How imaging views are used in Cardiac Electrophysiology.
The ability to view X-rays in real-time was initiated by Wilhelm Roentgen when he discovered “X” radiation in 1895. It was the beginning of the Medical Imaging Universe – now a Metaverse. We live in a future where 2D fluoroscopic imaging is used to create 3D renderings to better evaluate anatomy and procedural workflows. Today in cardiology, we take for granted the ability to view the heart in real-time, position catheters and guidewires, view contrast, and evaluate for complications.
So how did we advance imaging capabilities?
During the cardiac catheterization procedure, a C-Arm style X-Ray system moves around the patient and turns to the right, the left, towards the feet (caudal), and towards the head (cephalad) to display the cardiac structures from every side. This is necessary because the coronary arteries can appear superimposed or foreshortened, making the area of injury difficult to image. The angulation of the C-Arm provides various views which move one artery out of the way of the other.
But we do Electrophysiology…we look at electrograms, not fluoro images- why are all these angulations still needed?
While we typically do not evaluate the coronary arteries, EP uses fluoro to locate landmarks in the heart such as the Triangle of Koch. We depend on the slight density variations and shadows to display borders we must work within. EP catheters are visualized clearly with radiopaque electrodes that indicate proper positioning based on the electrograms they create. Contrast media is typically not needed because we know the desired path (IVC to the heart) and can easily see the catheter against the spine and ribs on the fluoro screen. Once inside the heart, RAO and LAO angles are used to visualize the boundaries of where catheters are positioned.
In RAO, the cardiac shadow is projected on the long axis, which is visually divided into atria (top) and ventricles (bottom). For Catheter placement, we would expect the High Right Atrial (HRA) catheter to be pointed up towards the top of the monitor. The Right Ventricular Apex (RVA) catheter should be pointing down towards the bottom of the monitor.
In RAO View:
The top of the atrium, the base of the heart (annular), and the bottom (apex) of the heart are visualized
Anterior and posterior are displayed in RAO
The left and right atria and ventricles are superimposed on each other
To complement the RAO view, the LAO view projects the heart shadow on a short axis through the apex. The heart appears more circular, and the AV valves are visualized on-face - such as a clock face. LAO demonstrates catheter relationships in proximity to the AV valves. Therefore, LAO is helpful with the catheter position of catheters placed along the valves (i.e., His and Coronary Sinus catheters).
First, the His catheter placement is more likely to be confirmed by feel and electrograms. The location of the His catheter helps to define the Triangle of Koch. However, the coronary sinus catheter needs to be placed through the Thebesian Valve and advanced in the coronary sinus to reach a lateral location. This is best shown in an LAO position.
In LAO View:
The lateral, septal/medial positions are confirmed
Superior and inferior locations (think clock face) are displayed
The apex and base of the ventricles are superimposed on each other
Due to the harmful effects of extended exposure to ionizing radiation, many physicians embrace a Very-Low/Zero Fluoro philosophy. The 3D Cardiac Mapping systems have made this a safe alternative to fluoroscopy. Although the 3D mapping images can be manipulated into any view, the standard RAO and LAO view are still considered standard positioning terminology used in fluoro.
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Abbreviations:
3D Cardiac Mapping – 3-dimensional electromagnetic cardiac mapping
AP - Anterior Posterior
AV – AtrioVentricular
CS – Coronary Sinus
EP - Electrophysiology
Fluoro - fluoroscopy
HRA – High Right Atrium
IVC – Inferior Vena Cava
LAO – Left Anterior Oblique
RAO – Right Anterior Oblique
RVA – Right Ventricular Apex
SVC - Superior Vena Cava
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Regina Kiefer is a 30-year ARRT registered Radiologic Technologist additionally credentialed in Cardiovascular Interventional Technology.
Her passion for Cardiac Electrophysiology led her to work with CHART Healthcare Academy. Regina is especially inspired to support new learners who are determined to conquer the squiggly lines.
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