Complex Lesions



Complex Lesions


Jeannette Lin

Prashanth Venkatesh

Weiyi Tan



INTRODUCTION

Congenital heart defects and surgical palliations included in this chapter are considered “complex” congenital heart defects1 and include D-transposition of the great arteries (D-TGA), congenitally corrected transposition of the great arteries (cc-TGA), hypoplastic left ventricle (LV) syndrome and the Fontan circulation, truncus arteriosus, and double outlet right ventricle (DORV). This diverse group of defects typically require complex surgical repairs and result in significant residual physiologic or anatomic abnormalities. Care of the patient with complex congenital heart disease (CHD) thus requires knowledge of the initial congenital cardiac diagnosis, as well as the surgical history and the anticipated sequelae and residual hemodynamic abnormalities. Advances in surgical and transcatheter interventions continue to modify morbidity and mortality for this patient population, and ongoing research is warranted to understand long-term survival with contemporary approaches in pediatric and adult congenital cardiac care.


D-TRANSPOSITION OF THE GREAT ARTERIES

D-TGA is a cyanotic congenital heart defect that accounts for 4% to 7% of all CHD, with a prevalence of 2.9 per 10,000 live births.2 Because of the failure of the aorticopulmonary septum to spiral around its longitudinal axis during the first trimester in utero, the connections of the great vessels to the ventricles are discordant, with the aorta arising from the morphologic right ventricle (RV) and the pulmonary artery (PA) arising from the morphologic LV. The pulmonary and systemic circulations exist in parallel, resulting in neonatal cyanosis. Patients with this diagnosis require surgical repair to survive to adulthood. Most patients born in developed countries prior to the late 1980s to early 1990s underwent an atrial switch repair, whereas most patients born in the early 1990s or later underwent an arterial switch repair.


D-TGA AFTER ATRIAL SWITCH REPAIR

The atrial switch repair involves creation of intracardiac baffles to divert deoxygenated blood from the inferior vena cava (IVC) and superior vena cava (SVC) across the mitral valve into the subpulmonary LV, and oxygenated blood from the pulmonary veins across the tricuspid valve into the subaortic RV. This reestablishes a circulation in series and corrects cyanosis, albeit at the cost of retaining a systemic RV (Figure 109.1).


CLINICAL PRESENTATION

Patients with D-TGA and atrial switch typically have normal growth and development, but have limited exercise capacity compared with their peers. Over time, chronic pressure overload of the systemic RV leads to RV systolic and diastolic dysfunction, which typically presents in the fourth to fifth decades of life as congestive heart failure. Furthermore, functional tricuspid regurgitation from RV dilation may exacerbate these symptoms.

Patients who have undergone the atrial switch are prone to arrhythmias, which affect 60% of patients by 20 years after atrial switch. Sinus node dysfunction is the most common cause of bradyarrhythmia presumably because of scarring related to the superior portion of the atrial redirection. Atrioventricular (AV) nodal dysfunction may also occur. Supraventricular tachyarrhythmias are very common, because of extensive intra-atrial scar.2

The intracardiac baffles may become obstructed or may develop baffle leaks. Obstruction of the SVC limb of the baffle mimics SVC syndrome with edema of the head and upper extremities. Obstruction of the IVC limb may result in hepatic congestion, abdominal bloating, early satiety, and lower extremity edema. Baffle leaks result in atrial-level shunting, typically “left-to-right” from the pulmonary venous atrium into the systemic venous atrium. As with all atrial-level shunts, this may increase the risk of paradoxical embolism. Large baffle leaks may cause volume loading of the subpulmonic LV and heart failure symptoms.


DIAGNOSTIC EVALUATION

Suspected arrhythmias should be evaluated with ambulatory electrocardiographic (ECG) monitoring. Transthoracic echocardiography (TTE) is useful to monitor valve and ventricular function and for surveillance of outflow tract obstruction, baffle leaks, or baffle stenosis. Transesophageal echocardiography (TEE) is superior to TTE for visualization of the baffles. Cardiac magnetic resonance imaging (CMRI) is an excellent tool for evaluation of RV size and function, baffle stenoses, and baffle leaks, particularly when combined with four-dimensional (4D) flow imaging. Computed tomography (CT) scans are a reasonable
alternative to CMRI, particularly if patients have implantable devices that are not compatible with CMRI. CT scans have high spatial resolution and are useful in identifying baffle stenoses.







