European Heart Journal (1992) 13 (Supplement E), 15-21

Left ventricular segmental volume by conductance catheter and Cine-CT E. T. VAN DER.VELDE*, A. D. VAN DIJK*, P. STEENDIJK*, L. DIETHELMI, T. CHAGASI, M. J. LIPTON*1\

S. A. GLANZt AND J. BAAN* *The Department of Cardiology, University Hospital Leiden, The Netherlands; fThe Department of Radiology, University of Chicago, U.S.A.

KEY WORDS: Ventricular volume, conductance catheter, computed tomography. The ability of the conductance catheter method to measure left ventricular segmental and total volume was evaluated by comparison with the Cine-CT technique. In the seven dogs studied, 19 conductance catheter and simultaneous Cine-CT runs were obtained. High correlation coefficients were found for total volume and segmental volumes, except in the basal segment. However, in most cases there was a significant variability in slope and intercept between animals. Both methods are promising tools for estimating dynamic segmental left ventricular volume, each having specific advantages such as a continuous signal (conductance catheter) or anatomic detail (Cine-CT). However, the results also show the need for further improvement of both methods.

Introduction

Methods

The conductance catheter method, developed in our laboratory in Leiden, has previously been shown to give reliable estimates of stroke volume and absolute left ventricular volume1'"31. It has thus been extensively used to study global left ventricular function'4"9'. However, the ability of the catheter to measure individual segmental volumes has thus far been only investigated in one theoretical study*101. The Cine-CT system, developed at the University of California in San Francisco (UCSF), can estimate segmental volumes at relatively high speeds, which makes it extremely suitable for a comparative study. Compared to other, conventional methods, the Cine-CT has the advantage of being a tomographic method, without using any geometric assumptions, while providing high spatial and temporal resolution1"-121. Recent experimental studies have indicated that the relation between conductance-derived left ventricular volume and 'real' volume may become non-linear when volume is varied over a wide range'13-1*1. Theoretical studies had already predicted this phenomenon110-151. Comparison of segmental and total ventricular volume measured by the conductance catheter and by the Cine-CT could shed some new light on the assumed non-linearity. Therefore, the purpose of the present study was to compare segmental volumes as well as total volume measured by the conductance catheter technique and by the Cine-CT system.

THE CONDUCTANCE CATHETER METHOD

Correspondence Enno T. van der Velde, PhD, Department of Cardiology, University Hospital Leiden, C5-P, P.O. Box 9600, 2300 RC Leiden, The Netherlands This work was supported in part by grant LGN 04.0061 from the Dutch Foundation for Technical Sciences (STW) to Dr Baan and by grant HL-25869 from NIM to Dr Glantz.

0195-668X/92/0E0015 + 07 $08.00/0

The conductance catheter method is based on measuring the time-varying electrical conductances of five segments of blood in the left ventricle, which are proportional to the intraventricular volume of each of those segments. The conductance catheter, in its original design as used in this study, has eight electrodes equidistantly placed^at the distal end. The catheter is positioned along the long axis of the left ventricle, with the tip in the apex, and the upper electrode just above the aortic valve (Fig. 1). Through the most proximal and most distal electrodes a constant alternating current is applied (30 //A RMS, 20 kHz), setting up an electrical field in the ventricular cavity. From the six remaining electrodes, which definefivesegmental volumes,fivetime-varying segment conductances, G|(t), (i = 1-5) are measured. Segmental ventricular volume Vj(t) then follows from G,(t) as:

V,(t) =

(1)

where en is a segmental slope constant, L is the inter-electrode distance, and Oi, is the conductivity of the blood. G? is the segmental parallel conductance (see below). Total left ventricular volume, V(t), is calculated from G(t), the sum of the five segmental conductances, as: V(t) = [l/a].[L*/ojJ.[G(t)-GP],

(2)

where a, is the slope factor and Gp is the parallel conductance for total volume. The average value for the slope factor, a, found theoretically1101, in the isolated heart'31 and in vivo12' is approximately 0-8. For clarity, in this study all slope factors (a, a;) are assumed to be 1-0. Comparison of segmental and total conductance catheter volumes with the corresponding segmental and total Cine-CT volumes will © 1992 The European Society of Cardiology

16

E. T. van der Velde et al.

Imatron Inc., San Francisco, CA, U.S.A.) at the department of Radiology, University of California at San Francisco, was used in this study. Conceived and built by Douglas Boyd, a physicist in the department of Radiology at the University of California, San Francisco, the Cine-CT scanner uses an electron beam instead of an X-ray tube source'11-12-16!. p o u r semicircular X-ray-generating tungsten target rings are sequentially activated by focusing and sweeping an ECGtriggered electron beam along each target ring. Each target ring may be activated in 50 ms, producing two contiguous, 8-mm thick tomographic slices. Each of the four targets is separated from its neighbour by 4 mm (Fig. 2). As a consequence of this, it can image eight 1-cm thick ventricular segmental cross-sections by consecutive scans on each of the four target rings without moving the subject. Acquired images are stored in fast memory (32.6 MBytes) or on hard disk (948 MBytes), enough to hold 4000 images. Images are reconstructed off-line in a matrix of 256 X 256 pixels. The pixel size ranges from 0-49-1-86 mm; thus, with an average pixel size of 1 mm and the height of a segment of 1 cm, this would result in a theoretical error due to digitization of 0-01 ml. INSTRUMENTATION AND PROTOCOL

Figure 1 Schematic representation of a conductance catheter positioned in the left ventricle. Electrodes 1 and 8 are the current electrodes, used to set up the electrical field. The other electrodes are to measurefivevoltage differences, which are used to calculate the electrical conductances of the five segments defined by the measuring electrodes (dotted lines).

then give an independent estimate of these slope factors. The system used for current generation and for processing the measured signals is the LEYCOM Sigma-5 signal-conditioner processor (CardioDynamics, Rijnsburg, The Netherlands). Measurement of blood conductivity, c^, needed for calibration, is incorporated in the Sigma-5, with a special cuvette to be filled with 4 ml of blood. This calibration was performed every half hour and also after infusions of fluids which might have altered blood conductivity (saline, sodium-bicarbonate). The conductance catheter not only senses the conductance of the blood in the ventricular cavity, but also the conductance of the myocardium and other surrounding tissues. This parallel conductance factor is estimated by injection of a small amount (0-5-2 ml) of hypertonic saline into the pulmonary artery121. In patients 5% or 10% NaCl is used, in a bolus of 5-10 ml. THE CINE-CT METHOD

Conventional computed tomography has not been widely used for cardiac diagnosis because the exposure time, which is in the order of seconds, is too long for cardiac applications. Moreover, one such scan only yields information about one selected tomographic level. Heat storage problems associated with the X-ray tube source of conventional rotating fan beams make it unfit for continuous exposures. The recently developed computed tomographic (CT) scanner (C-100,

The study was performed in eight anaesthetized closed chest dogs, but because no data were acquired in one dog (dog 55) owing to a faulty conductance catheter, the results were taken from only seven dogs For anaesthesia, 4 ml of droperidol and fentanyl (Innovar-Vet, 10 ml.10 kg"1 i.v.) were administered 30 min before delivery of the animal to the lab, and 3 ml of sodium pentobarbital on arrival of the animal. Each hour, 1-5 ml of Innovar-Vet was given, and additional sodium pentobarbital as needed. A conductance catheter (Cordis Europa, Roden, The Netherlands), with 1 cm electrode spacing chosen so that the height of each conductance catheter segment corresponded with the height of one segment of the Cine-CT scanner, was placed in the left ventricle under fluoroscopy. A balloon-flotation catheter was placed with its tip in the pulmonary artery for the injection of hypertonic saline in order to measure the parallel conductance. After these procedures, the animal was brought to the Cine-CT room and placed in the scanner. Image enhancement was achieved by intravenous injection of 30-50 ml of a non-ionic contrast agent (Angiovist). First, localization scans were acquired to assure proper position of the animal in the scanner, and to assure the correspondence of Cine-CT cross-sections and those of the conductance catheter. All Cine-CT acquisitions were performed in a short-axis position corresponding to the way the conductance catheter method 'sees' the left ventricle. Then, circulation time runs were taken to estimate the required amount and injection speed of the contrast medium. After this, the actual data runs were acquired under various loading conditions: control, after infusion of atropine (in single doses of 0-25 mg), after administration of dopamine (continuous infusion at a rate of 1 mg.min"1), after blood lettings and after successive retransfusion. During each run, segmental Cine-CT scans at two adjacent levels were obtained at 10 sequential 50 ms intervals. These were repeated every other heartbeat for the other three pairs so that eight segmental Cine-CT scans were available within 4 X 500 ms in eight

