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Late Aortic Root Dilatation in Tetralogy of Fallot may be Prevented by Early Repair in Infancy

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The objectives of this study were to examine the relative contributions of development and hemodynamics in aortic root dilatation of tetralogy of Fallot, to assess the impact of systemic to pulmonary artery shunt on aortic annular size, and to seek
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  Late Aortic Root Dilatation in Tetralogy of Fallot May Be Prevented by Early Repairin Infancy A.H. Bhat, C.J. Smith, R.E. Hawker Adolph Basser Cardiac Institute, The Children’s Hospital at Westmead, Locked Bag 4001, Westmead, NSW-2145, Sydney,Australia Abstract.  The objectives of this study were to exam-ine the relative contributions of development andhemodynamics in aortic root dilatation of tetralogyof Fallot, to assess the impact of systemic to pul-monary artery shunt on aortic annular size, and toseek any relationship between the timing of correctivesurgery and subsequent aortic root size. We per-formed a retrospective analytical study at a tertiaryreferral center of M-mode and two-dimensionolaortic root measurements in children with tetralogyof Fallot prior to any surgical or palliative interven-tion, after insertion of a surgical shunt, and onintermediate and long-term follow-up post-repair.The main outcome measures were aortic root diam-eter prior to correction, after palliative shunt inser-tion, and after definitive repair. The study found thatthe aortic root is enlarged in unrepaired tetralogy of Fallot irrespective of age, increased in the first 3– 6 months after palliative shunt surgery, and persistedinto adulthood in those repaired after 1 year of age.Age-corrected aortic root dimensions normalized bymidchildhood in those who were repaired in infancy.Preexisting aortic root dilatation normalizes by7 years of age in patients with tetralogy of Fallot whohave been repaired in infancy, whereas it persists intoadulthood in the group repaired postinfancy. Keywords:  Aortic root — Aortic root dilatation — Tetralogy of Fallot — Surgical shuntAortic root (AoR) dilatation is a characteristic fea-ture of tetralogy of Fallot (TOF) identifiable even infetal life [5]. Abnormal conoseptal developmentresulting in anterior malalignment of the interven-tricular septum, a large ventricular septal defect(VSD), and right ventricular outflow narrowingforms the basis of the developmental theory of TOFThe deficient outflow septum can no longer supportthe right coronary cusp, allowing AoR dilatation [1,8, 11, 18]. The entire left ventricular and a proportionof the right ventricular stroke output crosses theaortic valve and this increased throughput may be ahemodynamic basis of AoR dilatation [2, 9, 16].Systemic–pulmonary connections in the form of surgical shunt or aortopulmonary collaterals wouldfurther increase flow across the aortic valve, pro-moting AoR dilatation [2, 16]. Histological factorssuch as medial necrosis are also contributory [3, 15,17].Aortic regurgitation (AR) is infrequently de-scribed in unrepaired TOF [7, 10, 11] but more fre-quently mentioned as an age-related complicationfollowing corrective surgery [2, 13, 16]. Most of thesereports are limited case series of an older populationof TOF patients repaired at a later age with pro-longed intervening palliation. AoR dilatation is nowbelieved to be the dominant etiology of AR, and withthe addition of age-related and hypertensive arterialchanges it is an important and possibly avoidablelong-term morbidity in TOF [4, 17]. Definitive repairof TOF is increasingly performed at earlier ages, eveninfancy (up to 1 year of age). This study sought todetermine any differential trend of AoR dimensionsas well as AR in TOF repaired in infancy versus TOFrepaired post infancy. Methods This was a retrospective analysis of patients in whom a primarydiagnosis of TOF was made in either of the two study centersbetween 1985 and 2000. Follow-up was available until June 2002.Cases with associated abnormality (e.g., atrioventricular septaldefect, pulmononary atresia ‘‘absent’’ pulmonary valve, and dis-connected pulmonary arteries) were excluded. The primary studycenter, Adolph Basser Cardiac Institute of the Children’s Hospitalat Westmead, Sydney provided data on the group with TOF re-paired in infancy as well as all catheterization studies and shunt Correspondence