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ORIGINAL ARTICLE

Card iology Journal2009, Vol. 16, No. 1, pp. 2025Copyright 2009 Via Medica

ISSN 18975593

20 www.cardiologyjournal.org

Address for correspondence: Jacek Biakowski, Congenital Heart Diseases and Pediatric Cardiology Department,

Silesian Centre for Heart Diseases, Zabrze, Szpitalna 2, 41800 Zabrze, Poland, tel./fax: +48 32 271 34 01,e-mail: [email protected]

Received: 25.07.2008 Accepted: 2.10.2008

Utility of the dobutamine stress echocardiographyin the evaluation of the effects of a surgical repair

of aortic coarctation in children

Pawe Banaszak1, Magorzata Szkutnik1, Jacek Kusa1, Beata Banaszak2, Jacek Biakowski1

1Silesian Medical University, Silesian Center for Heart Diseases Congenital Heart Diseases

and Pediatric Cardiology Department, Zabrze, Poland2Silesian Medical University Peditrics Department, Zabrze, Poland

Abstract

Background: Exercise-induced hypertension following repair of the coarctation of the aorta(CoA) is a well known phenomenon. The most important functional parameters in the assess-

ment of the effects of a surgical repair of CoA are the maximal pressure gradient in the

descending aorta (GRAD) and systolic blood pressure (SBP). Results of treadmill exercise test

using the Bruce protocol (treadmill test) and dobutamine stress echocardiography (DSE) were

compared to determine utility of the DSE in the evaluation of the effects of surgical treatment of

CoA in children.

Methods:The studypopulation comprised of 29 patients, including 20 males and 9 females(mean age 12 years) who underwent a surgical repair of CoA. Changes of the cardiovascular

parameters including SBP, GRAD and heart rate (HR) during the treadmill test and DSE

were compared.Results: During the treadmill test, SBP at peak exercise ranged from 120 to 230 (mean

163.7) mm Hg, GRAD ranged from 29 to 109 (mean 59.8) mm Hg, and HR ranged from

140 to 188 (mean 169) bpm. At the end of DSE, SBP ranged from 123 to 215 (mean 164.7) mm Hg,

GRAD ranged from 29 to 113 (mean 55.4) mm Hg, and HR ranged from 76 to 155 (mean 111) bpm.

We found positive correlations of SBP (r = 0.68, p < 0.001) and GRAD (r = 0.82,

p < 0.001) values during both tests but no significant correlation for HR (r = 0.42, p = NS).

Conclusions:Dobutamine stress echocardiography is useful in the evaluation of the effects ofsurgical repair of CoA in children. (Cardiol J 2009; 16: 2025)

Key words: coarctation of the aorta, dobutamine stress echocardiography,

treadmill exercise stress test

Introduction

Coarctation of the aorta (CoA) comprises 47%of all congenital cardiovascular disease. Significantanatomic variance of CoA is seen, and its hemodyna-

mic effects depend on the degree of stenosis and thepresence of collateral circulation. Elective surgicalrepair of CoA is performed at the age of 612 mon-ths. If heart failure ensues, surgical treatment mustbe undertaken immediately following the diagnosis.


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Pawe Banaszak et al., Dobutamine stress after surgical repair of aortic coarctation

www.cardiologyjournal.org

The effects of surgical repair depend on localanatomical conditions, experience of the surgeon,and the age of the patient. Long-term follow-up stu-dies after surgical repair showed that left ventricu-lar function is impaired even after an apparently

successful repair, with persistence of left ventricu-lar hypertrophy and diastolic dysfunction, thus le-ading to shortened life expectancy compared tohealthy control subjects [1, 2]. Patients who under-went surgical repair of CoA are at risk of typicalcomplications of arterial hypertension includingatherosclerosis, myocardial infarction, stroke, andpremature death [1]. Data available in the literatu-re suggest that resting hypertension is present in1030% of patients following surgical repair, andexercise may induce hypertension in 3065% ofsuch patients [2]. Patients with normal resting blo-

od pressure but significant exercise-induced hyper-tension are a particular subset that may be identi-fied by a stress testing, most commonly an exerci-se test. As the latter is not feasible in the youngestchildren, we aimed to determine the utility ofa pharmacological stress testing such as dobutaminestress echocardiography (DSE) in the evaluation ofthe effects of surgical repair of CoA.

Methods

We studied 29 consecutive patients after a sur-gical repair of CoA who were seen at the Depart-ment of Congenital Heart Disease and PediatricCardiology in Zabrze, Poland. We included patientswho were operated at least one year before the stu-dy entry, were less then 18 years old at the time ofthe study, and were able to cooperate adequatelyduring the treadmill exercise test and DSE. Exclu-sion criteria included other coexisting congenitalheart disease including bileaflet aortic valve.