LV segmental volume

Electron biam /

17

Focus coil Oefltction coil

Vacuum pumps

Figure 2 Schematic illustration of the Imatron C-100 scanner. The electron beam is focused and deflected at an angle of 33° to 37°, then swept 210° along one of four fixed tungsten target rings, as depicted. The fan beam of radiation produced then passes through the subject, impinging on two rows of stationary detectors above the patient. (Reproduced from1"', with permission).

sequential heartbeats. With a heart rate of 120 b.mirr1, corresponding to an R-R interval of 500 ms, a run of 10 consecutive images at 50 ms intervals means that exactly one heart cycle can be acquired. However, at lower heart rates, a cardiac cycle can only partially be acquired. DATA ACQUISITION AND ANALYSIS

The five segmental conductance catheter signals plus ECG were recorded on FM analog tape. A Cine-CT sync pulse was also recorded to match the conductance catheter signal with the instant each Cine-CT image was taken. After the experiment, the analog signals were analog-to-digital converted on a DEC PDP 11/70 computer with a sample frequency of 250 Hz. Conductance catheter signal samples acquired during each Cine-CT scan, which takes 50 ms, were averaged and this mean value was used for comparison with the Cine-CT volume values from that scan. After reconstruction of the Cine-CT images, contour detection was performed using a semi-automatic edge detection method, and the cross-sectional area of each slice was computed. The volume of each segment then followed from multiplication by the height of each segment (1 cm). Total left ventricular volume was calculated as the sum of the five intraventricular Cine-CT segments, corresponding to the conductance catheter segments. For each run, linear regression analysis was applied to the segmental conductance catheter volumes versus the corresponding segment Cine-CT volume value. From the CineCT segments analysed, only those inside the left ventricle were used for comparison with the conductance catheter. If occasionally more thanfiveCine-CT segments were usable, the Cine-CT versus conductance catheter segment combination with the highest overall correlation coefficient was used. IN-VITRO MEASUREMENTS

Conductance catheter After all in-vivo data were recorded, the heart was arrested with KG and excised from the thorax. The coro-

nary ostia were ligated and tied, and the same conductance catheter as used during the in-vivo study was placed via the aortic root in the left ventricle. The left atrium was removed, and a plastic disc with a fluid inlet was placed in the mitral valve annulus. With a calibrated syringe, connected via a tube to the inlet of the plastic disc, the intracavitary volume could be changed from 0 to maximal volume (50-60 ml) in calibrated steps, and the measured conductances were recorded'17'. Note that this procedure only gives a calibration of total left ventricular volume. Cine-CT After the above procedure, the left ventricular cavity was filled with radiopaque cast made of silicone rubber (3110 RTV, Dow Corning Corporation, Midland, Michigan, U.S.A.). After settling of the material, Cine-CT scans were made of the heart with the cast inside the left ventricle. The myocardium was then removed, and the cast gradually submerged in water in steps of 1 cm using a home-made device. For each step, the amount of water displaced (and thus the volume of one segment with a height of 1 cm) was recorded. The volume of each segment, as measured by the Cine-CT scanner, was compared with that of the water-displacement method to check the accuracy of the Cine-CT method to measure segmental volumes. STATISTICAL ANALYSIS

