Fig. 3.1
RV enlargement after TOF repair. MRI imaging of a 29-year-old woman after the intracardiac repair of a TOF. Note the markedly enlarged RV. RV end-diastolic volume is 168 mL/m2 and RVEF is 35%
Moreover, a high index of suspicion must be maintained for pulmonary artery stenosis and right ventricular outflow tract (RVOT) stenosis in these patients.
The development of arrhythmias (atrial or ventricular) also indicates an underlying hemodynamic abnormality. In particular, right atrial and/or right ventricular enlargement eventually causes both atrial and ventricular arrhythmias. Basically, the common arrhythmogenic mechanisms include operative scars and natural conduction obstacles that create narrow corridors capable of supporting macro-reentry; however, the hemodynamic abnormalities may also affect arrhythmogenicity. It is reported that atrial reentrant tachycardia is observed during extended follow-up in more than 30% of patients. In addition, malignant ventricular arrhythmias have also been noted in about 10% of patients [4, 5]. Notably, the overall incidence of sudden cardiac death is estimated at 0.2% per year of follow-up [6, 7].
3.2.1 Catheter Intervention
Adult patients with TOF often have residual lesions amenable to catheter intervention. Patients with residual pulmonary artery stenosis are often treated using catheter balloon dilation and/or stent implantation [8, 9]. A peak instantaneous echocardiography gradient greater than 50 mmHg or an RV/LV pressure ratio greater than 0.7 should be an indication for catheter intervention. Pulmonary artery branch stenosis with a disproportional lung perfusion greater than 7:3 is also an indication for balloon dilatation.
Residual RV outflow tract obstruction may be relieved by RV outflow tract stenting. It is especially important that the RV outflow tract stenting is not allowed to cause coronary compression.
Currently, percutaneous pulmonary valve replacement (PVR) is performed worldwide. The original criteria for percutaneous Melody valve implantation (Medtronic, Inc., Minneapolis, Minnesota) for PR included RV-to-pulmonary artery conduits of 16 mm, balloon sizing of the narrowest area to 14 and 20 mm, and greater than moderate PR or severe conduit stenosis (gradient 35 mmHg) [10]. Some complications following Melody valve implantation such as stent fracture and endocarditis have been reported [10, 11]. Although there is a paucity of evidence concerning antibiotic prophylaxis for endocarditis in this situation, the current guidelines recommend prophylaxis for prosthetic valves [12].
Despite its rarity, hypoxemia in postoperative patients should be searched for the cause of that, in those possibly having a PFO or ASD with a right-to-left shunt that could be treated with percutaneous device closure.
As mentioned above, arrhythmias are important factor for the prognosis and outcome in adult TOF patients. Thus, appropriate antiarrhythmic therapy including catheter ablation and intracardiac device (ICD) implantation should be performed (see Chap. 5).
Lastly, when catheter intervention is considered for adult patients with congenital heart disease, collaboration between ACHD interventional cardiologists, electrophysiologists, and ACHD surgeons is mandatory to determine the most feasible treatment.
3.2.2 Surgical Intervention
PR is the most common indication for late reoperation. PVR is indicated for moderate to severe PR and decreased exercise tolerance. A successful PVR results in significant improvement in LV ejection fraction (EF), which correlates with the pre-PVR RV end-diastolic volume. It is reported that an increase in RV greater than 170 mL/m2 will not return to normal even after PVR. Furthermore, Therrien et al. reported that in order to maintain adequate RV contractility, PVR should be considered before RV function deteriorates (at least >EF 40%). Recently, the benefits of earlier reoperation (in adolescence or young adulthood) have been highlighted [13].
TR may be secondary to RV dilation due to significant PR or structural valve deformities possibly related to a VSD patch or chordal disruption at initial repair. TR can also be affected by permanent pacing or ICD leads. Tricuspid repair can be accomplished using an eccentric, purse-string, or ringed annuloplasty [14]. Tricuspid replacement may be required if prior repairs have failed or if there are major leaflet abnormalities, however, it is reported that the risk of surgery is greater with tricuspid replacement than tricuspid valve plasty [14].
VSD reclosure is indicated for significant L-R shunt that causes significant LV volume overload. In the acute phase after initial repair, LV volume overload due to a VSD leak may cause severe LV failure, because the LV in a TOF patient is relatively small before repair and is susceptible to acute volume overload. Also in the late period, when LVEF deteriorates with the progression of RV enlargement, a residual VSD leak may also affect LV function.
