Clinical value of Doppler echocardiography in the assessment of adults with aortic stenosis

Let there be light! The meteoric rise of cardiac imaging

Imaging plays a central role in modern cardiovascular practice. It is a field characterised by exciting technological advances that have shaped our understanding of pathology and led to major improvements in patient diagnosis and care. The UK has played a key international role in the development of this subspecialty and is the current home to many of the leading global centres in multimodality cardiovascular imaging. In this short review, we will outline some of the key contributions of the British Cardiovascular Society and its members to this rapidly evolving field and look at how this relationship may continue to shape future cardiovascular practice.

Performance Assessment of Row-Column Transverse Oscillation Tensor Velocity Imaging Using Computational Fluid Dynamics Simulation of Carotid Bifurcation Flow

In this work, the accuracy of row-column tensor velocity imaging (TVI), i.e., 3-D vector flow imaging (VFI) in 3-D space over time, is quantified on a complex, clinically relevant flow. The quantification is achieved by transferring the flow simulated using computational fluid dynamics (CFD) to a Field II simulation environment, and this allows for a direct comparison between the actual and estimated velocities. The carotid bifurcation flow simulations were performed with a peak inlet velocity of 80 cm/s, nonrigid vessel walls, and a flow cycle duration of 1.2 s. The flow was simulated from two observation angles, and it was acquired using a 3-MHz 62+62 row-column addressed array (RCA) at a pulse repetition frequency ( f_prf ) of 10 and 20 kHz. The tensor velocities were obtained at a frame rate of 208.3 Hz, at f_prf = 10 kHz , and the results from two velocity estimators were compared. The two estimators were the directional transverse oscillation (TO) cross correlation estimator and the proposed autocorrelation estimator. Linear regression between the actual and estimated velocity components yielded, for the cross correlation estimator, an R ² value in the range of 0.89-0.91, 0.46-0.77, and 0.91-0.97 for the x -, y -, and z -components, and 0.87-0.89, 0.40-0.83, and 0.91-0.96 when using the autocorrelation estimator. The results demonstrate that an RCA can, with just 62 receive channels, measure complex 3-D flow fields at a high volume rate.

Outcome predictors of ultrafiltration in patients with refractory congestive heart failure and renal failure

This study is an attempt to identify predictors of outcome from the use of ultrafiltration (UF) in patients with refractory congestive heart failure (CHF) and renal failure. The authors studied 30 patients in NYHA functional class IV in whom UF was utilized in the management of refractory CHF. Patients were retrospectively divided into two groups according to their outcome. Group A included 12 patients who improved and survived hospital admission, and group B included 18 patients who did not respond and died shortly after UF. Clinical, hemodynamic, and laboratory data before UF were fairly comparable between both groups. Renal function and hemodynamic parameters were compared and analyzed within the same group and between both groups before and after UF. The mean age in group A was sixty-three +/- thirteen years while in group B it was seventy +/- eleven years (P < 0.005). A mean of 9.6 liters of fluid were removed from group A and 3.2 liters from group B (P < 0.001). Group A showed greater reduction in the mean values of right atrial pressure (P < 0.005) and pulmonary capillary wedge pressure (P < 0.05) after UF. Additionally, group A showed a significant decrease in their blood urea nitrogen (P < 0.05) and serum creatinine values (P < 0.05), in contradistinction to group B patients who showed a major increase in those values after UF. There was no significant change in the mean values of cardiac index, systemic vascular resistance, and pulmonary vascular resistance after UF. These findings suggest that younger age groups, greater fluid removal, as well as significant decreases in blood urea nitrogen, serum creatinine, and right atrial and pulmonary wedge pressures after UF, are associated with favorable outcome. Conversely, older age groups, less fluid removal, and rising blood urea nitrogen and serum creatinine levels after UF were associated with poor outcome.

Effect of Doppler echocardiography on utilization of hemodynamic cardiac catheterization in the preoperative evaluation of aortic stenosis

OBJECTIVE

To examine the use of Doppler echocardiography in preoperative assessment of aortic stenosis and to determine its effect on subsequent use of hemodynamic cardiac catheterization.

MATERIAL AND METHODS

We retrospectively reviewed a consecutive series of 574 adult patients who underwent aortic valve replacement for aortic stenosis between 1990 and 1992 at our institution. The use of Doppler echocardiography and cardiac catheterization and the predictive factors for use of hemodynamic catheterization were analyzed.