Linear regression analysis was applied to compare conductance catheter volume and Cine-CT volume, both segmentally and in total. To test whether the results of the linear regression analysis (slope, intercept) on conductance catheter volume versus Cine-CT volume were different for different animals, or different under the various conditions (control, atropine or dopamine, blood letting, retransfusion) repeated-measures analysis of variance was performed by multiple linear regression with dummy variables using effects coding1'81. There were six dummy variables to represent the seven animals, and four dummy variables for thefiveconditions. To determine the statistical significance of the effects of different animals and of different conditions,

18

E. T. van der Velde et al.

Catheter Cine-CT

1

3

0-00

5

7

9

600 12-00 Cine-CT(mt)

Figure 3 Panel (a) Plot of time-varying segmental Cine-CT signal from one run in dog 54, and of the time-varying conductance catheter signal from the corresponding segment (segment three, see Fig. 1). Panel (b) the same two signals as in panel (a), but now plotted as conductance catheter signal versus Cine-CT signal. The dashed line is the line of identity, the drawn line results from applying linear regression analysis (slope: 106, intercept: 1-64 ml, correlation coefficient: 0-975).

an F-test was performed by dividing the mean square error of the set of (dummy) variables by the mean square of the residual error. Results In the seven animals studied, a total of 33 Cine-CT runs were acquired, under various conditions: control, after administration of dopamine (continuous infusion at a rate

of 1 mg.min ') or atropine (in single doses of 0-25 mg), after blood letting and after successive retransfusion. Generally, six or seven Cine-CT segments showed opacification. Of the 33 Cine-CT runs, only 19 were analysed; the other runs could not be analysed usually because of inadequate opacification. Figure 3(a) shows an example of segmental data obtained at 50 ms intervals during one heart beat: segment three from the conductance catheter and the corresponding Cine-CT segment, segment five. There was noticeable similarity between the two segmental volume signals. Figure 3(b) shows the same data but now plotted as conductance catheter volume versus Cine-CT volume. The drawn line is the result of applying linear regression analysis; the dashed line is the line of identity. Linear regression analysis was applied to all individual segmental conductance catheter and Cine-CT data. Results from the 19 analysed runs are summarized in Tables 1-3 and reveal good to excellent correlations in the four lower left ventricular segments (mean slopes: 0-78-0-99, mean intercepts: 0-2-3-9 ml, mean correlation coefficient (R): 0-900-0-940). Correlation in the upper segment (near the aorta) was poor (IRI < 0-6) in nine of 19 runs, probably because of uncertainty about the mitral valve position in the Cine-CT image. Total volume from both methods, obtained from summation of five segmental volumes, correlated well (mean R: 0-965) with an average slope of 0-82 and an average intercept of 7-52 ml. F-tests revealed statistically significant differences in slope and intercept in all segments between different animals, and in two of the four segments analysed between the interventions. No multiple regression analysis was applied on the results of segment 5 due to the small number of runs (10) available. For total volume, a statistically significant difference in the intercept was found between animals and between interventions, but not in the slope. When only end-diastolic and end-systolic conductance catheter and Cine-CT (total) volumes from each run were compared, this resulted in a plot as shown in Fig. 4. Linear regression analysis yielded the following relationships: for all data points (end-diastolic volume; EDV and end-systolic volume; ES V): conductance catheter volume = 0-71 X CineCT volume + 9-36 ml, R = 0-81. Linear regression analysis on EDV and ESV separately gave slopes of 0-48 and 0-71, intercepts of 21-32 ml and 7-79 ml, and correlation coefficients of 0-57 and 0-60 respectively. IN-VITRO MEASUREMENTS

After the in-vivo measurements, both methods were tested in an in-vitro situation, where the measured volume

Table 1 Results of multiple linear regression analysis on results of comparison between segmental and total volumes for 19 runs: slopes Slope Mean SD Between animals Between intervals

Segment 1

Segment 2

Segment 3

Segment 4

Segment 5

Total

0-93 0-59 P < 001 P 0-6 (10 out of 19). Multiple linear regression analysis was not applied in results for segment five (see text), ns = not significant; na = not applicable (see text).