MANAGEMENT: D-TGA AFTER ATRIAL SWITCH REPAIR

Bradyarrhythmias necessitate permanent pacemaker in a median of 10% of patients.2 Atrial arrhythmias after atrial switch can be malignant and predispose to sudden cardiac death.2 An upfront rhythm control strategy, with antiarrhythmic therapy and/or catheter ablation, is hence preferred.3

Pharmacotherapy for systemic RV dysfunction currently lacks robust evidence and is not recommended by current guidelines,3 though β-blockers may offer protection against appropriate implantable cardioverter-defibrillator (ICD) shocks,4 and angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) should be considered for patients with diabetes or hypertension.

Percutaneous baffle interventions such as angioplasty, stenting, and plugging of leaks have periprocedural success rates of 90% to 95%5 and are preferred over surgical reoperation, where mortality can be as high as 26%.6


D-TGA AFTER ARTERIAL SWITCH OPERATION

The arterial switch operation involves translocation of the aorta and PA to the opposite root via supravalvar anastomoses. The coronary arteries are translocated and reimplanted along with islands of pericoronary sinus tissue (“buttons”), whereas the PA is moved anterior to the aorta via the Lecompte maneuver.7

In contrast to atrial switch repairs, following arterial switch operation the LV is the systemic ventricle. This confers a better long-term survival (>95%) after 25 years, making the arterial switch operation the current standard of care for D-TGA repair.8


CLINICAL PRESENTATION

The most common complications after arterial switch operation are supravalvar PA stenosis from anastomotic scarring or stretching of the branch PAs, and progressive dilation of the neoaorta with consequent neoaortic valvular regurgitation. Neoaortic stenosis and AV block are less common.7,8 Ostial stenosis from the reimplanted coronary buttons may occur, and symptoms of angina, heart failure, or ventricular arrhythmias should prompt evaluation of the coronary arteries.7


DIAGNOSTIC EVALUATION

TTE, CMRI, and cardiac CT can define great vessel dilation/stenosis as well as ventricular and valvular function. Exercise testing, cardiac CT, and invasive angiography are useful if coronary stenosis is suspected. Baseline imaging of the coronary arteries as adult is recommended.1


MANAGEMENT: D-TGA AFTER ARTERIAL SWITCH OPERATION

Transcatheter balloon angioplasty and stenting is preferred over surgery for treating PA stenosis.7,8 Severe neoaortic valvular regurgitation is usually accompanied by significant neoaortic dilation and is managed with surgical valve replacement with concomitant aortic grafting.8 Coronary stenting and aortocoronary bypass grafting are management options for coronary artery stenosis.3,7



D-TGA WITH VENTRICULAR SEPTAL DEFECT AND PULMONIC STENOSIS AFTER RASTELLI OPERATION

The Rastelli operation is used as anatomic repair for D-TGA with concomitant ventricular septal defect (VSD) and pulmonary stenosis. Left ventricular outflow is baffled through the VSD into the aorta, and a valved conduit made of biologic or synthetic material directs blood from the RV to the PA, often with the proximal anastomosis on the RV free wall (Figure 109.2).


CLINICAL PRESENTATION

The mean life span of a RV-PA conduit in an adult is 10 to 15 years, with significant stenosis or regurgitation necessitating reoperation in 80% of patients by 20 years.3,9 Obstruction and leak of the LV-aorta baffle can cause heart failure, whereas arrhythmias occur because of ventricular scarring from surgery. Conduit endocarditis can occur, especially in bovine xenografts.10


DIAGNOSTIC EVALUATION

Although TTE is valuable to evaluate biventricular function and pressures, the RV-PA conduit is often not well seen with this imaging modality. CMRI or cardiac CT is useful for conduit visualization and accurate quantification of RV size and function, which helps inform the decision to intervene on the conduit.







