Left ventricular volume determination using colour superpositioning of contrast echocardiograms

m

,IOlmNd~ OF

European Journal of Ultrasound 2 (1995) 17-27

Clinical paper

Left ventricular volume determination using colour superpositioning of contrast echocardiograms Rainer J. Zotz*, Sabine Genth, Hansjiirgen Rupprecht, Rfidiger Brennecke, Raimund Erbel, Jiirgen Meyer 11. Medical Clinic, Johannes Gutenberg University, 55101 Mainz, Germany

Received 29 April 1994; revision received 2 September 1994; accepted 15 September 1994 Almraet Objective: To delineate the endocardium, selective colouring of contrast regions in left ventricular contrast echocardiograms was performed using digital image processing. Methods: Volume determinations were performed in enddiastolic and end-systolic frames before and after the injection of contrast agent into the left ventricle and were compared to cineventriculograms in 30 patients by two independent investigators. Results: The mean end-diastolic volume measured was 114 4- 44 ml in the native, 235 ± 79 ml in the contrast, 175 ± 70 ml in the color-superimposed (observer 1), and 187 ± 79 ml in the cineventriculographic images. Thus, native echocardiograms underestimated angiographic volumes by 39%, contrast echocardiographic pictures overestimated angiographic volumes by 26%o,and color-superimposed pictures underestimated angiographic volumes by 6%. The mean end-systolic volume measured was 61 ± 34 ml in the native, 126 ± 51 ml in the contrast, 88 ± 47 in the color-superimposed (observer 1) and 93 ± 53 in the cineventriculographic images. Ejection fractions were identical in the color-superimposed and angiograpliic images. In a two-factor cross classified analysis of variance the factor methodology showed significant differences for end-diastolic (P = 0.0001) and end-systolic volumes (P = 0.0001) and the ejection fraction (P = 0.0003), while the factor observer did not show significant differences (P = 0.046, 0.70 and 0.0435). Inter-observer variability was significantly lower for end-diastolic, end-systolic volumes and the ejection fraction (P = 0.0060, 0.0006 and 0.0001, F-test) in the color-superimposed images when compared to native echocardiographic images. Conclusion: Color superpositioning of contrast ecliocardiograms allows improved volume determination due to better left ventricular endocardial delineation. Keywords: Contrast echocardiography; Color superposition; Volume measurement; Ejection fraction

1. Introduction In conventional echocardiograms there are often so-called drop-outs, i.e. regions of left yen* Corresponding author.

tricular myocardium which do not reflect or scatter ultrasound beams back to the receiver. Consequently there is a large inter-observer variation in left ventricular volume measurements (Erbel et al. 1983). Contrast echocardiography allows better delineation of the left ventricular

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R.J. Zotz et al. /European Journal o f Ultrasound 2 (1995) 17-27

cavity in drop-out regions. There is however, fusion of contrast and tissue echoes, often due to the great echo intensity of the contrast agent. Digital subtraction echocardiography (Brennecke et al. 1982; Warm et al. 1984; Lange et al. 1985; Grube et al. 1987; Reval et al. 1987) has been used in the attempt to overcome this problem and has produced a selective visualization of contrast agent zones. Earlier work showed that subtraction imaging in echocardiography does not always achieve the improvements possible with digital subtraction angiography (Erbel et al. 1982; Mohr-Kahaly et al. 1987). The main disadvantage of the subtraction approach seems to be that tissue information, especially valvular and structural, is completely eliminated in the subtraction process. The aim of this study was to achieve a more correct volume determination, while avoiding the pitfalls of native echocardiography and digital subtraction echocardiography. Colour superpositioning of left ventricular contrast echocardiograms allows the simultaneous display of contrast and non-contrast echoes, combining the information from both imaging modalities.