to:  R.E. Hawker,  email:  rich@chw.edu.auPediatr Cardiol 25:654–659, 2004DOI: 10.1007/s00246-003-0665-2  surgeries. The Royal Prince Alfred Hospital, Sydney, provided dataon the late-presenting, uncorrected group as well as some of thelonger post-operative follow-up studies in the same period. Presurgical Aortic Root Aortic root dimensions from M-mode analysis of newly diagnosednon-palliated TOF patients presenting in the study period wereobtained from the computerized databases of both institutions. Correlation of Systemic Saturation with Aortic RootSize In patients who underwent pre-operative cardiac catheterization,systemic oxygen saturation reported on blood gas analysis wasplotted against AoR diameter determined on the closest echo studyperformed within 3 months of catheterization. If AoR M-modemeasurements were not noted in the database, AoR size (diastolic)was determined offline from the parasternal long-axis view afterappropriate image standardization and screen calibration. Datasets that did not meet the inclusion criterion or for which the aorticdimensions could not be determined confidently were excludedfrom analysis. Impact of Shunt Insertion on Aortic Root Size Aortic annular measurements from parasternal long-axis views of echo studies performed within a 3-month period of the shunt sur-gery were compared. The 3-month cutoff was arbitrarily taken soas to reflect relatively rapid changes in AoR. Thus, although dila-tation due to increased transaortic flow after shunt insertion shouldbe detected, the confounding effect of age-related or catch up so-matic growth could be minimized. Aortic Root Size on Post-repair Follow-up These data were analyzed according to the age at the time of definitive repair and were divided into two groups; the first groupcomprised, data on patients who underwent repair in the first yearof life (infancy), and the second group comprised data on patientswho underwent repair after the first year.Height and weight were not uniformly documented in thedatabase; hence, body surface area could not always be calculated.So as to maximize the number of cases that could be analyzed,while realizing the limitations of nonnormalized comparisons, weused an age-related conversion from the expected anthropometryfor each age bracket as recommended by the Center of Disease inChildren growth charts of the National Center for Health Statis-tics. This normal range was expressed graphically as a trendlinewith 95 %  confidence intervals (CIs) against which the study datawere plotted and compared.Statistical analysis was done based on Microsoft Excel chartsand using statistical package available with that software.Regression of means test as well as the paired t- test were used todetermine the significance of difference between the groups studied.Data are depicted as scatter plots and polynomial trendlines. Results Presurgical Aortic Root Size There were 208 echo studies of 160 uncorrected pa-tients (i.e., before any palliative or definitive surgery).Of these, there were 147 echo studies of 101 infants ata mean age of 3.6 months (median, 2.6 months) and61 studies from 59 postinfancy patients at a mean ageof 4.7 years (median, 2.9 years). AoR dimensions of all these patients were significantly larger than ex-pected for age, irrespective of the timing of definitiverepair that was later undertaken (Fig. 1 and 2). Correlation of Systemic Saturation with Aortic RootSize A total of 196 patients underwent cardiac catheteri-zation. Although 172 of these also had echo studies,only 54 data sets could be used for analysis. Theremaining were excluded since echoes had been done Fig. 1.  Aortic ( Ao ) root size in uncorrected, un-palliated tetralogy of Fallot patients of all ages( n  = 208) ( hatched line ) is significantly larger thanexpected. The lower two polynomial trend linesindicate the 95 % confidence intervals ( CI  ) of normal aortic root size.Bhat et al.: Aortic Root Dilatation in Tetralogy of Fallot 655  outside a 3-month period or aortic dimensions wereuncertain. Mean age at catheterization was 2.2 years(range, 4 months to 9 years). There was no statisticalcorrelation between AoR size and systemic satura-tions (r = 0.02). Impact of Shunt Insertion on Aortic Root Size Of 99 patients who underwent shunt surgery, 46could be analyzed (mean age, 8.9 months). In theremaining 53 cases, echo studies did not have ade-quate views or had not been done within a 3-monthperiod. Preshunt and