Quantification of mitral regurgitation with the proximal flow convergence method: a clinical study

Accurate quantitation of valvular incompetence remains an important goal in clinical cardiology. It has been shown previously that when color flow Doppler mapping is used, simple measurements of apparent jet size do not correlate closely with regurgitant flow rate and regurgitant fraction. Recently the proximal flow convergence method has been proposed to quantify valvular regurgitation by analysis of the converging flow field proximal to a regurgitant lesion. Flow rate Q can be calculated as Q = 2 pi r2v(a), where v(a) is the aliasing velocity at a distance r from the orifice. In 54 patients (43 with sinus rhythm and 11 with atrial fibrillation) who had at least mild mitral regurgitation according to semiquantitative assessment, regurgitant stroke volume, regurgitant flow rate, and regurgitant fraction were calculated with the proximal flow convergence method and compared with values that were obtained by the Doppler two-dimensional echocardiographic method. Regurgitant stroke volumes (Vr) as calculated by the proximal flow convergence method correlated very closely with values that were obtained by the Doppler two-dimensional method, with r = 0.93 (y = 0.95x + 0.55) and delta Vr = -0.3 +/- 4.0 cm3. Regurgitant flow rates (Q) as calculated by both methods showed a similar correlation: r = 0.93 (y = 0.95x + 54) and delta Q = -34 +/- 284 cm3/min. The correlation for regurgitant fraction (RF) as calculated by both techniques showed r = 0.89 (y = 0.98x + 0.006) and delta RF = -0.005 +/- 0.06. All correlations were slightly better for the group of patients with sinus rhythm than for the study group of patients with atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Isovolumic relaxation time varies predictably with its time constant and aortic and left atrial pressures: implications for the noninvasive evaluation of ventricular relaxation

The isovolumic relaxation time (IVRT) is an important noninvasive index of left ventricular diastolic function. Despite its widespread use, however, the IVRT has not been related analytically to invasive parameters of ventricular function. Establishing such a relationship would make the IVRT more useful by itself and perhaps allow it to be combined more precisely with other noninvasive parameters of ventricular filling. The purpose of this study was to validate such a quantitative relationship. Assuming isovolumic relaxation to be a monoexponential decay of ventricular pressure (pv) to a zero-pressure asymptote, it was postulated that the time interval from aortic valve closure (when pv = p(o)) until mitral valve opening (when pv = left atrial pressure, pA) would be given analytically by IVRT = tau[log(p(o))-log(pA)], where tau is the time constant of isovolumic relaxation and log is to the base e. To test this hypothesis we analyzed data from six canine experiments in which ventricular preload and afterload were controlled nonpharmacologically. In addition, tau was adjusted with the use of beta-adrenergic blockade and calcium infusion, as well as with hypothermia. In each experiment data were collected before and after the surgical formation of mitral stenosis, performed to permit the study of a wide range of left atrial pressures. High-fidelity left atrial, left ventricular, and aortic root pressures were digitized, the IVRT was measured from the aortic dicrotic notch until the left atrioventricular pressure crossover point, and tau was calculated by nonlinear least-squares regression.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of late patency of the infarct-related coronary artery on left ventricular morphology and regional function after thrombolysis

The use of early coronary angiography to assess the benefits of coronary patency on left ventricular size and function fails to account for subsequent reocclusion or spontaneous reperfusion. To investigate the relationship between late vessel patency and changes in left ventricular structure and function after thrombolysis, echocardiography was performed within 48 hours and at 6 to 12 weeks in 30 patients treated with intravenous thrombolysis. Left ventricular endocardial surface area index (ESAj; cm2/m2) and extent of abnormal wall motion were quantitated in those with a patent (n = 20) and those with an occluded (n = 10) infarct-related artery on coronary angiography performed 8 +/- 6 days after thrombolysis. Mean ESAi increased from (53 +/- 7 to 61 +/- 10 cm2/m2; p less than 0.02) in the occluded group during the follow-up period but remained unchanged (60 +/- 11 to 62 +/- 11 cm2/m2; p = NS) in the patient group. Mean percentage of abnormal wall motion decreased in the patent group (27 +/- 16% to 18 +/- 16%; p less than 0.01), whereas no significant change was noted in the occluded group (20 +/- 13% to 23 +/- 17%; p = NS). Thus coronary patency at days after thrombolysis is associated with both improvement in regional left ventricular function and attenuated left ventricular dilatation.

