Paul A. Grayburn

Quantitative assessment of mitral regurgitation by doppler color flow imaging: Angiographic and hemodynamic correlations

This study was performed to test the hypothesis that measurements of jet area by Doppler color flow imaging can predict the angiographic severity and hemodynamic consequences of mitral regurgitation. Doppler color flow imaging was performed in 47 patients undergoing cardiac catheterization and left ventriculography. The jet area was measured as the largest clearly definable flow disturbance in the parasternal and apical views, and expressed as the maximal jet area, the mean of the largest jet area (average jet area) in two views or as the ratio of these measures to left atrial area. Correlation of all Doppler color flow measurements with angiographic grades of mitral regurgitation were comparable, maximal jet area being closest at r = 0.76. A maximal jet area greater than 8 cm2 predicted severe mitral regurgitation with a sensitivity of 82% and specificity of 94%, whereas a maximal jet area less than 4 cm2 predicted mild mitral regurgitation with a sensitivity and specificity of 85% and 75%, respectively. All patients with an average jet area greater than 8 cm2 manifested severe mitral regurgitation. However, jet area measurements showed limited correlation with regurgitant volume and fraction (r = 0.55 and 0.62, respectively) for maximal jet area, and were not predictive of hemodynamic abnormalities, including those of pulmonary wedge pressure, stroke volume or ventricular volumes. Thus, in patients with mitral regurgitation, maximal jet area from Doppler color flow imaging provides a simple measurement that predicts angiographic grade, but manifests a weak correlation with regurgitant volume and does not predict hemodynamic dysfunction.

Observer variability in the quantitation of Doppler color flow jet areas for mitral aortic regurgitation

Early studies using Doppler color flow imaging have suggested that measurement of the regurgitant jet area provides information regarding the severity of valvular insufficiency. This study was performed to assess the observer variability of mitral and aortic regurgitant jet area measurements using the Doppler color technique. Color Doppler recordings from 45 patients were reviewed: 23 patients had aortic regurgitation and 22 had mitral regurgitation. To assess interobserver variability, the largest definable mitral regurgitant jets from three cardiac cycles were independently chosen and measured by planimetry by two observers who were unaware of other patient information. Measurements were repeated by both observers at a separate time to obtain intraobserver data. Videotapes from 23 patients with aortic regurgitation were similarly analyzed. Each observer measured the isovolumic aortic jet (before mitral valve opening) and the maximal aortic regurgitant jet (at any time during diastole) using computer-assisted planimetry. Both intraobserver and interobserver correlations were excellent for mitral regurgitant jet areas (r = 0.97 and r = 0.93, respectively). The intraobserver correlation for isovolumic aortic regurgitant jet was r = 0.73; the interobserver correlation for this measurement was only fair (r = 0.57). For the maximal aortic regurgitant jet area, intraobserver correlation was good (r = 0.86) and interobserver correlation was fair (r = 0.72). These findings suggest that intraobserver and interobserver reproducibility are acceptable for the measurement of mitral regurgitant jet area.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of exercise doppler echocardiography to evaluate cardiac drugs: Effects of propranolol and verapamil on aortic blood flow velocity and acceleration

