Electrophysiology of a gap created on the canine atrium.

OBJECTIVE: It is crucial to detect the unablated regions (="gap") in the radiofrequency linear ablation of atrial tachyarrhythmias. The purpose of this study was to examine the relationship between the electropysiological properties of the gap created in the canine atrium and its anatomicohistologic findings. METHODS AND RESULTS: In 17 dogs, a linear epicardial radiofrequency ablation lesion was created on the right atrial wall with a gap of surviving tissue in the mid-portion of the lesion. For each gap, the local electrogram (LE) from the gap and conduction pattern through the gap were recorded using an electrode catheter and a plaque electrode during pacing from each side of the gap and the gap size was measured. The gaps >5 mm exhibited a conductive property and the gaps <3 mm had no conduction property according to 3-D mapping. The size of the conductive gaps was larger than that of the non-conductive gaps (7.1 +/- 2.6 vs. 2.6 +/- 2.5 mm, p < 0.0001). The LE configurations were categorized into single, double and continuous potentials and single potentials were demonstrated only in wide gaps >7 mm. There was a significant inversed correlation between the duration of the LE and gap size and also between the LE duration and the conduction velocity. Histological examination showed that the conduction properties through the gap depended mainly on its size. CONCLUSIONS: The conductivity through the gap, which was affected by the size of the gap, may be evaluated by the duration and configuration of the local electrogram recorded from the gap.

Delayed thrombogenesis following radiofrequency catheter ablation.

The cause and duration of the thrombogenesis provoked by radiofrequency catheter ablation (RF-CA) was investigated by measuring the thrombin-antithrombin III complex (TAT) in 43 patients who underwent RF-CA and in 20 control subjects who underwent an electrophysiologic study. Blood samples were collected at 7 different times: before introducing the sheaths, during the ablation procedure and at 30 min, 6 and 24h, and 3 and 6 days after the procedure. Hepatocyte growth factor (HGF) was simultaneously measured in the ablation group. Plasma TAT concentration exhibited a double peaked pattern in the ablation group: the first peak occurred during the ablation procedure (42.8+/-15.5 ng/ml), and the second peak 3 days later. Plasma TAT at 3 days after the procedure was significantly higher than that of the control group (21.3+/-19.0 vs 2.5+/-1.4, p=0.0003). The first peak significantly correlated with the procedure time prior to the administration of heparin (r=0.669), but the second peak did not (r=0.132). A subgroup with a serum HGF >0.40 ng/ml at 6 h after the procedure exhibited a significantly high second peak. The thrombogenesis caused by RF-CA has 2 phases; in the acute phase, there is hemostasis during placement of the catheters, and in the delayed phase thrombogenesis is the result of endothelial damage from the RF current.