As the scope and complexity of percutaneous interventions for structural heart disease broadens, the need for precise, real-time adjunctive imaging becomes more acute. While fluoroscopy has served traditionally as the imaging technique for interventional cardiology procedures, it entails significant radiation exposure and requires the use of intravenous contrast for optimal visualization of soft tissue structures. It can be temporally and spatially imprecise in cases involving placement or removal of intracardiac devices and repairs of paravalvular leaks or other structural defects.
Transesophageal echocardiography (TEE), performed during interventional cardiology procedures (Interventional TEE) defines and creates a new indication for the modality. Interventional TEE is used to guide and assess the progress and outcome of interventions in a real-time, continuous, and stepwise fashion. In this context the interventional echocardiographer becomes a co-proceduralist, providing clear, time-efficient, step-by-step guidance for interventional cardiologists navigating the complexities of cardiac anatomy with catheters, balloons, and devices. It is critical that during intra-procedural imaging, the interventionalist and echocardiographer maintain constant communication regarding anatomic structure and function as well as the actual progress of the procedure.
Interventional TEE examinations are performed to guide placement and assess positioning of devices for a variety of procedures including septal occlusion, paravalvular leak repair, and valve replacement and repair. This establishes a new role for echocardiographers, who may routinely have performed cardiac assessments pre- and post-intervention, but are not necessarily familiar with guiding procedures while they are in progress.
The difference in acuity and timing, not just the venue change, makes important new demands of the echocardiographer, whether he/she is a cardiologist, cardiac anesthesiologist, or sonographer.
A comprehensive interventional TEE examination begins with both a structural and functional definition of the primary defect and consideration of any associated pathology in the context of the proposed procedural plan. Effective communication among team members is critical. The unique value of interventional two-dimensional (2D) and three-dimensional (3D) TEE can be neutralized by confusion regarding either the complexities of image acquisition or the goals of the procedure itself.
It is helpful for the interventional echocardiographer to be familiar with all of the imaging modalities used in the interventional suite. Fluoroscopic and echocardiographic images can augment each other, particularly when unusual clinical presentations or anatomy obtain. Each display should be visible to, understood, and discussed by all team members, particularly when seemingly contradictory interpretations arise.
A complete interventional TEE exam includes both 2D and Doppler imaging complemented by 3D and real-time 3D (RT3D) datasets. For the interventional echocardiographer it may be necessary to alternate between 2D and 3D imaging in order to specify temporal and spatial relationships, which are inconsistently depicted when only one modality is utilized. For example, proper placement of wires and catheters into small spaces from which high velocity jets emanate—such as paravalvular leaks or stenotic pulmonary veins—may require both types of imaging. Here, color-flow Doppler can be used to localize the defect, while RT3D images can guide temporal placement of intracardiac equipment.
RT3D imaging can nicely assess the proximity of equipment and devices to the target defect. It permits rotation of volumes in all directions in order to delineate structures in their native orientation. Although in the operating room it is possible to correlate actual anatomy with TEE images, such is not the case in the Cath lab, and therefore the quality of imaging and, especially, of interpretation is critical to achievement of the desired outcome.
As technology evolves, interventional cardiology procedures for structural heart disease will become more sophisticated. Increasingly, patients with congenital, acquired and surgically created defects will become candidates for modification via interventional cardiology procedures. While it is true that Interventional TEE has emerged as the next evolutionary phase of echocardiography, what is most important now is the development of optimal, collaborative relationships between interventional cardiologists and echocardiographers. Such relationships, and not new technology alone, are necessary in order to advance the cutting edge of medical practice.