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CHAPTER 19

Tetralogy of Fallot

Michael A. Gatzoulis

Septal Defects Atrial Septal Defects Ventricular Septal Defects Atriventricular Septal Defects

DEFINITION/ MORPHOLOGY

It was Etienne-Louis Arthur Fallot who, in a series of papers in 1888, separated the malformation we now describe with his name from other anatomic lesions responsible for the "maladie bleue". Although autopsy cases had been recognised previously, Dr. Fallot was the first to correlate clinical features with pathological findings. In anatomic terms, the malformation is composed of four constant features, namely subpulmonary infundibular stenosis, ventricular septal defect (VSD), rightward deviation of the aortic valve with biventricular origin of its leaflets, and right ventricular (RV) hypertrophy (Figure 19.1). Nonetheless, the malformation represents a morphological spectrum. At one end it can be difficult to distinguish hearts with tetralogy of Fallot from those with ventricular septal defect and aortic overriding with minimal pulmonary stenosis. At the other extreme, the pulmonary obstruction is so severe as to represent the commonest variant of pulmonary atresia with VSD (which will be discussed in the next chapter). One

morphological marker, however, unifies the overall entity. This is antero-cephalad deviation of the outlet septum (the muscular structure which separates the subaortic from the subpulmonary outlets) in relationship to the rest of the muscular septum. However, something over and above septal deviation is needed, to produce tetralogy of Fallot. This is hypertrophy of the septoparietal trabeculations, a series of normally small trabeculations, extending from the anterior margin of the septomarginal trabeculations and encircling the parietal margin of the subpulmonary infundibulum.

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Ventricular Septal Defect

The VSD in tetralogy is usually single and almost always large and non-restrictive, except in very rare cases where its right ventricular margin is shielded by accessory tricuspid valve tissue or where marked septal hypertrophy narrows the defect. In about 80% of cases the defect is perimembranous, the remainder having a muscular posteroinferior rim. Much less commonly the defect can be doubly committed juxta-arterial, with its cephalad border being formed by the conjoined aortic and pulmonary valves. It is questionable if such a heart should be called tetralogy of Fallot, since the outlet septum is absent. But the anatomy otherwise is exactly that of tetralogy. Furthermore, the free wall of the subpulmonary infundibulum is present and can possess hypertrophied trabeculations which may be obstructive following closure of the defect.

Fig 19.1 Anatomic features of tetralogy of Fallot. Tetralogy (Greek word meaning 4 parts) of Fallot is composed of four contrast features: subpulmonary infundibular stenosis, ventricular septal defect, aortic overriding and right ventricular hypertrophy.

(Fig 19.1 From Echo-morphologic correlations in congenital heart disease Textbook by Ho et al, Moseby 1995).

Pulmonary Stenosis

There is infundibular stenosis in almost all cases, which commonly coexists with obstruction/s at other sites. The crucial importance of anterocephalad deviation of

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the outlet septum and the hypertrophied septoparietal trabeculations has been described. Hypertrophy of the anterior limb of the septomarginal trabeculation, may contribute to this, but a second level of "subpulmonary" obstruction may be seen when there is hypertrophy of the moderator band and apical trabeculations, which produces more proximal stenosis and gives the arrangement of a twochambered RV. The pulmonary valve is abnormal in most cases, although rarely the major cause of obstruction. In young infants, however, valvar stenosis has been found at surgery as the major obstructive lesion. Acquired atresia of the infundibulum or the valve can also occur. Stenoses within the pulmonary arteries themselves are of major surgical significance, usually occurring at branch points from the bifurcation onwards. Hypoplasia of the pulmonary arteries has been reported as frequent as 50%. Lack of origin of one pulmonary artery (typically the left) from the pulmonary trunk is not infrequent.

Conduction System

The atrioventricular node is normally located in patients with tetralogy of Fallot. When the VSD is perimembranous, the His bundle penetrates at the postero-inferior rim of the defect in the area of tricuspid and mitral valve continuity. In most cases, the bundle and its left branch proceed on the left side of the defect, although occasionally they run directly on the crest of the septum. Nevertheless, most surgeons place their sutures along the right ventricular aspect of the defect, thus avoiding heart block. When the defect is muscular, i.e. there is muscular interruption between the tricuspid and aortic valve fibrous continuity, the bundle runs along the antero-superior aspect of the defect, and sutures can safely be placed on the lower rim of the VSD. Furthermore, the conduction tissue never runs along the outlet septum, the muscular structure separating the aortic from the pulmonary valve, which can be safely resected without risk of producing heart block.

Aortic Overriding

The degree of aortic override can vary from 5 to 95% of the valve being connected to the RV. Tetralogy of Fallot therefore, coexists with double outlet RV, when more than half of the aorta connects to the RV. This feature has surgical significance in that a much larger patch is required to connect the left ventricle (LV) to the aorta when it originates predominantly from the RV.

GENETICS/ EPIDIMIOLOGY

Tetralogy of Fallot is the most common from of cyanotic congenital heart defect. Its overall incidence is 10%. There is a slight male to female predominance. Approximately 15% of patients with tetralogy have a deletion of chromosome 22q11.1 This is tested with the FISH (Fluorescence In Situ Hybridisation) test.

Associated Lesions

Patency of the oval fossa, atrial septal defect (ASD), a second muscular inlet VSD or an atrioventricular septal defect -usually in the setting of Down's syndrome- can coexist with tetralogy. A right aortic arch

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is common. Coronary arterial abnormalities, the commonest being a left anterior descending from the right coronary artery crossing the right ventricular outflow tract, occur in about 3% and may be of surgical importance, sometimes necessitating the use of a right ventricular-to-pulmonary artery conduit.

