First in vivo Real-Time Imaging of Endocardial Radiofrequency Ablation by Optical Coherence Tomography: Implications on Safety and The Birth of “Electro-structural” Substrate-Guided Ablation

DOI: 10.19102/icrm.2011.020303

^1*CHRISTINE P. FLEMING, PhD, ²NOAH ROSENTHAL, MD, ¹ANDREW M. ROLLINS, PhD and ²MAURICIO ARRUDA, MD

¹Biomedical Engineering, Case Western Reserve University, Cleveland, OH
²Experimental Interventional Catheterization Laboratory, Harrington-McLaughlin Heart and Vascular Institute, University Hospitals Case Medical Center, Cleveland, OH

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ABSTRACT. We report the first in vivo use of optical coherence tomography (OCT), a high-resolution (∼10 µm) real-time imaging technology, to scan subendocardial tissue and to monitor radiofrequency (RF) lesion formation. Endocardial imaging during an open chest procedure in a female pig was conducted with a forward imaging catheter with a Fourier Domain OCT system at 20 frames per second. Images of the endocardial surface and subendocardial tissue were obtained when the catheter was in direct contact with the endocardial surface. The formation and progressive increase in size of cavities within the myocardium were observed in the OCT images when a steam pop was audible. Our initial findings suggest that imaging with a forward scanning OCT catheter can assess tip electrode–tissue interface contact, image subsurface myocardial structure, and visualize dynamic effects of intramural RF energy delivery.

KEYWORDS. radiofrequency catheter ablation, optical coherence tomography, image guidance.

*Present address: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA

The project was supported by the Wallace H. Coulter Foundation and by the National Institutes of Health (HL085939, HL083048, RR1246). The authors would like to thank Dr. Hui Wang and Wei Kang for their technical contributions.
Manuscript received January 19, 2011, final version accepted February 4, 2011.

Address correspondence to: Mauricio S. Arruda, MD, Director of Electrophysiology and AF Center, University Hospitals Heart & Vascular Institute, Case Western Reserve University School of Medicine, 11100 Euclid Avenue, Lakeside 5038, Cleveland, OH 44106. E-mail: mauricio.arruda@uhhospitals.org

Catheter ablation has become a therapeutic option in the management of cardiac arrhythmias. Innovative technologies and ablation strategies have optimized procedure safety and long-term efficacy. However, lack of real-time ablation lesion monitoring remains a major limitation of current ablation approaches. We report the first in vivo use of optical coherence tomography (OCT), a high-resolution (∼10 µm) real-time imaging technology, to scan subendocardial tissue and to monitor radiofrequency (RF) lesion formation. OCT generates images by detecting singly backscattered light as a function of depth, providing subsurface imaging to depths of approximately 1 mm with high spatial resolution (∼10 μm) and high sensitivity¹.

Endocardial imaging during an open chest procedure in a female pig was conducted with a forward imaging catheter using a Fourieromain OCT system at 20 frames per second.^2,3 The OCT catheter was secured to a commercially available RF ablation catheter, inserted directly into the right atrium (Figure 1a) and advanced and navigated within the heart under fluoroscopic guidance (Figure 1b). Image penetration through blood is low due to absorption and scattering (Figure 1c). However, high quality images of the endocardial surface and sub endocardial tissue were obtained when the catheter was in direct contact with the endocardial surface, thus displacing the blood (Figure 1d). In addition to increased imaging depth, the structured appearance of the myocardium (Figure 1d) is clearly different from the homogenous appearance of blood (Figure 1c).

To evaluate whether OCT can identify dynamic tissue change due to RF energy delivery in vivo, temperature-controlled RF energy was delivered for 60 s with a target temperature of 85°C using a Maestro 3000 generator (Boston Scientifi, St Paul, M) and an 8Fr, 5-mm tip Blazer II catheter (Boston Scientific) after 15 s of imaging with stable contact with the endocardial surface. The formation and progressive increase in size of cavities within the myocardium were observed in the OCT images when a steam pop was audible (Figure 2). The cavities may represent an early subsurface manifestation of the steam pop.

Our initial findings suggest that imaging with a forward scanning OCT catheter can assess tip electrode–tissue interface contact, image subsurface myocardial structure, and visualize dynamic effects of intramural RF energy delivery. Real-time OCT imaging may establish a new ablation paradigm. It may favorably impact on ablation safety and its outcome by predicting tissue overheating and intramyocardial steam pops, providing feedback to titrate RF energy delivery, and most importantly identifying differences in tissue characteristics to guide a potentially more specific “electro-structural” substrate ablation strategy, targeting culprit structures responsible for the initiation and maintenance of challenging cardiac arrhythmias such as atrial fibrillation and ventricular tachycardia.

References

1. Drexler W and Fujimoto JG, eds., Optical Coherence Tomography: Technology and Applications (Springer, 2008).
2. Fleming CP, Wang H, Quan KJ, Rollins AM. Real-time monitoring of cardiac radiofrequency ablation lesion formation using an optical coherence tomography forward imaging catheter. J Biomed Opt 2010; 15:030516. [CrossRef] [PubMed]
3. Fleming CP, Quan KJ, Rollins AM. Toward guidance of epicardial cardiac radiofrequency ablation therapy using optical coherence tomography. J Biomed Opt 2010; 15:041510. [CrossRef] [PubMed]