MANAGEMENT

Conduit degeneration is preferably managed via transcatheter pulmonary valve replacement with concomitant conduit angioplasty and stenting if indicated, though the conduit may need surgical replacement if this approach fails.3,9 Percutaneous approaches are also preferred for baffle complications. Arrhythmias may necessitate pharmacotherapy, pacemakers, ICDs, and/or catheter ablation.


CONGENITALLY CORRECTED TRANSPOSITION OF THE GREAT ARTERIES

In cc-TGA or L-TGA, the great arteries are transposed, but there is concomitant ventricular inversion that reestablishes the two circulations in series, thus “correcting” the problem of cyanosis caused by the transposed great vessels (Figure 109.3). Although the circulation is physiologically normal, the RV serves as the systemic ventricle and the LV as the subpulmonary ventricle in this anatomy.


CLINICAL PRESENTATION

Patients are usually not cyanotic and are sometimes diagnosed in adulthood, either incidentally or for evaluation of a murmur or heart failure symptoms. Systemic RV failure develops
in up to 67% of patients by age 40, whereas over 50% develop significant tricuspid regurgitation because of Ebstein-like malformation of the tricuspid valve or functional tricuspid regurgitation.11 Also, abnormal anterior displacement of the AV node confers a 2% annual risk of premature AV block,12 which may be the presenting symptom leading to the diagnosis of cc-TGA in adulthood.







DIAGNOSTIC EVALUATION

TTE establishes the diagnosis of cc-TGA in adults and delineates ventricular and valvular function. CMRI is useful for quantification of RV (systemic ventricle) function, whereas ambulatory ECG monitors may reveal transient AV block in symptomatic patients.


MANAGEMENT: CONGENITALLY CORRECTED TRANSPOSITION OF THE GREAT ARTERIES

Common interventions in cc-TGA patients include pacemaker implantation (45% of patients with cc-TGA) and surgical tricuspid valve replacement for tricuspid regurgitation.3,11 Valve replacement for tricuspid regurgitation has better outcomes than surgical repair, but must be done before RV (systemic ventricle) failure develops.13 Transcatheter technologies for AV valve regurgitation may be useful in TGA patients, particularly if surgical risk is prohibitive because of systemic RV dysfunction.14 Transplantation may be considered for severe RV systolic and/or diastolic failure refractory to medical management.

Patients with severe systemic RV dysfunction may benefit from ICD therapy for primary sudden cardiac death prevention, though current selection criteria lack robust evidence.15 Advances in multimodality imaging for procedural planning and guidance can improve success rates of these interventions.


FONTAN CIRCULATION


PATHOGENESIS

In CHD, the goal of surgical repair is to establish a biventricular circulation whenever possible, with two circuits in series: one atrium and ventricle receives systemic venous return and pumps it forward to the pulmonary circulation, whereas a second atrium and ventricle receives pulmonary venous return and pumps it forward to the systemic circulation. In some congenital heart defects, the cardiac anatomy prohibits separation of the systemic and venous circulations. For example, in mitral atresia with a hypoplastic LV, or tricuspid or pulmonary atresia with a hypoplastic RV, the hypoplastic ventricle is too small to accommodate normal cardiac output, and attempting to partition the ventricles would result in severely elevated filling pressures within the hypoplastic ventricle and poor cardiac output. In other cases, such as unbalanced AV canal, the AV subvalvar apparatus may straddle the ventricular septum and prevent partitioning of the AV valve into left and right orifices. In such patients, the Fontan procedure allows for separation of the systemic venous and arterial circulations by redirecting flow from the systemic veins directly to the PA. In the absence of a subpulmonary ventricle, blood is propelled forward through the pulmonary circulation by negative intrathoracic pressure with inspiration. The pulmonary venous flow then returns to the dominant ventricle, which serves as the systemic ventricle pumping oxygenated blood to the aorta.

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May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Complex Lesions
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