RESULTS

After Doppler echocardiography in 423 patients, invasive hemodynamic assessment of the severity of aortic stenosis was performed in only 42% (179 patients). The use of cardiac catheterization declined over time (54% in 1990, 40% in 1991, and 35% in 1992) (P = 0.003), whereas no significant change in the baseline clinical characteristics of the population or in severity of stenosis as determined by Doppler echocardiography occurred during that time. Multivariate analysis identified the following variables as independent predictors of use of cardiac catheterization after Doppler echocardiography: clinically not severe aortic stenosis, mean gradient of less than 50 mm Hg determined by Doppler echocardiography, Doppler-determined aortic valve area of more than 0.8 cm2 or not calculated, attending cardiologist not specialized in echocardiography, and earlier year of assessment.

CONCLUSION

After Doppler echocardiography, less than 50% of our patients undergoing aortic valve replacement for aortic stenosis have cardiac catheterization preoperatively. The use of cardiac catheterization after Doppler echocardiography--thus, duplication of hemodynamic assessment--declined significantly over time during the study period. Decline in the use of catheterization is related to the degree of diagnostic certainty provided by Doppler echocardiography and to the level of familiarity of the attending cardiologist with the technique.

Clinical and hemodynamic evaluation of the 19-mm Carpentier-Edwards supraannular aortic valve

The clinical and hemodynamic performance of the 19-mm Carpentier-Edwards supraannular aortic valve is largely unknown compared with that of the larger valves. Over 4 years we implanted the 19-mm Carpentier-Edwards supraannular aortic valve into 21 patients (20 female) with a mean age of 75 +/- 1.2 years (range, 59 to 86 years) and a mean body surface area of 1.6 +/- 0.03 m2 (range, 1.3 to 1.7 m2). There were four deaths, one operative and three late noncardiac deaths. Follow-up of the 17 survivors for a mean of 20 +/- 3.1 months (range, 2 to 42 months) demonstrated symptomatic improvement in all 17 (all are now in New York Heart Association functional class I or II). There were no valve-related complications and no patient required long-term anticoagulation. Doppler echocardiographic studies were used to assess the in vivo hemodynamic profile of the valve. Mean postoperative aortic valve gradient was 34.1 +/- 2.7 mm Hg (range, 19 to 52 mm Hg). Functional valve orifice area was 1.1 +/- 0.09 cm2 (range, 0.6 to 1.8 cm2). Mean cardiac output was 3.92 +/- 0.17 L/min (range, 3.2 to 5.1 L/min) with a mean cardiac index of 2.5 +/- 0.11 L.min-1 x m-2 (range, 2.1 to 3.2 L.min-1 x m-2). In conclusion, we have demonstrated that aortic valve replacement with the 19-mm Carpentier-Edwards supraannular aortic valve has a low operative mortality and offers major clinical benefits despite moderate transprosthetic gradients. This approach provides an alternative management strategy in elderly patients who would otherwise require low-profile mechanical valves or aortic root enlargement.

Subclavian artery stenosis masquerading as prosthetic aortic stenosis: a potential source of confusion in Doppler evaluation of aortic valve disease

In this case report we describe a patient with a prosthetic aortic valve in whom a high-velocity signal from a right subclavian artery stenosis initially was mistaken for the aortic jet signal. Differences in the shapes of the jets obtained from an apical and right supraclavicular position suggested different origins of these two high-velocity systolic signals. Correct identification of the origin of each signal was possible with pulsed Doppler recordings of the subclavian artery and high pulse-repetition-frequency pulsed Doppler interrogation of the aortic valve.

Colour Doppler flow mapping: providing an insight into cardiac hydrodynamics

Colour Doppler flow mapping can now provide spatial velocity information in relation to surrounding structural detail as imaged by conventional echocardiography and, as such, represents a major advance in non-invasive cardiac imaging. This article describes the basic principles of colour Doppler flow mapping, details how the Doppler information is processed and displayed to arrive at the real-time two-dimensional flow-enhanced image. Since colour Doppler flow mapping is really the first available technique which allows detailed real-time velocity information to be displayed in vivo and in relation to intracardiac structures, it can allow important insight into the haemodynamics of intracardiac flow. With the application of digital computer analysis techniques it may also be possible to extract valuable quantitative information from colour Doppler flow mapping.

