cctga dobutamine

Comparable Systemic Ventricular Function inHealthy Adults and Patients With UnoperatedCongenitally Corrected Transposition Using MRIDobutamine Stress TestingAli Dodge-Khatami, MD, Igor I. Tulevski, MD, Ger B. W. E. Bennink, MD, PhD,J. Francois Hitchcock, MD, PhD, Bas A. J. M. de Mol, MD, PhD,Ernst E. van der Wall, MD, PhD, and Barbara J. M. Mulder, MD, PhDDivisions of Cardiothoracic Surgery and Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, Division ofCardiothoracic Surgery, Wilhelmina Children’s Hospital, University of Utrecht, Utrecht, Department of Cardiology, LeidenUniversity Medical Center, Leiden, The Netherlands

Background. Failure of the systemic right ventricle(RV) often complicates adult survival in unoperated orphysiologically repaired congenitally corrected transpo-sition of the great arteries (CCTGA). Healthy controlsschematically represent an optimal outcome of anatomicrepair, which is increasingly performed to treat CCTGA.Magnetic resonance imaging dobutamine stress testingmeasures cardiac reserve, and sets to compare the leftventricle of controls with the systemic RV of unoperatedand physiologically repaired patients with CCTGA.

Methods. Baseline and stress magnetic resonance im-aging (maximum dobutamine dose, 15 �g/kg/min) as-sessed systemic RV function in 13 minimally or asymp-tomatic adult patients with CCTGA (unoperated, n � 7;physiologically repaired, n � 6). The left ventricles of 11healthy age-matched adults served as controls.

Results. Baseline and stress end-diastolic volumeswere similar between the systemic RV of unoperatedpatients and the left ventricle of controls, as well as baseline end-systolic volumes. Stress ejection fraction was

lower in unoperated and physiologically repaired pa-tients (70 � 6% and 60 � 5%, respectively, vs healthycontrols (84 � 8%). However, comparable with healthycontrols, both subsets of CCTGA patients respondedappropriately to dobutamine stress, as illustrated bysimilar RV stroke volume, heart rate, mean blood pres-sure, and cardiac index.

Conclusions. Compared with the left ventricles ofhealthy controls, both patient groups had larger systemicRV volumes, diminished ejection fraction, but an appro-priate response to dobutamine stress. Values of unoper-ated patients are closer to normal than physiologicallyrepaired patients. Magnetic resonance imaging dobut-amine may help to define the subgroups of CCTGApatients with favorable anatomy, whereby asymptomaticadult survival could be anticipated without the need foran operation.

(Ann Thorac Surg 2002;73:1759–64)© 2002 by The Thoracic Society of Surgeons

Right ventricular failure, tricuspid valve insufficiency,and complete heart block are established causes of

morbidity and mortality in patients with congenitallycorrected transposition of the great arteries (CCTGA)[1–7]. This may occur either in unoperated patients, orafter variants of the so-called “classic” or physiologicrepair, in which the morphologic right ventricle (RV) andatrioventricular valve remain in the systemic circulation.The disappointing natural history and surgical results ofphysiologic repair [1, 8–10] led to the concept of anatomicrepair, either the double switch procedure, or an atrialswitch plus Rastelli repair, which is increasingly pro-posed to treat symptomatic young patients with CCTGA.

Although the midterm follow-up of the anatomic repairhas shown encouraging results when performed early on[6, 11], the indication to do so remains uncertain in adults.Issues pertaining to left ventricular retraining beforeanatomic repair are paramount, and the extent to whichthis may be achieved is a major determinant of operativesuccess [11]. Furthermore, anatomic repair has met withits own set of complications, namely atrial arrhythmias,baffle obstructions, neoaortic valve insufficiency afterpulmonary artery banding, and the need for repeatconduit changes if a Rastelli repair is involved [6, 11, 12].In patients with CCTGA who are asymptomatic or older,or both, a large undertaking such as the anatomic repairwould seem questionable.

Magnetic resonance imaging (MRI) coupled with do-butamine stress testing can accurately assess cardiacreserve and represent an ideal noninvasive follow-upmodality in all patient groups with right ventricularoverload [13–15]. It allows for early detection of ventric-

Presented at the Poster Session of the Thirty-eighth Annual Meeting ofThe Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 28–30, 2002.