Progressive changes in ventricular structure and function during the year after acute myocardial infarction

To investigate the long-term changes in left ventricular structure and function after myocardial infarction, 51 patients with a first myocardial infarction (17 anterior, 23 inferior, and 11 non-Q wave) were studied by two-dimensional echocardiography at the time of entry into the hospital, at 3 months, and 1 year after infarction. The left ventricular endocardial surface was reconstructed from these echocardiograms, and the endocardial surface area (ESA) index (in cm2/m2) and area of abnormal wall motion (AWM in cm2) were quantitated. Despite different trends in the ESA index between entry and 3-month values in those with and without early infarct expansion, a decrease in the ESA index from 3 months to 1 year was noted in anterior and non-Q wave infarctions (anterior with early expansion: 96.3 +/- 8.6 to 81.5 +/- 4.2 cm2/m2, p less than 0.05; anterior without early expansion: 59.7 +/- 2.0 to 54.7 +/- 2.0 cm2/m2, p less than 0.01; non-Q wave: 64.1 +/- 3.5 to 57.9 +/- 4.4 cm2/m2, p less than 0.01). The mean decline in ESA from 3 months to 1 year of 8.9 +/- 2.5 cm2 was independent of initial infarct size. Regional function, as represented by the area of AWM, was also improved but the timing of the improvement was related to the location and size of the infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Variation in the color Doppler area of a regurgitant jet with changes in the absolute chamber pressure: an in vitro study

The color Doppler appearance of a regurgitant jet depends on jet momentum, determined in part by the pressure difference between the two chambers. However, it is not clear if absolute chamber pressure has an independent effect on jet area. To test this question, an in vitro experiment was performed in which dynamically decaying jets were created with identical initial pressure gradients but five different levels of absolute chamber pressures. At every level of chamber pressure, color Doppler images were recorded with two different transducers (3.5 and 5.0 MHz) and jet areas were measured at four different flow rates (0 to 9.9 cm3/sec). A multilinear regression model was created with jet area as the dependent variable and jet flow rate, transducer frequency, and absolute chamber pressure as independent parameters. Jet area was most strongly predicted by flow rate (univariate r = 0.90) and transducer frequency (r = 0.32). Even after adjusting for these effects, however, a small but significant (p less than 0.0001) effect of absolute chamber pressure on jet area was seen with jet area rising by 0.89 cm2 for each 10 mm Hg increase in absolute chamber pressure (multivariate r = 0.96, p less than 0.0001). We conclude that the color Doppler area of a regurgitant jet is dependent not only on the relative pressure and flow between the two chambers but also on the absolute chamber pressure.

Noninvasive measurement of the time constant of left ventricular relaxation using the continuous-wave Doppler velocity profile of mitral regurgitation

BACKGROUND

The time constant of isovolumic relaxation (tau) is an important parameter of ventricular diastolic function, but the need for invasive measurement with high-fidelity catheters has limited its use in general clinical cardiology. The Doppler mitral regurgitant velocity spectrum can be used to estimate left ventricular (LV) pressure throughout systole and may provide a new noninvasive method for estimating tau.

METHODS AND RESULTS

Mitral regurgitation was produced in nine dogs, and ventricular relaxation was adjusted pharmacologically and with hypothermia. High-fidelity ventricular pressures were recorded, and tau was calculated from these hemodynamic data (tau H) assuming a zero-pressure asymptote. Continuous-wave mitral regurgitant velocity profiles were obtained, and the ventriculo-atrial (VA) pressure gradient was calculated by the simplified Bernoulli equation; tau was calculated from the Doppler data from the time of maximal negative dP/dt until LV-LA pressure crossover. Three methods were used to correct the Doppler VA gradient to better approximate the LV pressure before calculating tau: 1) adding actual LA V wave pressure (to yield tau LA); 2) adding 10 mm Hg (tau 10); and 3) no adjustment at all (actual VA gradient used to calculate tau 0). The agreement between tau H and the three Doppler estimates of tau was assessed by linear regression and by the mean and standard deviation of the error between the measurements (delta tau). the measurements (delta tau). tau H ranged from 29 to 135 msec. Without correction for LA pressure, the Doppler estimate of tau seriously underestimated tau H: tau 0 = 0.30 tau H + 9.4, r = 0.79, delta tau = -35 +/- 18 msec. This error was almost completely eliminated by adding actual LA pressure to the VA pressure gradient: tau LA = 0.92 tau H + 7.6, r = 0.95, delta tau = 2 +/- 7 msec. Addition of a fixed LA pressure estimate of 10 mm Hg to the VA gradient yielded an estimate that was almost as good: tau 10 = 0.89 tau H + 4.9, r = 0.88, delta tau = -2 +/- 12 msec. In general, tau was overestimated when actual LA pressure was below this assumed value, and vice versa. Numerical analysis demonstrated that assuming LA pressure to be 10 mm Hg should yield estimates of tau accurate to +/- 15% between true LA pressures of 5 and 20 mm Hg.