A dilated ascending aorta is also a major problem in adult patients with TOF, and because its natural history and treatment outcomes are not well-known, the timing of aortic intervention remains controversial. Dissection and aortic rupture in this patient group are rare [15]. Aortic valve regurgitation does not necessarily accompany aortic dilation. In general, replacing the ascending aorta is indicated if it is greater than 55 mm in diameter [15].
Rarely, the surgical relief of a subaortic stenosis is needed in TOF patients. Diagnostic uncertainty may occur concerning a double outlet right ventricle in which the aorta overrides more than 50% of the right ventricle. In such cases, a VSD patch is more extensive and predisposes to postoperative subaortic obstruction, which should be carefully excluded.
Surgery for arrhythmias may be performed mainly for atrial tachyarrhythmias such as atrial reentry tachycardia, atrial fibrillation, and flutter, concomitant with reoperation [16]. Atrial flutter should be treated with cryoablation or radiofrequency ablation of the right atrial isthmus. Paroxysmal atrial fibrillation should be treated with right atrial maze, and chronic atrial fibrillation should be treated with biatrial maze procedure [17]. The most common arrhythmia following maze surgery is a junctional rhythm or sick sinus syndrome, which may require a permanent pacemaker implant.
Some postoperative patients may experience LV dysfunction. This may be related to a prolonged cardiopulmonary bypass, poor myocardial protection from an early surgical intervention, or trauma to a coronary artery at the time of repair, or it may be secondary to severe RV enlargement and/or dysfunction (ventricular-ventricular interaction). Although medications for heart failure may be necessary in RV and LV dysfunction, evidence for β-blockers and angiotensin receptor inhibitors in these patients have been scarce to date. Therefore, cardiac resynchronization therapy or heart transplantation may be applied when refractory heart failure inevitably progresses [17].
3.3 Dextro-Transposition of the Great Arteries
Dextro-transposition of the great arteries (d-TGA) is defined as combination of AV concordance and ventriculoarterial discordance. Consequently, in d-TGA, the aorta arises right and anterior to the pulmonary artery and arises from the right ventricle. Additional congenital cardiac lesions include VSD, which occurs in up to 45% of cases; left ventricular outflow tract (LVOT) obstruction, which occurs in approximately 25% of cases; and coarctation of the aorta occurring in approximately 5% of cases [18].
The infant with d-TGA will generally present with cyanosis, and some form of admixture of blood is required for survival. For the past two decades, arterial switch operation in the neonatal period has been the primary surgical repair of choice for uncomplicated d-TGA. In patients who present late (after 6–8 weeks of age), pulmonary artery banding to prepare the left ventricle is often necessary. Patients with d-TGA and associated VSD may undergo an initial pulmonary artery banding or shunt procedure, depending on the presence or absence of subpulmonary artery obstruction. If there is an associated large VSD, a right ventricle outflow reconstruction (Rastelli-type procedure) may be performed as a primary procedure. In the 1960s–1970s, atrial switch operations, such as the Senning or Mustard procedure were often performed on these patients [19]. The long-term outcomes differed depending on which procedure was selected.
The frequency of late complications may be determined by the degree of residual hemodynamic abnormalities, and these are becoming more common. All adult patients with d-TGA should be seen at least once annually by an ACHD specialist, with attention given to rhythm disorders, as well as ventricular and valvular function. Selected patients should undergo exercise testing, including stress radionuclide scintigraphy and cardiopulmonary exercise test. If significant abnormalities are found during these examinations, or if the patient is symptomatic, more frequent follow-up visits are indicated.
3.3.1 Residua and Sequelae After the Atrial Switch Procedure
These procedures involve an atrial baffle that redirects the systemic venous blood to the left ventricle through the mitral valve, which remains committed to the pulmonary artery. The pulmonary venous blood is redirected to the tricuspid valve and right ventricle, which remains committed to the aorta. The atrial switch (Mustard or Senning procedure) operation for d-TGA has characteristic long-term problems [19].