Blood flow: insights from ultrasound

Ultrasonic pulse-echo systems can provide range-finding, time-position and real-time two-dimensional images of soft-tissue structures within the body. The Doppler effect can be used to study motion and blood flow. Continuous wave Doppler instruments provide information about velocity and direction of flow; depth discrimination can be obtained by pulsing the ultrasound. Two-dimensional Doppler flow imaging can be achieved by manual scanning of a probe over the skin surface. The combination of real-time pulse-echo imaging with pulsed Doppler blood flow detection in the duplex scanner makes it possible to localize the anatomical position of the Doppler sample volume. Real-time Doppler colour flow imaging combines traditional ultrasonic scanning with a two-dimensional flow map. Using appropriate ultrasonic instruments, blood flow volume rates, blood flow velocity profiles, pressure gradients, orifice areas, flow disturbances, jets, characteristics of blood vessels and the circulatory system, and tissue perfusion can all be investigated. These investigations have clinical applications in the study of cardiac, cerebral and peripheral blood flow, blood flow in the female pelvis, the fetus, the abdomen, the neonate, and in malignant tumours. Contemporary ultrasonic diagnosis employs exposure levels that are apparently free from biological risk, but other factors need to be taken into account in considering the prudent use of ultrasonic methods. Promising research is being carried out into the mechanism of ultrasonic scattering by blood, Doppler speckle, time-domain processing for blood flow imaging, methods for increasing the scanning speed, Doppler flow microscopy and contrast agents. The new technology that will result from this research should lead to further substantial progress in ultrasonic blood flow studies.

Colour Doppler flow mapping

Images

Valvar stenosis: a comparison of clinical assessment, echocardiography, Doppler ultrasound and catheterisation

The relative merits of noninvasive techniques in the assessment of valve stenosis were examined by comparing the results of clinical assessment by two independent clinicians, the cross-sectional echocardiogram and Doppler ultrasound using the results of cardiac catheterisation as reference in 58 patients with a total of 60 stenotic valve lesions. Doppler ultrasound was the most reliable technique; it was correct in 57 (95%) of the 60 lesions. Clinical assessment and cross sectional echocardiography were correct in 48 (80%), and 46 (77%) of the 60 lesions, respectively. In 7 instances 2 noninvasive assessments were wrong in the same patient but on no occasion were all 3 techniques misleading in the same patient. In 17 patients with severe mitral stenosis, clinical assessment Doppler ultrasound and cross-sectional echocardiography were correct in 14 (82%), 16 (94%) and 17 (100%) patients, respectively, whilst in the 4 patients with moderate mitral stenosis the corresponding figures were 3 (75%), 4 (100%) and 2 (50%). In mild mitral stenosis (3 patients), the clinical assessment was correct in 2 (67%) patients, Doppler ultrasound in 3 (100%) patients and cross-sectional echocardiography in 2 (67%) patients. In 22 patients with severe aortic stenosis, the clinical assessment and Doppler ultrasound were correct in every patient (100%), whilst the cross-sectional echocardiogram was correct in 18 (82%) patients. In 11 patients with moderate aortic stenosis, the clinical assessment was correct in only 5 (45%) patients, the cross-sectional echocardiogram in 5 (45%) patients and Doppler assessment in 9 (82%) patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler color flow mapping of simulated in vitro regurgitant jets: evaluation of the effects of orifice size and hemodynamic variables

The spatial distribution of simulated regurgitant jets imaged by Doppler color flow mapping was evaluated under constant flow and pulsatile flow conditions. Jets were simulated through latex tubings of 3.2, 4.8, 6.35 and 7.9 mm by varying flow rates from 137 to 1,260 cc/min. Color jet area was linearly related to flow rate at each orifice (r = 0.96, SEE = 3.4; r = 0.99, SEE = 1.6; r = 0.97, SEE = 2.3; r = 0.97, SEE = 3.2, respectively), but significantly higher flow rates were required to maintain the same maximal spatial distribution of the jet at the larger regurgitant orifices. Constant flow jets were also simulated through needle orifices of 0.2, 0.5 and 1 mm, with a known total volume (5 cc) injected at varying flow rates and with differing absolute volumes injected at the same flow rate (0.2, 1.0 and 2.0 cc/s, respectively). Again, maximal color jet area was linearly related to flow rate at each orifice (r = 0.97, SEE = 2.3; r = 0.97, SEE = 2.4; r = 0.92, SEE = 3.9, respectively), but was not related to the absolute volume of regurgitation. Color encoding of regurgitant jets on Doppler color flow maps was demonstrated to be highly dependent on velocity and, hence, driving pressure, such that color encoding was obtained from a constant flow jet injected at a velocity of 4 m/s through an orifice of 0.04 mm diameter with flow rates as low as 0.008 cc/s. Mitral regurgitant jets were also simulated in a physiologic in vitro pulsatile flow model through three prosthetic valves with known regurgitant orifice sizes (0.2, 0.6 and 2.0 mm2). For each regurgitant orifice size, color jet area at each was linearly related to a regurgitant pressure drop (r = 0.98, SEE = 0.15; r = 0.97, SEE = 0.20; r = 0.97, SEE = 0.23, respectively), regurgitant stroke volume (r = 0.77, SEE = 0.55; r = 0.94, SEE = 0.30; r = 0.91, SEE = 0.41, respectively) and peak regurgitant flow rate (r = 0.98, SEE = 0.16; r = 0.97, SEE = 0.21; r = 0.93, SEE = 0.37, respectively), but the spatial distribution of the regurgitant jets was most highly dependent on the regurgitant pressure drop. Jet kinetic energy calculated from the summation of the individual pixel intensities integrated over the jet area was closely related to driving pressure (r = 0.84), but integration of the power mode area times pixel intensities provided the best estimation of regurgitant stroke volume (r = 0.80).(ABSTRACT TRUNCATED AT 400 WORDS)