CONCLUSIONS

This study demonstrates that the Doppler mitral regurgitant velocity profile can be used to provide a direct and noninvasive measurement of tau. Because mitral regurgitation is very common in cardiac patients, this method may allow more routine assessment of tau in clinical and research settings, leading to a better understanding of the role of impaired ventricular relaxation in diastolic dysfunction and the effect of therapeutic interventions.

Three-dimensional echocardiography: techniques and applications

Current echocardiographic devices provide only 2-dimensional views of the heart. To appreciate 3-dimensional structural relations, therefore, requires mental reconstruction of 2-dimensional views by an experienced observer. Our ability to answer new questions about the heart could be increased if 2-dimensional images could be combined to display 3-dimensional relations. Such 3-dimensional reconstruction would permit analysis of structures of unknown or complex shape and the noninvasive quantification of cardiac chamber size and function without making geometric assumptions. To overcome previous limitations, mechanisms have been developed for automated integration of images and positional data during routine echocardiographic scanning, thereby greatly enhancing the efficiency and application of image reconstruction. Refining the diagnosis of mitral valve prolapse has presented a uniquely 3-dimensional problem requiring information previously unavailable from the 2-dimensional technique. To date, 3-dimensional studies have demonstrated that the mitral valve is saddle-shaped in systole, so that apparent superior leaflet displacement in the mediolateral 4-chamber view, often seen in otherwise normal individuals, lies entirely within the bounds defined by the mitral annulus and occurs without leaflet distortion or actual displacement above the entire mitral valve. Other applications of 3-dimensional image reconstruction include calculation of ventricular volume and ejection fraction by transthoracic or transesophageal scanning without geometric assumptions; improving the standardization and accuracy of 2-dimensional measurements by improving spatial appreciation; and 3-dimensional reconstruction of vascular walls to guide interventions. In the future, systems for acquiring multiple views more rapidly by parallel processing and improving endocardial border extraction should allow more routine application of 3-dimensional methods as the next stage in the evolution of cardiac ultrasound, thereby expanding the range of questions that can be answered. Achieving these goals will depend, in large measure, on persistence in developing the necessary technology.

Impact of finite orifice size on proximal flow convergence. Implications for Doppler quantification of valvular regurgitation

Analysis of velocity acceleration proximal to a regurgitant valve has been proposed as a method to quantify the regurgitant flow rate (Qo). Previous work has assumed inviscid flow through an infinitesimal orifice, predicting hemispheric isovelocity shells, with calculated flow rate given by Qc = 2 pi rN2vN, where vN is user-selected velocity of interest and rN is the distance from that velocity to the orifice. To validate this approach more rigorously and investigate the impact of finite orifice size on the assumption of hemispheric symmetry, numerical and in vitro modeling was used. Finite-difference modeling demonstrated hemispheric shape for contours more than two orifice diameters from the orifice. More proximal than this (where the measured velocity vN exceeded 3% of the orifice velocity vo), flow was progressively underestimated, with a proportional error delta Q/Qo nearly identical to the ratio of contour velocity to orifice velocity, vN/vo. For the in vitro investigations, flow rates from 4.3 to 150 cm3/sec through 0.3 and 1.0 cm2 circular orifices were imaged with color Doppler with aliasing velocities from 19 to 36 cm/sec. Overall, the calculated flow (assuming hemispheric symmetry) correlated well with the true flow, Qc = 0.88Qo-7.82 (r = 0.945, SD = 12.2 cm3/sec, p less than 0.0001, n = 48), but progressively underestimated flow when the vN approached the orifice velocity vo. Applying a correction factor predicted by the numerical modeling, delta Q was improved from -13.81 +/- 13.01 cm3/sec (mean +/- SD) to +1.54 +/- 5.67 cm3/sec.(ABSTRACT TRUNCATED AT 250 WORDS)

