Direct measurement of cardiac output by gated equilibrium blood pool scintigraphy: Validation of scintigraphic volume measurements by a nongeometric technique

A nongeometric technique for the determination of left ventricular volumes from the count data derived from gated equilibrium blood pool scans was previously described and validated by the demonstration of an excellent correlation between the derived data and angiographically determined left ventricular volumes. To provide a further prospective evaluation of this method and to validate its ability to determine stroke volume and cardiac output by a technique that is itself independent of geometric assumptions, simultaneous measurements of cardiac output by the thermodilution technique and gated scintigraphy were performed in 21 patients without valve regurgitation or intracardiac shunts. To substantiate the reliability of scintigraphic measurements at high levels of cardiac output, seven patients had multiple measurements of cardiac output at rest and during an infusion of isoproterenol. There was an excellent correlation between thermodilution and scintigraphic values for cardiac output (scan cardiac output = 0.99 thermodilution cardiac output ? 0.005 liters/min; n = 31, standard error of the estimate [SEE]= 0.175 liters/min, r = 0.97) as well as between thermodilution and scintigraphic stroke volumes (scan stroke volume = 1.03 thermodilution stroke volume ? 2.8 ml; n = 31, SEE = 2.5 ml, r = 0.95). In addition, the relation between scintigraphic and angiographic measurements of left ventricular volumes continued to be excellent: In 15 patients with technically adequate angiograms, scintigraphic left ventricular volume = 0.90 angiographic left ventricular volume + 7 ml (n = 30, SEE = 10 ml, r = 0.91). Thus, this study further validates the nongeometric method of measuring left ventricular volumes with gated scintigraphy and demonstrates its ability to measure left ventricular stroke volume and cardiac output reliably.     

A new scintigraphic method for determining left ventricular volumes

A new scintigraphic count-based method for measuring absolute left ventricular volumes is presented. It is a fast and simple technique that allows geometrical assumptions to be avoided and is free of radiation attenuation corrections. This method requires the acquisition of an image of the left ventricle in the right anterior oblique projection and the collection of gated blood pool images in the left anterior oblique projection. To assess the accuracy of the method scintigraphic stroke volumes were compared with those derived from thermodilution measurements during cardiac catheterization in 20 subjects, and to assess its precision the technique was applied to phantom data of known radionuclide volumes. Excellent correlations were found between the scintigraphic and both the thermodilution (r = .98) and phantom data (r = .99). The reproducibility (r = .97) of results was investigated by repeating data acquisition and analysis for 15 subjects on two different days, and the interobserver variability (r = .97) of the method was studied by having two computer operators calculate volumes for the same patient data for 20 randomly selected studies.     

Nongeometric determination of left ventricular volumes from equilibrium blood pool scans

This study assesses the utility of a scintigraphic, nongeometric technique for the determination of left ventricular volumes. Accordingly, gated blood pool scintigraphy and cineangiography were performed within a 24 hour period in 22 patients. Scintigraphic volume measurements were calculated from individual frames of a modified 35 ° left anterior oblique projection using an algorithm designed to consider (1) the background-corrected left ventricular activity normalized for activity per milliliter of peripheral venous blood; (2) total study time; (3) number of frames acquired per cardiac cycle; and (4) percent of the cardiac cycle acquired. Angiographic volumes were calculated by the area-length method and the Kennedy regression equation. There was an excellent correlation between scintigraphic and angiographic methods for all volume measurements grouped together (r = 0.985, standard error of the estimate [SEE] = 14.6 ml) as well as for segregated end-diastolic volumes (r = 0.985, SEE = 16.2 ml) and end-systolic volumes (r = 0.988, SEE = 14.7 ml). Prospective testing of the independent ability of scintigraphy to estimate ventricular volumes was provided for by studying an additional 13 patients, and good agreement was found between scintigraphic and angiographic determinations of left ventricular end-systolic and end-diastolic volumes. Thus, radio nuclide techniques, which are independent of geometric assumptions, may be utilized for the quantitation of left ventricular volumes.     