2. s ~ i e m Ju~ ~

rowing over a length of 3 cm due to myocardial bridging. Subsequently, 18 patients were catheterized 1-6 months after successful PTCA as part of a routine follow-up. Seventeen patients had asynergy of the anterior myocardial wall, five asynergy of the inferior wall and one asynergy of both the anterior and inferior walls. 2.2. Catheterization

The left ventricle was catheterized retrogradely through a percutaneous puncture of the right femoral artery. The patients were fasting and were not taking any medication. In the 30° RAO projection, 35 ram cineventriculograms of the left ventricle were exposed at 50 frame~s with a contrast medium injection rate of 12 ml/s using a 0.5 ml/kg dose of meglumine sodium ioxalegiat (BYKGulden). During cineventriculography, the ECG and frame signals were recorded at a paper speed of 50 mm/s. No patient was in atrial fibrillation. End-diastole was identified from the Q wave of the ECG and end-systole from the frame with the smallest ventricular silhouette. The magnification

OUW~U~mlTIOU m'M'~'Amm~mualglY laoe~o~clIJix¢ m

2.1. Patients

Experiments were conducted in accordance with the ethical standards of the regional committee on human experimentation and with the Declaration of Helsinki. After obtaining informed consent, 35 consecutive patients were enrolled in the study. Five patients had to be excluded because the echocardiograms were unsatisfactory, leaving 25 males and 5 females who were undergoing catheterization for the evaluation of clinically suspected coronary artery disease. The mean age ( ± S.D.) was 55 ± 10 (range 35-75) years. Of these patients, 27 had coronary artery disease, one severe aortic insufficiency, one severe mitral stenosis and insufficiency, and one significant coronary nat-

Fig. 1. (a) Schematic diagram of the superpositioning principle. After analog to digital conversion the information obtained before the injection of contrast medium is displayed in two of the three channels of an ROB monitor. The information gathered after injection is displayed in the third channel, and thus in colour.

Fig. I (b) Schematic example of the superpositioning process. Fig. 2. Example of color superpositioning. (a) An example of a native end-diastolic echocardiographic picture. (b) Contrast enddiastolic image. (c) The image after the application of the superpositioning algorithm. (d) The native echocardiogram (a) with the contour of the color-superimposed echocardiogram (c).

R.J. Zot: et aL / European Journal of Ultrasound 2 (1995) 17-27

19

20

R.J. Zot: et al./ European Journal of Ultrasound 2 (1995) 17-27

factor was assessed by comparison with a metal ball filmed after catheterization in the position of the heart. Left ventricolar Wessure was recorded through a fluid-filledmtheter using a Statlmm P23 ID transducer. Selective coronary cimaltgiography was perfocmed by Judkins technique. Ventriculogrmns were reviewed by two experienced angiographers. 2.3. Two-dimensional echocardiography The cross-sectional echocardiographic studies were performed with a Toshiba SSH 160A realtime phased array sector scanner. The radius of the 2.25 MHz transducer was 0.6 cm at the site of skin contact. An 84° sector could be visualized and we selected a depth of 15 cm. Twenty-five frames/s were recorded on a video tape recorder (JVC BR6400U). Real-time and slow motion replays were qualitatively evaluated on a standard television monitor. Colour superpositioning was performed using a conventional R GB monitor. Echocardicq~phic images, made from an apical transducer position, were analyzed. From the region of the apex of the heart, they transected the long axis, providing images of the left ventricle, similar to those from the cineventriculographic RAO projection (Erbel et al. 1982; Erbel et al. 1983). Echoventriculography was performed before, during, and after the injection of the echo contrast agent into the left ventricular cavity. Satisfactory echocardiogram~ were obtained in 30 patients in the supine position. 2. 4. Contrast agent For echo contrast, 1 ml of Gclifundol (containing 55 g oxypolygelatine, 3.34 g Na +, 0.02 g Ca 2+, 3.55 g CI-, 1.83 g HCO 3- per 1000 ml) was injeeted into the left ventricle using a pigtail catheter (Mohr-Kahaly et al. 1987; product information Gelifundol 1990). The mean diameter of ~ air bubbles needed to create echo contrast w u 40 tan (range 8-60 ~m, M o h r - ~ y et al, 1987). 2.5. Color superpositioning After analog to digital conversion, end-diutotic and end-systolic frames of ~ beats, before and during contrast injection, were stored in a digital picture processing unit (FG100, ITI, USA) with a