The incidence of 22q11 deletion is especially high in patients with right aortic arch, pulmonary atresia and aortic-topulmonary collaterals. The clinical spectrum is summarized in the so called CATCH 22 syndrome (Cardiac defect, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcaemia [neonatal] and 22q11 deletion). Patients with 22q11 deletion may have a propensity to late psychiatric disorder, most commonly depression. Deletion of 22q11 is usually sporadic. Affected subjects, however, have a 50% risk of transmitting the deletion to their offspring, hence the need for family screening and genetic counseling.

EARLY PRESENTATION AND MANAGEMENT

Patients with tetralogy of Fallot invariably present with cyanosis. This is due to rightto-left shunting at ventricular level through the large, non-restrictive VSD. RV pressure is at systemic levels from birth. RV hypertrophy is rarely extreme and does not lead to cavity obliteration, in the way seen in patients with critical pulmonary stenosis or atresia with intact ventricular septum. Patients with tetralogy, therefore, have always an RV of adequate size, and from this perspective they are always suitable for biventricular repair. Extreme pulmonary valve hypoplasia, in contrast, may deem the occasional patient unsuitable for repair. The timing of presentation -with cyanosis- depends on the degree of right ventricular outflow track (RVOT) obstruction. The later can be labile, due to its infundibular component, leading to variable degrees of cyanosis for the individual patient. Although the severity of RVOT obstruction varies considerably, there always seems to be sufficient obstruction to protect the patient from developing pulmonary vascular disease. Patients with pulmonary atresia and multiple aorto-pulmonary collateral vessels represent an exemption to this,

however, as parts of the lungs supplied by non-restrictive collaterals may become hypertensive. The vast majority of patients with tetralogy of Fallot present in infancy. However, when the RVOT obstruction is mild, patients often have minimal cyanosis and may occasionally present in adulthood (so called "pink tetralogy" or "acyanotic Fallot"). Most adults will have had surgery, either palliative or, more commonly, reparative by the time they present to the cardiologist. Rarely, adults present without previous operations. For these patients, surgical repair is still recommended since the results are gratifying and the operative risk is comparable to peadiatric series (provided there is no significant co-existing morbidity). However, late morbidity and mortality in these patients undergoing late repair is higher compared to those who underwent repair in early childhood.2 This, in turn, is due to higher incidence of ventricular dysfunction, right heart failure and sudden cardiac death, presumably arrhythmic. Reparative surgery involves closing the VSD and relieving the RVOT obstruction. The latter may involve: · Pulmonary valvotomy (as in most instances the pulmonary valve is involved, being "bicuspid" and dysplastic) · Resection of infundibular muscle (which represents the major site of RVOT obstruction). · RVOT patch (a patch across the RVOT which does not disrupt the integrity of the pulmonary valve annulus). RVOT patching, combined with infundibular resection, augments the restrictive RV outflow. · Transannular patch (a patch across the pulmonary valve annulus which disrupts the integrity of the pulmonary valve annulus and creates the potential for free pulmonary regurgitation). A transannular patch is used when the pulmonary valve annulus is restrictive.

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homograft valve or porcine bioprosthesis). "Routinely" performed in adolescents and adults undergoing late repair, as these patients usually do not tolerate well pulmonary regurgitation, hence the need for a competent RVOT and bioposthetic valve implantation. · An extracardiac conduit placed between the RV and pulmonary artery (in patients with pulmonary atresia, congenital or acquired). · Angioplasty/patch augmentation of central pulmonary arteries, in patients with hypoplastic main pulmonary trunk and or stenoses of the central pulmonary arteries.. A patent foramen ovale or secundum ASD, if present, needs closure. Additional treatable lesions such as aortic regurgitation or muscular VSDs need also to be addressed. Surgical approach to repair of tetralogy has evolved over the years.3-7 Early cohorts underwent repair through a right ventriculotomy.3 Furthermore, complete relief of RVOT obstruction often necessitated the use of a transannular

Table 19.1 Palliative procedures augmenting pulmonary blood flow

t Blalock-Taussig shunt (classical): subclavian artery-to-pulmonary artery anastomosis (end-to-side). Infrequently, this may lead to pulmonary hypertension. t Blalock-Taussig shunt (modified): interposition graft between subclavian artery and ipsilateral pulmonary artery. Controlled augmentation of pulmonary blood flow. Usually a 4mm Gor-Tex shunt is required early in infancy. Larger shunts would be required for older patients, although the possibility of repair should always be explored first. t Waterston shunt: ascending aorta-to-main or right pulmonary artery (side-by-side). No artificial material used; shunt grows with the patient. May lead to pulmonary hypertension. Infrequently, problems have been encountered with pulmonary artery disruption, requiring extensive arterioplasty. t Potts shunt: descending aorta-to-left pulmonary artery (side-by-side). Frequent complication with narrowing and kinking of the left pulmonary artery at the site of the anastomosis. The latter necessitates reconstructive surgery during repair, occasionally through an additional thoracotomy, which made this shunt unpopular. t Central interposition tube graft: A Gor-Tex graft is often used for patients not suitable for early repair. t Infundibular resection (Brock procedure) or closed pulmonary valvotomy: Often effective palliative procedure from an earlier surgical era. t Relief of RVOT obstruction without VSD closure or with fenestrated VSD closure: in patients with multiple pulmonary artery stenoses or hypoplasia.

