Getting to the heart of the matter

Radiofrequency ablation (RFA) is a minimally invasive technique for blocking the spread of abnormal electrical signals from faulty heart cells, which are responsible for the rapid and irregular beating of the heart known as atrial fibrillation. It involves inserting a catheter into the heart through a vein and then applying a high-frequency alternating current through the catheter to the affected area of the heart, forming non-conducting lesions that block the spread of the signals.

Although highly effective, a major drawback of this technique is the difficulty of determining the precise extent of the lesions, as the heart is obviously hidden deep within the body. If the lesions aren’t extensive enough to stop of the spread of the signals, then this can lead to a recurrence of the atrial fibrillation, requiring further rounds of RFA.

What is needed is an analytical technique that can accurately detect the lesions caused by RFA and also be used with a catheter, and it turns out that NIR spectroscopy fits the bill exactly. To combine NIR spectroscopy with a catheter, Christine Hendon and her colleagues at Columbia University in New York utilized two 400µm-wide optical fibres, one of which illuminated the heart with NIR light while the other collected the reflected light, which they taped to the outside walls of a 3.6mm-wide steel tube. They then inserted an RFA catheter into the tube, which was narrow enough to fit inside the veins that lead to the heart.

As they report in Biomedical Optics Express, after conducting initial tests with samples of heart tissue, Hendon and her colleagues used it to analyse whole pig hearts and human hearts taken from recently deceased patients. This revealed that not only could NIR spectroscopy accurately identify the lesions caused by RFA, but it could also identify areas of the heart with high concentrations of fatty adipose tissue, which is useful as this kind of heart tissue doesn’t respond as well to RFA. In addition, they were able to use NIR spectroscopy to determine when the catheter was in physical contact with the heart wall, which is essential for RFA to work properly.

Following this success, Hendon is now planning to test the technique in the hearts of living animals.

Blog tags: