Spectral Mapping of Heart Tissue Could Help Improve Ablation Therapy

An ablation catheter incorporating near-infrared (NIR) spectroscopy mapping was able to distinguish various tissue types in hearts donated from patients with cardiovascular disease. Using this optical mapping approach, the research team from Columbia University could distinguish between fat and muscle tissue in the heart — a critical distinction when using radiofrequency ablation to treat ventricular tachycardia.

The researchers developed ablation catheters that included optical fibers for emitting and detecting light and a custom tip for tracking the instrument. They also developed new signal and data processing techniques, a workflow for rendering anatomical tissue maps, and a catheter tracking system to enable spatial mapping of the tissue.

While using the new catheter, they tracked the position of the instrument as it moved along the heart surface. At each location they recorded reflectance spectra. They used this data to compute an optical index for both fat and lesion tissues. The experiments were performed on donor hearts from deceased people with cardiovascular disease to replicate what would physicians would likely encounter in a patient.

A new ablation catheter incorporating near-infrared spectroscopy mapping can distinguish various tissue types in hearts. This distinction is critical when using radiofrequency ablation to treat heart rhythm problems. Courtesy of Christine P. Hendon, Columbia University, and John Abbott.

NIR spectroscopy works by shining light with a broad range of wavelengths onto the tissue and then detecting the light that is reflected back. “By using near-infrared wavelengths in addition to visible wavelengths, we can probe deeper into the tissue,” professor Christine P. Hendon said. “The technique lets us distinguish various types of tissue within human hearts because fat, muscle, and ablation lesions all have different scattering and absorption wavelength-dependent properties.

“Once an abnormal area has been identified and heated to form an ablation lesion, it is important for the operator to know if that lesion was placed successfully and had the desired effect,” Hendon said. “Direct measurement of tissue characteristics affords the possibility of improved ability both to find abnormal tissue and to determine how well it has been treated.” The approach could also be used to develop new computational models for advancing the understanding of mechanisms involved in arrhythmia.

The researchers are working on a new catheter prototype that will more fully integrate the mapping processes. They also plan to demonstrate the method in large animals to test how well it works with heart muscles moving and blood circulating through the heart. “So far we have extremely encouraging results. Our work shows that optics can have a large and impactful role within the field of cardiac electrophysiology,” Hendon said.

The research was published in Biomedical Optics Express (www.doi.org/10.1364/BOE.394294).

Researchers showed that a new mapping approach based on near-infrared spectroscopy can distinguish various types of tissue in the heart. The movie shows the sampling sites as well as 3D renderings of the adipose contrast index (ACI) and lesion optical index (LOI1). Courtesy of Christine P. Hendon, Columbia University.