Open-irrigated laser catheter ablation: influence of catheter irrigation and of contact and noncontact mode of laser application on lesion formation in bovine myocardium

Abstract

Lesions achieved by radiofrequency application increase with catheter irrigation and with catheter pressure on the endocardial surface. Purpose of this study was to test the influence of catheter irrigation and of contact vs. noncontact mode of laser application on lesion formation in bovine myocardium. By applying continuous wave 1,064 nm laser light via an open-irrigated catheter lesions were produced at 15 W (9.5 W/mm(2))/30 s (285 J/mm(2)), in stagnant blood (activated clotting time > 350 s) at 18 °C, on bovine myocardium. During flow rates of 15, 30, and 50 ml/min radiation was applied with the catheter end hole in contact (n = 10, each) or 2 mm away from the endocardial surface (n = 5, each). Lesions were evaluated morphometrically, and groups of lesions were compared by using the unpaired t test. By augmentation of irrigation flow from 15 to 30 ml/min, contact lesions increased significantly (p = 0.0001). A further increase of flow from 30 to 50 ml/min increased lesions significantly in depth (p = 0.0011) but not in width (p = 0.639) and volume (p = 0.218). Noncontact lesions were significantly smaller than contact lesions (p > 0.05). Lesions of homogenous coagulation necrosis were clear-cut and sharply demarcated from the surrounding normal myocardium. There was no occurrence of steam-pop with intramural cavitation or with tissue vaporization with crater or thrombus formation. It is suggested that by using an open-irrigated laser catheter as described in this study, catheter irrigation at flow rates of 30 to 40 ml/min are optimal for myocardial coagulation, and catheter pressure on the endocardial surface is not needed for lesion formation. Laser lesions can be achieved also without intimate endocardial catheter contact.

Laser catheter ablation of long- lasting persistent atrial fibrillation: Longterm results

“…Laser lesions can be achieved even without intimate endocardial catheter contact. Catheter contact force and catheter orientation towards the endocardial surface are not major determinants for laser lesion formation [29], [37], [38] . Albeit PVI is still considered the cornerstone for a successful AF ablation we did not target the pulmonary vein specifically, well-directed.…”

“…It allows for noncontact laser light application because a fiber tip to endocardial surface contact is avoided and continuous saline irrigation through the catheter endhole avoids blood penetration into the catheter [29] . It creates a transparent medium for the laser light and cools the illuminated endocardial surface.…”

Monitoring of laser effects on the conduction system by using an open-irrigated electrode-laser mapping and ablation catheter: laser catheter mapping

“…11 Ought to the low absorption and frequent scattering, the 1064 nm laser photons penetrate deep intramurally before they are absorbed and heat is induced. 12 It has been shown that catheter contact force is not a factor in whether a laser lesion is transmural, 10 and laser energy settings can be adjusted when ablating tissues of varying thickness, with higher energy applied to thicker tissue and lower energy applied to thinner structures in the heart. 8 The endocardial layers are translucent so that laser light passes through it without absorption of photons and without heating.…”

Influence of catheter orientation on lesion formation in bovine myocardium by using an open-irrigated laser ablation catheter

“…In our experience, by using an open-irrigated electrode-laser mapping and ablation (ELMA) catheter, the irrigation flow has an important role on lesion formation whereas catheter-tissue contact force is not a major determinant for transmural lesion formation. Laser lesions can be achieved even without intimate endocardial catheter contact [11,12]. In contrast to that, for the increase of radiofrequency (RF) lesions, increase of tissue catheter contact force, of power application, as well as longer application times are used.…”