resolution of 512 x 512 x 8 bits. This unit was interfaced to a personal computer (Compaq 386 25 MHz) ~ controlled i n ~ v e l y using interp r e t e r ~ commands (Microsoft C). A contrast picture was retrieved from the storage system and displayed in only one of the three colours of an RGB monitor (Fig. 1). A corresponding native picture, taken at the same time point within the cardiac cycle but before the injection of contrast medium, was then superimposed on the contrast picture in the remaining two colours of the RGB monitor, The difference, i.e. the contrast ~ t between corresponding fran'~es, was displayed in color. Regions in the pictures composed of equal information were displayed in all three colors and therefore appeared in the usual gray tones. Coloration of regions other than the contrast zones indicates one of the two following problems. Firstly, the selected pictures may not have originated from the same point within the heart cycle a ~ secondly, the ~ r i m p o s e d pictures may not have been obtained from the same position relative to the thorax w ~ . Different positions prod u ~ colour in all the regions of the picture, even where there was no contrast agent, especially at the left ventricular myocardial outer edges. In this way, the method marks regions of misregistration between the superimposed images. 2.6. Volume calculations End-dlagolic and end-systolic volumes were randomly analyzed and blinded to the results of ~ o g r a ~ y in the native (N), the contrast (C), and eolor-sul~rimposed (CO) echocardiographic ~ , as well as in the cineventriculograms (A) by two independent investigators using the same semiautomatic computer system by means of the slice method (Erbel et al. 1986; Erbel et al. 1987). The validity of the slice method has been confamed in asymmetric heart models for twoecbocardiography and radiography (Erbal et al. 1982). In all patients, the first three beats ~ the injection of contrast medium could be a a a t y ~ with both methods, without ext ~ interrupting the sequence. The time ~ by the first two investigators to outline the endocardial contour was measured by a third investigator.

R.J. Zot: et al./ European Journal of Ultrasound 2 (1995) 17-27

2.7. Statistics Mean values and standard deviations were calculated. According to the study design, two factors i.e. method of volume determination by either angiography, native, contrast and color-superimposed echocardiography and influence of observer, were analyzed using a two factor cross classified analysis of variance (Altman & Bland 1983; Bland & Altman 1986). For differences between the two methods regarding inter-observer variability the F-test (30, 30 degrees of freedom) was applied. For differences in time the investi-

21

gators needed to outline endocardial contours, a one way analysis of variance was calculated. Pvalues smaller than 0.01 were regarded as significant. In addition, for reasons of graphical clarity, for each variable (echo and angiograrns, observer 1 and 2), the percent differences to the angiographic 'true' values were calculated according to the formula:

.Echo (N

or C or CO) _ 1'~ x 100% Angio 1

Table la End-diastolic volumetric data for all 30 patients Patient

EDV(ml) AI

A2

NI

N2

C1

C2

COl

CO2

I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

203 224 96 158 204 304 84 164 151 178 115 178 152 201 105 349 96 144 185 131 234 141 113 202 219 122 344 407 222 188

189 215 lll 164 194 289 99 160 159 174 119 168 159 195 95 331 89 149 178 127 248 129 104 196 212 108 329 376 215 179

156 104 58 106 74 100 39 93 108 133 64 105 94 119 68 168 68 II0 Ill Ii0 121 ll5 79 132 141 94 209 252 151 132

184 165 65 89 139 176 58 112 95 119 79 123 112 139 59 245 62 99 131 84 165 88 65 155 171 82 246 325 178 119

275 259 149 189 243 354 123 189 179 221 165 231 186 239 176 389 162 169 232 166 290 189 189 230 293 206 422 438 267 235

245 289 167 231 271 369 135 204 202 209 134 212 206 257 155 365 137 175 255 188 303 192 169 239 303 188 388 451 278 245

204 169 97 153 159 268 86 156 149 176 119 117 157 205 96 288 93 141 175 ll5 219 142 III 183 176 162 321 389 229 201

208 179 90 149 173 258 79 152 144 168 101 125 143 195 112 292 109 155 166 122 222 131 122 199 169 144 322 370 225 184

Mean

187 79

182 73

114 44

131 63

235 79

239 79

175 70

174 67

S.D.

