ULTRASONIC CHARACTERIZATION OF MYOCARDIAL PHOTOCOAGULATION LESION SIZE IN-VIVO DURING ND-YAG LASER IRRADIATION

Endocardial coagulation lesions were created using transcatheter conti nuous-wave Nd:YAG laser irradiation. Ultrasound monitoring of thermal lesion dimensions was performed using 7.5-MHz and 10-MHz transducers d irectly from the epicardial surface in short-axis configuration (group A) or through the chest wall (group B). A total of 33 lesions were cr eated in 10 dogs at energy levels ranging from 300 J to 1000 J. Mean h istological lesion width (HW) compared with ultrasonically determined mean width (UW) showed that the differences (mean +/- standard deviati on) in group A (UW - HW) was = 1.14 +/- 0.8 mm, which was not statisti cally significantly different from zero. In group B, (UW - HW) = 2.04 mm +/- 0.7 mm (p<.05), which was statistically significantly different from zero. Mean histological depth (HD) differentially related to ult rasound mean depth (UD) for group A and B combined showed(UD - HD) = - 0.19 mm +/- 0.46 mm, not statistically significantly different from ze ro. The frequency distribution for width in group A showed \UW - HW\>3 mm in 32% of cases. In group B \Um - HW\>3 mm in 15%, whereas ultraso und width was larger than histology in 75% of the cases. For depth, \U D - HD\>3 mm in 15% of cases. With further refinement of the technique , ultrasonic tissue characterization may become a useful adjunct to mo nitoring lesion dimensions during transcatheter laser photocoagulation . (C) 1994 John Wiley and Sons, Inc.