Comparison of magnetic resonance imaging with echocardiography and radionuclide angiography in assessing cardiac function and anatomy following mustard's operation for transposition of the great arteries

CONGENITAL HEART DISEASE

Comparisonof MagneticResonanceImagingwith Echocardiography and RadionuclideAngiographyin AssessingCardiacFunctionand AnatomyFollowing Mustard’sOperationfor Transpositionof the Great Arteries SIMON REES, FRCR, JANE SOMERVILLE, MD, CAROLE WARNES, MD, RICHARD UNDERWOOD, MA, DAVID FIRMIN, BSC, MPhil, RICHARD KLIPSTEIN, MA, BM, and DONALD LONGMORE, FRCS

stroke volume ratio in those with Doppler evidence of tricuspid regurgitation was 1.6:l compared to 1.I:! in those without, and this difference reached significance (p
The Mustard operation in infancy and childhood has successfully palliated many patients with transposition of the great arteries who have now survived to adulthood. Right ventricular dysfunction and tricuspid regurgitation are important determinants of late morbldlty and mortality. The value of noninvasive magnetic resonance Imaging (MRI) in the assessment of cardiac function and anatomy 9 to 20 years after this procedure has been investigated, and compared with findings on echocardiography, radionuclide ventriculography and angiography in 17 adult patients. Ejection fractions measured by MRI were higher compared with radionuclide ventriculography. The correlation for the left ventricle was closer (r = 0.75) than for the right ventricle (r = 0.49). Tricuspid regurgitation was assessed by Doppler echocardiography and by MRI using the right/left ventricular stroke volume ratio. The mean

(Am J Cardiol 1966;61:1316-1322)

T

he introduction of the Mustard atria1 baffle operation in 1964l for transposition of the great arteries (TGA) dramatically changed the prognosis in patients with this condition and enabled many to survive to adult life. However, the basic cardiac abnormalities remain unchanged and concern continues about the ability of the right ventricle to support the systemic circulation, the competence of the tricuspid valve and the effects of left ventricular outflow tract obstruction. In adults, morbidity and mortality may arise quickly and sometimes unexpectedly from right ventricular

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failure and tricuspid regurgitation2 Other surgical options3 applied before irreversible changes are established may avert disaster. Thus regular follow-up, often with repeated invasive as well as noninvasive studies, is needed. Venous and arterial access is frequently difficult because of paucity of vessels and many scars, and the patient often has an understandable reluctance to undergo further cardiac catheterization. Thus accurate noninvasive assessment of both functional and anatomical alterations is required. We assessed the value of magnetic resonance imaging

June I. 1988

TABLE I

Clinical and Functional

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Data Magnetic Resonancet

Age (w)

Age at Operation

1

15

10 mo

2

15

5mo

3

17

6 yrs

4 5

17 18

7mo 22 mo

6

18

13 mo

R

Additional Surgery Ligated PDA Patched VSD Redo Mustard (age 7) Patched VSD Resected LVOT 0 Ligated PDA Redo Mustard (age 7) 0

Residual Lesions

Radionuclide Angiography’ LV EF RV EF

RVDV (ml)

LVDV (ml)