The numbers (!, 2) indicate the two observers. The mean and standard deviation (S.D.) are given at the bottom. EDV, end-diastolic volumes; A, angiographic volumes; N, volumes in native echocardiograms; C, volumes in contrast echocar. diograpms; CO, volumes in color-superimposed echocardiograms.

R.Z Zotz et al. I European Journal of Ultrasound2 (1995) 17-27

22 Table lb

End-systolic volumetric data for all 30 patients Patients

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Mean S.D.

ESV(ml) AI

A2

NI

N2

CI

C2

COl

CO2

142 114 45 85 59 184 43 55 70 102 36 34 59 89 59 218 63 55 62 78 146 46 49 99 llO 53 151 224 139 129

148 124 55 76 65 175 52 50 62 114 45 39 74 72 68 205 51 64 71 62 129 54 42 86 122 66 139 211 130 118

98 44 38 31 26 65 30 44 49 78 24 29 46 74 44 148 39 44 44 59 88 43 23 85 62 42 99 149 89 lOI

105 65 39 45 38 99 40 67 72 99 49 44 39 54 39 154 48 63 51 49 128 38 39 66 77 44 128 172 lOl 93

197 135 103 123 88 210 98 95 136 126 55 67 80 124 82 242 94 76 86 102 171 74 85 149 144 102 180 245 164 155

224 154 84 145 100 245 81 82 103 139 76 89 98 144 107 208 104 94 IOl 124 199 !02 99 138 173 92 165 274 145 165

145 77 49 76 40 157 42 58 72 98 40 26 58 91 56 t84 60 55 62 68 137 46 45 94 89 73 142 210 144 138

132 85 53 69 55 169 49 49 65 79 42 29 65 85 50 186 68 50 71 71 130 46 40 90 88 69 138 211 148 135

93 53

92 48

61 34

72 37

126 51

135 52

88 47

87 47

The numbers (1, 2) indicate the two observers. The mean and standard deviation (S.D.) are given at the bottom. ESV, end-systolic volumes; A, angiographic volumes; N, volumes in native echocardiograms; C, volumes in contrast echocardiograms; CO, volumes in color-superimposed echocardiograms.

where N represents native, C stands for contrast and CO marks color-superimposed echocardiograms (Echo), while Anglo stands for angiograms. The means of the percent differences ± the respective confidence intervals were plotted. Significance was anticipated, if the confidence interval did not include zero.

3. Remits An example of color superpositioning is demonstrated in Fig. 2, which displays the enddiastolic echocardiographic pictures of a patient after the injection of echo contrast medium into the left ventricle. The left bottom panel displays

R.J. Zotz et al. / European Journal~of Ultrasound 2 (1995) 17-27

23

Table lc Ejection fraction for all 30 patients Patients

EF(%) AI

A2

NI

N2

CI

C2

COl

CO2

1 2 3 4 5 6 7 8 9 10 11 12 13 14

30 49 53 46 71 39 49 66 54 43 69 81 61 56

22 42 50 54 66 39 47 69 61 34 62 77 53 63

37 58 34 71 65 35 23 53 55 41 63 72 51 38

47 73 42 65 81 63 48 61 48 34 70 76 59 47

28 48 31 35 64 41 20 50 24 43 67 71 57 48

9 47 50 37 63 34 40 60 49 33 43 58 52 44

29 54 49 50 75 41 51 63 52 44 66 78 63 56

37 53 41 54 68 34 38 68 55 53 58 77 55 56

15

44

28

35

25

53

31

42

55

16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

38 34 62 66 40 38 67 57 51 50 57 56 45 37 31

38 43 57 60 51 48 58 60 56 42 39 58 44 40 34

12 43 60 60 46 27 63 71 36 56 55 53 41 41 23

40 37 56 66 30 47 51 65 45 64 49 60 54 50 15

38 42 55 63 39 41 61 55 35 51 50 57 44 39 34

43 24 46 60 34 34 47 41 42 43 51 57 39 48 33

36 35 61 65 41 37 68 59 49 49 55 56 46 37 31

36 38 68 57 42 41 65 67 55 48 52 57 43 34 27

Mean S.D.

