6.3. Multimodality Fusion Imaging for Structural Interventions

These proceedings summarize the educational activity of the 16th Biennial Meeting of the International Andreas Gruentzig Society held January 31-February 3, 2022 in Punta Cana, Dominican Republic

Faculty Disclosures     Vendor Acknowledgments

2022 IAGS Summary Document

 Statement of the problem or issue

Imaging during structural interventions involves 3 levels or categories:

First-level imaging (Figure 1):

• Fluoroscopy or x-ray based.

• Differentiation based on x-ray attenuation by metals, bone/calcium, iodine (but not tissues).

• Identifies devices and accurate placement within a few millimeters.

• Advantages: large field of view; optimal device visualization.

• Disadvantages: 2D only; radiation exposure; cannot image soft tissues.

Second-level imaging (Figure 2):

• Ultrasound (echocardiography)-based.

• Differentiation based on tissue densities.

• Identifies specific tissues and spatial/temporal relationships.

        – Valve leaflets; myocardial chambers, and borders.

• TEE has been the workhorse:

        – 2D; live x-plane; Doppler; 3D; etc.

• ICE is another useful adjunct:

        – Newer catheters with larger field-of-view; live x-plane; 3D; etc.

• Advantages: no radiation; 3D; visualize soft tissues.

• Disadvantages: smaller field-of-view; less depth of view;  shadowing effects.

Third-level imaging (Figure 3):

• New and novel.

• Ultrasound-angiography-CT based.

      – Precise 3D location within tissue.

       – Leaflet-splitting (LAMPOON/BASILICA); removal (CATHEDRAL); suturing (PASTA).

      – Myocardial traversal (mitral cerclage).

      – Myocardial laceration-percutaneous myotomy (SESAME).

• Accuracy within millimeters.

Gaps in knowledge

Fusion imaging is also known as coregistration (Figure 4). These systems attempt to blend several imaging techniques into the same image on a viewing screen.

• Current approaches are in their infancy.

    –  X-ray and echo: EchoNavigator; Truefusion.

    –  X-ray and CT/MR: Heart Navigator; DynaCT.

    –  X-ray and electromagnetic positioning: EAM; CARTO.

• Multiple “live” images vs “live” blended with previously stored images.

• Developing and using reliable fiducial markers.

    –  Bony structures—issues with positioning.

    –  Contrast angio—issues with phase.

• X-rays are “projections” of a 3D structure onto a 2D screen.

3D-CT and 3D-echo: final image is a 2D derivative of a 3D composite.

Motion compensation (cardiac, respiratory) may not be the same for each method.

Can/will fusion imaging reduce radiation doses, contrast use, and procedure times?

Possible solutions and future directions

Developmental work in fusion imaging is underway at a rapid pace. Stereotopic and 3D image displays are being investigated. Partly, it is a question of what do interventionalists want, what do they need, and how can the new imaging techniques make procedures safer and more efficient, or even make the procedures possible at all.

References

1. Khan JM, Bruce CG, Greenbaum AB, et al. Transcatheter myotomy to relieve left ventricular outflow tract obstruction: the septal scoring along the midline endocardium procedure in animals. Circ Cardiovasc Interv. 2022;15(6):e011686. Epub 2022 Apr 5. doi:10.1161/CIRCINTERVENTIONS.121.011686

2. Lederman RJ, Babaliaros VC, Rogers T, et al. Preventing coronary obstruction during transcatheter aortic valve replacement: from computed tomography to BASILICA. JACC Cardiovasc Interv. 2019;12(13):1197-1216. doi:10.1016/j.jcin.2019.04.052