Laser catheter coagulation of normal and scarred ventricular myocardium in dogs

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

Catheter ablation of atrial fibrillation (AF) is a current therapeutic option but its efficacy for the treatment of long-lasting persistent AF (l-lpAF) remains suboptimal. We tested the laser method as an alternative for catheter ablation of l-lpAF by using an open-irrigated electrode laser mapping and ablation (ELMA) catheter. Laser ablation was attempted in 48 patients aged 50-81 years (69 ± 7.6 y, female = 28) with drug resistant (3.5 trials) l-lpAF (≥12 months). All of the patients had comorbidities: congestive heart failure NYHA II-III (100%), hypertension 29 (60%), coronary artery disease 19 (40%), and heart valve defect 17 (35%). None of the patients had diabetes or obstructive sleep apnea. All were in AF at the beginning of the procedure. Continuous wave (cw) 1064nm Nd:YAG laser applications at 15W/10-20s (14-26/patient) were applied via the ELMA catheter until local electrical activity displayed on the monitor in the bipolar focused local electrograms (LEG) recorded via the pin electrodes from the tip of the catheter was abolished permanently and sinus rhythm was achieved. Online monitoring of electrical potential amplitudes in the focused LEG recorded via the pin-electrodes of the ELMA catheter allowed for validation of ablation success. Procedure duration ranged from 82-175 min (118 ± 72 min), number of lesions were14-26 (19 ± 4) per patient and X-ray exposure times ranged from 15-82 min (23.2 ± 12 min). Interventions were without complications. After the ablation procedure all the patients were in sinus rhythm, off medication, however, 12 (25%) needed a repeat study for various arrhythmias. During followup of 9 months to 29.3 years (8.2 ± 6.5 years) patients' quality of life improved significantly and during final follow-up control all except two were off medication still in sinus rhythm (lifelong success rate = 96%). As compared to other catheter ablation methods the laser method is an intriguing alternative for catheter ablation of l-lpAF.

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

AIMS

To assess the laser effects on the conduction system in dog hearts by monitoring potential amplitudes (PA) in the focused local electrograms (LEG) recorded via pin electrodes (PEs) from the tip of an open-irrigated electrode-laser mapping and ablation (ELMA) catheter.

METHODS AND RESULTS

A total of 54 mapping guided laser impacts (continuous wave Nd:YAG 1064 nm), at 15 W, irrigation rate 30 mL/min, one per dog, were aimed at the sinus nodal (SN) (n = 20) and atrioventricular (AV) nodal (n = 24) areas, and at the His bundle and fascicles (n = 5, each). Laser effects were assessed by monitoring of PA in the bipolar focused LEGs. Electrophysiological and electropharmacological tests were performed prior to, immediately following, and 3-11 months after the experiments. Lesions were evaluated morphometrically and histopathologically. During laser application PA gradually dwindled. Radiation times limited to 3-5 s were allowed for recovery of PA without affecting functions of the conduction system. Graded laser application modulated SN and AV nodal functions permanently, or caused stable complete AV conduction block with a mapping-dependent escape rhythm and electrical axis deviation after radiation aimed at a fascicle.

CONCLUSIONS

Monitoring of PAs recorded in the LEG via PE of the ELMA catheter during laser application is a unique claim of the laser method that enhances the assessment of local electrical activity and ablation efficacy. It allows the assessment of laser effects on the conduction system during ablation. By using the ELMA catheter described, long-term modulation of SN and AV nodal functions are achievable and unwanted complete heart block or fascicular block can be avoided.

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

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.

Energy Sources for Ablation in the Pericardial Space

Catheter ablation has been widely used for the management of cardiac arrhythmias. Transvenous endocardial catheter ablation successfully eliminates or modifies the critical substrate for most arrhythmias. Most arrhythmias can be eliminated with conventional endocardial mapping and radiofrequency energy delivery, but some critical arrhythmic substrates are not accessible via endocardial access and this has led to epicardial mapping and ablation in addition to traditional endocardial mapping techniques. This article reviews current approaches to epicardial ablation and discusses the specialized tools that increase ablation efficacy and safety.