Reprint requests to Dr Dodge-Khatami, Division of CardiothoracicSurgery, Academic Medical Center, University of Amsterdam, Postbus22660, 1100 DD Amsterdam, The Netherlands; e-mail: [email protected].

© 2002 by The Thoracic Society of Surgeons 0003-4975/02/$22.00Published by Elsevier Science Inc PII S0003-4975(02)03553-1

ular dilation and impending failure, and may guidemedical or surgical management before symptoms ap-pear [13]. Our study uses dobutamine stress MRI in anattempt to define and predict the eventual subsets ofpatients who will never need an operation rather than ananatomic repair.

Patients and Methods

Thirteen asymptomatic or minimally symptomatic adultswith CCTGA (mean age, 28.1 � 11.5 years) and 11age-matched healthy volunteers were enrolled in ourstudy. Six patients with congenitally corrected transposi-tion had undergone multiple operations along the phys-iologic repair pathway between 1978 and 1995. Preoper-atively, 2 patients had presented with cyanosis, and 4 hadbeen in intractable heart failure. All were in New YorkHeart Association classes III-IV preoperatively, and allwere in sinus rhythm. Palliative procedures were per-formed in 3 patients at a mean age of 1.1 years (range, 0.4to 2 years), including pulmonary artery banding (n � 2),and a modified left Blalock-Taussig shunt (n � 1). Intra-cardiac physiologic repair was performed at a mean ageof 15.8 years (range, 3 to 61 years), and included closureof a ventricular septal defect (n � 3) or an atrial septaldefect (n � 3), tricuspid valve replacement (n � 2) orrepair (n � 1; reoperation), pulmonary valve commissur-otomy (n � 1), and insertion of a left ventricular-to-pulmonary artery valved homograft conduit (n � 1).There was no operative mortality and no incidence ofpostoperative complete heart block. At the time of theMRI dobutamine study, mean age was 29.5 � 18 years(range, 17 to 65 years). Three patients had residual 2 to3� tricuspid valve regurgitation, as assessed byechocardiography.

Equally studied were 7 asymptomatic adult patientswith unoperated CCTGA, with a mean age of 26.7 years(range, 22 to 35 years). One patient was in spontaneouscomplete heart block without a pacemaker, and the other6 were in sinus rhythm. Five of these patients had acombination of 9 associated intracardiac anomalies,namely an atrial septal defect in 2, a ventricular septaldefect in 3, pulmonary valve stenosis in 2, and Ebstein’sanomaly of the tricuspid valve in 2. Tricuspid valveregurgitation (2� to 3�), as assessed by echocardiogra-phy, was present in 4 patients.

Eleven age-matched healthy adults underwent thesame study protocol and served as controls (mean age,31 � 11 years).

Magnetic Resonance ImagingStudy subjects were placed supine in a 1.5 Tesla MRIscanner (Vision, Siemens, Erlangen, Germany) with highpower gradients. Electrocardiogram triggered T1-weighted turbo spin echo axial images were acquired,followed by four-chamber views of the heart. An electro-cardiogram-triggered, ultrafast, breath-hold gradient-echo cine sequence with the following measurements:repetition time � R-R interval; time of echo � 4.8 ms;slice thickness, 10 mm; imaging matrix � 256 � 256; field

of view � 350 mm; lip angle � 20° was then used toacquire images in the short axis plane in contiguous10 mm slices. End-systolic volumes and end-diastolicvolumes were calculated from this multi-slice, mul-tiphase image set. Velocity maps were acquired with aflip angle of 30°, Time to Echo � 5.0 ms, slice thickness �6 mm, field of view � 320 mm, and imaging matrix �256 � 256, velocity encoding � 250 cm per second. TheMRI protocol was repeated during dobutamine infusionwith an initial dose of 5 �g per kg per minute. Theinfusion rate was increased by 5 �g per kg per minuteevery 3 minutes to a maximum of 15 �g per kg perminute. The MRI protocol during the dobutamine studystarted 3 minutes after the maximum dose. During eachMRI measurement, the electrocardiogram, heart rate,and systolic and diastolic blood pressures weremonitored.