RVEF

SV LVEF

RVlLV SV Ratio

Doppler TR

Small VSD 0

0.17

0.24

342

153

0.31

0.29

2.1

+

0.50

0.40

118

108

0.60

0.62

1.1

0

LVOT obstruction 0 0

0.25

0.43

106

65

0.87

0.75

1.4

+

0.44 0.43

0.61 0.77

118 160

90 85

0.58 0.52

0.66 0.76

1.3 1.3

+ +

svc

0.30

0.46

118

113

0.54

0.49

1.2

0

0 SVC and IVC obstruction 0 0 VSD VSD

0.36 0.48

0.57 0.66

185 90

115 89

0.49 0.69

0.68 0.83

1.2 0.8

0 0

0.45 0.35 0.51 0.34

0.55 0.51 0.83 0.50

162 83 194 85

64 65 145 111

0.49 0.84 0.85 0.80

0.60 0.80 0.65 0.50

2.0 1.0 1.3 1.1

+ 0 + 0

Situs inversus 0 0 0 0

0.51 0.41 0.43 0.53 0.26

0.57 0.21 0.57 0.59 0.60

140 344 116 226 174

116 124 83 154 113

0.65 0.50 0.55 0.54 0.47

0.65 0.31 0.54 0.51 0.58

1.2 2.1 1.4 1.5 1.3

0 + 0 + +

obstruction 7 8

19 20

2 yrs 3 yrs

9 10 11 12

20 20 21 23

5 yrs 17 mo 8 yrs 13 yrs

13 14 15 16 17

24 25 25 26 27

13 5 6 6 6

yrs yrs yrs yrs yrs

0 Ligated PDA Patched VSD 0 0 Palliative Ligated PDA Resected CoA Palliative Palliative 0 0 0 0

l The upper and lower limits for RVEF are 0.45 and 0.20, respectively; the upper and lower limits for LVEF are 0.75 and 0.48, respectively. t The upper and lower limits for RVDV are 190 and 110, for LVDV are 160 and 100, for RVEF are 0.48 and 0.38, for LVEF 0.75 and 0.47, and for RVlLV SV ratio 1.2 and 0.8, respectively. COA = coarctation of the aorta; DV = diastolic volume; EF = ejection fraction; IVC = inferior vena cava; LV = left ventricle; LVOT = left ventricular outflow tract: PDA = patent ductus arteriosus; RV = right ventricle; SV = stroke volume; SVC = superior vena cava; TR = tricuspid regurgitation; VSD = ventricular sep tal defect: + = present, 0 = absent.

(MRI] in studying the problems that occur in adults who have had intraatrial baffle procedures for TGA and compared it with the results of echocardiography, radionuclide ventriculography and angiography.

Methods Patients: All patients 15 years and over with TGA and a previous Mustard operation who were receiving care at the National Heart Hospital and who agreed to be studied are included. An MRI study was contraindicated in 1 patient who had an epicardial pacemaker, and a further patient was unable to enter the MRI scanner because of claustrophobia. From the Magnetic Resonance Unit, The National Heart and Chest Hospitals, London, and the Pediatric and Adolescent Unit, National Heart Hospital, London, United Kingdom. This study was supported by the British Heart Foundation 1986 (Dr. Warnes), Viscount Royston Trust (Dr. Underwood), Halle Stewart Trust [Dr. Firmin) and the Wolfson Foundation (Dr. Klipstein). Manuscript received November 16, 1987; revised manuscript received February 24, 1988, and accepted February 25. Address for reprints: Simon Rees, FRCR, Magnetic Resonance Unit, National Heart and Chest HospitaIs, 39 Britten Street, London SW3 6NN, United Kingdom.

There were 17 patients (6 male and 11 female] whose ages at the time of the MRI study ranged from 15 to 27 years (mean 21). The Mustard operation had been performed between the ages of 5 months and 13 years, and the period of follow-up was from 10 to 21 years (mean 16). Three patients had had closure of a ventricular septal defect at the time of the operation and 3 patients had had a palliative procedure in which the ventricular septal defect was left open because of severe pulmonary hypertension. The clinical data and operative procedures are summarized in Table I. Real-time cross-sectional echocardiography was performed in all patients using an ATL mechanical sector scanner and 3.5- and ~-MHZ transducers, and included pulsed-wave Doppler assessment of mitral and tricuspid valve regurgitation. All patients also had equilibrium radionuclide ventriculograms obtained after in vivo erythrocyte labeling with 740 MBq of technetium-9grn sodium pertechnetate. Sixteen frames were acquired in the left anterior oblique projection with 30~ caudal tilt using a Siemens mobile gamma camera (200 mm field of view] and a Medical Data Systems A2 computer. Fourier phase and amplitude images were constructed and used together with the end-diastolic image to assign Ieft and right ventricular regions of interest. Counts within these regions

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were used to calculate left and right ventricular ejection fractions after automatic functional background subtraction4 Magnetic resonance images were acquired using a Picker International Vista MR2055 operating at 0.5 tesla. A spin echo sequence (echo time 24 ms) was used to generate multiple contiguous transverse images at end-diastole and end-systole. Two repetitions of 128phase encoding steps were used and the slice thickness was 10 mm. Images were acquired in pairs and acquisition time for each pair was 3 to 4 minutes depending on heart rate. Left and right ventricular volumes were calculated by summing the areas of the chambers in each section, and the stroke volumes, ejection fractions and the left to right ventricular stroke volume ratio were derived, using methods previously described. w Gated multislice images were also acquired in coronal and sagittal planes in order to demonstrate the internal anatomy of the atria. All studies were performed on an outpatient basis and total imaging time was up to 60 minutes.