The study protocol and a parent questionnairewere approved by a local Ethics Committee.

We studied 20 male and 9 female patients. Theirage ranged from 4.5 to 17.1 years (mean 12 years).

The subjects underwent treadmill exercise testusing the Bruce protocol. Blood pressure was me-asured on the right arm at rest, at the end of each3-minute exercise stage, at the end of the exercisetest, and every 3 minutes during a 12-minute reco-very. At the same time, blood flow velocity in thedescending aorta was determined using an echocar-diographic system by placing an Doppler ultraso-und probe in the suprasternal notch (Hewlett--Packard 2000 or Sonos 5500, CW Doppler 2.5MHz).Doppler tracings were recorded on a video casset-te and reviewed following the termination of the

exercise test. Maximal pressure gradient was cal-culated using the simplified Bernoulli equation as4 V2, where V is maximal flow velocity. The exerci-se test was terminated at submaximal exercise orif one of the following conditions was met: abnor-

mal ECG, excessive blood pressure rise, or patientrequest due to fatigue, pain, or dyspnea.

Dobutamine stress echocardiography was sub-sequently performed in a supine position, with con-tinuous dobutamine infusion initially at the dose of5 mg/kg/min, increased every 5 minutes by 5 mg//kg/min to the maximum dose of 20 mg/kg/min. Blo-od pressure measurements and determination ofblood velocity in the descending aorta and calcula-tion of pressure gradient were performed in a man-ner similar to the exercise test, at the end of each5-minute period of dobutamine infusion. The latter

was terminated after 20 minutes and subsequentlythree more sets of measurements of blood pressu-re and blood velocity in the descending aorta wereperformed at 5-minute intervals. ECG was monito-red throughout the DSE, and the stress test wasterminated when the dobutamine dose reached20 g/kg/min or prior to administration of sucha dose, in case of reaching submaximal heart rate,abnormal ECG, excessive blood pressure rise, orpatient request.

Statistical analysisStatistical analysis included determination ofcorrelations between maximal systolic blood pres-sure (SBP), pressure gradient in the descendingaorta (GRAD), and heart rate values at the end ofexercise during the treadmill test and upon termi-nation of dobutamine infusion during DSE. Calcu-lations of the Pearson linear correlation coefficientwere performed using Statistica 6.2 software, withp < 0.05 regarded as statistically significant.

Results

Figures 1 and 2 show maximal GRAD and SBPvalues during the exercise test and DSE, as well asPearson linear correlations for these parameters.

Resting SBP values were as follows: maximal150 mm Hg, minimal 91 mm Hg, and mean 118 mm Hg,and corresponding SBP values at peak exercisewere 230, 120 and 163 mm Hg, respectively. SBPat peak exercise reached 180 mm Hg in 4 subjects,exceeded 180 mm Hg in 4 subjects, and exceeded200 mm Hg in 5 subjects.

Resting GRAD determined using Doppler ul-trasound did not exceed 25 mm Hg in 14 subjects,and overall it ranged from 14 to 67 mm Hg (mean


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27.9 mm Hg). At peak exercise, maximal recordedGRAD was 109 mm Hg, minimal 29 mm Hg, andmean 59.7 mm Hg. SBP during infusion of a maximaldobutamine dose ranged from 123 to 215 mm Hg(mean 164.7 mm Hg). Heart rate (HR) was incre-ased during dobutamine infusion, with maximal re-corded value of 155 bpm, minimal 76 bpm, and mean111 bpm. At peak exercise, maximal recorded HRwas 188 bpm, minimal 144 bpm, and mean 169 bpm.

The exercise test was terminated due to re-aching submaximal heart rate in 20 subjects, fati-gue in 8 subjects, and an excessive blood pressure

rise in one female patient. In two subjects, DSE wasterminated at the dobutamine infusion rate of 10 mg//kg/min due to an excessive SBP rise to 197 and199 mm Hg, respectively. No complications of DSEwere noted. Five patients reported feeling of cold

in limbs, one patient reported perioral numbness,one patient reported scalp itching and pressure inthe suprasternal notch, one patient reported feelingof warmth in feet, and one patient reported markedpalpitations. ECG showed supraventricular prema-ture beats in 5 patients. All these symptoms andsigns were not considered dangerous or severeenough as to necessitate termination of DSE te-sting. At the end of dobutamine infusion, maximalrecorded GRAD was 113 mm Hg, minimal 29 mm Hg,and mean 55.4 mm Hg. Pearson linear correlationtest showed significant correlation of both SBP and

GRAD values at the end of treadmill exercise testand DSE. No such correlation was found for HR atthe end of both tests. The correlation coefficientswere as follows: r = 0.6852 (p < 0.0001) for maxi-mal SBP during the exercise test versus DSE,r = 0.8243 (p < 0.0001) for maximal GRAD duringthe exercise test versus DSE, and r = 0.4217(p = 0.147) for maximal HR during the exercise testversus DSE.