New perspectives in the assessment of cardiac chamber dimensions during development and adulthood

The use of body surface area to assess the normalcy of cardiac dimensions has several limitations. To determine whether cardiac dimensions can be assessed by other indexes of body size and growth, this study evaluated the relations between cardiac dimensions assessed by two-dimensional echocardiography and age, height, weight and body surface area. The study group included 268 normal persons aged 6 days to 76 years of age. The dimensions examined included the aortic anulus, left atrium and left ventricular end-diastolic diameter, each measured in the parasternal long-axis plane, and left ventricular length measured from the apical two-chamber view. The analysis confirmed that the heart and great vessels grow in unison and at a predictable rate after birth, reaching 50% of their adult dimensions at birth, 75% by 5 years and 90% by 12 years. Although each cardiac dimension related linearly with height (aortic anulus, r = 0.96; left atrium, r = 0.91; left ventricular diameter, r = 0.94; left ventricular length, r = 0.93), the relations among age, weight and body surface area were best expressed by quadratic equations. Multiple regression confirmed that after adjustment for height, other indexes including age, gender, weight and body surface area had no independent effect on the prediction of each dimension. Therefore, because height is a nonderived variable that relates linearly with cardiac dimensions independent of age, it offers a simple yet accurate means of assessing the normalcy of cardiac dimensions in children and adults.

Calculation of atrioventricular compliance from the mitral flow profile: analytic and in vitro study

The quantitative assessment of ventricular diastolic function is an important goal of Doppler echocardiography. Hydrodynamic analysis predicts that the net compliance (Cn) of the left atrium and ventricle can be quantitatively predicted from the deceleration rate (dv/dt) of the mitral velocity profile by the simple expression: Cn = - A/rho dv/dt, where A is effective mitral valve area and rho is blood density. This formula was validated using an in vitro model of transmitral filling where mitral valve area ranged from 0.5 to 2.5 cm2 and net compliance from 0.012 to 0.023 cm3/(dynes/cm2) (15 to 30 cm3/mm Hg). In 34 experiments in which compliance was held constant throughout the filling period, net atrioventricular compliance was accurately calculated from the E wave downslope and mitral valve area (r = 0.95, p less than 0.0001). In a second group of experiments, chamber compliance was allowed to vary as a function of chamber pressure. When net compliance decreased during diastole (as when the ventricle moved to a steeper portion of its pressure-volume curve), the transorifice velocity profile was concave downward, whereas when net compliance increased, the velocity profile was concave upward. Application of the preceding formula to these curved profiles allowed instantaneous compliance to be calculated throughout the filling period (r = 0.93, p less than 0.001). Numeric application of a mathematic model of mitral filling demonstrated the accuracy of this approach in both restrictive and nonrestrictive orifices.(ABSTRACT TRUNCATED AT 250 WORDS)

Papillary muscle traction in mitral valve prolapse: quantitation by two-dimensional echocardiography

Previous angiographic observations in patients with mitral valve prolapse have suggested that superior leaflet displacement results in abnormal superior tension on the papillary muscle tips that causes their superior traction or displacement. It has further been postulated that such tension can potentially affect the mechanical and electrophysiologic function of the left ventricle. The purpose of this study was to confirm and quantitate this phenomenon noninvasively by using two-dimensional echocardiography to determine whether superior displacement of the papillary muscle tips occurs and its relation to the degree of mitral leaflet displacement. Directed echocardiographic examination of the papillary muscles and mitral anulus was carried out in a series of patients with classic mitral valve prolapse and results were compared with those in a group of normal control subjects. Distance from the anulus to the papillary muscle tip was measured both in early and at peak ventricular systole. In normal subjects, this distance did not change significantly through systole, whereas in the patient group it decreased, corresponding to a superior displacement of the papillary muscle tips toward the anulus in systole (8.5 +/- 2.6 vs. 0.8 +/- 0.7 mm; p less than 0.0001). This superior papillary muscle motion paralleled the superior displacement of the leaflets in individual patients (y = 1.0x + 0.8; r = 0.93) and followed a similar time course.(ABSTRACT TRUNCATED AT 250 WORDS)