Method for quantitative analysis of regional left ventricular function with first pass and gated blood pool scintigraphy

The ability of radionuclide angiocardiography to quantitatively assess regional left ventricular function was studied in 33 patients undergoing biplane left ventricular cineangiography (45 ° right anterior oblique projection, and 60 ° left anterior oblique projection with 25 ° caudocranial angulation), and first pass (30 ° right anterior oblique projection) and multiple gated equilibrium (35 ° to 45 ° left anterior oblique projection with 20 ° to 25 ° caudocranial angulation) left ventricular scintigraphy within 48 hours. End-diastolic and end-systolic silhouettes of contrast angiograms were superimposed, and five segments were defined in each plane by radial lines originating from the end-diastolic center of mass. Segmental angiographic ejection fraction (end-diastolic area — end-systolic area/ end-diastolic area) was calculated for each segment by computerized planimetry. Similar segments were defined in the end-diastolic and end-systolic regions of interest of the first pass and gated left ventricular scintigrams, and the segmental scintigraphic ejection fraction (back-ground-corrected end-diastolic counts — background-corrected end-systolic counts/background-corrected end-diastolic counts) was obtained for each.A good correlation was observed between segmentai angiographic and scintigraphic ejection fraction in the segments corresponding to the anterobasal (r = 0.74), anterolateral (r = 0.70), apical (r = 0.77), diaphragmatic (r = 0.71), distal septal (r = 0.66), posterolateral (r = 0.71) and inferolateral (r = 0.60) left ventricular regions. The poor correlation in the posterobasal (r = 0.39), basal septal (r = ?0.02) and superolateral (r = 0.05) segments was probably related to difficulty in defining the aortic valve, overlap of the left atrium and the left ventricle, and inability to visualize the high septum with these scintigraphic techniques. The reproducibility of scintigraphic segmental ejection fraction was studied in 13 patients in whom a second gated scintigram was performed 2 hours after the initial one. Excellent agreement (r = 0.93) was observed for scintigraphic segmental ejection fraction in the distal septal, posterolateral and inferolateral segments. Segmental scintigraphic ejection fraction enables accurate quantitative evaluation of the function of the anterobasal, anterolateral, apical, diaphragmatic, distal septal, posterolateral and inferolateral left ventricular regions with high reproducibility.     

Left ventricular volumes by single-plane cineangiography: in vivo validation of the Kennedy regression equation

This study was performed to assess the accuracy and reliability of the regression equations of Kennedy et al and Wynne et al in the quantitation of single plane left ventricular (LV) volumes. In 15 patients with normal LV function and without intracardiac shunting or valvular insufficiency, gated equilibrium blood pool scintigraphy was performed simultaneously with the measurement of cardiac output (by thermodilution), after which left ventriculography was performed in the 30 degrees right anterior oblique (RAO) projection. From the scintigraphically determined LV ejection fraction (EF) and the thermodilution-measured stroke volume (SV), absolute LV volumes were calculated. The cineangiographic LV volumes obtained with the regression equation of Kennedy et al closely approximated those calculated by scintigraphy/thermodilution, whereas the volumes determined using the regression equation of Wynne et al were larger (p less than 0.05) than the calculated volumes. In 204 patients without intracardiac shunting or valvular insufficiency, SV was measured by the Fick or indicator dilution methods, after which single-plane left ventriculography was performed in the 30 degrees RAO projection. In the 83 patients without coronary artery disease with normal (n = 69) or depressed (n = 14) LVEF, cineangiographic SV (obtained using the regression equation of Kennedy et al) closely approximated forward SV. Similarly, this relation was excellent in the 142 patients whose LVEFs were greater than or equal to 0.50.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thermodilution measurement of the right ventricular ejection fraction

