Show notes
In this episode, CardioNerds (Amit Goyal), ACHD series co-chair, Dr. Josh Saef (ACHD fellow at University of Pennsylvania) and episode lead fellow, Dr. Brynn Connor (Pediatric Cardiology fellow at Lucile Packard Children's Hospital at Stanford) are joined by Dr. Maan Jokhadar (Advanced heart failure and adult congenital heart disease specialist at Emory University) to discuss transposition of the great arteries. Audio editing by CardioNerds Academy Intern, Dr. Maryam Barkhordarian.
For a brief review of the basic anatomy and physiology of D-TGA, check-out this great video by Dr. Maan Jokhadar!
The CardioNerds Adult Congenital Heart Disease (ACHD) series provides a comprehensive curriculum to dive deep into the labyrinthine world of congenital heart disease with the aim of empowering every CardioNerd to help improve the lives of people living with congenital heart disease. This series is multi-institutional collaborative project made possible by contributions of stellar fellow leads and expert faculty from several programs, led by series co-chairs, Dr. Josh Saef, Dr. Agnes Koczo, and Dr. Dan Clark.
The CardioNerds Adult Congenital Heart Disease Series is developed in collaboration with the Adult Congenital Heart Association, The CHiP Network, and Heart University. See more
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https://www.youtube.com/watch?v=Ifu8nVtXT_c
Pearls
(1) In D-TGA following an atrial switch operation, the right ventricle IS the systemic ventricle!
(2) Evaluation of systemic right ventricular function often requires use of both transthoracic echocardiography and cardiac MRI.
(3) Use of medical heart failure therapies should be individualized, without any proven long-term mortality benefit and potential unique complications in this patient population (i.e. SA node dysfunction).
Show notes
D-transposition of the great arteries (D-TGA) is one of the most common forms of cyanotic congenital heart disease presenting in the newborn period. Anatomically, d-transposition of the great arteries is characterized by atrioventricular concordance and ventriculoarterial discordance, such that the aorta arises from the morphologic right ventricle and pulmonary artery arises from the morphologic left ventricle. The resultant physiology is that of a parallel circulation, with deoxygenated blood recirculating in the systemic circulation (via the RA-RV) and oxygenated blood recirculating in the pulmonary circulation (via the LA-LV). At birth, this invariably results in cyanosis, with survival dependent upon adequate mixing of the two circulations via an atrial or ventricular level defect.
Prior to surgical advances in the late 1950s, this lesion was uniformly fatal, with most infants dying before their first birthday. The subsequent development of the Senning and Mustard atrial-level repairs led to good immediate outcomes and improved long-term survival. However, following these “physiologic” types of repair, patients are far from cured, with several long-term established complications, including (1) dysfunction of the systemic right ventricle, (2) tricuspid regurgitation (the systemic atrioventricular valve), (3) atrial and ventricular arrhythmias, and (4) systemic and pulmonary venous baffles leaks and obstruction. These complications ultimately lead to substantial morbidity and premature mortality, with ACHD providers facing unique challenges in the medical and surgical management of this heterogenous patient population.
1. What are the basic anatomic features of d-transposition of the great arteries (d-TGA)?
D-transposition of the great arteries is defined by the origin of the arterial trunks from the morphologically inappropriate ventricle, specifically with the aorta arising from the morphologic right ventricle (now the systemic ventricle) and the pulmonary trunk arising from the morphologic left ventricle.This is termed “ventriculoarterial discordance”, and importantly, does not define the spatial relationship of the great arteries. Rather, the “d” terminology refers to the looping of the ventricles and distinguishes d-TGA from l-TGA (or congenitally corrected transposition), where there is additional atrioventricular discordance. The resultant physiology is that of a parallel circulation, with deoxygenated blood recirculating in the systemic circulation and oxygenated blood recirculating in the pulmonary circulation. At birth, this invariably results in cyanosis, with survival dependent upon adequate mixing of the two circulations via an atrial or ventricular level defect.There are three major anatomic variations in dTGA, including dTGA with an intact ventricular septum (most common), dTGA with a ventricular septal defect, and dTGA with LVOT obstruction. These anatomic subtypes can lead to variable presentations in the neonatal period, as well as pose unique challenges to surgical repair, and are therefore important diagnostic considerations.The arrangement of the coronary arteries and their spatial course can additionally be highly variable, posing added complications when performing the arterial switch operation (which requires reimplantation of the coronary arteries into the neo-aortic root). The most common, “usual,” arrangement is the left coronary artery originating off the anterior facing sinus, and the right coronary artery originating off the posterior facing sinus.