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· Pulmonary valve implantation (human

patch, which creates the potential for free pulmonary regurgitation. Recent data, however, has shown detrimental long-term effects of right ventriculotomy and chronic pulmonary regurgitation on RV function and propensity to clinical arrhythmia and sudden cardiac death. This has lead to a modified approach of repairing the lesion with a combined transatrial/ transpulmonary approach involving closure of VSD and relief of the RVOT obstruction through the right atrium and the pulmonary artery.4 A limited RV incision is often required for patch augmentation of the RVOT and or the pulmonary valve annulus. Routine and generous transannular patching has been abandoned. In summary, every effort is now made to maintain the integrity and competence of the pulmonary valve. It is of note that residual RVOT pressure gradients present in the immediate postoperative period, previously thought to carry a poor long-term prognosis, often regress within days. Furthermore, mild to moderate residual RVOT obstruction in isolation is well tolerated long-term. Avoidance of free pulmonary regurgitation

at the expense of some, albeit not-severe residual pulmonary stenosis is well within the current therapeutic goal of reparative surgery. The timing of repair has also changed. Contemporary patients often undergo primary repair at presentation or when becoming symptomatic.5-7 This approach may convey long-term benefits as it abolishes early the cyanosis and by normalising pulmonary blood flow promotes pulmonary artery growth. Most adult patients with repaired tetralogy, however, had one or more previous palliative procedures prior to repair. There are occasional patients who reach adulthood with a palliative procedure only. The types of different palliative procedures, augmenting pulmonary blood flow in the setting of tetralogy are shown in Table 19.1.

increased to 4 and 6% at 25 and 35 years).8 With increasing age acquired heart disease may be contributory to late mortality for these patients and should not be overlooked. Palliated patients: Palliation with arterial shunts and relief of severe cyanosis has dramatically improved the early and midterm outcome for patients with tetralogy of Fallot. Recognised complications following palliative procedures for tetralogy are pulmonary arterial distortion and pulmonary hypertension. Pulmonary arterial distortion has been described with any type of previous arterial shunts, although more commonly seen after a Potts or Waterston shunt. Pulmonary hypertension, in turn, due to a large left-to-right shunt with volume and pressure pulmonary artery overload, is more common after a Waterston anastomosis. Despite early dramatic relief of symptoms, very long-term outcome for patients who underwent only palliative procedures for tetralogy is limited, compared to those who ultimately underwent repair. This is because in patients with palliative procedures only residual cyanosis, volume loading of the LV and pressure loading of the RV (with RV pressures at systemic pressures due to the large VSD) persist. With time, biventricular dysfunction ensues and ultimately these patients die prematurely usually from heart failure or sudden cardiac death. Unoperated patients: Twenty five percent of patients die in the first year of life, if not surgically treated. 9 Forty percent die before 3 years of age, 70% before 10 years and 95% before 40 years of age. Morbidity in adult survivors of tetralogy without surgery is high and relates to progressive cyanosis, exercise intolerance, arrhythmia, tendency to thrombosis and cerebral abscess. In those few naturally surviving into the fourth and fifth decades of life, death usually occurs due to chronic congestive heart failure, secondary to long-

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LATE OUTCOMES Survival and functional status

Repaired patients: The overall survival of patients who have had operative repair is excellent, provided the VSD has been closed, the RVOT obstruction has been relieved satisfactorily and there is no severe pulmonary regurgitation which may lead to RV dilation and RV dysfunction. A 32 to 36 year survival of 86% and 85% have been reported respectively.2,8 Older age at repair is consistently associated with decreased late survival. Death occurs primarily suddenly or due to congestive heart failure. The reported incidence of sudden death, presumably arrhythmic, in late follow-up series varies between 0.5-6%, accounting approximately for 1/3 to 1/2 of late deaths. In a recent study the risk of sudden death increased incrementally after the first 20 years from repair of tetralogy (1.2 and 2.2% at 10 and 20 years respectively

Diagnosis & Management of Adult Congenital Heart Disease

t Endocarditis t Aortic regurgitation with or without aortic root dilation: due to damage to the aortic valve during VSD closure or secondary to intrinsic aortic root abnormality (common in patients with pulmonary atresia and systemic to pulmonary artery collaterals) t LV dysfunction: secondary to inadequate myocardial protection during previous repair, chronic LV volume overload due to long-standing palliative arterial shunts and or residual VSD, injury to anomalous coronary artery (uncommon) t Residual RVOT obstruction: infundibular, at the level of the pulmonary valve and main pulmonary trunk and distally, beyond the bifurcation and occasionally into the branches of the left and right pulmonary arteries t Residual Pulmonary Regurgitation: Usually well tolerated if mild to moderate. Severe chronic pulmonary regurgitation, however, may lead to symptomatic RV dysfunction. Severity of pulmonary regurgitation, and its deleterious long-term effects are augmented by co-existing proximal or distal pulmonary artery stenosis. t RV dysfunction: usually due to residual RVOT lesions; can also be due to inadequate myocradial protection during initial repair. t Exercise intolerance: often due to pulmonary regurgitation and RV dysfunction t Heat block, late postoperative (uncommon) t Atrial tachyarrhythmia: atrial flutter and or atrial fibrillation t Sustained ventricular tachycardia t Sudden cardiac death

standing right ventricular hypertension or suddenly, arrhythmic (Table 19.2).

OUTPATIENT ASSESSMENT Repaired Patients

Most adults with previous repair of tetralogy of Fallot lead unrestricted lives.2,8,10 Late symptoms can be exertional dyspnoea,11 palpitations, syncope or sudden cardiac death. The latter can indeed be the first presentation in patients previously free of overt symptoms. Investigations are directed towards late complications (Table 2.) and preservation of bi-ventricular function. Investigations may vary according to the type of operation performed, the locally available facilities and the status of the patient.

All patients should have periodically a minimum of: · A thorough clinical examination (Observation Points 19.1): · ECG (sinus rhythm, PR interval, QRS duration12, QRS prolongation over time, QT dispersion13 [variables relating to propensity to sustained ventricular tachycardia and risk of sudden death ([Figure 19.2]; see arrhythmia). · Chest X-ray (cardiothoracic ratio on the PA view; left or right aortic arch; dilation or not of the ascending aorta and central pulmonary arteries; presence of retro-sternal filling on the lateral view, suggestive of RV dilation; calcified RV to PA conduit). · Echo Doppler examination (Observation Points 19.2) · Exercise testing to document functional capacity.11 Change with time on exercise performance may be useful in defining optimal timing for intervention. · Holter monitoring (when clinically indicated).