Discussion

Although the first surgical correction of CoAwas performed 63 years ago, criteria of successfulrepair are still disputed, and in particular doubts areincreasingly raised whether the achievement ofnormal aortic diameter really means cure of thedefect. Currently, it is commonly thought that CoAshould be viewed not only as a discrete aortic le-sion but as a more generalized cardiovasculardisorder with profound, long-term systemic effects.Outcomes of surgical treatment vary, and correc-ting the aortic anatomy does not guarantee blood

pressure normalization. Postulated caused of per-sistent hypertension following the repair of CoAinclude differences in vascular receptor reactivityabove and below the site of CoA, the shape of theaortic arch, and hypoplasia of the transverse arch.Thus, a diagnostic modality that would allow identifi-cation of patients at increased risk became desirable.

Residual coarctation or restenosis may be iden-tified using various approaches. The simplest oneis the physical examination, with significant findingsincluding a systolic murmur at the left sternal bor-der radiating to the interscapular area, differencein pulse volume between upper and lower limbs, andlower blood pressure in the lower limbs compared

Figure 1. Correlation between the maximal pressure

gradient in the descending aorta (GRAD) at peak exerci-

se (GRAD W) and at the end of dobutamine infusion(GRAD D) in patients after surgical repair of coarctation

of the aorta.

Figure 2. Correlation between systolic blood pressure

(SBP) at peak exercise (SBP W) and at the end of dobu-

tamine infusion (SBP D) in patients after surgical repair

of coarctation of the aorta.


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to the upper limbs. Chest X-ray and ECG are ofno significant diagnostic value in patients aftera surgical repair of CoA. More informative in regardto aortic anatomy and blood flow physiology is echo-cardiography combined with Doppler evaluation of

the aortic flow. Indications for reintervention in-clude significant aortic coarctation seen in imagingstudies and the maximal aortic pressure gradientexceeding 30 mm Hg. Multidetector computed to-mography is a particularly useful tool to imagine allstructures relevant to CoA, including other arterialanomalies and collateral vessels. However, largeradiation dose absorbed by the patient during ima-ging necessitates precise definition of indicationsfor computed tomography scanning. Magnetic re-sonance imaging is also a precise diagnostic tool thatallows delineation of coarctation anatomy and co-

existing abnormalities. In addition, magnetic reso-nance imaging allows hemodynamic evaluations bydetermination of blood flow velocity. However, car-diac catheterization and conventional aortographyremain gold standard modalities in the evaluationof CoA, although invasive nature of these studies,possible complications, need for general anesthe-sia in children, and radiation exposure limit indica-tions for aortography only to patients who are can-didates to reoperation or balloon angioplasty withor without stenting. Thus, attempts have been made

to adopt diagnostic tools that are useful in the eva-luation of cardiovascular disease risk in adults withhypertension, such as determination of intima-me-dia thickness. It was shown that intima-media thick-ness may be useful as a marker of cardiovascular riskin children with repaired CoA [3]. However, thesestudies may guide decisions regarding preventivemeasures or even help determine the effectivenessof medical treatment, but give no data regardingsuch critical parameters of CoA as SBP or abnor-mal flow in the descending aorta.

Another widely used diagnostic tool is 24-hour

blood pressure monitoring which has gained muchacceptance and is successfully used in children,including those with repaired CoA [4]. However,24-hour blood pressure monitoring also has somelimitations, such as inability to evaluate youngerchildren due to lack of appropriate reference valu-es [5] or motion artifacts commonly seen in thissubset of patients. In addition, some patients aftera repair of CoA only show blood pressure rise du-ring exercise, but limit their activity during 24-hourblood pressure recording due to such problems asdevice interference with active participation insports. These problems make interpretation of am-bulatory blood pressure data difficult.

Many publications described the utility of anexercise testing in the evaluation of abnormalcardiovascular parameters in patients with CoA. Cle-arly, this is a commonly used and useful tool, but itrequires significant patient cooperation, including

understanding of the purpose of the examination andadequate motivation to perform exercise. These con-ditions are hardly met in children, and exercise stresstesting is virtually impossible in the youngest patients.

When evaluating patients treated due to CoA,Cyran et al. [6] noted a relation between increasingaortic pressure gradient and an excessive bloodpressure rise during exercise. These authors werenot able to give a clear explanation of this pheno-menon but highlighted possible discrepancy betwe-en anatomically good procedural effect but insuf-ficient physiologic improvement upon treatment.