This study evaluated the ability of exercise Doppler echocardiography to identify hemodynamic changes due to cardiac medication. Twenty young healthy volunteers (mean age 30 years) underwent continuous wave Doppler examination from the suprasternal notch at rest, during each stage of a standard exercise protocol and immediately after exercise. On completion of the control test, each subject received either 60 to 80 mg of propranolol or 120 mg of verapamil orally, and the same exercise protocol was repeated after 90 min. During the control test, values for modal velocity, acceleration and flow velocity integral all increased significantly from baseline (p less than 0.0002 for each). When exercise was repeated after propranolol administration, values for all Doppler measurements were significantly altered. Modal velocity at baseline was significantly lower after propranolol when compared with control (0.53 +/- 0.11 versus 0.63 +/- 0.17 m/s; p less than 0.0001). Similarly, modal velocity at maximal exercise was significantly lower after propranolol (1.11 +/- 0.2 versus 1.25 +/- 0.21 m/s; p less than 0.0001). The effect of propranolol on acceleration was even greater, with blunting of baseline (11.4 +/- 2 versus 15.4 +/- 5 m/s per s; p less than 0.0005) and exertional (33.4 +/- 10 versus 56.3 +/- 15 m/s per s; p less than 0.0001) acceleration. The flow velocity integral during exercise was greater after propranolol (14.1 +/- 3.1 versus 10.1 +/- 3.2 cm; p less than 0.0005) than during the control test. Verapamil failed to influence any Doppler-measured index of aortic blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Pivotal role of aortic valve area calculation by the continuity equation for Doppler assessment of aortic stenosis in patients with combined aortic stenosis and regurgitation

Aortic regurgitation (AR) may result in overestimation of the aortic pressure gradient by continuous wave Doppler in patients with mixed aortic valve disease. However, few data are available regarding the effect of AR on noninvasive estimates of aortic valve area by the continuity equation. Therefore, 25 patients with angiographically documented severe AR and peak systolic aortic velocities of greater than 2.5 m/s were studied by continuous wave Doppler to determine the accuracy of pressure gradient and aortic valve area calculations in assessing the severity of aortic stenosis (AS) in this patient population. Peak instantaneous pressure gradient showed a general correlation to but was overestimated by Doppler (r = 0.78, Doppler = 0.70 catheter + 19.9) and did not predict aortic valve area. Mean pressure gradient by Doppler correlated more closely with catheter mean gradient (r = 0.86, Doppler = 0.79 catheter + 6.1) but was a poor predictor of the severity of AS. In contrast, the continuity equation accurately predicted the aortic valve area by catheterization (r = 0.92, Doppler = 0.89 catheter -0.08). Thus, the continuity equation provides a reliable estimate of aortic valve area in patients with severe AR and should be used to evaluate the extent of AS in such patients when high systolic aortic velocities are present.

Comparison of simultaneously performed digital and film-based angiography in assessment of coronary artery disease.

This study compared digital angiography (Digital) to conventional cineangiography (Cine) for the diagnosis and quantification of coronary artery disease. Digital and Cine were obtained simultaneously under identical radiographic conditions during routine coronary arteriography. Using visual inspection and manual calipers, four independent observers identified 131 stenoses in 18 patients with multivessel coronary disease. There was no difference in interobserver variability between Digital and Cine during multiple subgroup analyses. Overall, Digital yielded significantly greater estimates of stenosis severity than did either of two separate Cine observations (p less than 0.0001; average difference, 6.25%), but the differences fell below the level of statistical significance when only the group of stenoses 50% or greater were considered. Digital and Cine correlated well for the assessment of stenosis severity (r = 0.88), but linear regression comparisons of multiple subgroups consistently indicated modest overestimation of Cine by Digital. Smaller vessels, branch vessels, and mild lesions increased the likelihood of overestimation by Digital. Digital was highly sensitive for identification of clinically relevant stenoses, but less specific and less predictive than a second observation of Cine. Our results indicate that Digital and Cine are not interchangeable imaging techniques and that potential differences must be considered when Digital is used for clinical decision making.

Determination of left ventricular ejection fraction by computer densitometric analysis of digital subtraction angiography: Experimental validation and correlation with area-length methods