Results Anatomy: Great arteries: The connections and anatomic relations of the great arteries were visible in all

17 patients in both transverse and coronal slices (Figure 1). Patient 13 had a right-sided aortic arch with a patent ductus and a preductal coarctation that had been bypassed with a conduit; all of this was clearly seen by MRI but more difficult to detect on 2-dimensional echocardiography. Ventricular septal defect: Four patients (1, 11, 12 and 13) had a residual ventricular septal defect. Patient 1 had had an attempted patch closure at the time of the Mustard operation, and a residual small defect could be seen on angiocardiography, although it was not seen on &dimensional echocardiography or MRI. The defects in the other 3 patients who had had palliative operations (11, 12 and 13) were visualized on both &dimensional echocardiography and MRI (Figure 2). Left ventricular outflow tract obstruction: Patient 3 had slight left ventricular outflow tract obstruction suggested by the &dimensional echocardiogram, despite resection of left ventricular muscle at the time of her Mustard operation. Bulging of the interventricular septum and narrowing of the left ventricular outflow was visible on MRI (Figure 3). The gradient could not be assessedbut the Doppler echocardiogram suggested it to be about 30 mm Hg. The patient is asymptomatic and has not been recatheterized.

FIGURE 1. Contiguous l-cm coronal slices in patient 15 showing anatomy of transposition of the great arteries. A is posterior, D is anterior. AsA = ascending aorta: PT = pulmonary trunk; AA = aortic arch; WC = superior vena cava; RV = right ventricle; LV = left ventricle; RPA = right puimonary artery; LPA = left pulmonary artery, P = pericardium.

June 1, 1988

Baffles: The intraatrial baffle is constructed from a trouser-shaped patch that is sewn inside the atria1 cavity. The baffle directs the systemic venous blood from the venae cavae to the mitral valve and left ventricle. This connection could be followed best in contiguous transverse slices, and could be seen as a relatively narrow channel lying in the posterior part of the atria1 cavity (Figure 4). Two patients (6 and 8) had had slight caval obstruction with gradients of 3 and 5 mm Hg, documented at cardiac catheterization 15 and 7 years previously, but on MRI this was no longer evident. No patient had apparent caval or pulmonary venous obstruction on MRI and this correlated with the absence of clinical signs. Because of the complex oblique orientation of the baffle, however, it was not generally possible to follow the whole struture through contiguous slices and echocardiography may be a superior imaging method in patients in whom baffle obstruction is suspected. Function: Measurements of functional parameters are listed in Table I, together with the relevant normal ranges for ventricular function as measured by radionuclide ventriculography and MRI. MRI measurements of right ventricular diastolic volumes ranged from 83 to 344 ml (mean 162). Patients 1, 11,14 and 16 had diastolic volumes above the upper limit of normal; 2 of them (1 and 14) have developed severe symptomatic right ventricular failure and tricuspid regurgitation in the last 2 years. Both have pulmonary hypertension and are awaiting cardiopulmonary transplantation. Right ventricular ejection fractions, measured by MRI (0.31 to 0.69, mean 0.59), were consistently higher than those estimated by radionuclide ventriculography (0.17 to 0.53, mean 0.39). Correlation between the 2 was poor but significant (r = 0.50, p ~1.05, standard error of the estimate = 0.09) (Figure 51, but the data were all within the normal range for both techniques, except in patient 1 (Table I). MRI measurements of left ventricular diastolic volumes range from 64 to 154 ml (mean 105) and the ejection fractions ranged from 0.29 to 0.83 (mean 0.60). Comparable measurements by radionuclide ventriculography ranged from 0.21 to 0.77 [mean 0.52). Two patients (1 and 14) had low left ventricular ejection fractions and both have severe pulmonary hypertension. Left ventricular ejection fractions measured by MRI tended to be higher than those obtained by radionuclide angiography, but this was not invariable. The correlation between the 2 techniques is shown in Figure 6 (r = 0.66, p 1.2 in 10 patients, 9 of whom (1, 3, 4, 5, 9, 11, 14, 16 and 17) had clinical and Doppler evidence of tricuspid regurgitation. Patient 15 had a stroke volume ratio of 1.4, but no tricuspid regurgitation on Doppler. Using Student’s t test, there was a significant difference (p
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to those without [mean 1.12) [Figure 7); however, it should be noted that 4 of the patients had a residual ventricular septal defect, which would affect the interpretation depending on the size and direction of the interventricular shunt. In patients 1 and 12, the defects were small but in patients 11 and 13, who had larger defects, the assumption that an abnormal ratio was indicative of tricuspid regurgitation could not be made.

