Kent L. Richards

Comparative accuracy of apical biplane cross-sectional echocardiography and gated equilibrium radionuclide angiography for estimating left ventricular size and performance.

To compare measurements of left ventricular size and performance obtained by apical biplane cross-sectional echocardiography (CSE) and gated equilibrium radionuclide angiography (RNA), we studied 70 patients, all of whom had single-plane and 30 of whom had biplane left ventricular cineangiography. Wideangle, phased-array CSE images were obtained from two orthogonal apical views and left ventricular volumes were calculated using a microprocessor-controlled, video light-pen system programmed for a Simpsons rule algorithm. The average CSE end-diastolic volume (EDV) for all 70 patients of 158 ± 56 ml (± SD) was less than the single-plane angiographic value of 176 ± 68 ml (p < 0.001, r = 0.80). The average CSE end-systolic volume (ESV) of 78 ± 57 ml was not different from the angiographic value of 84 ± 70 ml (r = 0.88). The average CSE and single-plane angiographic ejection fraction (EF) values of 55 ± 16% and 57 ± 19% were not different (r = 0.90). In the 30 patients who underwent biplane angiography, the average CSE EDV of 166 ± 62 ml was less than the biplane angiographic EDV of 217 ± 87 ml (p < 0.001, r = 0.81), and the average CSE ESV of 89 ± 69 ml was also less than the angiographic value of 114 ± 89 ml (p < 0.001, r = 0.92). The average CSE LV EF of 52 ± 19% was not different from the biplane angiographic value of 52 ± 17% (r = 0.87). In the 25 patients who underwent CSE, RNA and biplane angiography, the average LVEF values were 51 ± 20%, 46 ± 18% and 50 ± 17%, respectively, and the CSE and RNA values correlated with the biplane angiographic value (r = 0.90 and 0.93, respectively). Therefore, apical biplane CSE estimates of left ventricular volume correlate linearly with single-plane and biplane cineangiographic determinations, and this CSE technique compares favorably with gated equilibrium RNA for assessing left ventricular performance.

Hydraulic estimation of stenotic orifice area: a correction of the Gorlin formula.

To determine the source of errors in the Gorlin formula for estimating stenotic valvular orifice area, we used a pulsatile flow model that emulated left ventricular and aortic pressures and flow and allowed control of ventricular outflow orifice area. After comparing orifice areas calculated by the Gorlin formula with actual orifice areas, the Gorlin formula constant (k) was found to be highly correlated with the square root of the mean transvalvular gradient (r = .95). A new formula was derived empirically and predicted areas more accurately and with smaller standard errors than the Gorlin formula in the model (r = .98, SEE = 0.11 and r = .87, SEE = 0.28, respectively) in a series of 19 patients with Hancock porcine xenograft valves (r = .89, SEE = 0.07 and r = .60, SEE = 0.12, respectively) and in the original series of patients reported by Gorlin and Gorlin in proposing the Gorlin formula (r = .93, SEE = 0.11 and r = .91, SEE = 0.12, respectively).

Calculation of aortic valve area by Doppler echocardiography: a direct application of the continuity equation.

The continuity equation suggests that a ratio of velocities at two different cardiac valves is inversely proportional to the ratio of cross-sectional areas of the valves. To determine whether a ratio of mitral/aortic valve orifice velocities is useful in determining aortic valve area in patients with aortic stenosis, 10 control subjects and 22 patients with predominant aortic stenosis were examined by Doppler echocardiography. The ratio of (mean diastolic mitral velocity)/(mean systolic aortic velocity), (Vm)/(Va), and the ratio of (mitral diastolic velocity-time integral)/(aortic systolic velocity-time integral), (VTm)/(VTa), were determined from Doppler spectral recordings. Aortic valve area determined at catheterization by the Gorlin equation was the standard of reference. High-quality Doppler recordings were obtained in 30 of 32 subjects (94%). Catheterization documented valve areas of 0.5 to 2.6 (mean 1.1) cm2. There was good correlation between Doppler-determined (Vm)/(Va) and Gorlin valve area (r = .90, SEE = 0.23 cm2); a better correlation was noted between (VTm)/(VTa) and Gorlin valve area (r = .93, SEE = 0.18 cm2). The data demonstrate the usefulness of Doppler alone in the determination of aortic valve area in adults with absent or mild aortic or mitral regurgitation and no mitral stenosis. Although the use of mean velocity and velocity-time integral ratios requires accurate measurement of mitral and aortic velocities, it does not require squaring of these velocities or measurement of the cross-sectional area of flow.