Spatial velocity distribution and acceleration in serial subvalve tunnel and valvular obstructions: an in vitro study using Doppler color flow mapping

To evaluate the spatial distribution of flow velocities, turbulence and spatial acceleration in serial tunnel-valve obstruction, Doppler color flow mapping was performed in a pulsatile flow model with a tunnel obstruction (1.0 or 1.5 cm2) inserted at 2, 20 and 40 mm proximal to a mildly stenotic bioprosthetic valve studied at flow rates of 1, 2.7 and 4.9 liters/min. Measured pressure gradients were consistently higher across the tunnel (mean +/- SD 32.7 +/- 26.5 mm Hg) than across the tunnel plus valve (28.8 +/- 26.9 mm Hg, p less than 0.01). Doppler color flow map images were analyzed using a Sony RGB video-digitizing computer, providing numerical velocity assignments for the blue, red and green (variance) pixel components to allow the flow maps to be constructed into digital velocity maps and pseudo three-dimensional velocity maps. The maximal velocity stream extended distal to the tunnel (2 to 19 mm), and the length of this extension correlated well with the pressure gradient measured across the tunnel (r = 0.89), with a rapidly decelerating and turbulent spray area seen immediately distal to the valve. Pressure gradient calculated from the maximal velocity derived from the color flow map, which could only be estimated from the velocity maps for the 1.5 cm2 tunnel, correlated well with the gradient measured across the tunnel (18.0 +/- 14.1 versus 19.2 +/- 14.5 mm Hg, respectively, r = 0.98). Acceleration was seen proximal to both tunnels.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental validation of Doppler echocardiographic measurement of volume flow through the stenotic aortic valve

In aortic stenosis, evaluation of aortic valve area by the continuity equation assumes that the volume of flow through the stenotic valve can be measured accurately in the left ventricular outflow tract. To test the accuracy of Doppler volume-flow measurement proximal to a stenotic valve, we developed an open-chest canine model in which the native leaflets were sutured together to create variable degrees of acute aortic stenosis. Left ventricular and aortic pressures were measured with micromanometer-tipped catheters. Volume flow was controlled and varied by directing systemic venous return through a calibrated roller pump and back to the right atrium. Because transaortic volume flow will not equal roller pump output when there is coexisting aortic insufficiency (present in 67% of studies), transaortic flow was measured by electromagnetic flowmeter with the flow probe placed around the proximal descending thoracic aorta, just beyond the ligated arch vessels. In 12 adult, mongrel dogs (mean weight, 25 kg), the mean transaortic pressure gradient ranged from 2 to 74 mm Hg, and transaortic volume flow ranged from 0.9 to 3.2 l/min. In four dogs, electromagnetic flow that was measured distal to the valve was accurate compared with volume flow determined by timed collection of total aortic flow into a graduated cylinder (n = 24, r = 0.97, electromagnetic flow = 0.87 Direct +0.13 l/min). In eight subsequent dogs, electromagnetic flow was compared with transaortic cardiac output measured by Doppler echocardiography in the left ventricular outflow tract as circular cross-sectional area [pi(D/2)2] x left ventricular outflow tract velocity-time integral x heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Limitations in assessing the severity of aortic stenosis by Doppler gradients