postshunt aortic dimensionswere compared (Fig. 3). Mean post shunt aorticannular size (14.3 mm) was significantly larger thanpreshunt annular size (12.8 mm) (  p  < 0.001). Aortic Root Size on Postrepair Follow-Up The infancy repair group was compared with thepostinfancy repair group. There were 468 studies of 342 patients repaired after infancy. The mean age atfollow-up was 9.8 years, (median, 7.3). Follow-upextended to 57 years of age (this patient was repairedat 32 years of age). Although 141 patients hadundergone more than two follow-up echo studies, themean number of studies in the overall group was 1.7per patient. There is an obvious persistence of AoRdilatation into adulthood in the group repaired afterinfancy (Fig. 4).There were 104 studies of 43 patients repairedin infancy. The mean age at follow-up was2.45 years (median, 1.38) and extended up to13.2 years. Although all these cases had at least onepostsurgical echo study, there were serial studies(more than two follow-up scans) in 32 patients,with a mean of 2.85 studies for each. Figure 5shows AoR sizes on follow-up of the group re-paired in infancy. As indicated in the figure, al-though still above the 95 %  CI in the initialpostoperative years, AoR size seems to decline intonormalcy by 7 years of age and thereafter remainin the normal expected range for age. Fig. 2.  Aortic ( Ao ) root size in uncorrected,unpalliated infants (<1 year) with tetralogy of Fallot ( n  =147) ( hatched line ) is significantlylarger than expected.  CI  , confidence interval. Fig. 3.  Postshunt aortic annulus( Ao an ) is significantly larger thanpreshunt annulus ( n  = 46;  p  < 0.001).656 Pediatric Cardiology Vol. 25, No. 6, 2004  Aortic Regurgitation on Follow-Up In the group repaired during infancy, trivial to mildAR was reported in 23 % . In the group repaired po-stinfancy, the incidence of AR was 18 % , with mostcases being reported as more than mild. Discussion Although iatrogenic valve damage, recurrent/residualVSD, or infective endocarditis were highlighted ascauses of postrepair AR in earlier studies, ‘‘idio-pathic’’ root dilatation seems to be the most commoncause today [6]. In an extensive review of surgicallyexcised aortic valves from 1965 onward, the incidenceof AoR dilatation increased from 17 % before 1980 to37 %  in 1980 and 50 %  in 1990 [14], Thus, AoR dila-tation and AR could represent an important long-term cause of morbidity as early and intermediateoutcomes of surgical repair of TOF improve con-stantly.AoR dilatation and AR due to long-term  insitu  shunts are well described [2, 13, 16]. Theimportant increase in AoR in our shunt groupindicates that increased antegrade aortic flow cancause dilatation as early as 3 months after shuntinsertion.There was no correlation between systemic sat-uration and AoR size in our study. Conceivably,AoR dilatation is proportional to pulmonary stenosis(developmental basis). Additionally, antegrade flowacross the AoR increases proportionately to theseverity of pulmonary outflow obstruction (hemody-namic basis). However, using systemic saturation asan index of pulmonary outflow obstruction in TOFmay be a simplification that does not address multiplelevels of obstruction or the presence of collateralblood supply. Fig. 4.  Aortic ( Ao ) root size in tetralogy of Fallot corrected after infancy continued to belarger than normal on late follow-up ( n  = 468). CI  , confidence interval. Fig. 5.  Aortic ( Ao ) root sizes intetralogy of Fallot corrected in in-fancy tend to ‘‘grow’’ into normal by7 years and thereafter continue with-in the normal ( n  = 104).  CI  , confi-dence interval.Bhat et al.: Aortic Root Dilatation in Tetralogy of Fallot 657  Aortic Root Size and Aortic Regurgitation on Postrepair Follow-Up: Relevance to the Timing of Surgery Definitive repair of TOF is increasingly beingundertaken at earlier ages and repair in infancy hasbecome standard in many institutions. Early repairobviates the need for palliative shunts with theirattendant complications, such as pulmonary arterydistortion and AoR dilatation. Early pressureunloading of the right ventricle would prevent rightventricular fibrosis and perhaps late-onset arrhyth-mias. Early volume unloading of aortic outflow withdefinitive repair may avoid progressive AoR dilata-tion. In our institution, definitive repair of TOF ininfancy was started more than a decade ago andfollow-up of 13 years is now available. Our data fromthe infancy repair group suggest