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Table 19.2 Late complications after repair

OBSERVATION POINTS 19.1 Late complications after repair

t Patients with repaired tetralogy should have normal oxygen saturations t A RV heave is common t Signs of right heart failure (oedema, elevated jugular veins and hepatomegaly) are uncommon. Presence of any of these signs may suggest neglected underlying right sided haemodynamic lesions. Patients need to be investigated thoroughly and the option of reintervention to be explored. t A single S2 is common, since only the aortic component can be heard. t A to and fro murmur in the pulmonary area are very common. The degree of pulmonary regurgitation can be difficult to ascertain on clinical grounds only. t Diastolic murmurs can be due to either pulmonary (common) and aortic (less common, but with increasing frequency observed with longer period of follow-up). t A new pansystolic heart murmur in the left lower sternal edge, varying with respiration would often indicate new onset tricuspid regurgitation. This, in turn, may be the result of further RV dilation secondary to pulmonary regurgitation, and may necessitate pulmonary valve implantation with or without tricuspid valve annuloplasty.

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a Fig 19.2 QRS duration predicts sustained ventricular tachycardia and sudden cardiac death. a) Standard 12-lead surface ECG from a patient presenting with sustaned monomorphic ventricular tachycardia 20 years after tetralogy repair. Maximum QRS duration in VI (magnification) occupies a large square, ie. exceeds 180 ms. b) Plot of maximum QRS duration in 182 patients with repaired tetralogy of Fallot. Those with syncope due to sustained monomorphic ventricular tachycardia (9 patients, squares), atrial flutter (1 patient, asterisk) and sudden cardiac death (4 patients, triangles) are plotted separately on the right column.

(Fig 19.2b from Gatzoulis et al, Circulation 1995; 92:231-7).

b

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t Measure RV size and assess RV function; change with time may guide you to optimal timing for reintervention t Assess septal motion (indirect sign of RV dilation) and RV hypertrophy t Interrogate the RVOT with 2-D, Doppler and colour flow mapping for residual pulmonary stenosis and regurgitation (Figure 19.3). Measure maximum velocities at any area t Detect and quantify tricuspid regurgitation t Estimate RV systolic pressure (from tricuspid regurgitation). This may disclose proximal and or peripheral pulmonary artery stenosis; the latter can be difficult to image. t Exclude residual VSD. If present, assess Doppler gradient across the VSD t Assess LV size and function t Exclude intra-atrial communications t Document left and right atrial size t Measure aortic root size and interrogate for aortic regurgitation

Fig 19.3 Echocardiogrophic assessment following repair of tetraology of Fallot. a) Colour Doppler interrogaton of the RVOT in the parasternal short axis view: Patient with free pulmonary regurgitation following previous tetralogy repair with a transannular patch. Laminar retrograde flow (red) from the plmonary artery in the RV outflow. Note RVOT aneurysm.

a b c) Pulsed-wave Doppler interrogation of the tricuspid valve from the same patient. Maximum pressure drop across the tricuspid valve of 36mmHg, excluding significant proximal or distal pulmonary stenosis.

b) Pulsed-wave Doppler from the same patient. Note early termination of pulmonary regurgitation (flow above the curve returning to equilibrium by mid-diatsole) indicative of severe pulmonary regurgitation. Forward blood velocity not increased suggesting absence of pulmonary stenosis.

c

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OBSERVATION POINTS 19.2 Echocardiography

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a Fig 19.4 Cardiac magnetic resonance (CMR) for biventricular function and mass pulmonary regurgitation fraction following repair of tetrology of Fallot. a) Sagital CMR view from a patient with severe pulmonary regurgitation. Note marked dilation of main pulmonary artery and RV. Patient underwent previous tratology repair with a transannular patch. Pulmonary valve is not visualised, whereas a small RVOT aneurysm can be seen below the flow velocity mapping lines ( see c). b) Transverse CMR view from the same patient. Marked RV dilation and flattened interventricular septum are both evident. Multiple contiguous cine acquisitions through both ventricles are employed for calculation of bi-ventricular volume, mass and ejection fraction. c) Phase velocity mapping measuring systolic (above the curve) and diastolic (under the curve) pulmonary artey flow for calculation of regurgitation fraction. Same patient with a and b with a regitant fraction of 43% consistent with severe pulmonary regurgitation.

b

c

and may require: · Cardiac magnetic resonance (CMR) for assessing RV and LV volumes and function, quantifying pulmonary regurgitation (Figure 19.4) and demonstrating pulmonary artery and aortic anomalies, proximal or distal. · Nuclear cardiac imaging at rest and during exercise should also be considered, when CMR is not readily available. Progressive RV dysfunction

· ·

or failure to increase RV ejection fraction during exercise are indications for elective re-operation on the RVOT. Quantitative lung perfusion scan in patients with suspected pulmonary artery branch stenosis. Cardiac catheterization if adequate assessment of hemodynamics can not be obtained by non-invasive means, for catheter intervention and usually when surgical reintervention is planned.

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·

Selective coronary angiography, when clinically indicated or as part of the preoperative assessment. Electrophysiologic studies (EPS) for patients being evaluated for clinical or suspected arrhythmia. Programmed ventricular stimulation appears to be more specific and less sensitive for suspected sustained ventricular tachycardia in the adult compared to paediatric patients. Failure to induce sustained monomorphic ventricular tachycardia in the catheter laboratory does not exclude clinical ventricular tachycardia. Invasive electrophysiologic investigation can also have a therapeutic goal-to guide drug therapy or attempt ablation of reentry circuits.