Conventional methods for calculating left ventricular (LV) ejection fraction (EF) require accurate edge definition and geometric assumptions, which may be compromised in the presence of dyssynergy. Computer densitometric analysis (CDA) of digital subtraction angiography offers the potential for calculation of EF, independent of LV shape, by comparing summated brightness for regions of interest at end diastole and end systole. Therefore, the accuracy of CDA was validated for 2 mechanical heart models of differing geometry, spherical and rectangular. Both models confirmed the close correlation between calculated and measured EF (r = 0.98 and r = 0.99, respectively). Subsequently, the CDA was compared with single and biplane area-length EF calculations in 72 patients, half with a previous myocardial infarction. In patients without previous myocardial infarction, CDA correlated closely with both single-plane and biplane EF (r = 0.91 and 0.93, respectively). The close correlation was maintained regardless of whether CDA was applied to direct LV injection or intravenous digital subtraction angiography. However, in 36 patients with previous myocardial infarction, CDA correlated less closely with single-plane (r = 0.74) than with biplane (r = 0.86) area-length EF. Thus, CDA permits calculation of EF without geometric assumptions, and may be superior to the area-length method in patients with LV dyssynergy after myocardial infarction.

Considerations in the Quantitation of Color Doppler Flow Imaging

The greatest clinical contribution of color Doppler flow imaging (CDFI) has been to provide information regarding the spatial characteristics of blood flow. Color Doppler mapping, by virtue of the ability to convey spatial information, has been utilized to characterize several fundamental features of flow streams and jets. CDFI has been invaluable in identifying the direction and profile of blood flow. Thus, studies have demonstrated that velocities may vary along a front of flow, and that jets produced by any specific lesion may assume different directions and shapes. In regard to flow disturbances, color Doppler flow imaging has been of value both in identifying and in characterizing the number of jets present. Thus, flow mapping has been able to identify and depict multiple flow streams in the setting of intracardiac shunts, in some cases of valvular regurgitation and in prosthetic devices with multiple orifices. The most important information that flow mapping has conveyed, however, has been in the size and shape of nonlaminar flow areas. The ability to derive quantitative estimates of size from CDFI has been particularly appealing not only because CDFI is unique in providing this information but also because it seems logical that the size of a flow abnormality correlates with its severity. In light of the above comments, it is not surprising that the major quantitative information thus far extracted from color flow imaging has been the size or area of disturbed flow. Attempts

Quantitation of aortic regurgitation by computer analysis of digital subtraction angiography

Digital subtraction angiography provides the potential to determine aortic regurgitant fraction by computer analysis of time-intensity curves generated from regions of interest positioned over the aorta and left ventricle after aortography. To validate this ability, we studied six dogs instrumented with an electromagnetic flow probe on the ascending aorta. Aortic regurgitation of varying severity was produced by a basket catheter introduced through the right carotid artery. Aortograms were performed using continuous fluoroscopy at 30 frames/s and stored in digital format in a 256 x 256 pixel matrix. An image-processing computer was utilized to plot summated pixel intensity versus time for both the aortic and the left ventricular regions of interest. Regurgitant fraction was calculated from the time-intensity curves using an algorithm analogous to that employed by dye-dilution methods. Regurgitant fraction determined from digital angiography was compared with that obtained by electromagnetic flow and was found to correlate well (r = 0.94, SEE = 7.4%) over a wide range of values. Thus, these data indicate that aortic regurgitant fraction can be accurately determined from computer analysis of digitally acquired aortograms in an animal model of acute aortic regurgitation.

Normal Blood Flow Patterns by Color Doppler Flow Imaging

Real time two-dimensional Doppler color flow imaging provides the unique ability to noninvasively image the direction, spatial distribution, and relative velocity of intracardiac blood flow. This latest step in the evolution of cardiovascular ultrasound is the logical combination of anatomical information provided by two-dimensional echocardiographic imaging, and information on blood flow provided by Doppler techniques. Accordingly, this marriage of technologies provides a visual representation of dynamic flow patterns within the heart and great vessels.

Quantitative Assessment of Aortic Regurgitation by Digital Subtraction Angiography

The severity of aortic regurgitation has been traditionally assessed by visual interpretation of cineaortograms utilizing a 1 to 4+ scale [1], This method is subjective and may be influenced by variations in left ventricular volume, radiographic technique, contrast dose, and interobserver agreement [2]. Despite these limitations, this semiquantitative technique continues to be the most widely accepted clinical measurement of the magnitude of aortic regurgitation.