Unusual sequelae after percutaneous mitral valvuloplasty: a Doppler echocardiographic study

Percutaneous mitral valvuloplasty is a promising new technique for the treatment of mitral stenosis, with a relatively low complication rate reported to date. To assess the sequelae of this procedure, Doppler echocardiographic studies were prospectively performed before and after percutaneous mitral valvuloplasty in a series of 172 patients (mean age 53 +/- 17 years). After balloon dilation, mitral valve area increased from 0.9 +/- 0.3 to 2 +/- 0.8 cm2 (p less than 0.0001), mean gradient decreased from 16 +/- 6 to 6 +/- 3 mm Hg (p less than 0.0001) and mean left atrial pressure decreased from 24 +/- 7 to 14 +/- 6 mm Hg (p less than 0.0001). Although most patients were symptomatically improved, six (4%) were identified who had unusual sequelae evident on Doppler echocardiographic examination immediately after percutaneous mitral valvuloplasty. These included rupture of a posterior mitral valve leaflet, producing a flail distal leaflet portion with severe mitral regurgitation detected on Doppler color flow mapping (n = 1); asymptomatic rupture of the chordae tendineae attached to the anterior mitral valve leaflet with systolic anterior motion of the ruptured chordae into the left ventricular outflow tract (n = 1); a double-orifice mitral valve (n = 1); and evidence of a tear in the anterior mitral valve leaflet (n = 3), producing on both pulsed Doppler ultrasound and color flow mapping a second discrete jet of mitral regurgitation in addition to regurgitation through the main mitral valve orifice. All six patients made a satisfactory recovery and none has required mitral valve replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Numerical modeling of ventricular filling

The fluid dynamical and physiological assumptions underlying general mathematical modeling of ventricular filling are outlined. We then describe the use of a lumped parameter model and computer simulation to study how the early transmitral velocity profile is affected by isolated changes in ventricular compliance and relaxation, atrial pressure and compliance, and valvular morphology. We show that the transmitral velocity is fundamentally affected by two physical determinants: the transmitral pressure difference and the net compliance of the atrium and the ventricle. These physical determinants in turn are specified by the various physiologic parameters of interest. This approach has shown that peak velocity is most strongly affected by initial left atrial pressure, lowered somewhat by prolonged relaxation, low atrial and ventricular compliance, and systolic dysfunction. Peak acceleration is directly affected by atrial pressure and inversely affected by the time constant of isovolumic relaxation, with little influence of compliance, whereas the deceleration rate is almost purely given by mitral valve area divided by instantaneous atrioventricular compliance at the end of the rapid filling wave.

Patterns of normal transvalvular regurgitation in mechanical valve prostheses

The magnitude and spatial distribution of normal leakage through mechanical prosthetic valves were studied in an in vitro model of mitral regurgitation. The effective regurgitant orifice was calculated from regurgitant rate at different transvalvular pressure differences and flow velocities. This effective orifice area was 0.6 to 2 mm2 for three tilting disc prostheses (Medtronic-Hall sizes 21, 25 and 29) and 0.2 to 1.1 mm2 for three bileaflet valves (St. Jude Medical sizes 21, 25 and 33). In the single disc valves, Doppler color flow examination disclosed a prominent central regurgitant jet around the central hole for the strut, accompanied by minor leakage along the rim of the disc (central to peripheral jet area ratio 3.3 +/- 1.2). The bileaflet prostheses showed a peculiar complex pattern: in planes parallel to the two disc axes, convergent peripherally arising jets were visualized, whereas in orthogonal planes several diverging jets were seen. Mounting the disc and bileaflet valves on a water-filled tube allowed reproduction and interpretation of this pattern: for the bileaflet valve, the jets originated predominantly from valve ring protrusions that contained the axis hinge points and created a converging V pattern in planes parallel to the leaflets and a diverging V pattern in orthogonal planes. Similar patterns were observed during transesophageal echocardiography in 20 patients with a normally functioning St. Jude prosthesis. In 10 patients with a Medtronic-Hall valve, a dominant central jet was observed with one or more smaller peripheral jets. The median central to peripheral jet area ratio was 5 to 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic assessment of patients with infectious endocarditis: prediction of risk for complications