Image AnalysisA Unix workstation (Sun Microsystems, Palo Alto, CA)was used for analysis of the MR images. The MASSimage analysis software (Medis, Leiden, The Nether-lands) was used to display multi-slice, multiphase im-ages, both individually and in a movie loop mode.Frames for end-diastolic and end-systolic volumes weredetermined by manual outlining of a midventricularslice. Papillary muscles and the moderator band were notincluded in the ventricular volume. The enclosed RV andleft ventricle cross-sectional areas were measured bycomputer, multiplied by section thickness, and summedup according to Simpson’s rule to provide RV and leftventricle volumes.

CalculationsStroke volume was defined as end-diastolic volume mi-nus end-systolic volume. The RV ejection fraction wascalculated as stroke volume divided by end-diastolicvolume. The dobutamine stress values were calculated asa percentage increase from values at rest. All volumetricmeasurements were corrected for body surface area.

Statistical AnalysisDifferences between groups were compared with theunpaired t test. The effects of dobutamine within groupswere compared with the paired t test. A p value less than0.05 was considered statistically significant.

Results

All patients tolerated and completed the protocol. Detailsof results are given in Table 1.

At rest and at dobutamine stress, heart rate was com-parable between patients with physiologic repair, unop-erated patients with CCTGA, and controls. Mean arterialblood pressure was similar among all three groups atrest, but remained lower in unoperated CCTGA patientsat stress, as compared with controls. While assessingsystemic ventricles, the right ventricle of patients withCCTGA, unoperated or after physiologic repair, wascompared with the systemic left ventricle of controls.

1760 DODGE-KHATAMI ET AL Ann Thorac SurgMRI EVALUATION OF UNOPERATED CONGENITALLY CORRECTED TRANSPOSITION 2002;73:1759–64

Baseline mean systemic ventricular end-diastolic vol-umes were larger in the physiologically repaired groupper body surface area compared with controls. Afterdobutamine infusion, there was no significant differencein end-diastolic volumes between the three groups (Fig1). At rest the indexed mean systemic ventricle end-systolic volume was similar among unoperated and con-trols, but larger with dobutamine stress in unoperatedpatients as compared with controls. Mean systemic ven-tricle end-systolic volume was significantly larger in thephysiologically repaired group, both at rest and withdobutamine stress, as compared with controls. Meansystemic ventricular ejection fraction was lower at baseline (p � 0.002) and at stress (p � 0.001) in physiologicallyrepaired patients as compared with controls. Base linemean systemic ventricular ejection fraction was similar inunoperated patients as compared with controls, but waslower after dobutamine stress (p � 0.005). Mean indexedsystemic ventricular stroke volume and cardiac indexwere similar at baseline values among the three groups,and increased appropriately during dobutamine infusion(Figs 2, 3).

Comment

This is the first study to evaluate cardiac reserve inpatients with congenitally corrected transposition, eitherwithout previous operations or after physiologic repair,using stress dobutamine MRI. The MRI dobutamineprovides for an accurate and reproducible quantitativeassessment of RV volumes and function, and its routineuse in the follow-up of patients with RV overload hasbeen validated [13–15] to detect right ventricular dilation,or impending failure, or both. Disadvantages include thecost and the general contraindications to MRI, namelythe presence of metal implants, claustrophobia, andarrhythmia [13–15].

Assuming that the perfect result after anatomic repairentails normalization of systemic left ventricular functionand reserve, the left ventricle of healthy controls was

Fig 1. Variation of systemic ventricular end-diastolic volume(SVEDV) between baseline values and after dobutamine stress.(ns � not significant; PHYS � physiologically repaired; UN �unoperated.)

Fig 2. Variations in percentage between baseline values (0) and afterdobutamine stress testing. (BP � blood pressure; CI � cardiac index;EDV � end-diastolic volume; EF � ejection fraction; ESV � end-systolic volume; HR � heart rate; PHYS � physiologically re-paired; SV � systemic ventricle; SV sv � systemic ventricle strokevolume; UN � unoperated.)