LV segmental volume

19

Table 2 Results of multiple linear regression analysis on results of comparison between segmental and total volumes for 19 runs: intercepts (ml) Intercept Mean SD Between animals Between intervals

Segment 1

Segment 2

Segment 3

Segment 4

Segment 5

Total

113 1-62 P 0-6 (10 out of 19). Multiple linear regression analysis was not applied in results for segment five (see text), ns = not significant; na = not applicable (see text). Table 3

Results of comparison between segmental and total volumes for 19 runs: correlation coefficients

Correlation coefficient Mean SD

Segment 1

Segment 2

Segment 3

Segment 4

Segment 5

Total

0-926 0-107

0-923 0-126

0-940 0-076

0-900 0105

0878* 0-095*

0-965 0037

*For segment five, only results are included where R > 0-6; mean and standard deviation of correlation coefficient of all runs was 0-535 ± 0-417.

was compared against 'real' volume. The results of these invitro measurements were not used to calibrate either of the methods, but are shown only as a reference to appraise the accuracy of each method. Conductance catheter In five hearts, isolated after the in-vivo measurements, conductance catheter volume was compared with 'real' left ventricular volume. The results are shown in Table 4. Linear regression analysis yielded high correlation coefficients, an average slope of 0-62 and average intercept of 29-39 ml. Note the small variability in slopes between the different animals. The intercept reflects the parallel conductance term, as mentioned earlier. Cine-CT The volume values of all segments, as measured afterwards by the Cine-CT with the cast material inside the left ventricle, were compared with the values obtained from

32 48 Cine-CT (ml)

64

80

Figure 4 End-diastolic (closed squares) and end-systolic (closed diamonds) volumes measured with the conductance catheter method, versus those measured by the Cine-CT method, in the 19 runs obtained. The lines drawn are the results of linear regression analysis on end-diastolic points only (dashed line), on end-systolic points only (dashed/dotted line) and on all points (fully drawn line). For numerical results of linear regression analysis, see text.

submerging the cast in steps of 1 cm. Data from a total of 29 segments (from five ventricles) resulted in a linear relation of Cine-CT segmental volume versus cast segmental volume: Cine-CT-volume = 111 X Cast-volume + 1-71 ml, R = 0-782. Discussion

Conventional CT scanners can be used to estimate left ventricular volume'1'1, but their major problem is the relatively long exposure time of 1 to 5 s compared with the length of the cardiac cycle. The Cine-CT system, as developed at UCSF, employs an electron beam instead of an X-ray tube source, and therefore can acquire one image in 50 ms. The advantages of the conductance catheter method are, compared to routine methods for measuring ventricular volume such as angiography, that it gives a continuous volume signal, that it requires no human interaction such as image selection and borderline detection, and that it does not affect ventricular performance or ventricular volume itself, such as may be induced by the (bolus) injection of contrast medium necessary for measuring ventricular volume by angiography120"221. The present study was designed to evaluate the ability of the conductance catheter technique to estimate total and segmental left ventricular volume, by comparison with ventricular volume as measured with the Cine-CT system. In seven dogs, Cine-CT and simultaneous conductance catheter runs were acquired at various loading conditions. Also, in vitro calibrations of both the conductance catheter method and Cine-CT method were performed. The segmental volume and total volume values from 19 Cine-CT runs were compared with the corresponding values from the conductance catheter method. High correlation coefficients were found when linear regression analysis was performed on conductance catheter volume versus Cine-CT volume, for total volume and for four out of five segmental volumes. Only the upper segment, near the mitral and aortic valve, gave a poor correlation coefficient of 0-535. Comparison of total volume resulted in an average corre-

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E. T. van der Velde et al.

