Atrial fibrillation (AF) is the most common arrhythmia worldwide. An increasingly common treatment option is catheter ablation. During this procedure, the clinician steers a catheter into the left atrium and ablates a lesion fence around the pulmonary veins, a common source of ectopic signals. This lesion fence blocks arrhythmogenic tissue from initiating an erroneous heartbeat. However, if the disease has progressed from paroxysmal to persistent, pathogenic tissue exists throughout the atrium, and common ablation schemes are not as effective. In this case, technologies exist to electroanatomically map the atrium and guide clinicians in targeting adjunctive AF ablation targets. Low voltages mapped in vivo are a well-documented way of identifying atrial fibrosis, an important substrate for AF. Ablating low voltage zones in patients with a more developed disease can help terminate AF and improve long-term outcomes, but low voltage measurements are not specific to fibrosis. Treatment results vary because the targeting that electroanatomical mapping provides is incomplete. Our group has shown that polarization-sensitive optical coherence tomography (PSOCT) and near infrared spectroscopy (NIRS) can monitor lesion formation in vivo and differentiate tissue types in the atrium. Now, we are investigating the technology’s utility in identifying AF targets prior to ablation. We have collaborated in developing a swine model of AF that shows the atria remodels during the diseased state. Because of this, we can electroanatomically map these diseased hearts in vivo to measure low voltage zones. Subsequently, we examine the left atrium ex vivo using benchtop PSOCT, NIRS, and optical mapping (OM) and register these optical measurements to the in vivo low voltage zones. We show that OM confirms abnormal conduction, while PSOCT- and NIRS-derived metrics have promise for identifying low voltage zones. We confirm these measures with histological identification of fibrosis. This suggests the feasibility of using PSOCT-NIRS at the catheter tip to detect AF ablation targets.
Atrial fibrillation is a global epidemic linked to millions of deaths each year. One increasingly relevant treatment for the disease is catheter ablation. In this procedure, an electrophysiologist burns lesions to isolate pathogenic tissue in the pulmonary veins from initiating an ectopic heartbeat. Long term efficacy of the procedure still needs to improve. Current intraprocedural feedback does not allow the clinician to properly visualize individual lesions. We developed an integrated polarization sensitive optical coherence tomography (PSOCT) and near infrared spectroscopy (NIRS) catheter to measure lesions during an ablation procedure. By combining both modalities, we overcome their individual limitations and provide complementary metrics. Using the PSOCT-NIRS catheter to analyze lesions, we show that we can mitigate the imaging depth limitations of PSOCT and inform spectral measurements made by NIRS to provide a more informative view of lesion quality.
Atrial fibrillation (AF) is the most common arrhythmia worldwide. An increasingly common treatment option is catheter ablation. During this procedure, the electrophysiologist steers a catheter into the left atrium and ablates a lesion fence around common sources of ectopic signals. This blocks arrhythmogenic tissue from initiating an erroneous heartbeat. Technological advancements in this maturing procedure have made ablations more widespread and effective for patients, but there is still a need to improve long term efficacy of the procedure. The national rate of recurrent AF after an ablation is 20% to 40% and this is almost universally due to reconnection via poor lesion quality. With current catheter feedback available to clinicians, it is difficult to assess whether a lesion line will remain durable or heal to initiate recurrent AF. We have previously shown that polarization-sensitive optical coherence tomography (PSOCT) can monitor lesion formation in vivo during an ablation procedure. This feedback at the catheter tip may help clinicians assess lesion quality by measuring tissue changes. To further understand the technology’s utility and limitations, we are conducting experiments to characterize PSOCT detection of gaps between lesions. Lesion gaps are a common failure mode when AF recurrence is caused by reconnection. We ablate left atrial swine myocardium ex vivo and collect PSOCT images to compare with histology and identify the detection limits of small lesion gaps. Using PSOCT at the catheter tip to detect small gaps in lesion lines could help clinicians reduce recurrence by decreasing opportunities for reconnection.
An intraoperative tool that accurately provides detailed structural information and classifies endocardial substrates could help improve guidance during ablation therapy. With our custom near infrared spectroscopy-integrated radiofrequency catheter, here we demonstrate atrial substrate mapping on ex vivo swine and human left atria. Optical contrast indices and classification algorithms were developed, which classified pulmonary vein, lesion, and fibrosis using optically derived parameters based on endogenous tissue spectral signatures with high accuracy. Predicted lesion depth percentage linearly corresponded with ground truth measurements from trichrome histology. These results suggest near infrared-integrated mapping catheters can serve as a complementary tool to currently-available electroanatomical mapping systems to improve treatment efficacy.
Atrial fibrosis is an important cause of atrial fibrillation (AF) and is often targeted for radiofrequency ablation (RFA) treatment. However, fibrosis identification during an RFA procedure is indirect and not well established. Polarization-sensitive optical coherence tomography (PSOCT) provides high-resolution in-depth noninvasive structural and tissue birefringence images, which can be effective for detecting fibrosis. In this work, combining histology and optical mapping of atrial action potential activity, we demonstrated the identification of atrial fibrosis that caused abnormal impulse propagation in a pig model of AF with PSOCT. Results indicate that PSOCT may provide effective guidance for RFA procedures in the future.
KEYWORDS: Optical coherence tomography, Tissue optics, In vivo imaging, Heart, Fluoroscopy, Visualization, Tissues, Safety, Real time imaging, Ionizing radiation
Transseptal puncture (TSP) is commonly conducted under the guidance of fluoroscopy and/or intracardiac echocardiography (ICE) at the fossa ovalis (FO) to gain percutaneous access to the left atrium for intracardiac procedures. Issues with traditional TSP include: additional vascular access through a sheath, and fluoroscopy exposes patients to ionizing radiation. TSP, if not done appropriately can result in serious complications. We studied the feasibility of optical coherence tomography (OCT) guidance of TSP with ex vivo and in vivo experiments. Results show that OCT can provide detailed structure information to identify FO allowing for safe TSP.
Pulmonary vein isolation with radiofrequency ablation (RFA) has become the most common procedure to treat Atrial Fibrillation (AF). However, current RFA lesion formation is guided only with indirect information (e.g. temperature, impedance, contact force), which does not guarantee transmural lesions. Non-transmural lesions are understood to contribute to AF recurrence. We have previously demonstrated that polarization-sensitive optical coherence tomography (PSOCT) can monitor RFA lesion transmurality in the left atrium (LA) of living swine. However, it requires expert interpretation. Here, we demonstrate quantitative image quality and lesion transmurality evaluation metrics applied to the in vivo LA RFA PSOCT lesion monitoring data.
Atrial fibrillation (AF) is the most common sustained arrhythmia in the western world. Pulmonary vein isolation (PVI) using radiofrequency ablation (RFA) is frequently conducted to treat AF. However, current PVI procedures for lesion formation are guided only with indirect information, which may lead to non-transmural lesions, and contribute to the high recurrence of AF. Therefore, direct lesion quality feedback may potentially improve PVI efficacy. To study the real-time direct guidance capability of polarization sensitive optical coherence tomography (PSOCT), a custom-designed integrated PSOCT-RFA catheter was prototyped and tested in RFA procedures in the left atria of living swine.
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