The most important long-term complication of this procedure is the failure of the systemic right ventricle and TR, which indicates systemic AV valve regurgitation. These complications have a major impact on morbidity and mortality in patients with d-TGA. Other complications include conduction and arrhythmia disturbances, such as sick sinus syndrome, supraventricular tachyarrhythmia, and complete AV block, which may lead to sudden death or the implantation of permanent pacemakers for prevention of that [20]. In addition, common early structural complications such as baffle obstruction, which commonly affects the superior limb rather than the inferior vena cava, may be encountered. Facial suffusion and edema, that is the “superior vena cava syndrome,” occasionally occur. Inferior vena cava obstruction may cause hepatic congestion or even cirrhosis. Baffle leaks are known to occur in up to 25% of patients. Most are small but cause cyanosis to some extent and predispose to paradoxical embolism, particularly in the presence of atrial arrhythmias and an endocardial pacemaker. Pulmonary venous obstruction may be rarely seen. Moreover, pulmonary stenosis (subpulmonary and/or valvular) may occur, in part related to the abnormal geometry of the left ventricle, which becomes distorted and compressed by the enlarged systemic right ventricle. Finally, rare but important complications including pulmonary arterial hypertension (PAH) and residual VSD may also arise.
Cardiac echocardiography is the first-line and also the main tool for anatomic and hemodynamic assessment in most d-TGA patients after an atrial switch operation. Evaluation for intraatrial baffle anatomy and shunting or obstruction may warrant echocardiography with contrast medium injection. However, the assessment of systemic RV function is challenging using echocardiography. In addition to the routine evaluation of ventricular size and function, measurement of the dP/dt of the AV regurgitant jet, tricuspid annular plane systolic excursion (TAPSE), and the Tei index may provide further information [21–23]. Tissue Doppler evaluation of myocardial acceleration during isovolumic contraction has been validated as a sensitive, noninvasive method of assessing RV contractility [24]. One advantage of the Tei index is its ability to represent the indices of both systolic and diastolic function without geometric constraints. In addition, a relationship between the Tei index and brain natriuretic peptide (BNP) has been shown and may provide valuable information if assessing RV function in the adult patient using echocardiography becomes difficult [22]. Transesophageal echocardiography (TEE) is an informative tool that may be used to visualize the atrial anatomy, presence of a baffle leak or obstruction, and intracardiac thrombus. MRI or CT is used to further assess atrial baffle patency, systemic ventricular function, and coronary anatomy [25]. Cardiac MRI is usually superior to TEE for evaluating the configuration of the extracardiac great arteries and veins. MRI has also been shown to be closely correlated with the equilibrium radionuclide ventriculography assessment of RVEF [26].
Cardiac catheterization is the definitive tool for assessing hemodynamics, baffle leak, superior vena cava or inferior vena cava pathway obstruction, pulmonary venous pathway obstruction, myocardial ischemia, unexplained systemic RV dysfunction, subpulmonary stenosis, LVOT obstruction, or PAH, with a possibility for vasodilator testing. Cardiac catheterization in patients after the atrial switch operation also provides the opportunity for intervention.
Concerning arrhythmic complications, regular ECG follow-up is mandatory to detect sick sinus syndrome (SSS) which represent a slow junctional rhythm or complete AV block. Other rhythm abnormalities such as tachyarrhythmia may be further elucidated by ambulatory rhythm monitoring (Holter or event recorder). Exercise testing to determine functional capacity and the potential for arrhythmias may be helpful.
3.3.2 Residua and Sequelae After the Arterial Switch Procedure
The health-related quality of life of patients after the arterial switch operation is known to be better than those undergone the atrial switch operation [27, 28]. Long-term concerns after the arterial switch procedure include coronary perfusion abnormality, myocardial ischemia, ventricular dysfunction and arrhythmias, and pulmonary stenosis (branch stenosis and/or stenosis at anastomotic sites), as well as the development of aortic or pulmonary regurgitation (Figs. 3.2 and 3.3). Significant neoaortic root dilatation and valve regurgitation may develop with time, in part related to older age at the time of the operation or to an associated VSD with previous pulmonary artery banding [28, 29].
Fig. 3.2
Pulmonary branch stenosis after an arterial switch operation for d-TGA. Bilateral pulmonary branch stenotic lesions are shown
Fig. 3.3
Aortography after an arterial switch operation for d-TGA. Aortic root dilatation is shown, as well as sinus of Valsalva dilatation
In the clinical setting, many patients may be asymptomatic. However, it should be noted that systolic murmurs related to pulmonary and/or aortic obstruction, and diastolic murmurs of aortic regurgitation should not be overlooked.
ECG can be helpful in detecting ischemic changes, occasionally noted at rest, which suggests the presence of coronary stenosis. This should be evaluated further by stress ECG testing. Moreover, RV and LV hypertrophy suggest the presence of ventricular outflow obstruction or arterial regurgitation; this should also be noted.