Table 1. Effects of Dobutamine Stressa

Controls

PhysiologicallyRepaired

CongenitallyCorrected

Transposition ofthe Great Arteries

UnoperatedCongenitally

CorrectedTransposition of

the Great Arteries

Controls VersusPhysiologically

Repaired

ControlsVersus

Unoperated

Rest Stress Rest Stress Rest Stress p Rest/p Stressp Rest/p

Stress

Heart rate (bpm) 65 (12) 100 (14) 68 (15) 90 (9) 65 (14) 98 (27) NS/NS NS/NSMean BP (mm Hg) 82 (8) 95 (12) 70 (3) 88 (13) 70 (5) 87 (10) NS/NS p � 0.03/NSSVEDV/BSA (mL/m2) 62 (17) 63 (19) 92 (12) 88 (13) 78 (27) 76 (35) p � 0.02/NS NS/NSSVESV/BSA (mL/m2) 19 (9) 10 (4) 43 (5) 35 (4) 26 (12) 22 (10) p � 0.001/p � 0.001 NS/p � 0.005SVsv/BSA (mL/m2) 43 (10) 52 (16) 49 (11) 53 (11) 52 (15) 53 (26) NS/NS NS/NSSV EF (%) 71 (8) 84 (8) 53 (8) 60 (5) 68 (4) 70 (6) p � 0.002/p � 0.001 NS/p � 0.005CI (L/min/m2) 2.7 (0.6) 5.3 (1.7) 3.2 (0.1) 4.7 (0.6) 3.4 (1.3) 4.8 (1.8) NS/NS NS/NS

a Values in parentheses represent standard deviation.

BP � blood pressure; bpm � beats per minute; BSA � body surface area; CI � cardiac index; EDV � end-diastolic volume; EF �ejection fraction; ESV � end-systolic volume; NS � not significant; SV � systemic ventricle; SVsv � stroke volume.

1761Ann Thorac Surg DODGE-KHATAMI ET AL2002;73:1759–64 MRI EVALUATION OF UNOPERATED CONGENITALLY CORRECTED TRANSPOSITION

used to compare with the systemic RV of CCTGA pa-tients. In our study, the systemic right ventricle of asymp-tomatic adults with unoperated CCTGA showed similarejection fraction at rest, and lesser values at stress,compared with the systemic left ventricle of age-matchedhealthy controls. Suboptimal results were noted in pa-tients after physiologic repair. In these patients, both atbaseline and at stress testing, we found larger systemicventricular end-systolic volumes. Also, baseline systemicventricular end-diastolic volumes were larger after phys-iologic repair, compared with controls. As a snapshotvalue, the significance of this is unknown and difficult tointerpret. Is this the result of surgical insult to the rightventricle, the result of long-standing volume overload ofthe RV, or the normal response of a morphologic rightventricle when chronically faced with systemic pres-sures? Furthermore, what are the true implications ofthese morphometric deviations in light of an apparentproper response to effort? Indeed, with stress testing, wefound cardiac index to increase appropriately in bothsubsets of patients with CCTGA, without undue increasein heart rate or mean blood pressure, as compared withcontrols.

Symptomatic patients with CCTGA were originallytreated with a combination of surgical procedures, eitherpalliative or corrective, known as the “classic” or physi-ologic repair of CCTGA, leaving the right ventricle andtricuspid valve in the systemic circulation. In general, theresults of physiologic repair have been disappointing,despite an acceptable operative mortality rate of 2% to15% [1, 8–10, 16, 17]. In a 40-year review from the TorontoHospital for Sick Children, including 118 patients havingundergone a physiologic repair for CCTGA, Yeh andcolleagues [8] reported a 6% operative mortality. How-ever, 10 years after repair, survival was only 74%, and at20 years it was an unsatisfactory 48% [8]. Termignon andcolleagues [16] reported an even more concerning 55%survival rate at 10 years, when obstruction to the pulmonaryventricle was associated. Major concerns with physiologicrepair include the nonnegligible incidence of completeheart block (14% to 38%) [8, 10, 16, 18] and the frequentneed for reoperation on the tricuspid valve (Fig 4), but moreimportantly, the long-term failure of the right ventricle,which must chronically sustain systemic pressures.

