198. ACHD: Cardiovascular Multimodality Imaging in Congenital Heart Disease with Dr. Eric Krieger

CardioNerds (Daniel Ambinder), ACHD series co-chairs, Dr. Josh Saef (ACHD fellow, University of Pennsylvania) Dr. Daniel Clark (ACHD fellow, Vanderbilt University), and ACHD FIT lead Dr. Jon Kochav (Columbia University) join Dr. Eric Krieger (Director of the Seattle Adult Congenital Heart Service and the ACHD Fellowship, University of Washington) to discuss multimodality imaging in congenital heart disease. Audio editing by CardioNerds Academy Intern, Dr. Maryam Barkhordarian. Special introduction to CardioNerds Clinical Trialist Dr. Shiva Patlolla (Baylor University Medical Center). In this episode we discuss the strengths and weaknesses of the imaging modalities most commonly utilized in the diagnosis and surveillance of patients with ACHD. Specifically, we discuss transthoracic and transesophageal echocardiography, cardiac MRI and cardiac CT. The principles learned are then applied to the evaluation of two patient cases – a patient status post tetralogy of Fallot repair with a transannular patch, and a patient presenting with right ventricular enlargement of undetermined etiology. 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. 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Pearls - Cardiovascular Multimodality Imaging in Congenital Heart Disease Transthoracic echocardiography (TTE) is the first line diagnostic test for the diagnosis and surveillance of congenital heart disease due to widespread availability, near absent contraindications, and ability to perform near comprehensive structural, functional, and hemodynamic assessments in patients for whom imaging windows allow visualization of anatomic areas of interest.Transesophageal echocardiography (TEE) use in ACHD patients is primarily focused on similar indications as in acquired cardiovascular disease patients: the assessment of endocarditis, valvular regurgitation/stenosis severity and mechanism, assessment of interatrial communications in the context of stroke, evaluation for left atrial appendage thrombus, and for intraprocedural guidance. When CT or MRI are unavailable or contraindicated, TEE can also be used when transthoracic imaging windows are poor, or when posterior structures (e.g. sinus venosus, atrial baffle) need to be better evaluated.Cardiac MRI (CMR) with MR angiography imaging is unencumbered by imaging planes or body habitus and can provide comprehensive high resolution structural and functional imaging of most cardiac and extracardiac structures. Additional key advantages over echocardiography are ability to reproducibly quantify chamber volumes, flow through a region of interest (helpful for quantifying regurgitation or shunt fraction), assess for focal fibrosis via late gadolinium enhancement imaging, and assess the right heart.Cardiac CT has superior spatial resolution in a 3D field of view which makes it useful for clarifying anatomic relationships between structures, visualizing small vessels such as coronary arteries or collateral vessels, and assessing patency of larger vessels (e.g branch pulmonary arteries) through metallic stents which may obscure MR imaging. Downsides relative to CMR include requirement of nephrotoxic contrast for imaging of intracardiac/intravascular structures, and while gated images can be obtained throughout the cardiac cycle similarly to CMR, this is particularly costly from an ionizing radiation standpoint.When working up an unknown congenital lesion, it is critical to communicate the differential diagnosis when ordering a test so that the imager can protocol the study accordingly. Not all echocardiograms, CT or MRI scans are the same. Show notes - Cardiovascular Multimodality Imaging in Congenital Heart Disease What are the key strengths and weaknesses of transthoracic echocardiography? STRENGTHS: (1) “Most important ability is availability”: Transthoracic echocardiography is the first line imaging modality in the assessment of patients with congenital heart disease because it is widely available at significantly lower cost with no contraindications or risks to the patient. (2) Versatility: A wide array of echo approaches can be employed to provide comprehensive structural and physiological data. 2D echo techniques are most useful for visual assessment of cardiac structural abnormalities. Color doppler provides qualitative data regarding flow, and spectral doppler (inclusive of tissue doppler imaging) provides quantitative data defining intracardiac hemodynamics. 3D echo can be applied to optimize imaging planes for valve area planimetry and quantify chamber volumes as well as global contractile function. Strain imaging using 2D speckle tracking techniques can be employed to evaluate regional contractility. (3) High temporal resolution: High temporal resolution makes echocardiography a superior modality for imaging fast-moving structures (e.g., valvular vegetations or intracardiac masses). WEAKNESSES: (1) “You can’t study what you can’t see”: Suboptimal ultrasound penetration can limit transthoracic imaging quality in patients with large body habitus, or patients in the post-operative state. Furthermore, imaging planes are limited by sonographic windows - many anatomic cardiac (e.g., sinus venosus and coronary sinus defects, anomalous coronary arteries) and extracardiac (e.g., aortic dilation/coarctation, anomalous venous return) abnormalities are often incompletely evaluated by echocardiography in adult patients. This is a major limitation as many ACHD conditions are associated with aortopathy and anomalous pulmonary or systemic venous return which may necessitate dedicated cross-sectional imaging. Finally, right ventricular imaging is limited by near field artifact and complex chamber geometry; and similarly anterior structures such as right ventricular to pulmonary arterial conduits are poorly evaluated with transthoracic echocardiography. What differentiates a congenital echocardiogram from a standard adult protocol? Congenital echocardiograms obtain more comprehensive anatomic evaluation to visualize structural anomalies that might not be evident in standard imaging planes. Most congenital echo protocols begin with a subcostal short axis and long axis sweep to determine segmental anatomy, visceral and atrial situs, cardiac position, cardiac looping, and arterial situs. Additional views are attempted from the suprasternal position to better characterize major venous and arterial connections and anatomy (bidirectional Glenn, etc.). Sweeps are often obtained between views within the same window to clarify the relationships between anatomic structures and identify abnormalities (e.g. inter-chamber connections) not apparent in the standard imaging planes. What is the role of transesophageal echocardiography in adult congenital cardiology imaging? In adult patients with acquired cardiovascular disease, transesophageal echocardiography (TEE) is most commonly employed for the assessment of endocarditis, valvular regurgitation/stenosis severity and mechanism, assessment of interatrial communications in the context of stroke, evaluation for left atrial appendage thrombus, and for intraprocedural guidance. Each of these indications are also commonly encountered in an ACHD population. In congenital cardiology, improved spatial resolution of posterior heart structures can similarly be leveraged to image pathology not well visualized by a transthoracic approach such as for identifying sinus venosus defects, characterizing secundum atrial septal defects to determine feasibility of percutaneous closure, or for assessment of baffle leak on Fontan or atrial switch D-TGA patients. Additionally, TEE increasingly plays a critical role in the perioperative setting (e.g., examining physiology pre- and post-bypass) and for monitoring and guidance of percutaneous interventions in the cardiac catheterization lab. What are the key strengths and weaknesses of Cardiac MRI? STRENGTHS: (1) Unencumbered imaging planes: Unlike echocardiography, for which views are limited by echocardiographic windows, cardiac MRI technicians can prescribe unlimited imaging planes for a more complete coverage of both intracardiac and extracardiac anatomy – particularly with addition of MR angiography. This allows for improved assessment of anterior structures (e.g., the RV, RV-PA conduits), posterior structures (e.g., atrial baffles, sinus venosus or coronary sinus defects), and extracardiac anomalies (e.g., anomalous venous return, aortopathies, pulmonary arterial stenoses), which are usually poorly imaged by echocardiography in adults. Additionally, imaging is generally unaffected by body habitus, and may be used as the primary imaging modality for patients with poor transthoracic windows. (2) Reproducible volumetric quantification: Cardiac MRI is the gold standard for chamber volume assessment. Chamber volumes are obtained from endocardial contouring of Cine-CMR short axis stacks,