LATE MANAGEMENT OPTIONS (Table 19.3) Repaired patients

Indications for Reintervention Reintervention is necessary in approximately 10% of patients following reparative surgery over a 20 year follow up.14 It is anticipated that with increasing lengths of follow-up from repair, the incidence of reintervetion, particularly on the RVOT, will increase. The following situations following repair warrant consideration for reintervention: · Residual VSD with a shunt >1.5:1. · Residual patent arterial shunts (leading to LV volume overload). · Residual pulmonary stenosis with RV pressure ( 2/3 of systemic pressure (native RVOT or valved conduit). · RVOT aneurysms; relatively common in patients with previous RVOT or transannular patch repair and significant pulmonary regurgitation. Aneurysmal dilation of the RVOT is associated with regional RV hypokinesis often providing the substrate for sustained ventricular tachycardia. · Branch pulmonary artery stenosis; particularly when combined with significant pulmonary regurgitation. · Free pulmonary regurgitation associated with progressive RV enlargement, new onset tricuspid regurgitation, arrhythmia, or symptoms such as deteriorating exercise tolerance. · Significant aortic regurgitation associated with symptoms and/or progressive LV dilation or deterioration of LV function. · Progressive aortic root enlargement;

Palliated-Only or Unoperated Patients

For those patients who have had previous palliation/s, assessment of pulmonary artery pressure and anatomy is mandatory at some point, since these shunts have inherent complications (distortion of the pulmonary arteries, development of pulmonary hypertension [rare], and LV dysfunction secondary to volume overload). Peripheral pulmonary artery stenosis, when present, may augment pulmonary regurgitation, with its deleterious long-term effects on the RV. Patients presenting as adults who have not been repaired may have elevated pulmonary artery pressures despite severe RVOT obstruction. This can either be due to chronic cyanosis or LV dysfunction. However, this does not preclude repair, as the RV functions at systemic pressure levels from birth, and, therefore, is "prepared" for post-operative hypertension. Lung "reperfusion injury" presenting with pulmonary oedema (bilateral or unilateral), is a recognised complication in adult patients with marked cyanosis and severely restricted

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pulmonary blood flow immediately after late repair. It may require positive pressure ventilation and usually resolves after 24 to 48 hours.

·

·

patients with aortic root ( 55 mm in diameter should be considered. The development of clinical arrhythmia, most commonly atrial flutter or fibrillation, or sustained ventricular tachycardia with underlying hemodynamic substrate (often RV dilation with or without hypertrophy) amenable to intervention. The combination of residual ASD or VSD, residual pulmonary stenosis and pulmonary regurgitation, all mildmoderate but leading to progressive RV enlargement, reduced RV function or symptoms.

· · · ·

Surgical/Catheter Interventional Options

Patients requiring intervention should be treated at a tertiary referral centre with appropriate cardiology and cardiac surgical expertise. The following are possible interventional options: · Surgery may be necessary for residual pulmonary stenosis; this may involve resection of residual infundibular stenosis or placement of RVOT or transannular patch. A valved conduit may be necessary. · Pulmonary valve implantation (either homograft or porcine bioprosthesis) may be necessary for severe pulmonary regurgitation or a grossly calcified pulmonary valve. It carries a low operative risk15 and leads to symptomatic improvement.15-17 Tricuspid valve annuloplasty may also be necessary when at least moderate tricuspid regurgitation is present. Metalic prostheses in the pulmonary position have been complicated with a relatively high incidence of valve thromboses and early valve failure, hence not widely used. · RVOT aneurysm resection. · Balloon dilation and stenting or surgery for branch pulmonary artery stenosis. Relief of distal peripheral pulmonary

· ·

stenosis reduces severity of pulmonary regurgitation.18 However, such patients may ultimately require pulmonary valve implantation. A joint management planning between cardiologists and cardiac surgeons is, therefore, essential. Patients with free pulmonary regurgitation and evidence of RV dysfunction should undergo primary pulmonary valve implantation with concomitant relief of pulmonary stenosis with pulmonary angioplasty. More distal peripheral pulmonary artery stenoses can always be dealt with stenting. Suture or patch closure of a residual VSD if the shunt is ( 1.5:1 or if the patient is undergoing reoperation for other reasons. Catheter or surgical closure of residual arterial shunts, leading to LV volume overload. Aortic valve and/or root replacement may be necessary for those with aortic valve regurgitation and/or root dilation. Ablative therapy for arrhythmia, either atrial or ventricular. This can be performed either percutaneously or intra-operatively during reoperations to restore residual hemodynamic lesions. Modified Maze procedure for patients with documented atrial flutter undergoing reoperation for residual haemodynamic problems. Insertion of automated implantable cardioverter defibrillator (AICD) for secondary prevention of sudden cardiac death, if sustained ventricular tachycardia recurs following restoration of haemodynamics. In the absence of residual haemodynamic substrate amenable to catheter or surgical reintervention, AICD should be part of secondary prevention of sudden cardiac death for patients presenting with sustained monomorphic ventricular tachycardia. AICD should also be considered for primary prevention of patients at risk of sudden cardiac death without target haemodynamic lesions,

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t Repair of suitable patients: with previous palliative procedures or the occasional adult survival without previous surgery t Preservation of RV function by: A) RV volume offloading (restoration of RVOT competence, when severe pulmonary regurgitation with progressive right ventricular dilation are present), and B) relief of RV hypertension (due to native RVOT, conduit and or distal pulmonary artery stenoses) t Preservation of LV function: by volume offloading (closure of significant residual VSDs, residual palliative shunts and, very occasionally -in the setting of tetralogy with pulmonary stenosis- occlusion of systemic-topulmonary artery collaterals) t Risk modification for sustained arrhythmia and sudden cardiac death

·

although prospective data for these patients are clearly required. Closure of ASD or persistent foramen ovale, if there is persistent cyanosis, history of transient ischaemic attacks or evidence of significant left-to-right shunt, leading to RV dilation.