Discussion Survivors of the Mustard operation, however well, are likely to develop problems at some time in adult life, because the right ventricle supports the systemic circulation and any diminution in function with tricuspid regurgitation has serious consequences.7 Tricuspid regurgitation may develop independently of right ventricular failure and valve replacement may be consid-

FIGURE 2. A, transverse slice through atria and ventricles in patient 12 showing small ventricular septal defect (arrow). B, transverse slice through atria and ventricles in patient 13 showtng dextrocardia and a large inlet ventricular septal defect (curvedarrow). The mitral and tricuspid valves are attached to the same point at the base of the atrial septum (sfraighf arrow). LV = left ventricle; RV = right ventricle: LA = left atrium; RA = right atrium; DA = descending aorta.

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ered. Early detection of right ventricular dysfunction is important so that treatment can be given to prevent further deterioration. Alternatively, a Z-stage proce-

dure involving banding of the pulmonary artery to “retrain” the left ventricle, followed by an arterial switch and take-down of the atria1 baffle, may be indi-

FIGURE 3. Contiguous transverse silces in patient 3 passing craniaiiy through ventricles (A) to great arteries (D) showing thick interventricular septum (straight arrow) and narrowing of left ventricular outflow tract (curved arrow). RV = right ventricle; LV = left ventricle; AA = ascending aorta; PT = pulmonary trunk; WC = superior vena cava.

FIGURE 4. A, transverse slice in patient 7 through upper atrium showing intraatriai baffle (small arrows). The right pulmonary veins (large arrow) enter the atrium behind it and the superior vena cava in front of it. B, slice below A showing connecting channel (arrow) between superior vena cava and left ventrlcle via mitral valve. C, transverse slice through lower atrium showing inferior vena cava posterior to atriai cavity. D, slice above C showing connection of inferior vena cava behind intraatriai baffle (smaff arrows) to left ventricle via mitral valve. SVC = superior vena cava; AA = ascending aorta; PT = puimonary truck; DA = descending aorta; LV = left ventricle; IVC = inferior vena cava; RV = right ventricle.

June 1, 1968

cated in some patients3 This can only be considered if the ventricular dysfunction is not too advanced and has not already affected the left ventricle as a result of pulmonary hypertension. Two-dimensional echocardiography is currently the routine method of noninvasive assessment, although minor early changes in ventricular size and function may not be detectable. Left ventricular ejection fraction can be measured accurately by equilibrium radionuclide ventriculography, although it exposes the patient to a small dose of radiation and involves an intravenous injection. Right ventricular ejection fraction can also be measured using this method,8 although the results are less accurate and consistently low because of the overlap between the right ventricle and atrium in the left anterior oblique projection.g The first pass technique is more reliable but the older single crystal gamma cameras may not be capable of handling the high count rates involved in a first pass study. The advantages of MRI are that it involves no ionizing radiation and no genetic or biologic effects at the field strengths used. It is also completely noninvasive and causes no patient discomfort. The tomographic images can be acquired in any plane, and the absence of signal from moving blood using spin echo sequences provides natural contrast. The technique has been shown to be accurate in the diagnosis of congenital heart disease.lO It has also been shown to be dimensionally accurate. In normal subjects measurement of the left to right ventricular stroke volume ratio by the transverse multislice method yields a figure close to the theoretical value of 1 and in any individual volume measurement the error is approximately 2% .5The disadvantages include the cost, the necessity of having RIGHT VENTRICULAR