Echocardiography after the arterial switch procedure may mostly reveal anatomical complications, including pulmonary stenosis [30, 31], aortic root dilatation, and neoaortic valve regurgitation [32]. Although coronary complications cannot be assessed properly using echocardiography, stress echocardiography may help to detect myocardial ischemia. MRI and CT angiography have been particularly useful for diagnosing aortic dilatation and coronary stenosis. Patients with intramural or single coronary arteries are at risk of coronary complications [33, 34]. Evaluating coronary ischemia using noninvasive methods may not be sufficiently sensitive. Notably, typical symptoms of coronary ischemia may be absent even when significant ostial coronary stenosis exists in these patients. In such cases, coronary arteriography using a cardiac catheter is recommended. Apart from ordinary coronary arteriography, aortic root angiography, especially the “cusp shot,” is highly recommended for detecting ostial stenosis (Fig. 3.4).
Fig. 3.4
Coronary stenotic lesion after an arterial switch operation for d-TGA. Coronary arteriography revealed stenotic lesion of left main trunk, segment 5
3.3.3 Residua and Sequelae After the Rastelli-Type Operation
The Rastelli-type operation for d-TGA with pulmonary stenosis (PS) and VSD (the so-called d-TGA type 3) has recognized complications, which include RVOT or pulmonary conduit obstruction, suprasystemic RV pressure leading to RV dysfunction, and significant TR [18]. Subaortic stenosis may also occur due to the insufficient size of the intraventricular rerouting pathway. Tachyarrhythmias may arise from atriotomy and/or ventriculotomy incisions, residual VSD, RV enlargement due to PR, aortic root dilatation, and aortic valve regurgitation. These concerns are similar to those of TOF.
Echocardiography is the primary imaging modality in patients with prior Rastelli-type operations. Recurrent RV or LV outflow obstruction can be usually and properly detected by Doppler echocardiography. Assessing RV pressure and the occurrence of conduit obstruction can be facilitated by measuring TR velocity. Additional important features should include the assessment of PR, residual or baffle-margin VSD, and the development of PAH.
3.3.4 Management and Intervention
With regard to medication, the positive role of ACE inhibitors and beta blockers remains unclear. Moreover, it should be noted that beta blockers may precipitate complete AV block in patients with preexisting sinus node dysfunction. Therefore, it should be used cautiously, particularly after an atrial switch operation.
Interventional catheterization plays a crucial role in the management of adult patients after an atrial switch, arterial switch, or Rastelli-type operation. Successful stent implantation for the relief of a symptomatic atrial baffle obstruction, as well as percutaneous placement of transcatheter implants for baffle leak elimination, has been reported in adult survivors of the atrial switch operation. Transcatheter dilation and stenting of central pulmonary artery stenosis are possible therapeutic choices. When branch pulmonary artery stenosis is found in adults after a Rastelli-type operation, hybrid management, which includes preoperative stenting, intraoperative stenting, or intraoperative patch with or without conduit replacement, is recommended. Dilation with or without stent implantation of conduit obstruction may be indicated when RV pressure is greater than 70% of systemic levels or the peak-to-peak gradient is greater than 50 mmHg.
Reoperation for patients with d-TGA is occasionally inevitable and is important for preserving good health. Although conversion to an arterial switch in adulthood has previously been attempted, it has not been generally considered a reasonable option for the management of RV failure in patients after an atrial switch [35]. Patients with severe symptomatic superior or inferior vena cava obstruction or pulmonary venous pathway obstruction should be referred for reoperation when catheter intervention is not effective. It has been noted that when attempting endocardial pacemaker implantation in these patients, a detailed assessment of the atrial baffle for obstruction and leakage must be undertaken, because an endocardial pacing device may exacerbate any obstruction in the atrial baffle. Patients with a baffle leak that demonstrates a Qp/Qs greater than 1.5 or a right-to-left shunt with arterial desaturation at rest or with exercise should be considered for surgery when device placement is impossible. Severe TR may need a surgical intervention such as tricuspid valve replacement (TVR,) but a major part of TR after an atrial switch operation is the consequent on severe RV dysfunction. Therefore, TVR is not common in these patients comparing with adults with congenital corrected transposition of the great arteries. In cases of severe RV dysfunction with severe TR, heart transplantation should be the last option.