This study addressed the clinical reproducibility and validity of the thermodilution (TD) measurement of the right ventricular ejection fraction (RVEF). Forty-one patients underwent right heart catheterization, including TD RVEF, within 2 h of gated first pass (GFP) and gated blood pool (GBP) radionuclide ventriculography; 21 had single plane contrast right ventricular angiography (ANGIO) during the same catheterization. Analysis of variance showed no difference among three successive TD RVEF measurements. (table; see text) Stroke volume by RV ANGIO correlated with Fick (n = 10, r = .86) and thermodilution stroke volume (n = 21, r = .88). It is concluded that although the thermodilution method is an accurate way to measure flow, it is not an accurate way to measure right ventricular ejection fraction, and by inference, ventricular volumes. The most likely explanation for this finding is incomplete mixing as in previous studies of indicator methods of measuring left ventricular volumes.     

Gated radionuclide angiographic evaluation of valve regurgitation

Gated radionuclide angiography is a new noninvasive technique that can be used to calculate the ratio of left and right ventricular stroke volumes. This stroke volume ratio, which must be unity in normal subjects, increases in patients with aortic or mitral regurgitation in direct proportion to the degree of left ventricular volume overload, provided no shunts or regurgitant right heart lesions are present. In 22 patients with aortic or mitral regurgitation there was excellent correlation between the stroke volume ratio determined with gated radionuclide angiography and with standard quantitative catheterization methods (r = 0.79). Measurement of valve regurgitation with this radionuclide method also correlated well with data obtained from semiquantitative aortic root or left ventricular cineangiography (r = 0.72). Twenty-one of the 22 patients with valve regurgitation had an abnormally elevated stroke volume ratio, thereby suggesting that gated radionuclide angiography may be useful in detecting or excluding hemodynamically significant valve regurgitation.     

Estimation of left ventricular volumes in man from biplane cineangiograms filmed in oblique projections

In patients with coronary artery disease, right and left anterior oblique views of the left ventricle are considered optimal for assessment of regional wall motion, but the accuracy of ventricular volumes determined from these projections has not been validated. Eleven postmortem left ventricular casts were filmed with the 35 mm cine technique in the 30 ° right anterior oblique and 60 ° left anterior oblique positions, and volumes were calculated using the area-length method. True volume, assessed from volume displacement, ranged from 15 to 185 cc. Calculated volume (V_oblique) slightly but consistently overestimated true volume (V_T), with close correlation and a small standard error of the estimate (SEE):V_T = 0.989 V_oblique ? 8.1 cc, r = 0.99, SEE = 8 cc. With use of this regression equation, values for left ventricular volumes and ejection fraction were calculated from biplane oblique (30 ° right anterior oblique/60 ° left anterior oblique) cineanglograms In 17 normal adults. Values for end-diastolic volume index (72 ± 15 cc/m² [mean ± standard deviation]), end-systolic volume index (20 ± 8 cc/m²), stroke volume Index (51 ± 10 cc/m²) and ejection fraction (0.72 ± 0.08) were similar to those reported by others. Examination of the effects of variable obliquity suggests that strict standardization of the degree of obliquity is necessary to offset variation In the long axis in the left anterior oblique projection caused by foreshortening.     

Accurate estimates of absolute left ventricular volumes from equilibrium radionuclide angiographic count data using a simple geometric attenuation correction

