Presentation on theme: "Transposition of the Great Arteries"— Presentation transcript:
1Transposition of the Great Arteries Eric OsbornJanuary 27, 2010
2Outline Definitions Embryology Epidemiology Complete transposition (D-TGA)Congenitally corrected transposition (L-TGA)EchocardiographyTypes of repairs and outcomes
3DefinitionsThe key anatomic characteristic of transposition complexes is ventriculoarterial discordance.The aorta arises from the morphological RVThe PA arises from the morphological LV
4Definitions Complete transposition (D-TGA) Atrioventricular concordanceD=dextroRV is on the right and anterior = systemic ventricleAorta is to the right and anteriorGreat arteries are parallel rather than crossingTV = systemic AV valve because always associated with the morphological RV
5Definitions Congenitally corrected transposition (L-TGA) Atrioventricular discordanceL = levoRV is to the left and posterior = systemic ventricleAorta is on the left and anteriorGreat arteries may be side-by-sideTV = systemic AV valve because always associated with the morphological RV
6Embryology 22 days gestation … the primitive straight cardiac tube is formedComposed of 5 chambers with patterning regulated by homeobox genesTruncus = aorta and pulmonary arteryBulbis = outflow tracts and ventricle
7Embryology23 days gestation … the straight cardiac tube elongates and bends forming the cardiac loop.Cephalic portion bends ventrally, caudally, and right-ward.Caudal portion moves dorsally, cranially, and left-ward.The rotational motion folding over of the bulboventricular portion bringing the future ventricles side-by-side.Fig 11.6 LangmansThis process is completed by 28 days.Normal rightward rotation of the tube results in the normal D configuration with the RV anterior and to the right – AV concordanceLeft-handed looping of the heart tube leaves the morphologic RV posterior and to the left – AV discordance
8Embryology4th-7th weeks gestation … the heart divides into 4 chambers via formation of swellings (cushions) of tissue that exhibit differential growth.Endocardial cushions divide the AV canal forming the mitral and tricuspid valves.Conotruncal cushions form the outflow tracts, aortic and pulmonary roots.
9Embryology 5th week gestation … the conotruncal cushions. Right superior truncal cushion grows distally and left-ward.Left inferior truncal cushion grows distally and right-ward.The net effect is a twisting motion.The truncal cushions fuse to form the truncal septum.Additional cushions develop in the conus which grow down and towards each other until they fuse with the truncal septum to form the RVOT and LVOT.RVOT (anterolateral) and LVOT (posteromedial)The subpulmonic conus elongates and the subaortic conus resorbs, allowing the aorta to move posteriorly and connect with the left ventricule
10Embryology Mechanism of great artery transposition Conotruncal cushion defectLeads to failure of the conotruncal septum to spiral and instead extends straight downwardAorta fuses with the RV and PA with the LVFig LangmansConotruncal cushion defect of neural crest cellsTruncus = aorta and pulmonary trunksConus = aortic and pulmonary outflow tractsResorption of the subpulmonic instead of the subaortic conus may be central to TGA
11Epidemiology~0.8% of live births are complicated by a cardiovascular malformation*.>750,000 adult patients with congenital heart disease.Transposition of the great arteries occurs in approximately 1 per 5,000 live births.More common in malesDiagnosis possible in utero with fetal echocardiographyTransvaginal ultrasound at weeks (limited views)Transabdominal ultrasound at 16 weeksAntenatal detection rates between 20-70%.*not including bicuspid aortic valve and mitral valve prolapse
12Complete transposition (D-TGA) Pulmonary and systemic circulations are in parallelLethal, if no mixing (ASD, PDA, VSD)¾ are simple with no major associated abnormalities¼ are complexVSD (16%)Pulmonary/subpulmonary stenosis (9%)Coarctation of the aorta (4%)Fig in Braunwalds shows parallel configuration (path/echo) of PA and AoNearly all have an intraatrial connection, 2/3 with PDA, and 1/3 with VSDThe amount of mixing determines the systemic oxygen saturation and thus the clinical courseSmall PFO or PDA with intact septum are most severely hypoxemic and cyanotic; similarly LVOT obstructionLarge PDA or VSD may result in minimal cyanosis, but they develop heart failure in the first few weeks of life
13Complete transposition (D-TGA) Clinical Presentation and Outcomes Larger size and weight at birthDyspnea and cyanosisProgressive hypoxemiaCongestive heart failureWithout treatment, the outlook is dismal30% mortality within the 1st week90% mortality within the 1st year
14Complete transposition (D-TGA) Management Prostaglandin E1 to maintain the PDAAtrial septostomy (balloon or surgical)Palliative prior to corrective surgeryRepair within the first days to weeks of life2-4% mortality with 90% 1 year survivalAtrial switchMustard or SenningArterial switchRastelli procedurePGE1 does not enhance mixing at the PDA, but maintains its patency and dilates the pulmonary bed increasing pulm blood flow/LA pressure to enhance transatrial mixing.Septostomy can palliate for >1 year in some cases prior to requiring surgical correction.