51 13

50 13

47 15

52 15

46 13

43 12

51 13

51 12

The numbers (1, 2) indicate the two observers. The mean and standard deviation (S.D.) are given at the bottom. EF, ejection fraction; A, angiographic volumes; N, volumes in native echocardiograms; C, volumes in contrast echocardiograpms; CO, volumes in color-superimposed echocardiograms.

the image that results f r o m the a p p li c a ti o n o f the superpositioning algorithm. T h e right b o t t o m panel shows the native e c h o c a r d i o g r a m with the c o n t o u r o b t a i n e d f r o m the c o l o r - s u p e r i m p o s e d picture, d e m o n s t r a t i n g that the c o n t r a s t m e d i u m flows into all the left ventricular trabeculations. Thus, greater v o l u m e s are o b t a i n e d by using

superpositioning than in native e c h o c a r d i o g r a m s alone. Tab l e 1 gives the e c h o c a r d i o g r a p h i c and angiographic v o l u m e s and ejection fraction data for all 30 patients. T h e results are shown for b o t h examiners (1 and 2) for the native (N), contrast (C), and c o l o r - s u p e r i m p o s e d (CO) pictures. Final-

R.J. Zotz et aL / European Journal of Ultrasound 2 (199S) 17-27

24

o.--..o H

o

= Observer

•

Observer

o

I 2

N

o

o •

o

o

= Observer = Observer

0

C

1 2

0

H

CO

CO

H

[

[

I

[

I

[

-50-40-.30-20-10

0

I

I

10 20

I

I

I

30 40 50

I

I

60 70

Fig. 3. Mean percent differences of end-diastolic angiographic values 4- confidence intervals. N = differences between native end-diastolic echocardiographic and angiographic values, C = differences between end-diastolic contrast cchocardiographic and angiographic values, CO = differences between end-diastolic color-superimposed echocardiographic and enddiastolic angiographic values.

ly, the angiographic results of one experienced angiographer are also listed.Angiography is still the accepted gold standard for this procedure. The mean end-diastolic volume by angiography was 187 4- 79 ml; the corresponding values reported by examiner 1 in the native images was 114 4- 44 ml, in the contrast images 235 4- 79 mi, and in the color-superimposed images 175 4- 70 ml. Thus, compared to the results of angiography, native cchocardiograms underestimated angiographic volumes by 39%, contrast echocar-

I

I

I

I

I

-50-40-30-20-10

0

I

I

I

v

o • v

EI~V

O O

O

= =

•

H

Observer Observer

I

70

diograms overestimated angiographic volumes by 26%, and color-superimposed pictures underestimated angiographic volumes by 6%. Similar results were found for the end-systolic volumes. The mean end-systolicvolume by angiography was 93 4- 53 ml; the corresponding values reported by examiner I in the native images was 61 4- 34 ml, in the contrast images 126 4- 51 ml, and in the color-superimposed images 88 4- 47 ml. Thus, compared to the results of angiography, native systolic cchocardiograms underestimated angiographic volumes by 340/0,contrast cchocardiograms overestimated angiographic volumes by 33%, and color-superimposed pictures underestimated angiographic volumes by 5%.

•

v

C

I

60

Fig. 5. Mean percent differences of angiographic ejection fractions 4- confidence intervals. For abbreviations see Fig. 3.

o----

N

I

10 20 .30 40 50

= Anglo = Echo = Contrast = Colour

o

I 2

ESV

•

'O "7

o

o

EF OO

CO

I

I

I

I

I

I

--50--40--30--20--10

)

0

I

I

I

I

10 20 30 40 50

I

I

60

70

Fig. 4. Mean percent differences of end-systolic angiographic values 4- confidence intervals. For abbreviations see Fig. 3.