To simplify and clarify the methods of obtaining attenuation-corrected equilibrium radionuclide angiographic estimates of absolute left ventricular volumes, 27 patients who also had biplane contrast cineangiography were evaluated. Background-corrected left ventricular end-diastolic and end-systolic counts were obtained by semiautomated variable and hand-drawn regions of interest and were normalized to cardiac cycles processed, frame rate and blood sample counts. Blood sample counts were acquired on (d degree) and at a distance (d') from the collimator. A simple geometric attenuation correction was performed to obtain absolute left ventricular volume estimates. Using blood sample counts obtained at d degree or d', the attentuation-corrected radionuclide left ventricular end-diastolic volume estimates using both region of interest selection methods correlated with the cineangiographic end-diastolic volumes (r = 0.95 to 0.96). However, both mean radionuclide semiautomated variable left ventricular end-diastolic volumes (179 +/- 100 [+/- 1 standard deviation] and 185 +/- 102 ml, p less than 0.001) were smaller than the average cineangiographic end-diastolic volume (217 +/- 102 ml), and both mean hand-drawn left ventricular end-diastolic volumes (212 +/- 104 and 220 +/- 106 ml) did not differ from the average cineangiographic end-diastolic volume. Using the blood sample counts obtained at d degree or d', the attenuation-corrected radionuclide left ventricular end-systolic volume estimates using both region of interest selection methods correlated with the cineangiographic end-systolic volumes (r = 0.96 to 0.98). Also, using blood sample counts at d degree, the mean radionuclide semiautomated variable left ventricular end-systolic volume (116 +/- 98 ml, p less than 0.05) was less than the average cineangiographic end-systolic volume (128 +/- 98 ml), and the other radionuclide end-systolic volumes did not differ from the average cineangiographic end-systolic volume. Therefore, it is concluded that: 1) a simple geometric attenuation-correction of radionuclide left ventricular end-diastolic and end-systolic count data provides accurate estimates of biplane cineangiographic end-diastolic and end-systolic volumes; and 2) the hand-drawn region of interest selection method, unlike the semiautomated variable method that underestimates end-diastolic and end-systolic volumes, provides more accurate estimates of biplane cineangiographic left ventricular volumes irrespective of the distance blood sample counts are acquired from the collimator.     

Sources of variability in the radionuclide angiographic assessment of ejection fraction: A comparison of first-pass and gated equilibrium techniques

Measurements of ejection fractions (EF) determined by first-pass and gated equilibrium radionuclide angiography are widely believed to be equivalent. To compare these measurements in a large group of patients over a wide range of EF values, left ventricular (LV) and right ventricular (RV) EFs at rest were measured in 135 consecutive patients who underwent the 2 methods of radionuclide angiography within 1 hour: first-pass upright with a multi-crystal camera in the anterior projection and gated equilibrium supine with a single-crystal camera in the left anterior oblique projection. The population included 18 normal patients and 117 patients with various cardiac and pulmonary disorders. First-pass and gated equilibrium LVEF correlated well (r = 0.83, p <0.001), but the slope of the regression line was different from unity, with the first-pass values lower than the gated equilibrium values (0.51 ± 0.16 vs 0.56 ± 0.15, p <0.05 [mean ± standard deviation]). Among the 45 patients with a gated equilibrium LVEF of <0.50, the correlation (r = 0.84) was better than that for the 90 patients with a LVEF > 0.50 (r = 0.44, p <0.05). However, in the latter group, the correlation remained good in the 15 patients with cardiomegaly due to aortic or mitral regurgitation (r = 0.80). Inter- and intraobserver error was similar for both methods. In contrast, there was a poor correlation between first-pass and gated equilibrium RVEF, with the first-pass values higher than the gated equilibrium values (0.51 ± 0.11 vs 0.43 ± 0.11, p <0.01). Interobserver error was similar for both the methods, but intraobserver error was better for the first-pass method (p <0.05). Thus, there may be considerable variability in the radionuclide EF at rest in the same patient because of differences in the method of measurement. Caution is suggested when EF values that have been derived using different radionuclide methods are compared.     