15Complete transposition (D-TGA) Atrial switch (Mustard/Senning) Developed in the 1950sBaffle directs venous return to contralateral ventricleFig from Braunwald or Fig 1 LoveEstimated to be ~9000 atrial switch adult patients currently alive in the USBlood is redirected via baffles made of atrial flaps (Senning) or Dacron or pericardium (Mustard)Described in one paper as complicated ‘origami-style’ cutting and folding of tissues.Systemic venous return is directed to the lungs and oxygenated pulmonary venous return to the periphery.The RV functions as the systemic ventricle; the LV pumps blood to the lungs.Both Senning and Mustard tried to switch the great arteries but were unsuccessful primarily due to transposing the coronaries.
16Complete transposition (D-TGA) Atrial switch (Mustard/Senning) DisadvantagesRV functions as the systemic ventricleSeveral significant long term complicationsCongestive heart failureArrhythmiasBaffle leaks and obstructionPulmonary hypertensionParadoxial embolusEndocarditisOverall survival 75% at 25 yearsSenning may be better than Mustard [Moons et al, Heart 2004]340 patients (~⅔ Senning) comparedLess obstruction (1 vs. 15%) and better functional class with SenningNo significant mortality benefitExcellent midterm results, but multiple longterm complicationsFig 4 from Love et al, Nature
17Complete transposition (D-TGA) Atrial switch (Mustard/Senning) Arrhythmias Palpitations, presyncope, and syncope are not uncommonBoth brady and tachyarrythmias frequently seen50% develop sinus node dysfunctionPhysical damage during surgery and baffle constructionDisruption of blood supply leading to ischemia20% develop atrial flutterSensitive to nodal agents due to conduction system disease11% required pacemakers at 20 years [Gelatt et al, J Am Coll Cardiol 1997]Pacemakers are difficult to place due to distorted anatomyShould be avoided if residual intracardiac communications due to risk of paradoxical embolus and strokePredominately atrial conduction disorders until more develop ventricular failureScar lines across the atrium are substrate
18Complete transposition (D-TGA) Atrial switch (Mustard/Senning) Congestive heart failure Most adult patients develop congestive heart failureBy 20 years most are NYHA Class I or IIRV filling compromised due to defects in baffle constructionBaffle leaks (Mustard>Senning)Left-to-right shunts with pulmonary hypertension (7%)Risk of paradoxical embolus and strokeIndications for intervention include >1.5:1 left-to-right shunt or any right-to-left shuntBaffle obstruction (5-15%, Mustard>Senning)SVC>IVC manifesting as SVC syndrome or hepatic congestion/cirrhosisOften undetected due to collateral venous drainage (e.g. azygous vein)40% develop right ventricular dysfunction10-40% develop 2+ or greater tricuspid (systemic AV valve) regurgitationAnnular dilatation from RV failureDamage from surgery or endocarditis?RV ischemia plays role in dysfunction
20Complete transposition (D-TGA) Arterial switch Developed in the 1980sGreat arteries and coronaries are transected and re-anastamosedFig from Braunwald; first reported by Jatene (1976) now the procedure of choice for transposition repairArterial trunks are transected and reanastamosed to the proper root positions (aorta brought under the PA bifurcation).VSDs are closed during the operation.Coronary arteries are excised along with a button and transposed; this is the most challenging portion of the procedure and accounts for most mortality (<2% at most centers).LV is the systemic pump; RV pumps to the lung; maintanance of sinus rhythm.
