Can pulsed ultrasound increase tissue damage during ischemia? A study of the effects of ultrasound on infarcted and non-infarcted myocardium in anesthetized pigs.
BACKGROUND
The same mechanisms by which ultrasound enhances thrombolysis are described in connection with non-beneficial effects of ultrasound. The present safety study was therefore designed to explore effects of beneficial ultrasound characteristics on the infarcted and non-infarcted myocardium.


METHODS
In an open chest porcine model (n = 17), myocardial infarction was induced by ligating a coronary diagonal branch. Pulsed ultrasound of frequency 1 MHz and intensity 0.1 W/cm2 (ISATA) was applied during one hour to both infarcted and non-infarcted myocardial tissue. These ultrasound characteristics are similar to those used in studies of ultrasound enhanced thrombolysis. Using blinded assessment technique, myocardial damage was rated according to histopathological criteria.


RESULTS
Infarcted myocardium exhibited a significant increase in damage score compared to non-infarcted myocardium: 6.2 +/- 2.0 vs. 4.3 +/- 1.5 (mean +/- standard deviation), (p = 0.004). In the infarcted myocardium, ultrasound exposure yielded a further significant increase of damage scores: 8.1 +/- 1.7 vs. 6.2 +/- 2.0 (p = 0.027).


CONCLUSIONS
Our results suggest an instantaneous additive effect on the ischemic damage in myocardial tissue when exposed to ultrasound of stated characteristics. The ultimate damage degree remains to be clarified.
Olivecrona
Göran K
GK
Department of Cardiology, Lund University, SE-22185 Lund, Sweden. Goran.Olivecrona@med.lu.se
Härdig
Bjarne Madsen
BM
Roijer
Anders
A
Block
Mattias
M
Grins
Edgars
E
Persson
Hans W
HW
Johansson
Leif
L
Olsson
Bertil
B
D000818:Animals; D004195:Disease Models, Animal; D009203:Myocardial Infarction / Q000473:pathology*; D017202:Myocardial Ischemia / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis; D013552:Swine; D013696:Temperature; D013997:Time Factors; D014465:Ultrasonics