External,noninvasive cardiac assistance and nitrate administration for patients with unstable angina pectoris or acute coronary insufficiency

The influence of external, noninvasive counterpulsation, alone and in combination with sublingual nitroglycerin or isosorbide dinitrate, on left ventricular volumes and ejection fractions was investigated. Patients with unstable angina pectoris or acute coronary insufficiency were selected for this evaluation. Left ventricular volumes and ejection fractions were estimated using a gated blood pool scintigraphic technique. Twenty minutes of external counterpulsation did not significantly alter left ventricular end-diastolic volumes, end-systolic volumes, or ejection fractions in 13 patients. When sublingual isosorbide dinitrate (10 mg.) was combined with 20 minutes of external counterpulsation in eight patients, left ventricular end-diastolic volumes decreased 16 ± 7 per cent (p = .05), but neither left ventricular end-systolic volumes (12 ± 7 per cent) nor ejection fractions were significantly changed. When sublingual nitroglycerin (0.4 mg.) was combined with 15 minutes of external counterpulsation in three patients, left ventricular end-diastolic volumes decreased 21 ± 3 per cent (p < .01), end-systolic volumes decreased 25 ± 4 per cent (p < .02), and ejection fractions were not significantly changed. When left ventricular volumes and ejection fractions were measured 30 and 65 minutes after isosorbide dinitrate administration, 10 and 45 minutes after cessation of external counterpulsation, respectively, left ventricular end-diastolic volumes and end-systolic volumes were significantly decreased by approximately 20 per cent while ejection fractions were unchanged. When left ventricular volumes and ejection fractions were measured 25 minutes after nitroglycerin administration, 10 minutes after cessation of external counterpulsation, end-systolic volumes decreased 23 ± 2 per cent (p < .005) and end-diastolic volumes decreased 27 ± 3 per cent (p < .005). No significant changes in left ventricular end-diastolic or end-systolic volumes were seen 60 minutes after nitroglycerin administration. As in the other studies, left ventricular ejection fractions were unchanged. The results suggest that relatively short periods of external, noninvasive cardiac assistance do not alter left ventricular volumes or ejection fractions in patients with unstable angina pectoris or acute coronary insufficiency. Although external counterpulsation combined with a vasodilator such as isosorbide dinitrate or nitroglycerin decreases left ventricular volumes, it offers no advantage over vasodilator treatment alone.     

Quantification of valve regurgitation by radionuclide angiography before and after valve replacement surgery

Radionuclide gated cardiac blood pool imaging was used to quantify the severity of valve regurgitation in 20 patients, by calculating the ratio of left ventricular to right ventricular stroke counts (end-diastolic minus end-systolic counts in right and left ventricular regions of interest). This ratio (the stroke index ratio) was substantially higher in patients with aortic and mitral regurgitation (3.91 ± 1.45) than in a control group of 10 patients without regurgitation (1.32 ± 0.15), p < 3.001. The stroke index ratio correlated closely (r = 0.947) with measurements of regurgitant fraction derived from simultaneous determinations of total and forward stroke volumes during cardiac catheterization.After aortic and mitral valve replacement in 18 patients, the stroke index ratio decreased from 4.03 ± 1.46 to 1.38 ± 0.23 (p < 0.001), a value not significantly different from that observed in patients without regurgitation. All three patients with residual postoperative regurgitation had a stroke index ratio greater than 2 standard deviations above the mean values for the control group (>1.62), whereas the remaining 15 patients, who had no evidence of regurgitation, had values within the normal range. Therefore, radionuclide gated blood pool scanning provides a noninvasive method of quantifying valve regurgitation and assessing the results of medical or surgical interventions.     

Limitations of comparing left ventricular volumes by two dimensional echocardiography,myocardial markers and cineangiography