To enhance the echocardiographic identification of high risk lesions in patients with infectious endocarditis, the medical records and two-dimensional echocardiograms of 204 patients with this condition were analyzed. The occurrence of specific clinical complications was recorded and vegetations were assessed with respect to predetermined morphologic characteristics. The overall complication rates were roughly equivalent for patients with mitral (53%), aortic (62%), tricuspid (77%) and prosthetic valve (61%) vegetations, as well as for those with nonspecific valvular changes but no discrete vegetations (57%), although the distribution of specific complications varied considerably among these groups. There were significantly fewer complications in patients without discernible valvular abnormalities (27%). In native left-sided valve endocarditis, vegetation size, extent, mobility and consistency were all found to be significant univariate predictors of complications. In multivariate analysis, vegetation size, extent and mobility emerged as optimal predictors and an echocardiographic score based on these factors predicted the occurrence of complications with 70% sensitivity and 92% specificity in mitral valve endocarditis and with 76% sensitivity and 62% specificity in aortic valve endocarditis.

The effects of regurgitant orifice size, chamber compliance, and systemic vascular resistance on aortic regurgitant velocity slope and pressure half-time

The determinants of the aortic regurgitant velocity profile have been investigated using computer and in vitro simulations in which regurgitant orifice area, ventricular and aortic compliance, and systemic vascular resistance could be independently varied. In the study, regurgitant fraction was altered, either by changing the size of the regurgitant orifice or by holding the regurgitant orifice constant and changing chamber compliance or systemic vascular resistance. Upon increasing regurgitant fraction by increasing the size of the regurgitant orifice, the slope got steeper and the pressure half-time shortened, the response anticipated in current clinical practice. However, when the regurgitant orifice was kept constant and regurgitation fraction was increased by increasing the systemic vascular resistance or by increasing the compliance of the left ventricle, slope became less steep and pressure half-time lengthened. Multivariate analysis was used to quantify the relationship of regurgitant fraction to slope and pressure half-time. When orifice area was allowed to vary, slope was related directly (multiple r = 0.78, p less than 0.001) and half-time was related inversely (multiple r = 0.66, p less than 0.001) to regurgitant fraction. With the orifice area fixed, however, directionally opposite responses were seen; slope varied inversely (multiple r = 0.87, p less than 0.001), whereas half-time varied directly (multiple r = 0.88, p less than 0.001) with regurgitant fraction. This study suggests that the utility of the slope and pressure half-time of the regurgitant velocity tracing in clinical practice relates to their ability to discriminate regurgitant orifices of differing sizes.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of impinging wall jet on color Doppler quantification of mitral regurgitation

BACKGROUND

In clinical color Doppler examinations, mitral regurgitant jets are often observed to impinge on the left atrial wall immediately beyond the mitral valve. In accordance with fluid dynamics theory, we hypothesized that a jet impinging on a wall would lose momentum more rapidly, undergo spatial distortion, and thus have a different observed jet area from that of a free jet with an identical flow rate.

METHODS AND RESULTS

To test this hypothesis in vivo, we studied 44 patients with mitral regurgitation--30 with centrally directed free jets and 14 with eccentrically directed impinging wall jets. Maximal color jet areas (cm2) (with and without correction for left atrial size) were correlated with mitral regurgitant volumes, flow rates, and fractions derived from pulsed Doppler mitral and aortic forward flows. The groups were compared by analysis of covariance. Mean +/- SD mitral regurgitant fraction, regurgitant volume, and mean flow rate averaged 37 +/- 17%, 3.06 +/- 2.65 l/min, and 147 +/- 118 ml/sec, respectively. The maximal jet area from color Doppler imaging correlated relatively well with the mitral regurgitant fraction in the patients with free mitral regurgitant jets (r = 0.74, p less than 0.0001) but poorly in the patients with impinging wall jets (r = 0.42, p = NS). Although the mitral regurgitant fraction was larger (p less than 0.05) in patients with wall jets (44 +/- 20%) than in those with free jets (33 +/- 15%), the maximal jet area was significantly smaller (4.78 +/- 2.87 cm2 for wall jets versus 9.17 +/- 6.45 cm2 for free jets, p less than 0.01). For the same regurgitant fraction, wall jets were only approximately 40% of the size of a corresponding free jet, a difference confirmed by analysis of covariance (p less than 0.0001).