2. What surgical approaches have been utilized in the management of D-TGA?What are the key features of aortic coarctation anatomy?
Prior to surgical advances in the late 1950s, this lesion was uniformly fatal, with most infants dying before the age of 1 year.Infants were initially palliated with an atrial septostomy, which allowed for mixing at the atrial level and improved survival in the immediate newborn period. However, these infants were still left with profound cyanosis, with inevitable mortality in the first year of life.In the mid-1950s, the Senning (1958) and Mustard (1964) atrial-level repairs were first performed, with good short-term outcomes and improved long-term survival.In the Senning procedure, a baffle is created within the atria that redirects the deoxygenated caval blood to the mitral valve and the oxygenated pulmonary venous blood to the tricuspid valve with use of native atrial tissue.Mustard subsequently described a simpler technique with creation of an atrial baffle using synthetic patch material.
By the late 1980s, late complications of these repairs became well recognized, with the ultimate adoption of the neonatal arterial switch operation, which remains the gold standard for surgical management of transposition.
3. What are the long-term complications of the Mustard and Senning procedures?
Systemic Right Ventricular Dysfunction:Clinical Features - Systemic RV dysfunction is an evitable consequence of the atrial switch operation, with 50% of patients developing right ventricular systolic dysfunction by 30 years of age.While right ventricular dysfunction is often mild and clinically asymptomatic for several years, patients ultimately develop related symptomatology over the subsequent 10-20 years.Most commonly, patients present to care with diminished exercise tolerance, with symptomatic arrhythmias being an additional common reason for patients to seek care.
DiagnosisAccurate assessment of RV size and function in this population is critical for adequate surveillance and management planning. However, quantitative right ventricular assessment remains challenging, with no model for comparison and no clear criteria for abnormalities.Volumetric assessments are the gold standard, although made difficult by the complex geometry of the right ventricle.Cardiac MRI is most commonly utilized to assess RV size and systolic function, and additionally permits simultaneous evaluation of the systemic and pulmonary venous baffles and quantitative assessment of the degree of tricuspid regurgitation (the systemic AV valve).Transthoracic echocardiography is still routinely employed for serial evaluation of systemic right ventricular function. However, providers should have a low threshold to obtain further advanced imaging with any significant change in symptomatology or qualitative decrement in right ventricular systolic function on serial echocardiographic assessment.ManagementMedical Therapy: In contrast to ischemic cardiomyopathy, there are no long-term, randomized, placebo-controlled drug trials evaluating the efficacy of ACEI/ARB/ARNI or beta-blockers on systemic RV function. Small studies performed to date have not shown any appreciable benefit of ACEI/ARB on improving right ventricular ejection fraction or exercise capacity, which may reflect minimal baseline activation of the renin-angiotensin-aldosterone system in this form of heart failure. Use of beta-blocker therapy pathophysiologically makes sense, specifically reducing myocardial oxygen demand and allowing for improved ventricular filling; however, prior studies have produced mixed results, with evidence of improved right ventricular remodelingalthough no appreciable improvement in right ventricular ejection fraction, functional class, or long-term survival. Use of beta-blockers should also be cautioned in patients with established SA node dysfunction.Left Ventricular Re-Training: Conversion to an arterial switch operation often requires a staged approach to ensure that the left ventricle is adequately “trained” to handle systemic pressures.