Measurement of left ventricular volume at end-diastole or end-systole with both two dimensional echocardiography and either Cineangiography or radionuclide scans, not recorded simultaneously, has shown large echocardiographic underestimation of volumes even in normal ventricles. In this study fluoroscopic and two dimensional echocardiographic recordings were obtained in 18 patients with abnormal wall motion and previously implanted myocardial markers. The echocardiographic values for volume and those derived from myocardial markers correlated well (r = 0.87), and there were no statistically significant differences in values obtained with the two methods at end-diastole or end-systole. The ejection fractions obtained with two dimensional echocardiography (mean ± standard deviation 46 ± 7 percent) and with fluoroscopic recording of the markers (41 ± 9 npercent) did not differ statistically.These results were compared with those in another 18 patients (nine with abnormal wall motion) having two dimensional echocardiography within 24 hours of a 30 ° right anterior oblique contrast left ventriculogram. Again, two dimensional echocardiographic ventricular volume correlated well with the angiographic volume (r = 0.85), although echocardiographic end-diastolic volume was consistently 20 percent less than angiographic end-diastolic volume (p < 0.01). Ejection fraction obtained with echocardiography (47 ± 8 percent) was less than that obtained with angiography (60 ± 7 percent) (p < 0.001). Interobserver variability in calculating volume with echocardiography was 4 percent.Probable reasons for the lack of severe underestimation of volume with echocardiography even in very abnormal ventricles, relative to that demonstrated in prior reports, include improvements in ultrasonic beam width, tracing method, transducer position and scan plane orientation within the ventricle. In addition, the possible effects of angiographic dye in the ventricular trabeculae are discussed and the effect of simultaneous studies by two different methods are compared.     

Evaluation of right ventricular volumes measured by magnetic resonance imaging

Right ventricular volumes were determined in 12 patients with different levels of right and left ventricular function by magnetic resonance imaging (MRI) using an ECG gated multisection technique in planes perpendicular to the diastolic position of the interventricular septum. Right ventricular stroke volume was calculated as the difference between end-diastolic and end-systolic volume and compared to left ventricular stroke volume and to stroke volume determined simultaneously by a classical indicator dilution technique. There was good agreement between right ventricular stroke volume determined by MRI and by the indicator dilution method and between right and left ventricular stroke volume determined by MRI. Thus, MRI gives reliable values not only for left ventricular volumes, but also for right ventricular volumes. By MRI it is possible to obtain volumes from both ventricles simultaneously in a noninvasive way and without exposing the patient to radiation.     

Evaluation of segmental left ventricular wall motion by equilibrium gated radionuclide ventriculography

The ability of equilibrium gated radionuclide ventriculography to detect segmental left ventricular (LV) wall motion abnormalities was determined in 26 patients undergoing cardiac catheterization. Multiple gated studies obtained in 30° right anterior oblique and 45° left anterior oblique projections, played back in a movie format, were compared to the corresponding LV ventriculograms. The LV wall in the two projections was divided into eight segments. Each segment was graded as normal, hypokinetic, akinetic, dyskinetic, or indeterminate. Thirteen percent of the segments in the gated images were indeterminate; 24 out of 27 of these were proximal or distal inferior wall segments. There was exact agreement in 86% of the remaining segments. The sensitivity of the radionuclide technique for detecting normal versus any abnormal wall motion was 71%, with a specificity of 99%. Equilibrium gated ventriculography is an excellent noninvasive technique for evaluating segmental LV wall motion. It is least reliable in assessing the proximal inferior wall and interventricular septum.     

Evaluation of magnetic resonance imaging for determination of left ventricular ejection fraction and comparison with angiography

Left ventricular ejection fraction was measured by magnetic resonance imaging (MRI) and compared with standard monoplane left ventriculography in 46 patients with various cardiac diseases. Two different MRI strategies were used. In 28 patients (group 1), ejection fraction was determined using a single slice comparable with the right anterior oblique projection of the ventriculogram. Comparison of left ventricular ejection fraction yielded a poor correlation between single slice MRI (y) and ventriculography (x) (y = 28.7 + 0.47 x, r = 0.65). In 18 patients (group 2), a multiple contiguous slice MRI technique was used to allow ejection fraction and stroke volume determination by summing up the volumes of ventricular cavity intersections. Regression analysis showed a high correlation between multiple slice MRI (y) and ventriculography (x) (y = 7.2 + 0.88 x, r = 0.98). Also, correlation between MRI right (y) and left (x) ventricular stroke volumes was satisfactory, (y = -12.8 + 1.09 x, r = 0.83). It is concluded that the multiple slice imaging technique in MRI provides an accurate noninvasive means for quantification of left ventricular ejection fraction that can be extended to the determination of left ventricular volume.     