These imperfections led to the development of theanatomic repair concept, combining an atrial and arterialswitch, also known as the double switch, or an atrialswitch with a Rastelli procedure in patients with leftventricular outflow tract obstruction [19]. The currentoperative mortality after anatomic repair varies between0% to 15% [6, 11, 12, 19–22]. However, anatomic repair isnot exempt of its own set of complications, and increas-ing concern is present as to the long-term developmentof atrial dysrhythmias and venoatrial obstructions, whichare well-documented after the atrial switch procedures[6, 12, 19, 21, 22]. Furthermore, certain timing issuesremain unanswered. The proponents of the anatomicrepair insist on the better outcome of the procedurewhen it is performed in a younger age group, namelybefore 15 to 16 years of age [6, 11]. This presumablyrelates to the degree to which the left ventricle may beretrained as the neosystemic ventricle by pulmonaryartery banding [11]. Indeed, older patients have higherearly and late mortality when submitted to the anatomicrepair protocol, and the results of left ventricle retraininghave been more uncertain when performed after the ageof 15 years [11].

The driving impetus towards the development of theanatomic repair of CCTGA stems from the preformedconcept that a left ventricle, with or without retraining,will ultimately perform better in the systemic circulationthan the right ventricle. However, there is no long-termdata to support this [6, 12, 23]. In a series of 27 patientsundergoing anatomic repair without early or late mortal-ity, Imamura and colleagues [20] reported normal post-operative ejection fractions of both left and right ventri-cles, as assessed by echocardiography at the time ofhospital discharge without further follow-up. Imai andcolleagues [6] reported an operative mortality of 7.9% ina series of 76 patients with CCTGA who underwentanatomic repair at less than 16 years of age. At a mean

Fig 3. Variation of cardiac index between baseline values and afterdobutamine stress. (PHYS � physiologically repaired; UN �unoperated.)

Fig 4. Gradient echo magnetic resonance imaging at rest. End-dia-stolic 4-chamber view of a patient with physiologically repairedcongenitally corrected transposition of the great arteries. (LV � leftventricle; RV � right ventricle; TP � tricuspid valve prosthesis.)


postoperative follow-up of 4.9 years, they actually ob-served a slight decrease in left ventricular ejection frac-tion, no increase in RV ejection fraction, and unchangedleft ventricular end-diastolic volumes [6]. Yagihara andcolleagues [22] found subnormal postoperative left ven-tricular ejection fractions as assessed by cardiac catheter-ization, at a mean follow-up of 11 months after anatomicrepair in their series of 10 patients.

Frequent failure of the right ventricle to chronicallyfunction as a systemic ventricle is another driving force topromote anatomic repair. However, findings across theliterature differ, and multiple reports of normal adultsurvival without limitation to effort or arrhythmia exist,in unoperated CCTGA without associated intracardiacanomalies (Fig 5) [2, 7, 24, 25]. Peterson and colleagues [4]compared 17 children after atrial baffle procedures forcomplete transposition of the great arteries, with 8 unop-erated patients with uncomplicated CCTGA, and 10normal controls. Using radionuclide angiocardiography,stress testing revealed a normal increase in pulmonaryventricular ejection fraction in patients with CCTGA, ascompared with controls. However, the systemic ventri-cles of patients with CCTGA did not significantly in-crease their ejection fractions with exercise, and bothend-diastolic and end-systolic volumes were larger thancontrols. Cardiac index augmented appropriately in allgroups, mainly because of an increase in heart rate in theCCTGA group [4]. In accordance with these findings,Parrish and colleagues [5] found subnormal increases inright and left ventricular ejection fractions in response toan effort in 5 children with CCTGA, although theirexercise capacity, heart rate, and blood pressure re-sponded appropriately. Supporting our findings, Bensonand colleagues [3] found normal systemic right ventric-ular ejection fractions at exercise in 8 patients withuncomplicated and unoperated CCTGA, whereas the

function of the pulmonary ventricle was subnormal. Intheir study using radionuclide angiocardiography, end-diastolic and systolic volumes of the systemic right ven-tricle decreased appropriately from rest to exercise [3].