ARRHYTHMIA AND SUDDEN CARDIAC DEATH Conduction abnormalities

Right bundle branch block (RBBB) pattern is almost universal in patients who underwent repair of tetralogy of Fallot via a right ventriculotomy. Characteristically, the RBBB involves a short and narrow first part with a taller and broader second part of the QRS complex (Figure 19.2). RBBB with left anterior hemiblock, so-called bifascicular block, is also common (approximately 15% of postoperative patients). Bifascicular block, when isolated, seldom leads to complete heart block (unless there has been transient AV block in the immediate post-operative period) nor does it relate to increased risk of sudden death. Bifascicular block combined with late PR prolongation, however, occasionally heralds high-degree AV block. Such patients warrant further investigation and may require pacing. Pacemaker implantation is mandatory in all cases of postoperative complete heart block and in true trifascicular block, confirmed by EPS. It has to be emphasised that for the majority of patients with previous tetralogy repair, late onset of complete heart block is rare.

Palliated-only or Unoperated Patients

Late repair of tetralogy should be considered in unoperated adult patients or those with previous palliative shunts only as most of them are suitable for repair. Their work-up should include: · Assessment of biventricular size and function. · Assessment of pulmonary arterial size and pressure. · Demonstration of additional VSD's, if present. · Exclusion of systemic-to-pulmonary artery collaterals (amenable to catheter occlusion prior to repair). · Exclusion of coronary artery disease (that can be addressed at the time of repair).

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Table 19.3 Late management options

Supraventricular arrhythmia

Atrial flutter and atrial fibrillation are relatively common in the adult with previous tetralogy repair. Atrial tachyarrhythmia occurred in one third of adult patients in a single-institutional report and was contributory to late morbidity and even mortality.19 Atrial flutter and fibrillation were more common in patients who had long-lasting systemicto-pulmonary artery shunts -and therefore persisting volume overload- and those who required early reoperations for residual haemodynamic lesions, i.e. patients with suboptimal result from reparative surgery. Older age at repair and moderate-to-severe tricuspid regurgitation were found to be additional predictors of late sustained atrial flutter and or fibrillation in a recent multi-centre study.10 It is of note that previously documented atrial flutter or fibrillation does not preclude sustained ventricular tachycardia or propensity to it in these patients. Such an overlap between sustained atrial and ventricular tachyarrhythmia is more likely in patients with residual right-sided haemodynamic lesions, most often in the setting of pulmonary regurgitation and progressive RV dilation. Atrial tachyarrhythmia usually presents with palpitations. Occasionally, however, patients can present with presyncope or syncope, and atrial flutter has been postulated as a possible cause of sudden cardiac death, as these relatively young adult patients have the ability for one-toone atrio-ventricular conduction. Patients presenting with sustained atrial flutter and or atrial fibrillation, should undergo thorough assessment of their haemodynamics and should have target residual heamodynamic lesions restored. Radiofrequency ablation, following mapping for atrial reentry, is now yielding better results for classical atrial flutter and or incisional re-entry tachycardia and has

to be considered. Anti-arrhythmic medication and the new generation atrial anti-tachycardia pacemakers are further therapeutic tools available.

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Ventricular arrhythmia

Non-sustained ventricular arrhythmia on Holter is very common (up to 60%) following repair of tetralogy. Ventricular ectopy of grade > II according to the modified Lown criteria (> 30 uniform ventricular extrasystoles in any hour) appeared to be associated with increased risk of sudden cardiac death. However, more recent studies failed to show such a relationship.10,20 Sudden cardiac death following repair of tetralogy is relatively uncommon.2,8,10 There is no place, therefore for prophylactic anti-arrhythmic therapy to suppress Holetr ventricular arrhythmia in this low risk population. Sustained monomorphic ventricular tachycardia, in contrast, is relatively uncommon.10 Re-entry is the most common pathophysiologic mechanism and multiple factors have been implicated for its pathogenesis.21 The usual arrhythmia focus is in the RVOT in the area of previous infundibulectomy or VSD closure during tetralogy repair. In approximately 20% of cases the re-entry focus can be multiple, involving the body of the RV. RV dilation22 and stretch with slowed ventricular activation12 are also contributory to the creation of re-entry circuits within the RV, whereas impaired haemodynamics are responsible for sustaining ventricular tachycardia, once initiated. QRS duration from the standard surface ECG has been shown to correlate well with RV size in these patients.12 A maximum QRS duration of 180 ms or more is a highly sensitive and relatively specific marker for sustained RV and sudden cardiac death in adult patients with previous repair of tetralogy12 (Figure 19.2). QRS prolongation in these patients reflects: A) initial damage to the bundle, during tetralogy repair23 (right