CONCLUSIONS

Patients with mitral regurgitation frequently have jets that impinge on the left atrial wall close to the mitral valve. Such impinging wall jets are less predictable and usually have much smaller color Doppler areas in conventional echocardiographic views than do free jets of similar regurgitant severity. Jet morphology should be considered in the semiquantitative interpretation of mitral regurgitation by Doppler color flow mapping. Future studies of the three-dimensional morphology of wall jets may aid in their assessment.

Quantitative relation between increased intrapericardial pressure and Doppler flow velocities during experimental cardiac tamponade

To establish whether a quantitative relation exists between pericardial pressure and respiratory variation in intracardiac blood flow velocities, a spontaneously breathing closed chest canine model of pericardial tamponade was created. In seven dogs, pericardial pressure was sequentially increased in stages from a mean of -4 +/- 1 to 10 +/- 2 mm Hg while aortic and pulmonary Doppler flow velocities, pleural pressure changes (respiratory effort), blood pressure and cardiac output were measured. The variation in the Doppler-detected peak transaortic velocity (AV) during inspiration (IV) increased linearly from -5 +/- 3% at baseline (pericardial pressure -4 mm Hg) to -32 +/- 9% at a pericardial pressure of 10 mm Hg [IVAV = -2 (pericardial pressure)--13.1; r = 0.78, p less than 10(-6)]. The inspiratory variation in the peak transpulmonary velocity increased from 13 +/- 3% at baseline to 71 +/- 19% at a pericardial pressure of 10 mm Hg. The inspiratory variation in the pulmonary Doppler peak velocity (IVPV) was dependent on both pericardial pressure and degree of respiratory effort [IVPV = 3.8 (pericardial pressure) + 2.6 (respiratory effort) + 10.9; r = 0.88, p less than 10(-8)]. Thus, quantitative relations exist between increases in intrapericardial pressure and increases in inspiratory variation of peak aortic and pulmonary flow velocities. Additionally, pulmonary artery flow velocity is influenced more than aortic velocity by intrathoracic pressure.

Noninvasive estimation of the instantaneous first derivative of left ventricular pressure using continuous-wave Doppler echocardiography

BACKGROUND

The complete continuous-wave Doppler mitral regurgitant velocity curve should allow reconstruction of the ventriculoatrial (VA) pressure gradient from mitral valve closure to opening, including left ventricular (LV) isovolumic contraction, ejection, and isovolumic relaxation. Assuming that the left atrial pressure fluctuation is relatively minor in comparison with the corresponding LV pressure changes during systole, the first derivative of the Doppler-derived VA pressure gradient curve (Doppler dP/dt) might be used to estimate the LV dP/dt curve, previously measurable only at catheterization (catheter dP/dt).

METHODS AND RESULTS

This hypothesis was examined in an in vivo mitral regurgitant model during 30 hemodynamic stages in eight dogs. Contractility and relaxation were altered by inotropic stimulation and hypothermia. The Doppler mitral regurgitant velocity spectrum was recorded along with simultaneously acquired micromanometer LV and left atrial pressures. The regurgitant velocity profiles were digitized and converted to VA pressure gradient curves using the simplified Bernoulli equation. The instantaneous dP/dt of the VA pressure gradient curve was then derived. The instantaneous Doppler-derived VA pressure gradients, instantaneous Doppler dP/dt, dP/dtmax, and -dP/dtmax were compared with corresponding catheter measurements. This method of estimating dP/dtmax from the instantaneous dP/dt curve was also compared with a previously proposed Doppler method of estimating dP/dtmax using the Doppler-derived mean rate of LV pressure rise over the time period between velocities of 1 and 3 m/sec on the ascending slope of the Doppler velocity spectrum. Both instantaneous Doppler-derived VA pressure gradients (r = 0.95, p less than 0.0001) and Doppler dP/dt (r = 0.92, p less than 0.0001) correlated well with corresponding measurements by catheter during systolic contraction and isovolumic relaxation (pooled data). The Doppler dP/dtmax (1,266 +/- 701 mm Hg/sec) also correlated well (r = 0.94) with the catheter dP/dtmax (1,200 +/- 573 mm Hg/sec). There was no difference between the two methods for measurement of dP/dtmax (p = NS). Although Doppler -dP/dtmax was slightly lower than the catheter measurement (961 +/- 511 versus 1,057 +/- 540 mm Hg/sec, p less than 0.01), the correlation between measurements by Doppler and catheter was excellent (r = 0.93, p less than 0.0001). The alternative method of mean isovolumic pressure rise (896 +/- 465 mm Hg/sec) underestimated the catheter dP/dtmax (1,200 +/- 573 mm Hg/sec) significantly (on average, 25%; p less than 0.001).

