Imaging of the Porcine Fossa Ovalis Using Optical Coherence Tomography

Background: Optical coherence tomography (OCT) is a non-invasive imaging modality that uses near-infrared light to produce high resolution in-depth tissue images from optical scattering. The purpose of this study was to determine if OCT can be utilized to differentiate the fossa ovalis (FO) from the surrounding muscular atrial septum in ex-vivo porcine heart

Methods: Five adult porcine hearts were dissected to expose the atrial septum and the FO was identified visually. FO and 4 additional points i.e., anterior, antero-superior, superior and posterior to FO were imaged from the right atrial surface using a benchtop OCT scanner. The penetration depth of the OCT system was1500 micrometer. Images were reviewed offline to discern tissue thickness and presence of endocardial surface. Measurement of FO were made using a micrometer and correlated with the measurements obtained from a computer-generated digital caliper on the OCT image

Results: The OCT images of the FO shows two well defined borders of endocardial tissue from the right and left atrial aspects. The average thickness of the FO was 847 micrometer (range 693 to 1024 micrometer). The other 4 locations had one endocardial lining, that of the right atrial surface. The endocardium from the left atrial surface of the septum was absent due to increased thickness and the limitation of the penetration depth of the OCT system.

Conclusion: In explanted, ex-vivo testing, optical coherence tomography (OCT) can reliably identify the FO and distinguish it from the surrounding thicker muscular atrial septal tissue by identifying the endocardial surface from the right and left atrial aspect of the septum and by measuring the thickness of the tissue. This study has clinical a implication. If an OCT based imaging system can be incorporated within a transseptal needle, it may potentially help to guide the operator during a transseptal puncture procedure in humans by accurately identifying the location of FO