A Percutaneous Catheter for In Vivo Hyperspectral Imaging of Cardiac Tissue: Challenges, Solutions and Future Directions

Abstract

Multiple studies have shown that spectral analysis of tissue autofluorescence can be used as a live indicator for various pathophysiological states of cardiac tissue, being it ischemia, ablationinduced damage or scar formation. Yet today there are no percutaneous devices that can detect autofluorescence signals from inside a beating heart. Multiple surgical interventions can benefit from the development of such a device. It can help to reduce recurrence rates of atrial fibrillation ablation procedures by in-surgery identification of viability gaps between the lesions, guide hydrogel or stem cell injections to the boundaries of scarred tissue, or distinguish between tissue ischemia and terminal muscle damage during surgical interventions to terminate ventricular arrhythmias. Here we summarize the technical solutions leading to the development of a percutaneous catheter capable of hyper or multispectral imaging of intracardiac surfaces.

Key factors behind autofluorescence changes caused by ablation of cardiac tissue

“…Compared to UVB or UVC, the UVA exposure causes the least damage due to its longer frequency which translates to lower photon energy. Secondly, our recent quantitative analysis 16 has shown that the levels of UV needed for percutaneous Auf-HSI imaging are well below the established thresholds that can damage the skin. Lastly, the layer of endocardial collagen essentially shields the underlying muscle cells from direct UV exposure further minimizing any potential damage.…”

“…The dimensions and the shape of the lesions delineated by Auf-HSI were in perfect agreement with the conventional post-ablation staining methods such as TTC [10][11][12][13][14] . These promising bench findings have led to our ongoing efforts to incorporate Auf-HSI technology into a percutaneous imaging catheter 11,15,16 . The design of this catheter includes a saline-filled balloon to displace optically dense blood from the endocardial surface.…”

Quantification of irrigated lesion morphology using near-infrared spectroscopy

“…OCT-integrated catheters enabled real-time imaging feedback to identify tissue structures and direct monitoring of RF lesion formation, ex vivo 19 , 22 – 24 and in vivo 15 , 25 . Recently, acute necrotic areas in atrial tissue were identified using hyperspectral imaging system based on ultraviolet-excited tissue autofluorescence 11 , 26 – 28 . Another promising technique, near-infrared spectroscopy (NIRS), uses broadband light to interrogate tissue volumes deeper than OCT and ultraviolet-excited tissue autofluorescence.…”

Autofluorescence properties of balloon polymers used in medical applications

“…19,20 In the latter case, optically dense blood must be displaced from an optical path, either by influx of saline or via an inflatable balloon. 21,22 Such balloons must exhibit minimal levels of fluorescence within optical ranges of biological fluorophores. Otherwise, they can diminish Auf-HSI's ability to reveal the target tissue due to inherent autofluorescence of their material.…”

“… 19 , 20 In the latter case, optically dense blood must be displaced from an optical path, either by influx of saline or via an inflatable balloon. 21 , 22 …”