CONCLUSIONS

The present study demonstrated an accurate and reliable noninvasive Doppler method for estimating instantaneous LV dP/dt, dP/dtmax, and -dP/dtmax.

Physical and physiological determinants of transmitral velocity: numerical analysis

The Doppler transmitral velocity curve is commonly used to assess left ventricular diastolic function. Recent investigations, however, relating Doppler mitral indexes to ventricular compliance, relaxation, and preload have been inconclusive and at times contradictory. We used a mathematical formulation to study the physical and physiological determinants of the transmitral velocity pattern for exponential chamber pressure-volume relationships with active ventricular relaxation (2,187 combinations investigated). We showed that transmitral velocity is fundamentally affected by two principal physical determinants, the transmitral pressure difference and the net atrioventricular compliance, as well as the impedance characteristics of the mitral valve. These physical determinants in turn are specified by the compliance and relaxation parameters of physiological interest. We found that the peak mitral velocity is most strongly related to initial left atrial pressure but lowered by prolonged relaxation, low atrial and ventricular compliance, and systolic dysfunction. Peak acceleration varies directly with atrial pressure and inversely with the time constant of isovolumic relaxation, with little influence of compliance, whereas the mitral deceleration rate is approximately valve area divided by atrioventricular compliance. We then used these data to suggest possible strategies for improved analysis of noninvasive data (Doppler indexes, planimetered valve area, and isovolumic relaxation time) to estimate ventricular compliance and relaxation and atrial pressure.

Effects of prolonged transesophageal echocardiographic imaging and probe manipulation on the esophagus--an echocardiographic-pathologic study

Transesophageal echocardiography is being increasingly utilized in the operating room and intensive care and ambulatory settings. However, to date no data are available concerning possible trauma of the transesophageal echocardiographic technique to the esophagus due to probe insertion, manipulation or direct ultrasound energy transmission. To test the hypothesis that transesophageal manipulations caused no traumatic or thermal injury to the esophageal mucosa, 12 animals were studied with continuous transesophageal echocardiography for a period of variable duration (mean 4.6 h +/- 51 min). The study group consisted of four monkeys (mean weight 5.7 +/- 0.6 kg and eight mongrel dogs (mean weight 29.8 +/- 1.4 kg). The eight dogs were studied during right heart bypass with full heparinization for 6.6 +/- 0.2 h, whereas the four monkeys were studied for 60 to 90 min in the absence of cardiopulmonary bypass and anticoagulation. Immediately after completion of transesophageal echocardiography in each case, the esophagus was entirely excised. Detailed macroscopic and microscopic examination of the esophagus revealed no significant mucosal or thermal injury. This preliminary animal study suggests that transesophageal echocardiography is safe for the esophageal mucosa in animals as small as 5 kg in weight, despite prolonged use and in the presence of systemic anticoagulation.

Adjacent solid boundaries alter the size of regurgitant jets on Doppler color flow maps

Recent studies have attempted to predict the severity of regurgitant lesions from jet size on Doppler flow maps. Jet size is a function of both regurgitant volume and fluid entrained from the receiving chamber and, for a free jet, is a function of its momentum at the orifice. However, regurgitant jets often approach or attach to cardiac walls, potentially altering their momentum and ability to expand by entrainment. Therefore, this study addressed the hypothesis that adjacent walls influence regurgitant jet size as seen on Doppler flow maps. Steady flow was driven through circular orifices (0.02 to 0.05 cm2) at physiologic velocities of 2 to 5 m/s. At a constant flow rate and orifice velocity, orifice position was varied to produce three jet geometries: free jets, jets adjacent to a horizontal chamber wall lying 1 cm below the orifice and wall jets with the orifice at the level of the wall. Doppler color flow imaging was performed at identical instrument settings for all jets. Two long-axis views of the jet were obtained: a vertical view perpendicular to the wall, resembling that most commonly used in patients to image the length of the jet, and a horizontal view parallel to the chamber wall. Velocities along the jet were also measured by Doppler mapping.(ABSTRACT TRUNCATED AT 250 WORDS)