Catheter-directed laser coagulation of atrial myocardium in dogs

The feasibility of transcatheter laser coagulation of atrialmyocardium was tested in a canine model by using a combinedelectrode-laser catheter. In 17 anaesthetized beagles a totalof 264 lesions, 12–19 per dog, and 3–5 in each areawere produced in: (1) the lateral walls, (2) the posterior rightatrial walls, (3) the inter-atrial septum, and (4) the atrialappendage. The power source was a continuous wave Nd: YAG laser.Irradiance was 1 kW. cm^–2, at a wave length of 1064 nm,the irradiated spot diameter was 2.0–2.5 mm, and the pulseduration 5–60 s. Local intra-cardiac atrial potentialsrecorded from the targeted areas during laser irradiation dwindledafter onset of the laser pulse, and their amplitude was reducedpersistently by pulses of 15 s or longer. Histopathologically,the acute lesions showed intramural haemorrhage and coagulationnecrosis, but there was no tissue vaporization or crater formation.Chronic lesions showed clear-cut oval-shaped areas of transmuralfibrosis. Diameters of lesions, dependent on the amount of laserenergy applied, measured from 4.6 ± 0.5 mm (450 J) to7.8 ±1.4 mm (1800 J). Follow-up lasted 6–25 months(average 10.5). All the animals survived the procedure withoutcomplications. Transcatheter laser coagulation of atrial myocardium is safeand can be performed in a controllable manner by using the cathetersystem presented.