Table 4 Calibration of conductance catheter: results of linear regression analysis on total conduaance catheter volume versus 'real' volume, measured in post mortem heart

Dog 52 Dog 53 Dog 54 Dog 57 Dog 58 Average

Range (ml)

Correlation coefficient

Slope

Intercept (ml)

0-60 0-60 0-60 (MO 0-60

0-996 0-994 0-996 0-999 0-995 0-996 ±0-002

0-62 0-57 0-65 0-69 0-59 0-62 ±0-04

30-42 47-60 30-00 17-53 21-64 29-44 ± 10-33

lation coefficient of 0-965, and a slope and intercept of 0-82 and 7-52 ml respectively. Repeated measures analysis of variance, using multiple linear regression with dummy variables for the different animals and conditions, revealed statistically significant differences between dogs for the slopes of all segments but not for total volume, and also for the intercepts in all segments and in total volume. There was a significant difference between the slopes in two out of four segments, but not in total volume. A significant difference between intercepts was found in one out of four segments, and in total volume. Thus, slopes and intercepts varied significantly from dog to dog, and also between different conditions, albeit not in all cases. Inspection of Fig. 3(b) reveals slight hysteresis, with a faster decrease in Cine-CT volume than in conductance catheter volume, which might lead to an uncertainty in slope and intercept of the conductance catheter versus Cine-CT relation. This phenomenon, which was present to some degree in all runs, is probably caused by the relatively low sample frequency of the Cine-CT system. Although we decided to average the conductance catheter signal over the 50 ms period that the Cine-CT system needs to acquire one scan, a different presentation of the conductance catheter data might have led to different results. The results of comparing end-diastolic and end-systolic data, as presented in Fig. 4, have also probably been influenced by this timing phenomenon, leading to a rather large scatter in the data points. Also, the low sample frequency of the Cine-CT system will make exact timing of the EDV or ESV point difficult. However, the observed scatter has probably been predominantly determined by the inter-animal variability in slopes and intercepts. It was interesting to note that the slope for the ESV relation is somewhat steeper than for the EDV relationship, which indicates a slight non-linearity in the relation between conductance catheter volume and Cine-CT volume. This resembles the results from a recent study where conductance catheter volume was compared with volume obtained by angiography113'. Also, the results of the in-vitro measurements with the conductance catheter in the present study, where volume was varied over a wide range (see Table 4), showed slight non-linearity. However, the presence of this non-linearity is probably influenced by the type of experiment or the range over which volumes are measured, since in another recent study no significant influence of volume on parallel conductance was found'81. A recently introduced modification of the conductance catheter method, which employs a second electrical field, has been shown to reduce the variability in segmental slopes and to further

improve the linearity1231. However, this modified method was not available when the present study was performed. Results of the in-vitro measurements of Cine-CT volumes of casts of the left ventricle show that the Cine-CT method slightly overestimates 'real' volume, with a slope of 1-11. The linear regression correlation coefficient was moderate (0-782), demonstrating the existence of considerable scatter in the results. Conclusion The aim of this study was to evaluate the ability of the conductance catheter method to measure segmental left ventricular volume. The Cine-CT method, as developed at the department of Radiology of UCSF, was chosen because it is capable of estimating segmental ventricular volume at high speed. A highly linear correlation was found for total volume and for four out of five segmental conductance catheter volume signals. However, correlation in the upper segment was poor, most likely due to uncertainties in defining the upper boundaries of the Cine-CT segment in this region. Also, considerable differences in slopes existed between segments, and for total volume, between animals. These results reveal the need for further improvement of the conductance catheter method, e.g. the dualfieldmethod which has been recently developed by our group'23'241. Both methods are promising tools for estimating dynamic segmental left ventricular volume. The conductance catheter offers five segmental volume signals continuously and on-line with a relatively inexpensive system, while the Cine-CT system gives a real 3-D reconstruction of the left ventricle showing more anatomical details, but only during a few consecutive heart beats. This study could not have been accomplished without the excellent experimental skills of Jim Stoughton and of Leona Campbell in managing the Cine-CT scanner. We also thank Steve Sizemore for his help with the software and hardware to analyse the data and for helping with the BitNet connection between the CVRI and Leiden after we left San Francisco.