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ventriculotomy, relief of muscular subpulmonary stenosis and suture placement for VSD closure) and B) late progressive QRS prolongation, secondary to RV dilation, which in turn is almost invariably the result of chronic pulmonary regurgitation. A recent multi-centre study10 has shown that QRS change with time may be a more sensitive and specific predictor of patients at risk. New, absolute QRS predictive values for sustained ventricular tachycardia will be required for patients undergoing tetralogy repair in the current era, as most of them undergo repair via the right atrium and pulmonary artery and not through a right ventriculotomy, which used to be the norm until the late 1980's. Initial QRS prolongation immediately after repair is, therefore, significantly shorter in contemporary cohorts. QT dispersion -the difference between the shortest and longest QT interval in any of the 12 leads of the standard surface ECG, a marker of inhomogeneous repolarization- has also been shown to be predictive of sustained monomorphic ventricular tachycardia late after repair of tetralogy.13 A QT dispersion >60 ms combined with a QRS duration of > 180 ms refines further risk stratification for sustained RV for these patients. Recent reports demonstrating depressed heart rate variability and baroreflexes sensitivity, suggest that the autonomic nervous system may also be involved in the pathogenesis of sustained ventricular tachycardia in these patients. Abnormal right-sided haemodynamics, predominantly RV dilation due to pulmonary regurgitation with or without pulmonary stenosis have been very common in patients at risk for or indeed patients presenting with sustained ventricular tachycardia10 (Figure 19.5). Detailed haemodynamic assessment is, therefore, of paramount importance. Furthermore, interventions to restore underlying residual lesions, usually rightsided, should be an essential part of risk modification and arrhythmia management in these patients. Other invasive therapeutic tools are transcatheter or intraoperative ablative procedures and AICD

implantation. AICD implantation is usually an adjacent therapy for secondary prevention of sustained ventricular tachycardia and sudden cardiac death, following restoration of residual haemodynamic problems. AICD may also be considered for primary prevention for patients at risk, when advanced ventricular dysfunction is present and no target haemodynamic lesions for catheter and or surgical intervention are to be found. Antiarrhythmic therapy has clearly a role for the symptomatic patient, but one cannot overemphasise the need for addressing underlying haemodynamic lesions. Prophylactic antiarrhythmic therapy, in contrast, for the asymptomatic patient with Holter ventricular ectopy has no role. Patients with repaired tetralogy are low risk subjects for sustained ventricular tachycardia and sudden cardiac death, and the potential pro-arrhythmic side effects of anti-arrhythmic therapy can be more hazardous.

Sudden Cardiac Death

Sudden cardiac death has been reported in all large series with an incidence varying between 0.5 and 6%.2,8,10 Older age at repair and relative postoperative RV hypertension (to LV) have been previously shown to be risk factors for late sudden death.2 Transannular patching, predisposing to free pulmonary regurgitation, and accelerated rate of QRS prolongation were additional predictors of sudden death in our recent multi-centre study10 (Figure 19.5). RV hypertension (RV systolic pressure > 60mmHg) in isolation was not predictive of sudden cardiac death or sustained ventricular tachycardia in this study. Patients with sustained monomorphic ventricular tachycardia and those dying suddenly, shared a common electrophysiologic and haemodynamic substrate, suggesting a common pathogenic and pathophysiologic mechanism. Patients who died suddenly,

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19 TETRALOGY OF FALLOT

cardiac death. Furthermore, this approach is shown to preserve ventricular function,16 which in turn is one of the major determinants of the very long-term outcome for these patients.25

19 TETRALOGY OF FALLOT

PREGNANCY

Pregnancy in unoperared patients constitutes a considerable risk of maternal and fetal complications and death. This risk is greater when resting oxygen saturations in air are < 85%. The fall in peripheral resistance during pregnancy and hypotension during labour and delivery may increase the right to left shunt and aggravate pre-existing cyanosis. Fetal loss may be as high as 30% and maternal mortality is reported at 4 to 15%, with risk increasing proportional to heamatocrit. The risk of pregnancy in repaired patients depends on the hemodynamic status. The risk is low, approaching that of the general population, in patients with good underlying hemodynamics. In patients with significant residual RVOT obstruction, severe pulmonary regurgitation with or without tricuspid regurgitation and RV dysfunction, the increased volume load of pregnancy may lead to heart failure and arrhythmias. Furthermore, LV dysfunction, usually due to previous volume overload, may be present. This in turn increases the likelihood of complications during pregnancy and requires independent consideration. All patients with tetralogy should have specialist cardiologic counselling preconception and check-up during pregnancy. The FISH test, to exclude 22qD should also be considered.

N=793 patients

Fig 19.5 haemodynamic substrate in patients with sustained tachyarrhythmia and sudden cardiac death late after repair of tetralogy of Fallot. Echocardiographic data from 456 patients obtained during the preceeding 12 months from occurrence of sustained ventricular tachycardia, sudden cardiac death, atrial flutter/fubrillation or at the end of thew study for arrhythmia-free patients. Pulmonary regurgitaion was the main underlying haemodynamic lesion for patients with sustained ventricular tachycardia and sudden cardiac death.

(Fig 19.5 from Gatzoulis et al, Lancet 2000;356:975-981)

however, had a much later repair compared to patients presenting with sustained ventricular tachycardia. This in turn suggests that LV dysfunction, secondary to long-lasting cyanosis and volume overload (from palliative arterial shunts) may also be contributory to sudden death. It is of note that none of the 16 patients who died suddenly from this multi-centre study had undergone reoperations or catheter intervention to address existing important residual haemodynamic problems. Despite obvious limitations with the existing data from retrospective studies,24 it is becoming clear that preservation or restoration of RV and pulmonary valve function may reduce the risk of sudden cardiac death in these patients. As with sustained ventricular tachycardia, addressing residual haemodynamic lesions should be part of the risk modification approach for sudden

LEVEL OF FOLLOW UP

All patients should have periodic review at an adult congenital heart centre. A

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Diagnosis & Management of Adult Congenital Heart Disease

minimum of history taking, physical examination, ECG and Echo are required per visit. Further assessment of right ventricular size and function preferably by CMR is advisable, as it provides robust data on bi-ventricular size and function; interval change in these parameters provide reliable guidance on the need for and the optimal timing of re-intervention. CMR should be considered as a baseline assessment for all patients and can be repeated with variable frequency depending on the severity of residual haemodynamic lesions.

ENDOCARDITIS

All patients will tetralogy of Fallot, repaired, palliated or unoperated require life-long endocarditis prophylaxis.

