Defining the transmurality of a chronic myocardial infarction by ultrasonic strain-rate imaging: implications for identifying intramural viability: an experimental study.
BACKGROUND
In a correlative functional/histopathologic study, we investigated the regional deformation characteristics of both chronic nontransmural and transmural infarctions before and after a dobutamine challenge.


RESULTS
After stenosing copper-coated stent implantation to produce circumflex artery endothelial proliferation, 18 pigs were followed up for 5 weeks. Posteuthanasia histology showed 10 to have a nontransmural and 8 a transmural infarction. Eight nonstented animals served as controls. Regional radial function was monitored by measuring ultrasound-derived peak systolic strain rates (SR(SYS)) and systolic strains (epsilon(SYS)) (1) before stent implantation and (2) at 5 weeks, at baseline (bs) and during an incremental dobutamine infusion. In controls, dobutamine induced a linear increase in SR(SYS) (dobutamine: bs, 4.8+/-0.4 s(-1); 20 microg x kg(-1) x min(-1), 9.9+/-0.7 s(-1); P<0.0001) and an initial increase of epsilon(SYS) at low dose (bs, 58+/-5%; at 5 microg x kg(-1) x min(-1), 78+/-6%; P<0.05) but a subsequent decrease during higher infusion rates. In the nontransmural group, bs SR(SYS) and epsilon(SYS) were significantly lower than prestent values (SR(SYS), 2.9+/-0.5 s(-1) and epsilon(SYS), 32+/-6%, P<0.05 versus prestent). During dobutamine infusion, SR(SYS) increased slightly at 5 microg x kg(-1) x min(-1) (4.7+/-0.6 s(-1), P<0.05) but fell during higher infusion rates, whereas epsilon(SYS) showed no change. For nontransmural infarctions, transmural scar extension correlated closely with epsilon(SYS) at bs (r=0.88). For transmural infarctions, SR(SYS) at bs was significantly reduced and epsilon(SYS) was almost not measurable (SR(SYS), 1.8+/-0.3 s(-1); epsilon(SYS), 3+/-4%). Both deformation parameters showed no further change during the incremental dobutamine infusion.


CONCLUSIONS
Ultrasonic deformation values could clearly differentiate chronic nontransmural from transmural myocardial infarction. The transmural extension of the scar could be defined by the regional deformation response.
Weidemann
Frank
F
Department of Cardiology, University Hospital Gasthuisberg, Leuven, Belgium.
Dommke
Christoph
C
Bijnens
Bart
B
Claus
Piet
P
D'hooge
Jan
J
Mertens
Paul
P
Verbeken
Eric
E
Maes
Alex
A
Van de Werf
Frans
F
De Scheerder
Ivan
I
Sutherland
George R
GR
D000818:Animals; D002470:Cell Survival; D002908:Chronic Disease; D004195:Disease Models, Animal; D004280:Dobutamine; D004452:Echocardiography; D025401:Echocardiography, Stress; D006321:Heart / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D009203:Myocardial Infarction / Q000145:classification* / Q000175:diagnosis* / Q000473:pathology; D011237:Predictive Value of Tests; D015607:Stents; D013314:Stress, Mechanical; D013552:Swine; D013599:Systole; D014055:Tomography, Emission-Computed
D004280:Dobutamine