that the dilatedaortic root regresses toward the 95 % CI expected by6 or 7 years and then grows within the normal range,whereas the AoR continues to be significantly dilatedin the group repaired after infancy. No more thanmild AR was reported in 23 %  of the infancy repairgroup, whereas more than mild AR was observed in18 %  of the postinfancy repair group. Inferior echowindows in adolescents and adults after sternotomyas well as less sensitive Doppler modalities that wereavailable earlier in the series may have led to und-erreporting in this group. Improved transducertechnology in the past decade of studies has made thetiniest of leaks more visible.Ours is the first study that attempts to differen-tiate growth trends of AoR based on the age atdefinitive repair and is a preliminary step towardaddressing the influence of surgical timing on AoRsize in later life. Study Limitations This study had the inherent disadvantages of a ret-rospective study. A large number of cases had to beexcluded from analysis because of heterogeneity inecho data and body surface area (BSA) was notavailable in all records. By using age-based normalAoR size data, we were able to include a largernumber of cases and derive a more population-basedsense of the trend of the AoR size. In their assessmentof cardiac dimensions (aortic annulus, left atrium,and ventricle) in subjects younger than 19 years of age, Nidorf et al. [12] used multiple regression anal-ysis in comparison with age. The 95 %  CI of eachvariable when compared to age, was similar to thatcompared to BSA, reflecting a strong relationshipbetween age and BSA in the pediatric age groups.Offline two-dimensional measurements are lessideal than dedicated imaging of the AoR, but M-mode measurements of the AoR have been shown tocorrelate accurately with two-dimensional measure-ments [17]. Nevertheless, we do not believe thatregression of AoR size seen in the infant repair groupis an artifact of improved echo technology in recentyears. In fact, inaccuracies arising due to the reasonsmentioned previously should be distributed acrossthe entire study group. Conclusions Repair of TOF in infancy is associated with nor-malization of aortic root size in midchildhood withcontinuing normalcy into later childhood, whereasrepair after infancy allows the persistence of markedaortic dilatation. Acknowledgments.  We acknowledge Prof. David Celermajer forassistance in the data collection from the Royal Prince AlfredHospital and also for encouragement and suggestions. References 1. Bahnson HT, Spencer FC, Landtman B, et al. (1962) Surgicaltreatment and follow up of 146 cases of tetralogy of Fallottreated by correction.  J Thorac Cardiovasc Surg 44 :419–4292. Capelli H, Ross D, Somerville J (1982) Aortic regurgitation intetrad of Fallot and pulmonary atresia.  Am J Cardiol 49 :1979– 19833. Dare AJ, Veinot JP, Edwards WD, Talezaar HD, Schaff HV(1993) New observations on the etiology of aortic valve dis-ease: a surgical pathologic study of 236 cases from 1990.  HumPathol 24 :1330–13384. Davies MJ, Brooksby I, Leech GJ, Parker J, Baimbridge MV(1978) Pathology of aortic regurgitation.  Br Heart J 40 :4605. DeVore GR, Siassi B, Platt LD (1988) Fetal echocardiography.VIII. Aortic root dilatation–a marker for tetralogy of Fallot. Am J Obstet Gynecol 159 :129–1366. Dodds GA, Warnes CA, Danielson GK (1997) Aortic valvereplacement after repair of pulmonary atresia and ventricularseptal defect or tetralogy of Fallot.  J Thorac Cardiovasc Surg113 :736–7417. Glancy DL, Morrow AG, Robert WC (1968) Malformationsof the aortic valve in patients with the tetralogy of Fallot.  AmHeart J 76 :755–7598. Guiney TE, Davis MJ, Parker DJ, Leech GJ, Leatham A(1987) The aetiology of isolated severe aortic regurgitation: aclinical, pathological, and echocardiographic study.  Br Heart J 58 :358–3689. Kirklin JW, Karp RB (1970)  The Tetralogy of Fallot from aSurgical Viewpoint .  Saunders , Philadelphia, p 3410. Matsuda H, Ihara K, Mori T, Kitamura S, Kawashima Y(1980) Tetralogy of Fallot associated with aortic insufficiency. Ann Thorac Surg 29 :529–53311. Nagao GI, Baud GI, McAdams AJ, Schwartz DC, Kaplan S(1967) Cardiovascular anomalies associated with Tetralogy of Fallot.  Am J Cardiol 20 :206–21512. Nidorf SM, Picard MH, Triulzi MO, et al. (1992) New per-spectives in the assessment of cardiac chamber dimensions658 Pediatric Cardiology Vol. 25, No. 6, 2004
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