Precision of measurements of right and left ventricular volume by cine computed tomography

Precise determination of left and right ventricular stroke volumes is limited with conventional imaging techniques. We determined whether right and left ventricular stroke volumes could be precisely measured with cine computed tomography (CT). Cine CT enables simultaneous imaging of the right and left ventricles at an 8 mm slice thickness with a maximal scanning rate of 17 frames/sec (50 msec acquisition intervals). In eight dogs, true right ventricular and left ventricular stroke volumes were determined by dividing thermodilution cardiac output by heart rate and/or with the use of an aortic electromagnetic flow probe implanted over a long term. After at least 5 sec of suspended respiration, cine CT images were acquired during central venous injection of a nonionic contrast agent. Multiple perturbations in stroke volume were induced in each dog by the administration of dobutamine, sodium pentobarbital, or sodium nitroprusside or by coronary artery occlusion. Right and left ventricular stroke volumes were obtained by Simpson's reconstruction of end-diastolic and end-systolic short-axis tomograms from apex to base. The cine CT left ventricular stroke volume (range 11 to 45 ml) correlated highly with the true left ventricular stroke volume (r = .99, slope = 1.01, y intercept = -0.2 ml, SEE = 1.5 ml, n = 25). The cine CT right ventricular stroke volume (range 11 to 34 ml) also correlated highly with the true right ventricular stroke volume (r = .98, slope = 0.9, y intercept = 2.2 ml, SEE = 1.7 ml, n = 15). In 12 studies, the mean difference between nearly simultaneous right and left ventricular stroke volumes by cine CT was 1.1 ml (range 0.1 to 3.2 ml). Calculation of right and left ventricular stroke volumes from data from cine CT were highly reproducible. Intraobserver variability in measurements of right ventricular stroke volume (r = 1.0, slope = 0.99, y intercept = 0.19 ml) and left ventricular stroke volume (r = 1.0, slope = 1.02, y intercept = -0.21 ml) was minimal. Interobserver variability in measurements of right ventricular stroke volume (r = .98, slope = 0.90, y intercept = 1.66 ml) and left ventricular stroke volume (r = .99, slope = 0.97, y intercept = -0.02 ml) was likewise minimal. Thus, precise and highly reproducible measurements of right and left ventricular stroke volumes can be obtained with cine CT.     

Quantitative radionuclide angiography in the right anterior oblique view: Comparison with contrast ventriculography

Because the right anterior oblique view is widely accepted as the best “single” projection for assessing wall motion, the utility of this view during first pass radionuclide angiography was studied in 44 patients who also underwent contrast ventriculography and coronary arteriography. Of the 44 patients, 8 had a normal heart and 14 had coronary artery disease with normal wall motion on contrast ventriculography. All also had normal contraction on radionuclide angiography. On contrast ventriculography, 22 patients had coronary artery disease and asynergy involving 34 left ventricular segments. Of 17 segments localized to the anterior and apical asynergic areas on contrast ventriculography, 16 were accurately localized with radionuclide angiography. Similarly, of 17 inferior asynergic areas, 13 were also shown to be inferior on radionuclide angiography. In addition, quantitative assessment of the severity of asynergy using the hemiaxis method demonstrated a good correlation between asynergic severity as defined with radionuclide angiography and contrast ventriculography. Of 11 anterior areas, 7 defined as hypokinetic with contrast ventriculography demonstrated chordal shortening of 20.1 ± 5.2 percent (mean ± standard error of the mean) (P < 0.005 compared with normal) on radionuclide angiography. Similarly, four akinetic or dyskinetic segments on contrast ventriculography demonstrated a greater reduction (4.0 ± 4.0 percent) in chordal shortening on radionuclide angiography (P < 0.05 compared with hypokinetic segments). Akinetic apical and inferior segments as defined with contrast ventriculography also showed a marked reduction in wall motion to 10.4 ± 7.3 percent and 7.5 ± 4.1 percent, respectively.After appropriate background subtraction, determination of ejection fraction using radionuclide angiography showed a correlation of 0.839 between the left anterior oblique and right anterior oblique projections independent of the sequence of injection. In addition, ejection fraction determined with radionuclide angiography in the left (r = 0.824) and right (r = 0.801) anterior oblique views correlated well with ejection fraction assessed from contrast ventriculography. Thus, first pass radionuclide angiography performed in the right anterior oblique view is a sensitive noninvasive means of assessing the location and severity of asynergy as well as global left ventricular performance in patients with coronary artery disease.     