Patients with a good haemodynamic result following repair of tetralogy, preserved biventricular function and mild residual lesions need no exercise restrictions. They can participate in endurance sports, athletic competitions and contact sports. Patients with moderate residual lesions (defined as RV systolic pressure less than half systemic pressure, or moderate pulmonary regurgitation or residual VSD) and normal bi-ventricular function are suitable and should be encouraged to participate in moderate levels of exercise, including running, tennis, football and aerobics. Patients with moderate to severe residual lesions (RV systolic pressure between 1/2 and 2/3 of systemic pressure and severe pulmonary regurgitation) preserved bi-ventricular function.

References

1. Goldmuntz E, Clark BJ, Mitchell LE, et al. Frequency of 22q11 deletions in patients with conotruncal defects. J Am Coll Cardiol 1998;32:492-8 2. Murphy JG, Gersh BJ, Mair DD, et al. Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot. N Engl J Med 1993;329:593-9. 3. Lillehei CW, Cohen M, Warden HE, et al. Direct vision intracardiac surgical correction of the tetralogy of Fallot, pentalogy of Fallot, and pulmonary atresia defects; report of first ten cases. Annals of Surgery 1955;142:418-445. 4. Kawashima Y, Kitamura S, Nakano S, et al. Corrective surgery for tetralogy of fallot without or with minimal right ventriculotomy and with repair of the pulmonary valve. Circulation 1981;64:147-153. 5. DiDonato RM, Jonas RA, Lang P, et al. Neonatal repair of tetralogy of Fallot with and without pulmonary atresia. J Thorac Cardiov Surg 1991;101:126-137. 6. Karl TR, Porniviliwan S, Mee RBB. Tetralogy of Fallot: favourable outcome of nonneonatal transatrial, transpulmonary repair. Annals of Thoracic Surgery 1992;54:903-907. 7. Reddy VM, Liddicoat JR, McElhinney DB, et al. Routine repair of tetralogy of Fallot in neonates and infants less than three months of age. Annals of Thoracic Surgery 1995;60:S592-596. 8. Nollert G, Fischlein T, Bouterwek S, et al. Longterm suRVival in patients with repair of tetralogy of Fallot: 36-year follow-up of 490 suRVivors of the first year after surgical repair. J Am Coll Cardiol 1997;30:1374-83 Betranou EG, Blackstone EH, Hazelrig JB, et al. Life expectancy without surgery in tetralogy of Fallot. Am J Cardiol 1978;42:458-466. Gatzoulis MA, Balaji S, Webber SA, et al. Risk factors for arrhythmia and sudden death in repaired tetralogy of Fallot: a multi-centre study. Lancet 2000;356:975-981. Wessel HU, Cunningham WJ, Paul MH, et al. Exercise performance in tetralogy of Fallot after intracardiac repair. Journal of Thoracic and Cardiovascular Surgery 1980;80:582-593. Gatzoulis MA, Till JA, Somerville J, et al. Mechanoelectrical interaction in tetralogy of Fallot. QRS prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death. Circulation 1995;92:231-7 Gatzoulis M, Till JA, Redington AN. Depolarisation-repolarisation inhomogeneity after repair of tetralogy of Fallot. Circulation 1997;95:401-404. Oechslin EN, Harrison DA, Harris L, et al. Reoperation in adults with repair of tetralogy of Fallot: indications and outcomes. J Thorac Cardiovasc Surg 1999;118:245-51

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10.

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14.

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EXERCISE

15. Yemets IM, Williams WG, Webb GD, et al. Pulmonary valve replacement late after repair of tetralogy of Fallot. Annals of Thoracic Surgery 1997;64:526-530. 16. Bove EL, Byrum CJ, Thomas FD, et al. The influence of pulmonary insufficiency on ventricular function following repair of tetralogy of Fallot. Journal of Thoracic and Cardiovascular Surgery 1983;85:691-696. 17. Warner KG, Anderson JE, Fulton DR, et al. Restoration of the pulmonary valve reduces right ventricular volume overload after previous repair of tetralogy of Fallot. Circulation 1993;88:II-189-II197 18. Chaturvedi RR, Kilner P, White P, et al. Increased airway pressure and simulated branch pulmonary stenosis increase pulmonary regurgitation after repair of tetralogy of Fallot: real-time analysis using conductance catheter technique. Circulation 1997;95:643-649. 19. Roos-Hesselink J, Perlroth MG, McGhie J, et al. Atrial arrhythmias in adults after repair of tetralogy of Fallot. Correlations with clinical, exercise, and echocardiographic findings. Circulation 1995;91:2214-9 20. Cullen S, Celermajer DS, Franklin RC, et al.

21.

22.

23.

24.

25.

Prognostic significance of ventricular arrhythmia after repair of tetralogy of Fallot: a 12 year prospective study. J Am Coll Cardiol 1994;23:11511155. Kugler JD, Pinsky WW, Cheatham JP, et al. Sustained RV after repair of Fallot: new electrophysiological findings. Am J Cardiol 1983;51:1137-1143. Marie P-Y, Marcon F, Brunotte F, et al. Right ventricular overload and induced sustained ventricular tachycardia in operatively "repaired" tetralogy of Fallot. Am J Cardiol 1992;69:785-789. Norgard G, Gatzoulis M, Moraes F, et al. The relationship between type of outflow tract repair and postoperative right ventricular diastolic physiology in tetralogy of Fallot: implications for long-term outcome. Circulation 1996;94:3276-3281. Saul JP, Alexander ME. Preventing sudden death after repair of tetralogy of Fallot: Complex therapy for complex patients. J Cardiovasc Electrophysiol 1999;10:1271-1287. Graham TP, Cordall D, Atwood GF, et al. Right ventricular volume characteristics before and after palliative and reparative operation in tetralogy of Fallot. Circulation 1976;54:417-423.

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