Surgery is inevitable and clearly warranted in one formor another for symptomatic patients presenting in failureor cyanosis. In patients with associated intracardiacanomalies, such as pulmonary valve stenosis, Ebstein’smalformation with severe insufficiency of the tricuspidvalve, or important degrees of intracardiac shunting,early right ventricular dilation and failure occurs, indi-cating early surgical intervention. For these patients, weacknowledge the anatomic repair as the surgical proce-dure of choice [6, 11, 12, 17, 20–22]. However, we questionthe recommendation for anatomic repair in asymptom-atic patients by some [6, 12, 17], based on echocardio-graphic evidence of an enlarged right ventricle andtricuspid valve insufficiency. Our findings and otherevidence of satisfactory long-term RV function in unop-erated adults with CCTGA [3, 7, 24, 25] would suggest amore conservative attitude in the management of asymp-tomatic patients, which includes patients with and with-out associated lesions. Although it is intuitive and gen-erally agreed that asymptomatic patients with CCTGAand intact ventricular septum require no surgery, theyrepresent a minority. Given the potential complicationsof both surgical pathways and the relative unfavorablelong-term outcome of physiologic repair, we make a casefor surgical abstinence even in CCTGA patients withassociated lesions. Indeed, 5 out of 7 of our studiedpatients with unoperated CCTGA have intracardiacanomalies, but are otherwise asymptomatic, withoutmedication, have near normal ventricular volumes, andrespond appropriately to stress testing.

In conclusion, defining the eventual subsets of patientswith CCTGA who may never require an operation is ofparamount clinical importance. With current diagnosticmodalities, no such definition exists, and the therapeuticdilemma persists. Even respectable centers with a largerexperience of the anatomic repair provide no long–termfollow-up data to demonstrate improved systemic leftventricular function postoperatively [6, 11]. Accordingly,the open-ended question remains as to the true benefitand age cutoff to perform an anatomic repair in asymp-tomatic patients with CCTGA. Robust evidence is neededbefore more CCTGA patients with normally functioningright ventricles are enrolled in anatomic repair protocols.In those asymptomatic or minimally symptomatic pa-tients, the use of a noninvasive follow-up modality, suchas MRI dobutamine stress, could help to define morpho-logic and hemodynamic criteria justifying nonoperativemanagement. As a corollary, deviations from these crite-ria, especially in asymptomatic patients, could serve asan early indicator of impending cardiac failure, andindicate timely surgical intervention, preferably in theform of anatomic repair.

Study LimitationsOur ongoing MRI dobutamine stress protocol strives todefine noninvasive criteria, whereby asymptomatic patients

Fig 5. Gradient echo magnetic resonance imaging at rest. End-dia-stolic 4-chamber view of a patient with unoperated congenitally cor-rected transposition of the great arteries. Note the convex interven-tricular septum toward the left ventricle. (LV � left ventricle; RV �right ventricle.)

1763Ann Thorac Surg DODGE-KHATAMI ET AL2002;73:1759–64 MRI EVALUATION OF UNOPERATED CONGENITALLY CORRECTED TRANSPOSITION

with CCTGA may be judged as not requiring operations, oron the contrary, as impending failures and candidates fortimely anatomic repair. The small number of patients di-minishes statistical power, which limits the significance ofour results, and does not allow yet for a clear-cut manage-ment protocol according to the sought after criteria. To date,perhaps by unfortunate serendipity, we have had no pa-tients enrolled who either presented initially with normalvalues, which then degraded over time, or presented infailure with highly abnormal MRI dobutamine stress val-ues. These findings would strengthen the definitions of“normality” and deviations therefrom.

Using the left ventricle of healthy controls as a mea-suring stick to compare with the RV of patients withCCTGA is a potential weakness of the study. Although thetwo respective ventricles perform the same function in eachgroup, their intrinsic morphology and geometry are clearlydifferent.

As a group, patients with CCTGA present with a widevariety of morphology and resulting physiology, makinggeneralizations and recommendations across such a het-erogenous group hazardous. Owing to unfavorable anat-omy and physiology in many instances, we fully recog-nize that anatomic repair is often inevitable andindicated. Our data only illustrates and quantifies thepotential for a morphologic right ventricle to sustain thesystemic circulation, even in the presence of associatedintracardiac lesions. This view is supported by otherreports, which show normal exercise tolerance and qual-ity of life, in asymptomatic and unoperated adults withCCTGA [2, 3, 7, 24].

Doctor Tulevski is supported by The Netherlands Heart Foun-dation (NHS) and Interuniversity Cardiology Institute of TheNetherlands (ICIN-KNAW).

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