-10

0

I

I

I

I

10

20

30

40

Fig. 6. Mean percent differences 4- confidence intervals between observer measurements concerning native (N), contrast (C), color-superimposed and angiographic (A) values.

R.J. Zot: et al. /European Journal of Ultrasound 2 (1995) 17-27

Mean ejection fractions were identical in the colour-superimposed and angiographic images. Both native and contrast echocardiography underestimated the angiographic ejection fraction by 8-16%. The mean percent differences reflect the same circumstances as depicted in Figs. 3-5. In the two factor cross classified analysis of variance the factor methodology showed significant differences for end-diastolic (P = 0.0001) and endsysatolic volumes (P = 0.0001) and the ejection fraction (P = 0.0003) using the different imaging modalities, while the factor observer did not show significant differences (P = 0.046, 0.70 and 0.0435). Colour superpositioning resulted in smaller differences between b o t h observers than with the other echocardiographic techniques for both enddiastolic and end-systolic volumes and the ejection fraction (Figs. 3-6). To compare the methods concerning interobserver variability, the F-test was applied (30, 30 degrees of freedom). For the differences between native and color-superimposed images concerning end-diastolic, end-systolic volumes and the ejection fraction, P values were = 0.0060, 0.0006 and 0.0001. There were no significant differences concerning the three parameters between contrast and color-superimposed images. The time both observers needed to outline the endocardium (including several approaches) averaged 75 ~- 33 s in the native, 63 4- 24 s in the contrast and 43 4- 17 s in the colour-superimposed images (P = 0.001). 4. Discussion

Since new contrast agents, capable of passing the capillary filter in the lungs, are currently being studied (Zotz et al. 1990; Schlief et al. 1991; Meltzer et al. 1982), it is of clinical significance to assess the value of methods using echo contrast medium to define the left ventricular border. Apart from the measurement-of myocardial perfusion (Feinstein et al. 1986; Clas et al. 1987; Ten Cate et al. 1987, Monaghan et al. 1988; Zotz et al. 1991, 1992, 1994) the analysis of left ventricular function remains the traditional application of contrast echocardiography (Wann et al. 1984;

25

Lange et al. 1985; Rovai et al. 1987). However, the relatively small difference in echo intensity between the left ventricular cavity and the myocardium, which is well opacified after the injection of suitable echocardiographic contrast agents, makes it rather difficult to differentiate between the left ventricular cavity and the myocardium. For this reason we employed the newly developed colour-superpositioning method to determine end-diastolic and end-systolic volumes and endocardial contours. The endocardial contours, found using contrast echocardiography and colour superpositioning, differed from those in the native echocardiograms. An example is depicted in Fig. 2. At the top left is the native echocardiographic picture; at the bottom fight it is overlayed with the left ventricular endocardial contour of the color-superimposed picture. The endocardial contour from color superpositioning extends partly into the left ventricular myocardium. Volume determinations performed in the native echocardiograms in this study were consistently less than those obtained using contrast echocardiography (Figs. 3-5). This is due to the fact that the contrast agent flows into all the left ventricular trabeculations, delineating the outer contour, as in cineventriculography. Due to the selective colouring of the contrast agent, which helped the observers discriminate between contrast medium and tissue echoes, smaller volumes were obtained using color superpositioning than contrast echocardiography. The visualization of the valve plane in particular facilitates definition of the left ventricular border, since in a large proportion of the cases, echo contrast also appeared in the atrium (in-dwelling catheter, mitral insufficiency). Finally, good agreement was obtained between the color-superimposed contrast echocardiograms and cineventriculography. By combining all the information provided by the native echocardiogram and the contrast echocardiogram, the colorsuperpositioning method overcomes the shortcomings of digital subtraction contrast echocardiography, which eliminates the information common to native and contrast images, i.e. echoes from tissue and especially from valves (Rovai et al.