Continuous wave Doppler echocardiography was performed before cardiac catheterisation in 69 consecutive patients with suspected aortic stenosis. Agreement between the maximum and the mean Doppler gradients and catheterisation gradients was good. Doppler echocardiography, however, systematically underestimated the maximum and mean gradients, particularly in the high range. Stepwise regression analysis of the small pressure difference between the two methods showed that it could not be explained by age, sex, stroke volume, differences in heart rate, ejection fraction, the presence of coronary artery disease, or severity of aortic regurgitation. There was a negative curvilinear correlation between the maximum and mean Doppler gradients and the aortic valve areas that were measured at catheterisation in patients with pure aortic stenosis. The degree of correlation decreased when patients with concomitant aortic regurgitation were included. The scatter of gradients above and below the correlation line was large and this was caused by low and high transvalvar flow. These results show that the usefulness of Doppler gradients for judging the severity of aortic stenosis, both in relation to immediate diagnosis and follow up, is severely limited if transvalvar flow is not taken into account.

Color Doppler flow mapping in patients with coarctation of the aorta: new observations and improved evaluation with color flow diameter and proximal acceleration as predictors of severity

We performed color Doppler flow mapping in 15 patients, 1 week to 17 years old (mean 42 months), with coarctation of the aorta that was confirmed subsequently by angiography and/or surgery. Twelve patients had native coarctation and three had mild recoarctation after surgical repair. Color Doppler flow maps were analyzed with a digital analysis package and a Sony computer system. The diameter in the region of coarctation from the color Doppler flow map (mean = 2.0 +/- 0.8 mm [SD]) correlated well with the coarctation diameter measured at angiography (mean = 1.8 +/- 0.8 mm; r = .83, SEE 0.43 mm) in the 10 patients with native coarctation undergoing angiography, but the coarctation diameter measured by two-dimensional echocardiography (3.9 +/- 1.5 mm) was poorly predictive of the angiographic severity (r = .23). Additionally, spatial acceleration was seen in all patients proximal to the coarctation site, with an aliased and accelerating stream narrowing progressively as it proceeded toward the coarctation site, a pattern that is not seen in healthy subjects. Computer analysis of the color Doppler images provided pseudo three-dimensional and digital velocity maps for blue, red, and green (turbulent) flow velocities to allow an enhanced appreciation of the accelerating stream, easily separating this from normal descending aortic aliasing patterns. The narrowing of the acceleration area in the proximal descending aorta (distal/proximal acceleration zone ratio) was also predictive of the angiographic severity of coarctation (r = .83). The distribution of low-level turbulence seen proximally paralleled the distribution of the proximal accelerating stream.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic assessment of aortic valve area in elderly patients with aortic stenosis and of changes in valve area after percutaneous balloon valvuloplasty

Echocardiographic studies, adequate for analysis of aortic valve area using the continuity equation, were obtained in 31 patients aged greater than or equal to 60 years who were undergoing catheterization for assessment of suspected aortic stenosis. Catheterization-determined aortic valve area was 0.74 +/- 0.30 cm2 (mean +/- SD) and Doppler-determined aortic valve areas were 0.68 +/- 0.27 and 0.65 +/- 0.27 cm2, depending on whether peak or mean velocities, respectively, were entered into the continuity equation. There were significant correlations between both of the Doppler-derived and the catheterization-determined aortic valve areas (r = 0.86, p less than 0.001 for both the continuity equation employing peak velocities and the continuity equation employing mean velocities) which were demonstrated to be linear by F test (catheterization area = -0.03 + 1.13 X Doppler area determined using peak velocities, SEE = 0.163 cm2, p less than 0.001; and catheterization area = -0.02 + 1.16 X Doppler area determined using mean velocities, SEE = 0.165 cm2, p less than 0.001). Both sets of correlations had linear regression parameters meeting the conditions for identity. Significant linear correlations were also noted between the non-invasive measurements of aortic valve excursion, ventricular ejection time, time to one-half carotid upstroke, maximal Doppler velocity and maximal Doppler gradient and catheterization aortic valve area, but the correlations were less tight than those between valve areas determined by catheterization and by Doppler continuity equation. Ten of the patients underwent percutaneous balloon aortic valvuloplasty. There were significant linear correlations between aortic valve areas determined by Doppler and catheterization methods both before valvuloplasty (r = 0.77, p = 0.01; p less than 0.001 by F test, SEE = 0.134 cm2) and after valvuloplasty (r = 0.85, p less than 0.01; p = 0.0001 by F test, SEE = 0.161 cm2). Linear regression parameters met the conditions for identity. There was also a significant linear correlation between catheterization and Doppler measurements of absolute change in aortic valve area (r = 0.79, p less than 0.01; p less than 0.001 by F test, SEE = 0.11 cm2). Aortic valve area can be determined reliably by continuity equation in elderly patients. In addition, results of balloon valvuloplasty, measured by changes in catheterization-determined aortic valve area, are accurately reflected by changes in aortic valve area determined using the continuity equation.