This work prompted search for a modality thatmight be used to evaluate aortic flow during exer-cise. Echocardiography and Doppler evaluation du-ring treadmill exercise test is technically deman-ding, requires significant operator experience, andthe evaluation of abdominal aortic flow in these con-ditions is impossible. Cycloergometry, and in par-ticular supine cycloergometry is a more convenientform of exercise for echocardiographic evaluation,but this form of exercise is more difficult for chil-dren, as cycling requires more coordinated, rhyth-

mic effort compared to treadmill exercise. An idealsolution might be an echocardiographic evaluationof a supine patient undergoing pharmacologicalstress testing that results in a cardiovascular wor-kload similar to conditions existing in an exercisingsubject. During such testing, increased aortic flowresults not from exercise but from administrationof a pharmacological stress agent, the dose of whichmay be precisely set and easily modified.

One commonly used and well-known tool ful-filling these conditions is DSE. Initial attempts ofusing dobutamine during echocardiographic exami-

nation were done already in 1970s [7]. Currently,DSE is a routine diagnostic modality in adult cardio-logy practice that allows evaluation of left ventricu-lar function, myocardial perfusion, and valvularfunction. DSE is also a useful to estimate compli-cation risk associated with vascular surgery [8, 9].It has been used in pediatric populations as well,including evaluation of the left ventricle in Kawa-saki disease, after anatomical correction of thetransposition of great vessels, to evaluate pulmo-nary valve function following repair of the tetralo-gy of Fallot, to assess changes in ventricular inflowfollowing the Mustard operation, and to evaluate theeffect of chemiotherapy agents on the heart [1015].


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Similar cardiovascular response to dobutami-ne and exercise is supported by data published byDerric et al. [14] who found similar hemodynamicparameters during exercise and dobutamine infu-sion in patients after physiological correction of the

transposition of great vessels. These authors showedsignificant correlation of stroke volume increase andother cardiac function parameters between thesetwo tests.

In this regard, contrasting findings were publi-shed by Cnota et al. [16] who showed differencesin the evaluated left ventricular function parame-ters between DSE and exercise testing. However,this study used supine cycloergometry and thus itsfindings may have been affected by an increase invenous return and cardiac preload in these condi-tions, complicating interpretation of the data as

noted by the authors.Utility of pharmacologic stress testing in pa-

tients after repair of CoA is suggested by a studyby Miller et al. [17]. These authors selected patientsfor reintervention based on the results of pharma-cologic stress using isoprenaline during a hemody-namic study. The patients were treated with repe-ated balloon angioplasty at the site of coarctation ifaortic pressure gradient increased above 30 mm Hgduring administration of isoprenaline. Followingsuccessful intervention, reduced aortic pressure

gradient was seen both in rest and during isopre-naline administration, clearly indicating the valueof such testing. However, pharmacologic characte-ristics of isoprenaline makes it unsuitable for routi-ne pharmacologic stress testing. Isoprenaline hasa positive chronotropic effect but also significantlyreduces peripheral vascular resistance, thus leadingto marked tachycardia. In addition, it increasesmyocardial oxygen demand and often provokes ar-rhythmia [18]. These properties prevented wide-spread adoption of isoprenaline as a diagnostic phar-macologic stress agent.

Although pharmacologic stress testing is routi-nely performed in current clinical practice, we arenot aware of any previous study describing the useof DSE to evaluate the effect of CoA repair. Weshowed statistically significant correlation of GRADand SBP values upon termination of exercise anddobutamine infusion. These data suggest the utili-ty of DSE in the evaluation of the effects of surgi-cal repair of CoA.

Some limitations of the current study shouldbe noted. Statistical analysis showed significantcorrelations of aortic pressure gradient and SBP,but these evaluations would benefit from includinga larger group of patients. We had no data on the

anatomy of the transverse arch that is consideredby some a risk factor for exercise-induced hyper-tension. Finally, our patients underwent differenttypes of repaired procedures, were evaluated fol-lowing a varying time that elapsed from the repair,

and were of different age, with all these factors cal-ling for more cautious interpretation of our data.

Finally, additional advantages of DSE shouldalso be noted, such as lack of dependence of patientmotivation to cooperate and exercise, as well stan-dardization and reproducibility of cardiovascularworkload by using strictly defined doses of the phar-macologic stress agent, thus facilitating both com-parisons between different patients and serial eva-luation of the same patient during a longer-term fol-low-up. The ability to monitor changes in thecardiovascular system that occur during many years

following a surgical repair of CoA might prove veryuseful.

Conclusions

Our findings suggest that dobutamine stressechocardiography may be useful in the evaluationof the effects of surgical repair of CoA in children.

Acknowledgements

The authors appreciate help of dr Piotr Jdru-sik with preparation of the authorized English ver-sion of the manuscript.

The authors do not report any conflict of inte-rest regarding this work.

This work has been supported by a grant by thePolish Ministry of Science and Higher EducationNo. N 40304432/2376.

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