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[4] Thormann J, Huttin J, Kremer P et al. Do class 1 antiarrhythmic drugs impair myocardial contractility? The class 1A examply of ajmaline (conductance catheter technique). J Cardiovasc Pharmacol 1990; 16:182-90. [5] Kass DA, Marino P, Maughan WL, Sagawa K. Determinants of end-systolic pressure-volume relations during acute regional ischemia in situ. Circulation 1989; 80:1783-94. [6] Kass DA, Grayson R, Marino P. Pressure-volume analysis as a method for quantifying simultaneous drug (amrinone) effects in arterial load and contractile state in viva J Am Coll Cardiol 1990; 16: 726-32. [7] Van Der Velde ET, Burkhoff D, Steendijk P et al. Nonlinearity and load sensitivity of end-systolic pressure-volume relation of canine left ventricle in vivo. Circulation 1991; 83: 315-27. [8] Teitel DF, Klautz R, Steendijk P et al. The end-systolic pressure-volume relationship in the newborn lamb)—effects of loading and inotropic interventions. Pediatr Res 1991; 29: 473-82. [9] Schreuder JJ, Biervliet JD, Van Der Velde ET et al. Systolic and diastolic pressure-volume relationships during cardiac surgery. J Cardiothor Vase Anesth 1991; 5: 539-45. [10] Mur G, Baan J. Computation of the input impedances of a catheter for cardiac volumetry. IEEE Trans Biomed Eng 1984; BME-31:448-53. [11] Garrett JS, Lanzer P, Jaschke W et al. Measurement of cardiac output by cine computed tomography. Am J Cardiol 1985; 56: 657-61. [12] Fanner D, Lipton MJ, Higgins CB et al. In vivo assessment of left ventricular wall and chamber dynamics during transient ischemia using cine computed tomography. Am J Cardiol 1985; 55: 560-5. [13] Boltwood CJ, Appleyard RF, Glantz SA. Left ventricular volume measurement by conductance catheter in intact dogs. Parallel conductance volume depends on left ventricular size. Circulation 1989; 80:1360-77.

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[14] Applegate RJ, Cheng CP, Little WG Simultaneous conductance catheter and dimension assessment of left ventricle volume in the intact animal. Circulation 1990; 81: 638-48. [15] Spinelli JQ Valentinuzzi ME. Conductivity and geometrical factors affecting volume measurements with an impedancimetric catheter. Med Biol Eng Comput 1986; 24: 460-64. [16] Boyd DP, Gould RG, Quinn JR et al. A proposed dynamic cardiac 3-D densitometer for early detection and evaluation of heart disease. IEEE Trans Nucl Sci 1979; NS-26: 2724. [17] Van Der Velde ET. Ventricular pressure-volume relations and loading conditions in vivo; methods and mechanisms. The Netherlands: Leiden University, 1989: Chapter 3. [18] Glantz S A, Slinker BK. Primer of applied regression and analysis of variance. New York: McGraw-Hill, Inc., 1990. [19] Herfkens JR, Axel L, Lipton MJ et al. Measurement of cardiac output by computed transmission tomography. Invest Radiol 1982; 17: 550. [20] Chapman CB, Baker O, Reynolds J, Bonte FJ. Use of biplane cinefluorography for measurement of ventricular volume. Circulation 1958; 18:1105-17. [21] Dodge HT, Sandier H, Ballew DW, Lord JJ. The use of biplane angiocardiography for the measurement of left ventricular volume in man. Am Heart J I960; 60: 762-776. [22] Dodge HT, Sandier H, Baxley WA, Hawley RR. Usefulness and limitations of radiographic methods for determining left ventricular volume. Am J Cardiol 1966; 18:10-24. [23] Steendijk P, Bouman P, Van Der Velde ET, Baan J. Total and segmental LV volume by dual excitation of the conductance catheter. Circulation 1988; 78 (Suppl II): 225. [24] Baan J, Van Der Velde ET, Steendijk P, Koops J. Calibration and application of the conductance catheter for ventricular volume measurement. Automedica 1989; 11: 357-65.

Left ventricular segmental volume by conductance catheter and Cine-CT.

The ability of the conductance catheter method to measure left ventricular segmental and total volume was evaluated by comparison with the Cine-CT tec...
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