Real-time percutaneous optical imaging of anatomical structures in the heart through blood using a catheter-based infrared imaging system.

The ability to optically image structures and instrumentation within the heart during procedures is limited by the presence of blood in the field. The goal of our research was to design, develop, and evaluate technology for a catheter-based optical imaging system that enables intracardiac and intravascular visualization in real time through blood. Based on Mie optical scattering theory, imaging through blood using infrared light was theoretically feasible, but scattering in the near-infrared wavelengths (1100 to 1300 nm) generated substantial noise in the image despite relatively low absorption. Using illumination between 1550 and 1650 nm provided better images, as the effect of scattering is less while the effect of absorption is greater. Absorption losses can be overcome by increasing light intensity. Infrared (IR) transmitting endoscopes were constructed using novel flexible illumination and imaging bundles. Endoscope designs, all 7.5 Fr. in outer diameter, were used to obtain images of the coronary sinus, tricuspid valve, and great vessels in 25 pigs, 16 dogs, 1 calf, and 1 sheep. Imaging was successful in all 43 animals, but the coronary sinus was not always visualizable. After obtaining FDA 510(k) approval, the device was used to acquire images in 50 patients during placement of electrophysiologic leads via right heart catheterization. Clinical experience demonstrates successful visualization in the heart in 45 patients, although coronary sinus images were obtained only in 39 patients. High heart rates, large dilated hearts, and problems with catheter design prevented visualization in all patients. On occasion, it was possible to visualize the tricuspid valve. Infrared endoscopy allows for visualization of intimal surfaces of blood vessels, cardiac chambers, and valves through flowing blood. While technical challenges remain, the feasibility of the approach has been demonstrated.

Direct imaging of transvenous radiofrequency cardiac ablation using a steerable fiberoptic infrared endoscope.

BACKGROUND: Direct imaging through blood has been achieved in vivo using fiberoptics and infrared wavelength technology. OBJECTIVES: The purpose of this study was to determine the feasibility of using a percutaneous, steerable, fiberoptic infrared endoscope to identify and characterize the electrode-tissue interface during transvenous cardiac ablation. METHODS: Infrared endoscopy was performed during 24 catheter ablation attempts in 10 mongrel dogs. Infrared imaging was performed through a transparent dome located at the tip of a 7Fr steerable endoscope using an imaging wavelength of 1,620 nm. Radiofrequency ablation was performed using a 4-mm-tip electrode catheter. Attempts were made to identify the electrode-endocardial interface at each ablation site and to characterize any signal changes during ablation. RESULTS: The electrode-tissue interface could be identified at 19 of the 24 ablation sites. Changes at the electrode-tissue interface were observed during ablation at 14 sites, which included a gradual increase in the tissue signal intensity at 12 sites. Small lucencies near the ablation electrode were observed at six sites. There was no interference during energy delivery. Endocardial features identified by endoscopy correlated with the postmortem appearance. CONCLUSION: Direct imaging of intracardiac structures and the electrode-tissue interface can be achieved through blood during transvenous catheter ablation with infrared endoscopy using a steerable, fiberoptic, infrared endoscopic catheter. Ablation lesion formation can be seen as a gradual increase in signal intensity. Fiberoptic infrared endoscopy appears to be a promising new tool for guiding catheter ablation.

Direct visualization of coronary sinus ostium and branches with a flexible steerable fiberoptic infrared endoscope.

BACKGROUND: Placement of electrophysiology catheters and pacing leads in the coronary sinus is challenging in some patients, particularly those with dilated cardiomyopathy. We hypothesized that cannulation of the coronary sinus and its branches can be facilitated by direct visualization. This study reports our experience with navigation into and within the coronary sinus in a closed-chest animal preparation, using a flexible steerable fiberoptic infrared endoscope that allows visualization through flowing blood. OBJECTIVES: The purpose of this study was to assess the feasibility of direct visualization of endocardial structures through infrared endoscopy. METHODS: Internal jugular venous access was obtained in 10 healthy mongrel dogs (weight 35-45 kg). The infrared endoscope (2900 fiber imaging bundle, wavelength 1,620 nm, frame rate 10-30/s, 320 x 256 pixels) was advanced to the coronary sinus ostium and branches by direct visualization of anatomic landmarks, such as the tricuspid valve and inferior vena cava. Localization was confirmed by fluoroscopy, contrast injection, and pathologic examination. RESULTS: Structures such as the tricuspid valve and inferior vena cava were visualized at distances of 1 to 2 cm, allowing successful coronary sinus identification and engagement in all 10 dogs. Coronary sinus branch images closely resembled pathologic findings. CONCLUSION: Direct visualization of the coronary sinus ostium and branches is possible through infrared endoscopy. This technique likely will facilitate coronary sinus engagement and navigation for pacing lead and catheter placement.