Usefulness of the postexercise response of systolic blood pressure in the diagnosis of coronary artery disease.

The normal decline in systolic blood pressure (SBP) during the recovery phase of treadmill exercise does not occur in some patients with coronary artery disease (CAD). In others the recovery values of SBP exceed the peak exercise values. To examine the diagnostic value of this observation, we studied 31 normal subjects and 56 patients undergoing treadmill exercise before coronary cineangiography. Because of large differences in peak exercise pressures between the two groups, recovery ratios were derived by dividing the SBP at 1, 2, and 3 min after exercise by the peak exercise SBP. The 1, 2, and 3 min ratios in the normal subjects declined steadily from 0.85 +/- 0.07 (SD) to 0.79 +/- 0.06 and to 0.73 +/- 0.06, respectively, while the ratios in the patients with CAD remained elevated at 0.97 +/- 0.12 to 0.97 +/- 0.11 to 0.93 +/- 0.13. With use of the upper limits defined by two SDs of the normal value, recovery ratios were compared with the occurrence of angina and with ST segment depression on the exercise electrocardiogram in the patients with CAD. Abnormal ratios were more frequent in patients with CAD (53/56, 95%) than in those with ST segment depression (33/56, 59%), angina (37/56, 66%), and either ST segment depression or angina (42/56, 75%). Twenty of the patients with CAD who were on no medication underwent an additional treadmill exercise test on a separate day and no significant differences were found in the ratios from the two tests. Ten additional patients with CAD underwent treadmill exercise testing while on placebo and while on a beta-blocker.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictive value of early postmyocardial infarction modified treadmill exercise testing in multivessel coronary artery disease detection

We evaluated 57 patients with modified treadmill exercise testing and angiography early post-infarction (MI) to determine the predictive value of ST segment depression, angina, and an inadequate blood pressure response for multivessel coronary artery disease (MVCAD). ST segment depression alone identified MVCAD stenoses (greater than or equal to 70% diameter narrowing in two or more vessels) with sensitivity 54%, specificity 75%, and accuracy 60%. When ST segment depression and angina were considered a positive treadmill test result, a significant improvement in sensitivity (88%, p less than 0.01) and accuracy (82%, p less than 0.05) for MVCAD was observed. An inadequate blood pressure response was associated with MVCAD (12 of 13 patients) and a significantly reduced average left ventricular (LV) ejection fraction of 39 plus or minus 13% compared to 58 plus or minus 14% for patients without this treadmill abnormality (p less than 0.01). Therefore, we conclude that (1) ST segment depression and angina on early post-MI modified treadmill exercise testing are superior predictors of MVCAD compared to ST segment depression alone and (2) an inadequate blood pressure response during modified exercise testing early following MI is observed in patients with MVCAD and reduced LV performance.

Accuracy of mitral Doppler echocardiographic cardiac output determinations in adults

The Doppler echocardiographic estimation of cardiac output at the mitral valve site is often underestimated in adults with slow heart rates because the mitral valve remains open in mid-diastole when flow is markedly reduced. Therefore we tested several approaches to this measurement in 17 adults with nonvalvular heart disease who had thermodilution catheters in the right side of the heart. Superior correlations with thermal output values were obtained by a new method that excludes mitral orifice measurements during mid-diastole when flow less than 10 cm/sec (r = 0.94) compared with the standard method (r = 0.89). Also, the new method resulted in significantly less underestimation of thermal cardiac output in patients with heart rates less than 70 beats/min (-10%) compared with the standard method (-34%). In addition, use of a constant maximal two-dimensional echocardiographic mitral orifice correction factor of 0.77 with the new method to account for variations in mitral valve orifice during the cardiac cycle, as opposed to 0.68 with the standard method, resulted in similar results as compared with determining individual correction factors from M-mode echoes. We conclude that: (1) the mitral orifice approach is accurate for measuring cardiac output in adult patients with nonvalvular heart disease; (2) a new method that excludes mid-diastolic mitral orifice measurements is superior to the standard method; and (3) use of a constant two-dimensional echocardiographic mitral valve orifice correction factor obviates the need for M-mode echoes.