26

R.J. Zot: et al./ European Journal of Ultrasound 2 (1995) 17-27

1987). This problem means that contrast medium in the atrium cannot be distinguished from that in the left ventricular cavity. A more complete comparison of the imaging capabilities of noncontrast and contrast echocardiography and of subtraction and color-superpositioning imaging is given in Table 2. The left ventricular cavity is visualized in native, contrast, and digital subtraction echocardiography. It can also be easily seen with colorsuperpositioning echocardingraphy. While the valves can be visualized by native echocardiography, they cannot be seen with contrast and digital subtraction echocardiography (Table 2). Since color superpositioning requires only limited computer capacity it could be readily incorporated into clinical instruments. A color Doppler instrument with a cine loop capability could implement these techniques at virtually no extra cost. 4.1. Criticism o f the method

There was insufficient opacification of the left ventricular cavity near the valve plane and increased inter-observer variation in patients with aortic and mitral regurgitation. It is striking that end-systolic native echocardiograms only tended to underestimate angiographic volumes which could have been caused by a bias of, in particular, the second observer. With superposition, the observers felt more comfortable outlining the valves and greater volumes were obtained mostly due to the effect of the new method on outlining the base of the heart. Since hing-passing echo contrast agents are not yet available, the introduction of a pigtail catheter into the left ventricular cavity continues to be a

Table 2 Comparison of methods N Cavity Valves Myocardium

C

DSE CSE

+

+

+

-

+

+

+ -

++ ++ ++

Advantages of different methods: N, nativeechocardiography; C, contrast echocardiography; DSE, digital subtraction echocardiography/angiography; CSE, contrast superposition echocardiography.

rather invasive procedure. However, with the advent of new lung-passing contrast agents with defined small bubble size, it seems very likely that they will be used for accurate volume determination providing a rather non-invasive possibility. However, our experience with SHU 508 and Albunex has shown that left heart opacification is dependent on pulmonary artery pressure for SHU 508 (Zotz et al. 1994) and on left ventricular pressure for Albunex (Zotz et al. 1990). Whether a completely newly designed substance (Zotz et al. 1991), with a defined small particle size with small size distribution insensitive to pressure, and with the capacity to opacify the peripheral arteries and organs (Zotz et al. 1992) in addition to the left ventricle, left ventricular volume determination with small amounts of contrast medium (less than 50 mg per examination) could become a clinical reality, remains to be investigated. There remained 10-15% of patients for whom we could not obtain satisfactory transthoracic echocardiograms due to emphysema, adipositas, and thorax malformations. In these patients the transesophageal echocardiographic approach would seem to be the appropriate alternative. 4.2. Clinical implication

Since one study could demonstrate that contrast echocardiography is probably a safe procedure (Mohr-Kahaly et al. 1987), this modality should be considered as a serious alternative to conventional cineventriculngraphy, especially in patients with allergies to conventional contrast agents, poor left ventricular function, hyperthyroidism, and impaired renal function.

We thank K. Schicketanz, M.D., Ph.D. (Institute for Medical Information and Documentation) for statistical advice and computation. Refereaces

Altman DG, BlandJM. Measurementin medicine:the analysis of method comparison studies. The Statistician 1983; 32: 307-317. BlandJM, Altman DG. Statisticalmethodsfor assessingagree-