Characterization of the human right ventricular pressure-volume relation: effect of dobutamine and right coronary artery stenosis

Right ventricular function was assessed in 15 patients using right ventricular pressure-volume loops. Right ventricular pressure using a micromanometer-tipped catheter, thermodilution cardiac output and gated blood pool scintigrams were simultaneously obtained. To help isolate the right ventricle, a slant hole collimator was used. The measurements were repeated during dobutamine infusion, which was titrated so there was minimal change in systemic pressure and heart rate. The right ventricular pressure-volume loop resembles the usual left ventricular loop except that the isovolumic contraction phase is often not as distinct, and right-sided ejection may continue well beyond right ventricular peak systolic pressure. Systolic but not diastolic function improved with dobutamine administration. There was no significant difference in right ventricular systolic function (ejection fraction, stroke work index, stroke volume index and cardiac index) or in end-diastolic volume index between patients without (Group I) and with (Group II) significant right coronary artery stenosis. However, there was a small but significant difference in right ventricular end-diastolic pressure (5.3 +/- 2.5 and 8.1 +/- 1.8 mm Hg [p less than 0.05]) for Group I and II, respectively. Thus, the right ventricular pressure-volume loop can be used to graphically display right ventricular function and improvement in contractility with dobutamine. The right ventricular isovolumic contraction phase and ejection phase differ from those in the usual left ventricular loop. Although there was a small difference in right ventricular end-diastolic pressure in patients with and without right coronary artery stenosis, the right ventricular pressure-volume loop did not provide additional discriminatory information between these two groups of patients.     

Comparative value of eight M-mode echocardiographic formulas for determining left ventricular stroke volume. A correlative study with thermodilution and left ventricular single-plane cineangiography.

Sixty-six consecutive patients without left ventricular volume overload, significant arrhythmia or significant pericardial effusion were examined by M-mode echocardiography immediately before diagnostic left- and right-heart catheterization. Using various echocardiographic measurements, left ventricular stroke volume (SV) was calculated according to eight different echocardiographic formulas (SVE) that have been proposed previously. At catheterization SV was also determined by thermodilution (SVT) and by single-plane left ventricular cineangiography in the right anterior oblique projection (SVA). When comparing SVE with SVT, the four formulas developed to calculate mitral or aortic flow failed (r = 0.10 to 0.54). As expected, poor correlations (r = 0.22 to 0.47) were also found when formulas used to calculate ventricular volumes from the ventricular diameter or SV from the change in diameter (left ventricular formulas) were used in coronary patients with grossly asymmetrical ventricular contraction patterns. When the use of the left ventricular formulas was confined to patients with symmetrical or almost symmetrical contraction, two formulas yielded favorable correlations of r = 0.84, SEE = 12.7 ml and r = 0.86, SEE = 12.2 ml, respectively. These correlations were comparable to the correlation between our two invasive reference techniques (r = 0.81; SEE = 12.2 ml). The comparison between SVE and SVA confirmed the results of the thermodilution study, though the correlations were generally weaker. We conclude that the formula of Teichholz et al., which was the best of all tested formulas, may be used to obtain a clinically useful estimate of SV in patients in whom symmetrical or almost symmetrical left ventricular contraction can be anticipated.