EJECTION FRACTION

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the patient lie still during acquisition of the images, the time required for each study (about 1 hour), the problems of image degradation from atria1 fibrillation, the occasional failure due to claustrophobia and the contraindication of a pacemaker. LEFT VENTRICULAR

EJECTION

FRACTION

1

d I6’ 0 0.6

0.4

0.2

0 0

0.2

0.4

0.6

0.8

1

Magnetic resonance FIGURE 6. The dotted line represents the line of identity; r = 0.66; standard error of the estimate = 0.12

TRICUSPID

REGURGITATION

3

1

2.5

; 0.8

,

0

2

I #’

0.6

1.5 0.4 1

0.2

0.5

0

0 0

0.2

0.4 Magnetic

0.6

0.8

1

resonance

FIGURE 5. The dotted line represents the line of identity; standard error of the estimate = 0.09.

r = 0.50;

Absent

Present

Doppler FIGURE 7. MRI measurement of right/left ventricular stroke volume ratio compared to Doppler assessment of tricuspid regurgitation.

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We have described our early experience with MRI in adolescents and adults with TGA following Mustard’s operation. MRI provides a complete anatomical and functional assessment, which can be repeated as often as necessary and which compares favorably with other noninvasive methods.

References 1. Mustard WT. Successful two-stage correction of transposition of the great vessels. Pediatr Sure 1964:55:469-472. iI Warnes CA, Somirville 1, Transposition of the great arteries: results in adolescents and adults late after the Mustard procedure. Br Heart J 1987;58: 148-156.

3. Mee RBB. Severe right ventricular failure after Mustard or Senning operation. J Thorac Cardiovasc Surg 1986;92:385-390. 4. Goris ML, Briandet PA, Huffer E. Automation and operator independent data processing of cardiac and pulmonary functions: role, methods and results. In: Di Paofo R, Kahn E, eds. Information Processing in Medical Imaging. Proceedings of the 6th International Conference. Paris: INSERM 1979:88:

427-448.

5. Longmore DB, Klipstein RH, Underwood SR, Firmin DN, Hounsfield GN. Watanabe M, Bland C, Fox K. Poole-Wilson PA, Rees RSO. Denison D, McNeilly AM, Burman ED. Dimensional accuracy of magnetic resonance in studies of the heart. Lancet 1985;1:1360-1362. 6. Underwood SR. Klipstein RH, Firmin DN, Fox KM, Poole-Wilson PA, Rees RSO, Longmore DB. Magnetic resonance assessment of aortic and mitral regurgitation. Br Heart / 1986;56:455-462. 7. Park SC, Neches WH, Mathews RA, Fricker FJ. Lee BB, Fischer DR, Lenox CC, Zuberbuhler JR. Hemodynamic function after the Mustard operation for transposition of the great arteries. Am 1 Cardiol 1983;51:1514-1519. 8. Murphy JH, Barlai-Kovach MM, Mathews RA. Beerman LB, Park SC, Neches WH, Zuberbuhler JR. Rest and exercise right and left ventricular function late after the Mustard operation: assessment by radionuclide ventriculography. Am J Cardiol 1983;51:1520-1525. 9. Underwood SR, Klipstein RH, Firmin DN. Fox K, Poole-Wilson PA. Rees RSO. Longmore DB. Magnetic resonance assessmentof the accuracy of radionuclide methods for the ouantification of valvular regurgitation and atria1 shunting. In: Hoejer R. B&gm& H. eds.‘Radioactive&oropes in Medicine and Research. Vienna: Verfag H. Egerman 1986;17:299-305. 10. Didier D, Higgins CB, Fisher MR. Osaki L, Silverman NH, Cheitlin MD. Congenital heart disease: gated MR imaging in 72 patients. Radiology 1986;158:227-235.