Sa. Strickberger et al., Extracardiac ablation of the canine atrioventricular junction by use of high-intensity focused ultrasound, CIRCULATION, 100(2), 1999, pp. 203-208
Citations number
27
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-High-intensity focused ultrasound has been applied to internal o
rgans from outside the body to ablate tissue. No published study has assess
ed the feasibility of ablating cardiac tissue within the beating heart by u
se of this type of therapeutic ultrasound. The purpose of this study was to
determine whether high-intensity focused ultrasound can be used to ablate
the atrioventricular (AV) junction within the beating heart.
Methods and Results-Ten dogs were anesthetized and underwent a thoracotomy.
The heart was covered with a polyvinyl chloride membrane. The thorax above
the membrane was perfused with degassed water, which functioned as a coupl
ing medium for the ultrasound. A 7.0-MHz diagnostic ultrasound probe was af
fixed to a spherically focused 1.4-MHz high-intensity focused ultrasound tr
ansducer with a 1.1X8.3-mm focal zone 63.5 mm from the ablation transducer.
The diagnostic ultrasound probe was calibrated such that the location of t
he focal zone of the ablation transducer was identifiable on the 2-dimensio
nal ultrasound image. Target sites were identified with the diagnostic ultr
asound. The maximum ultrasound intensity for ablation (2.8 kW/cm(2)) was de
livered to the AV junction only during electrical diastole and for a total
of 30 seconds. Complete AV block was achieved in each of the 10 dogs with 6
.5+/-5.6 (range, 3 to 21) 30-second applications of therapeutic ultrasound.
Gross inspection showed that the mean lesion volume was 124+/-43 mm(3), wi
th a depth of 6.7=/-3.6 mm, a length of 5.7+/-2.5 mm, and a width of 4.7+/-
1.8 mm, Four hours after the dogs were killed, histopathological study demo
nstrated a well-demarcated area of necrosis and early inflammation.
Conclusions-High-intensity focused ultrasound produces well-demarcated lesi
ons and appears to be a feasible energy source to create complete AV block
within the beating heart without damaging the overlying or underlying cardi
ac tissue. This energy source may allow for a noninvasive approach to ablat
ion of cardiac arrhythmias.