21Complete transposition (D-TGA) Arterial switch AdvantagesLV is the systemic pumpNo disruption of atrial conduction (sinus rhythm)Fewer long term complications compared to atrial switchCoronary ostial stenosisSupravalvular pulmonary/aortic stenosisIntervention indicated for RVOT gradient >50 mmHgNeoaortic regurgitationArrhythmiasFollow up with normal LV function and good exercise capacityNormal examination in uncomplicated patientsOutcomes for adults just starting to be realized but appear favorableLess arrythmias than atrial switch procedureCoronary patency and growth are not generally impacted
22Complete transposition (D-TGA) Rastelli procedure TGA with VSD and LVOT obstructionOutcomesRV-PA conduit obstructionExercise intolerance/anginaRV failureIntervention for RV-PAgradient >50 mmHgLV-Ao patch obstructionDyspnea or syncopeCirc 2006 Fig 3VSD is patched to allow LV outflow to the aortaPulmonary valve is oversown and a synthetic valved bypass graft is placed from the RV to the PA to bypass the pulmonary stenosisLV is systemic ventricle but conduit replacement is inevitable, requiring re-operation
23Complete transposition (D-TGA) RV Failure after Atrial Switch Standard heart failure therapies are unprovenThe two-stage arterial switchStage 1 – the PA is banded to ‘re-train’ the LV to handle systemic pressuresStage 2 – the atrial baffles and pulmonary band are taken down and an arterial switch is performed50% survival at 8 years in early resultsAppears to be more successful in patients under 12As more patients with atrial switch reach adulthood and develop severe RV failure +/- severe TR, additional interventions may be necessaryMedical management with standard heart failure therapies is unprovenTwo-stage switch still experimental in adultsPulmonary banding allows ‘retraining’ of the LVEarly results – 50% survival at 8 years
24Congenitally corrected transposition (L-TGA) A rare disorder that may present in adulthood.Associated anomalies (95% of patients)VSD (75%, commonly perimembranous)Pulmonary stenosis (75%, commonly subvalvular)Tricuspid valve anomalies (>75%)Congenital complete heart block (5%)Fig in BraunwaldsTV anomalies similar to Ebsteins with apical displacement but leflet structure often distinctIn the absence of associated anomalies (isolated L-TGA) patients live normal life span
25Congenitally corrected transposition (L-TGA) Outcomes ArrhythmiasAbnormal AV node and His positionsDual AV nodes2% per year incidence of complete heart blockSusceptible to fibrosis of conduction systemMedian survival 40 yearsMortality from progressive RV failure or arrhythmiasTricuspid regurgitation is major predictorCoronary anatomy is concordant, and therefore the systemic RV is supplied by the single RCA.
