Bruce G Keith, Bunch T Jared, Milton Mark A, Sarabanda Alvaro, Johnson Susan B, Packer Douglas L
Division of Cardiovascular Disease, Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA.
Circulation. 2005 Aug 16;112(7):954-60. doi: 10.1161/CIRCULATIONAHA.104.492439. Epub 2005 Aug 8.
It is not known whether catheter tip temperatures with a cooled-tip ablation can be reliably extrapolated to estimate actual tissue temperatures. The relationship between catheter tip temperatures, tissue temperatures, power, and microbubble formation is not known.
Nine dogs underwent 111 radiofrequency energy deliveries at the pulmonary vein ostia with a cooled-tip catheter. Catheter tip and tissue temperatures were markedly discrepant. Catheter tip temperature plateaus at 36 degrees C to 39 degrees C with increasing power, whereas tissue temperature increases to a mean of 75+/-3 degrees C at 45 W (maximum temperature >100 degrees C). Seventy-two energy deliveries were performed, titrating power to microbubble formation guided by intracardiac echocardiography. Type I and II microbubble formation occurred in 45 (63%) and 19 (26%) ablations, respectively. Type I microbubble emergence occurred at lower powers (21+/-8 versus 26+/-4 W; P=0.05), catheter tip temperatures (38+/-5 degrees C versus 48+/-10 degrees C; P=0.02), and tissue temperatures (65+/-19 degrees C versus 81+/-9 degrees C; P<0.001) than type II microbubble formation. Maximum impedance decreases during ablation before microbubble formation were less with type I microbubble (20+/-9 versus 37+/-11 Omega; P<0.001) compared with type II microbubbles. One quarter of type I microbubbles abruptly transitioned to type II microbubbles with significant changes in power or catheter tip temperature. No microbubbles were seen in 19 ablations (26%) despite powers up to 26+/-9 W and tissue temperatures up to 81+/-17 degrees C.
Catheter tip and tissue temperatures are markedly discrepant during cooled-tip ablation. Type I and II microbubble formation occurs at overlapping power and catheter tip and tissue temperature ranges. Neither the absence of microbubbles nor the presence of type I microbubble formation ensures against excessive tissue heating. The appearance of microbubbles may indicate possible tissue overheating and signal a need to decrease energy.
尚不清楚冷盐水灌注导管消融时的导管尖端温度能否可靠地外推以估计实际组织温度。导管尖端温度、组织温度、功率和微泡形成之间的关系尚不清楚。
9只犬使用冷盐水灌注导管在肺静脉开口处进行了111次射频能量释放。导管尖端温度与组织温度明显不同。随着功率增加，导管尖端温度稳定在36℃至39℃，而在45W时组织温度平均升高至75±3℃（最高温度>100℃）。进行了72次能量释放，在心内超声心动图引导下将功率滴定至微泡形成。I型和II型微泡形成分别发生在45次（63%）和19次（26%）消融中。I型微泡出现时的功率（21±8W对26±4W；P=0.05）、导管尖端温度（38±5℃对48±10℃；P=0.02）和组织温度（65±19℃对81±9℃；P<0.001）均低于II型微泡形成。与II型微泡相比，I型微泡在消融过程中微泡形成前最大阻抗的降低幅度较小（20±9Ω对37±11Ω；P<0.001）。四分之一的I型微泡在功率或导管尖端温度发生显著变化时突然转变为II型微泡。尽管功率高达26±9W且组织温度高达81±17℃，但在19次消融（26%）中未观察到微泡。
冷盐水灌注消融期间，导管尖端温度与组织温度明显不同。I型和II型微泡形成发生在重叠的功率、导管尖端温度和组织温度范围内。微泡的缺失或I型微泡的形成均不能确保避免组织过度加热。微泡的出现可能表明组织可能过热，并提示需要降低能量。