Patients needing reoperation after an arterial switch operation are uncommon. The most common reoperation is a repeat RVOT reconstruction because of a severe RVOT obstruction with a peak-to-peak gradient greater than 50 mmHg or RV/LV pressure ratio greater than 0.7, which is not amenable or responsive to catheter intervention. PVR should be considered when severe PR is present, and there is significant RV dilatation or RV dysfunction; however, reoperation of this reason is uncommon. Coronary ostial stenosis may be repaired using coronary bypass grafting or ostial arterioplasty techniques. Significant AR presenting with LV enlargement should be considered as an AVR. Patients who have developed aortic root dilation (greater than 55 mm) may be treated with root replacement.
Reoperation after a Rastelli-type operation should be considered for symptomatic conduit and/or pulmonary artery stenosis with a peak gradient greater than or equal to 50 mmHg and/or RV/LV pressure ratio greater than 0.7. Reoperation for severe conduit regurgitation should be performed when decreased exercise tolerance; severe RV dysfunction; severe RV enlargement, development, and/or progression of atrial or ventricular arrhythmias; and greater than moderate TR are present. Relief of severe symptomatic subaortic stenosis with a mean gradient greater than 50 mmHg should be considered.
3.4 Congenitally Corrected Transposition of the Great Arteries
Congenitally corrected transposition of the great arteries (CCTGA) is defined as an abnormality consisting of atrioventricular discordance and ventriculoarterial discordance. Therefore, the left ventricle pumps blood to the pulmonary artery, and the right ventricle has the heavier workload of pumping blood to the aorta. In other words, the morphological right ventricle functions as the systemic ventricle, whereas the morphological left ventricle functions as the pulmonary ventricle (Fig. 3.5). These features definitely influence both the natural history and postoperative sequela and determine the patient’s lifelong outcome.
Fig. 3.5
Senning route of the patients with CCTGA after the double switch operation. Baffle obstruction (red arrow) is shown (contrast imaging from inferior vena cava)
The clinical course of CCTGA varies depending on the presence and severity of associated lesions [36, 37]. Predominant are the following: VSD (70%), PS (40%), and some abnormalities of the tricuspid valve (90%). Tricuspid abnormality, most commonly, is an Ebstein-like deformity in which the valve is displaced inferiorly toward the cardiac apex [38]. Conduction abnormalities are also common, with spontaneous complete heart block occurring at a rate of approximately 2% per year [39, 40]. If the patients do not have any associated lesions, they may be asymptomatic but more often they present with congestive heart failure and usually with moderate to severe TR.
3.4.1 Physiologic Repair for CCTGA
Traditionally, physiologic repair is performed for patients with CCTGA, such as VSD closure, PS release, and (TVR). The indication for surgery in adult patients is not reasonable but often the onset of symptoms due to associated TR or RV dysfunction. Surgical intervention in the adult often consists of TVR alone. Ideally, it should be performed before the RVEF is less than 45% [41, 42]. However, in physiologic repair, the problem remains in which the RV as the systemic ventricle. Graham et al. reported that 25% of adult patients have advanced systemic RV dysfunction in their 40s, even without any associated lesions [43]. This rate is thought to increase as time progresses. Furthermore, complete AV blocks are common after surgical repair of a VSD or following a TVR. Thus, there are several severe postoperative problems following physiologic repair.
3.4.2 RV Failure of CCTGA
Most patients eventually have severe TR and an RVEF less than 45% [41, 42]. With progressing RV dysfunction, the RV and the annulus dilate causing the failure of leaflet coaptation and progressive regurgitation. Moreover, the tricuspid valve is often morphologically abnormal, and with time, there is worsening of regurgitation. Progression of TR may also occur as a result of pacemaker implantation, related to septal shift and further distortion of the tricuspid valve (TV) annulus. VSD closure may also exacerbate TR, probably by the same mechanism. It has been proposed that the TV should always be replaced if the regurgitation is moderate or severe at the time of intracardiac repair of other lesions [44]. Because the morphological RV may not be intrinsically suited to function long term as the systemic ventricle, such patients live for relatively shorter periods, and survival to the seventh decade is very rare. The precise mechanisms of RV failure are not clear but are probably related to microscopic structural features of the RV myocardium and coronary perfusion mismatch [45]. Certainly, RV failure is a major cause of morbidity and mortality in adult patients with CCTGA [46]. Atrial tachyarrhythmias are also common and occur more commonly in those with RV dysfunction and TR [47].
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