26Congenitally corrected transposition (L-TGA) Double Switch Procedure Traditionally only fixed associated congenital defects leaving RV as systemic ventricleDouble switch procedure uses atrial and arterial switch to restore the LV as the systemic pumpAs with the two-stage arterial switch, the PA must be banded to ‘re-train’ and hypertrophy the LV prior to surgeryDecreases the incidence of TR and RV failure which lead to death
27Echocardiography Segmental approach to congenital heart disease Position of the apexSitus of the atriaMorphological atria based on anatomic appearance of their appendages75% concordance with abdominal situs (aorta and IVC positions)Atrioventricular relationshipDifferentiate the morphological RV from LV:Trabeculated apexModerator bandSeptal attachment of the tricuspid valveLower (apical) insertion of the tricuspid valveVentriculoarterial relationshipPulmonary artery is distinguished by its early branching patternCurved contour of the aortic arch with three major branchesStandard subcostal view with the probe 90° to spineSolitus = aorta on left and IVC on right, inversus is oppositeTricuspid valve is always attached to the morphological RV (similarly mitral valve with morphological LV); Pulmonary valve always with PA (similarly aortic valve with Ao)Following segmental analysis, move to usual echo windows
28Echocardiography Complete Transposition with Atrial Switch Hallmark is parallel great arteries (parasternal long axis)Aorta is anterior to PA
29Echocardiography Complete Transposition with Atrial Switch Systemic hypertrophied RV septum bows into LVMay impact TR and enhance subpulmonary stenosisFig 5 Love, short axis echo of patient with TGA following atrial switch – bowing of RV septum towards LV – can worsen TR and increase subpulmonary stenosis
30Echocardiography Complete Transposition with Atrial Switch Aortic and pulmonic valves lie in the same planeAorta is anterior and to the right (parasternal short axis)Also cardiac apex points to the left
31Echocardiography Congenitally Corrected Transposition Hallmark is reversed offsetting of the AV valvesAorta is anterior and to the left (parasternal short axis)Close evaluation of ventricular morphology shows systemic ventricle with apically displaced AV valveGreat vessels are parallel as in D-TGACardiac apex points to the right which may cause poor windows due to shadowing from the sternum
32Echocardiography Special Considerations Atrial switchRV functionTricuspid regurgitationSubpulmonary obstructionBaffle leak or obstruction (color Doppler)Normal baffle flow is phasic with peak velocity <1 m/secArterial switchNeoaortic valve regurgitationSupraneopulmonary valve stenosisWall motion abnormalities due to coronary artery ostial stenosisRastelli procedureLV-Ao tunnel patch obstructionRV-PA conduit degeneration (stenosis/regurgitation)Normal baffle flow is phasic with respiratory variation, and peak velocity < 1m/sec
33Echocardiography Special Techniques Index of myocardial performancedP/dT from tricuspid regurgitant velocityIsovolumic myocardial accelerationTissue Doppler measurement of myocardial acceleration during isovolumic contraction?sensitive assessment of RV contractility that is less load dependentNormal baffle flow is phasic with respiratory variation, and peak velocity < 1m/sec
34Endocarditis Prophylaxis ACC/AHA 2008 Guidelines state that antibiotic prophylaxis is reasonable to consider for patients at the highest risk of adverse outcomes (Class IIa)Prosthetic valvesPrior endocarditisCongenital heart diseaseUnrepaired cyanotic, including palliative shunts and conduitsCompletely repaired with prosthetic material or device (6 months)Repaired with defects at or near a prosthetic devicePost-cardiac transplant with valvular diseaseThere are no Class I indications*endothelialization
36ReferencesWebb et al., Congenital Heart Disease in Braunwald’s Heart Disease, 8th ed., Chapter 61,Sadler, Cardiovascular System in Langman’s Medical Embryology, 8th ed., Chapter 11,Otto, The Adult with Congenital Heart Disease in Clinical Echocardiography, 4th ed., Chapter 17,Warnes, Transposition of the Great Arteries, Circulation :Love et al., Evaluation and Management of the Adult Patient with Transposition of the Great Arteries Follow Atrial-level (Senning or Mustard) Repair, Nature Clinical Practice Cardiovasc Med :Verhuegt et al., Long-term Prognosis of Congenital Heart Defects: A Systematic Review, Int J Cardiol :25-32.Skinner et al., Transposition of the Great Arteries: from Fetus to Adult, Heart :ACC/AHA Guidelines for the Management of Adults with Congenital Heart Disease, J Am Coll Cardiol :e1-121.