascular collapse occurred. At each stage, the area at risk (measured by myocardial contrast echocardiography), hemodynamic variables, and left ventricular ejection fraction (LVEF) were measured. Hemodynamic variables became abnormal when the area at risk was large (25% to 40% of the left ventricle), whereas LVEF became abnormal when the area at risk was of moderate size (18%). When cardiac output and LVEF were normalized to baseline values, a close inverse relationship was noted between these variables and area at risk. In contrast, there was a poor relationship between normalized mean arterial pressure and area at risk (r = .42). In group II dogs (n = 9) the area at risk was measured serially over 6 hr after coronary occlusion. The size of the area at risk remained unchanged regardless of the transmural extent of the ultimate infarct. The circumferential endocardial extent of the area at risk closely predicted the circumferential endocardial extent of the infarct at 6 hr in eight of nine dogs that developed an infarct. Group III dogs (n = 7) underwent the same protocol as group II dogs, but the duration of occlusion was 3 hr. The circumferential endocardial extent of the area at risk closely predicted the circumferential endocardial extent of the infarct. Group IV dogs (n = 5) underwent subtotal coronary occlusion. Although regional wall motion abnormalities were noted in this group, no area at risk could be defined. We conclude that although a close inverse relationship is noted between normalized cardiac output and area at risk, the absolute values for cardiac output and other hemodynamic variables become abnormal only when the area at risk is large (25% to 40%); measurement of LVEF may provide a better assessment of the size of the area at risk than hemodynamic variables.(ABSTRACT TRUNCATED AT 400 WORDS)

The relationship of mitral annular shape to the diagnosis of mitral valve prolapse

The geometric or anatomic diagnosis of mitral valve prolapse, as opposed to the pathologic diagnosis of myxomatous valve disease, is based on the relationship of the mitral leaflets to the surrounding anulus. Current echocardiographic criteria for this diagnosis include leaflet displacement above the annular hinge points in any two-dimensional view; implicit in this equivalent use of intersecting views is the assumption that the mitral anulus is a euclidean plane. Prolapse by these criteria is found in a surprisingly large proportion of the general population. In most of these individuals, however, prolapse is present in the apical four-chamber view and absent in roughly orthogonal long-axis views of the left ventricle. This frequently observed discrepancy between leaflet-annular relationships in intersecting views suggests an underlying geometric property of the mitral apparatus that would produce the appearance of prolapse in one view without actual leaflet distortion. To address this possibility, a model of the mitral valve and anulus was constructed. When the model anulus was given a nonplanar, saddle-shaped configuration, the clinical observations were reproduced: the leaflets appeared to lie above the low points of the anulus in one plane, and below its high points in a perpendicular plane. Therefore, the appearance of mitral valve prolapse can occur without actual leaflet displacement above the most superior points of the mitral anulus if the anulus is nonplanar. To determine whether this pattern is reflected in the human mitral anulus, two-dimensional echocardiographic views of the mitral apparatus were obtained by rotation about the cardiac apex in 20 patients without evident annular or rheumatic valvular disease. In all cases the mitral anulus, as reconstructed from these views, had a nonplanar systolic configuration, with high points located anteriorly and posteriorly. This is consistent with the findings of other groups in animals, and would favor the appearance of prolapse in the four-chamber view and its absence in long-axis views that are oriented anteroposteriorly. This model can therefore explain the frequently observed discrepancy between leaflet-annular relationships in roughly orthogonal views. It challenges the assumption that the mitral anulus is planar as well as the diagnosis of prolapse in many otherwise normal individuals based on that assumption.

An integrated mechanism for systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy based on echocardiographic observations

Although many mechanisms have been proposed to explain systolic anterior motion (SAM) of the mitral valve in hypertrophic cardiomyopathy, the precise mechanism of its onset and cessation remain undefined. The Venturi theory, based on increased flow velocity in a narrowed outflow tract, is widely accepted but fails to explain several important characteristics of SAM. It also neglects the potential role of drag forces generated by interposition of the leaflets into the path of ejection and of factors that would decrease the effectiveness of papillary muscle restraint. In order to obtain further insight into the mechanism of SAM, a detailed geometric study of the left ventricle and mitral apparatus was performed with cross-sectional echocardiography in three equal-sized groups of patients with hypertrophic cardiomyopathy and SAM, patients with hypertrophy and no anterior motion, and normal control subjects. A salient finding was that SAM began prior to ejection in patients with hypertrophic cardiomyopathy, which cannot be explained by the Venturi theory. Further, SAM began and was most prominent in the central portion of the leaflet as opposed to its lateral edges; this finding is not predicted by the Venturi mechanism. In addition to outflow tract narrowing, other structural changes unique to patients with SAM included anterior and inward displacement of the papillary muscles, anterior displacement of the mitral leaflets, and elongation of the mitral leaflets, which were, on the average, 1.5 to 1.7 cm longer than in the other subjects (p less than 0.0001). On the basis of these observations, an integrated mechanism for the initiation and resolution of SAM is proposed that would explain observed features such as onset before ejection and central prominence. This mechanism combines the effects of outflow tract narrowing with those of papillary muscle displacement. In particular, anterior and inward displacement of the papillary muscles can be predicted to alter the effectiveness of chordal support so that the central leaflet portions become relatively slack and are more readily displaced anteriorly. The altered distribution of chordal tension can also be predicted to orient the distal leaflets upward into the outflow tract at the onset of systole, prior to aortic valve opening, so that ventricular ejection will actually drag the interposed leaflets anteriorly. The resolution of SAM can be understood in terms of a reverse Venturi effect created by mitral regurgitation, as well as continued traction of the centrally displaced papillary muscles on the lateral leaflet margins.(ABSTRACT TRUNCATED AT 400 WORDS)