Historically, structural heart disease has been a field limited to surgical interventions, with periprocedural imaging providing the initial diagnosis and indication for intervention (eg, to determine the severity of mitral regurgitation). Over time, cardiac surgical procedures have become increasingly complex (ie, valve repair as an improved alternative to replacement), requiring a deeper understanding of the mechanisms involved in the disease (eg, presence of mitral prolapse, flails, perforations, clefts, annular dilatation) to guide the surgical approach and assess its success before leaving the operating room.
More recently, catheter-based procedures have been utilized in the treatment of structural heart disease because studies have shown less invasive percutaneous interventions are better tolerated, with faster recovery and favorable outcomes compared to surgery. For each intervention, multiple devices may be available, each with a specific design and with different implanting techniques. Understanding how each device is designed, how it is to be implanted, and how it is meant to work is critical for the success of these procedures.
With percutaneous interventions, the “field of view” of the operator is significantly limited when compared to open-heart surgery. Therefore, the role of cardiovascular imaging has become critical to assist in planning and guiding interventions and to evaluate immediate success or the presence of procedural complications. Accordingly, the cardiovascular imager must have a thorough understanding of multimodality imaging and the complexity of structural pathologies, devices, and procedural techniques.
INDICATIONS AND FUNDAMENTALS OF PERIPROCEDURAL IMAGING
The role and indications for imaging in patients with cardiovascular disease is dependent on the clinical characteristics, presentation, and overall patient conditions. Professional societies have developed numerous guidelines,1,2,3,4,5 appropriateness use criteria, decision pathways for management,6,7 and other standards documents that help the clinician approach patients according to their existing or suspected pathology and decide when—and which—imaging modality may be warranted.
Transthoracic echocardiogram (TTE) is usually the initial imaging modality to evaluate patients with valvular disease or other suspected structural heart diseases, because it is widely available, noninvasive, and has almost no contraindications. A complete TTE allows for a comprehensive evaluation of cardiac chamber size and function, including visualization of valves and identification of most cardiac pathologies. The use of Doppler imaging (color and spectral) in addition to two- and three-dimensional (2D and 3D) TTE is critical to evaluate hemodynamic abnormalities such as intracardiac shunts, valvular stenosis, and valvular regurgitation. On certain occasions, TTE can be improved by using related techniques such as agitated saline injection (for detection of right-to-left shunts), ultrasound enhancing agents (for better delineation of the endocardium, intracardiac thrombus or masses, and myocardial perfusion imaging for alcohol septal ablation), or myocardial strain imaging (for left ventricular [LV] function).
Once a pathology is identified, a thorough evaluation must include quantifying severity, size, morphology, and mechanisms underlying the pathology, as well as the consequences of the pathology to other structures within the heart (ie, ventricular or atrial remodeling, pulmonary hypertension, etc).
TABLE 39.1 Role and Goals of Cardiac Imaging in Structural Heart Disease
Preprocedural
Diagnose the pathology
Determine its severity and need for intervention
Evaluate indications and contraindications for intervention
Determine the most appropriate procedure
Intraprocedural
Assist in procedural planning and device selection and sizing
Guide the procedure to maximize efficacy and safety
Postprocedural
Monitor the patient post intervention, including complications
Long-term follow-up to evaluate device function and cardiac response
Although TTE frequently provides most of the information needed, the cardiac imager must understand the limitations of this modality and utilize alternative imaging modalities (ie, transesophageal echo [TEE], cardiac computed tomography [CT], cardiac magnetic resonance imaging [CMR]) when some of the needed information cannot be addressed with confidence by TTE. Although the severity of valvular disease or shunts is best assessed with TTE, detailed anatomy and morphology is best evaluated with TEE or CT. Furthermore, 3D imaging provides anatomic information that cannot be obtained from 2D imaging and allows for more accurate measurements of structures in all their dimensions, including perimeter, volume, area, and circumference, which is critical for the selection of the appropriate-sized devices. For the most part, 3D imaging for structural procedures can be obtained through TEE, multislice cardiac CT, or CMR.
TEE offers better spatial resolution than TTE (structures are better seen except those in the apex of the LV) with a similarly high temporal resolution; however, it is more invasive and requires moderate sedation. TEE‘s main contraindication is known or suspected obstructive disease of the upper gastrointestinal tract (ie, oropharyngeal, esophageal, or gastric).
TABLE 39.2 Role, Goals, and Types of Cardiac Imaging in Patients Undergoing TAVR
Preprocedural
Determine aortic stenosis severity and need for intervention (TTE)
Evaluate indications and contraindications for intervention (TTE)
Data from Otto CM, Kumbhani DJ, Alexander KP, et al. 2017 ACC expert consensus decision pathway for transcatheter aortic valve replacement in the management of adults with aortic stenosis: a report of the American College of Cardiology Task Force on Clinical Expert Consensus Documents. J Am Coll Cardiol. 2017;69(10):1313-1346.
TABLE 39.3 Role and Goals of Cardiac Imaging in Patients Undergoing Mitral Valve Repair With Edge-To-Edge Leaflet Approximation
Data from Bonow RO, O’Gara PT, Adams DH, et al. 2020 Focused Update of the 2017 ACC expert consensus decision pathway on the management of mitral regurgitation: a report of the American College of Cardiology Solution Set Oversight Committee. J Am Coll Cardiol. 2020;75(17):2236-2270.
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