Doppler ultrasound in the assessment of severity of coarctation of the aorta and interruption of the aortic arch

Doppler ultrasound was used to investigate 48 infants and children (age 2 days-16 years, weight 1.0-58 kg) with aortic arch abnormalities. In only 38 of the 42 with an important coarctation was an increased blood flow velocity from the distal arch demonstrated. In three with interruption of the aortic arch an increased velocity recorded from the region of the distal arch was thought to represent ductal flow. There was little difference between the peak to peak and instantaneous maximum gradients in the 20 patients with important coarctation in whom direct pressure measurements both proximal and distal to the obstruction were made at catheterisation. There were poor agreements between Doppler and measured peak to peak and instantaneous gradients in the 17 patients found to have both an increased velocity and important coarctation. It is concluded that although an increased blood flow velocity in the distal arch is usually demonstrated in coarctation this may not occur with severe obstruction. Furthermore, the maximum velocity is not related to the anatomical severity of the obstruction and the Doppler estimate of pressure drop in coarctation may not even reliably predict that measured at catheterisation.

Non-invasive assessment by Doppler ultrasound of 155 patients with bioprosthetic valves: a comparison of the Wessex porcine, low profile Ionescu-Shiley, and Hancock pericardial bioprostheses

One hundred and fifty five patients with 167 bioprosthetic valves (68 Wessex porcine, 54 Hancock pericardial, and 45 low profile Ionescu-Shiley pericardial valves) were studied by Doppler ultrasound. Valve gradients were calculated from the mitral and aortic flow velocities by the modified Bernoulli equation. Mean mitral gradients were significantly smaller across the Ionescu-Shiley valves than across the Wessex porcine or Hancock pericardial valves. Mitral pressure half time was, however, significantly longer in the Hancock pericardial than in the Wessex porcine or Ionescu-Shiley valves. No significant differences were seen among the groups of aortic bioprostheses, though the comparable size of Wessex porcine valves showed significantly higher gradients. Bioprosthetic regurgitation was detected in 13 of 103 mitral and 11 of 59 aortic valves, though it was suspected clinically in only 12 mitral and six aortic bioprostheses. Doppler ultrasound is a repeatable non-invasive method of acquiring haemodynamic information in vivo from a variety of bioprostheses and it can detect bioprosthetic regurgitation at an early stage.

Instantaneous pressure gradient: a simultaneous Doppler and dual catheter correlative study

To more precisely measure the beat to beat and instantaneous pressure gradients across outflow stenotic lesions, simultaneous Doppler and dual catheter pressure gradient measurements were performed in 95 patients (mean age 42 years, range 1.5 to 85). There were 38 right ventricular and 62 left ventricular outflow obstructive lesions. Forty-nine patients also had a nonsimultaneous Doppler study performed within 7 days before catheterization. The simultaneous pressure waveforms and Doppler spectral velocity profiles were digitized at 10 ms intervals deriving maximal, mean and instantaneous gradients (mm Hg). For simultaneous maximal Doppler and catheter gradient measurements, the correlation coefficient (r) was 0.95 (SEE = 10 mm Hg), for Doppler and catheter mean gradients it was 0.94 (SEE = 8 mm Hg) and for maximal Doppler and peak to peak catheter gradients it was 0.92 (SEE = 13 mm Hg). The correlation of maximal and mean Doppler gradients with the respective catheter gradients was similarly high when the right and left ventricular outflow lesions were analyzed separately. However, the maximal Doppler gradient was significantly higher than the peak to peak catheter gradient. This was more evident with left ventricular outflow stenotic lesions. The correlation of the outpatient maximal Doppler and catheter gradients (r = 0.80, SEE = 17 mm Hg) was significantly lower than the simultaneous correlation (r = 0.96, SEE = 10 mm Hg) in the 49 patients with two Doppler studies. Continuous wave Doppler echocardiography accurately measures the instantaneous pressure gradient across both left and right ventricular outflow obstructive lesions. The maximal Doppler gradient should not be equated with the peak to peak catheter gradient.(ABSTRACT TRUNCATED AT 250 WORDS)