R.J. Zot: et al./ European Journal o f Ultrasound 2 (1995) 17-27

ment between two methods ofclinical measurement. Lancet 1986; I, 1: 307-310. Brennecke R, Hahne HJ, Wessel A, Heintzen PH. Computerized enhancement techniques for echocardiographic sector scans. Computers in Cardiology, IEEE Computer Society 1982; 9-1 !. Clas W, Brennecke R, Zotz R, Erbel R, Jung D, Meyer J. Colour superposition: A new modality for contrast echocardiography, int J Card |mag 1987; 2: l l l - l l 9 . Erbel R, Krebs W, Henn G, schweizer P, Richter H, Meyer J, Effert S. Comparison of single-plane and biplane volume determination by two-dimensional echocardiography. !. Asymmetric model hearts. Eur Heart J 1982; 3: 469-480. Erbel R, schweizer P, Lambertz H, Henn G, Meyer J, Krebs W, Effert S. Echoventriculography - - A simultaneous analysis of two-dimensional echocardiography and cineventriculography. Circulation 1983; 67: 205-215. Erbel R, Pop T, Henrichs KJ, Olshausen Kv, Schuster C J, Rupprecht HI, $teuemagel C, Meyer J. Percutaneous transluminal coronary angioplasty after thrombolytic therapy: a prospective controlled randomized trial. J Am Coil Cardiol 1986; 8: 485-495. Erbel R, Zotz R, Henkel G, Schrciner (3, Steuernagei C, Zahn R, Kopp H, Clas W, Brennecke R, Schweizer P, Meyer J. Reliability and accuracy of echocardiography for follow-up studies after intervention. In: Roelandt J, ed. Digital techniques in echocardiography. Dordrecht, Netherlands: Martinus Nijhoff Publishers, 1987; 133-154. Feinstein $B. Myocardial perfusion imaging: contrast echocardiography today and tomorrow. J Am Coil Cardiol 1986; 8: 232-235. Grube E, Becher H, Backs B. Automatic contour finding and digital subtraction technique in 2-dimensional echocardiography. In: Roelandt J, ed. Digital techniques in echocardiography. Dordrecht, Netherlands: Martinus Nijhoff Publishers, 1987; 99-122. Lange PE, Sciffert PA, Pries F, Wessel A, Onnasch DGW, Hahne H J, Heintzen PH. Value for image enhancement and injection of contrast medium for right ventricular volume determination by two-dimensional echocardiography in congenital heart disease. Am J Cardiol 1985; 55: 152-157.

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Meltzer RS, Roclandt J, eds. Contrast ¢chocardiography. The Hague: Martinus Nijhoff, 1982. Mohr-Kahaly S, Erbel R, Zotz R, Duwe L, schreiner G, Meyer J. Left ventricular contrast ¢chocardiography using an oxypolygelatine solution - - influence on left ventricular hacmodynamic and contractility parameters. Z Kardiol 1987; 76: 699-705. Monaghan MJ, Quigiey PJ, Metcalfe JM, Thomas SD, Jewitt DE. Digital subtraction contrast echocardiography, a new method for the evaluation of regional myocardial pcrfusion. Br Heart J 1988; 59: 12-19. Product information Gelifundol. Frankfurt, FRG: Biotest Inc. Rovai D, Nissen S, Elion J, Distante A, DcMaria A. Limitations of digital subtraction contrast echocardiography in enhancing left ventricular endocardial definition. Am Heart J 1987; 113: 1437-1444. schlief R. Blood-pool enhancement with SHU-5OSA. Results of phase I! clinical trials. Invest Radiol 1991; 26: 188-189. Ten Cate FJ. Myocardial contrast 2-dimensional echocardiography: Analysis of myocardial perfusion. In: Roelandt J, ed. Digital techniques in echocardiography. Dordrecht, The Netherlands: Martinus Nijhoff Publishers, 1987; 39-46. Wann LS, Stickels KS, Bamrah VS, Cross CM. Digital processing of contrast echocardiograms: a new technique for measuring right ventricular ejection fraction. Am J Cardiol 1984; 53:1164-1168. Zotz R, schanz C, Erbel R, Waaler A, Meyer J. Improved left ventricular volume determination using i.v. injection of a lung passing echo contrast agent. Eur Heart J 1990; 11: 261. Zotz R J, Erbel R, Walch A, Krone V. A new biocompatible and biodegradable contrast agent for left heart opacification. Circulation 1991; 84; 11-161. Zotz R J, Walch A, Krone V. Left heart echocardiography and peripheral a/tery visualization using biodegradable microparticles intravenously. Circulation 1992; 86: 1-574. Zotz R J, Erbel R, Meyer J. Left heart contrast echocardiography - - An independent predictor of pulmonary artery pressure. Int J Card Imag 1994; 10: 195-203.