Functional recovery of subepicardial myocardial tissue in transmural myocardial infarction after successful reperfusion: an important contribution to the improvement of regional and global left ventricular function.
BACKGROUND
The transmural extent of myocardial necrosis after an acute coronary artery occlusion can vary considerably. The contribution of residual subepicardial viable myocardium to global left ventricular function is largely unknown.


RESULTS
We studied 12 patients with single-vessel disease 1 week after successful reperfusion of a first transmural anterior myocardial infarction (MI). With PET, myocardial blood flow (MBF) and glucose metabolism were measured regionally, and the viability was graded as normal, mismatch, or match with severely (<50% of normal) or intermediately (50% to 80% of normal) impaired MBF. Magnetic resonance tagging was used to regionally quantify fiber strains, wall thickening, and ejection fraction in patients 1 week and 3 months after the MI and in age-matched healthy volunteers. From 1 week to 3 months, subepicardial fiber shortening improved significantly in the match region (MBF <50%, -5.1+/-7.0% to -9.9+/-8. 7%; MBF of 50% to 80%, -7.1+/-7.6% to -14.9+/-7.9%). This was associated with an improvement in regional ejection fraction in the infarcted myocardium (29.6+/-21.8% to 43.5+/-15.5%, P<0.0001) and in normal regions (54.3+/-15.1% to 56.5+/-13.1%, P=0.013), contributing to an increase in global ejection fraction from 44.2+/-22.2% to 49. 3+/-17.9% (P<0.0001).


CONCLUSIONS
Functional recovery of viable subepicardial regions is a mechanism of late improvement in regional and global ejection fraction after a so-called transmural MI.
Bogaert
J
J
Department of Radiology, Gasthuisberg University Hospital, Leuven, Belgium.
Maes
A
A
Van de Werf
F
F
Bosmans
H
H
Herregods
M C
MC
Nuyts
J
J
Desmet
W
W
Mortelmans
L
L
Marchal
G
G
Rademakers
F E
FE
D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D017023:Coronary Angiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D015425:Myocardial Reperfusion; D009336:Necrosis; D010496:Pericardium / Q000503:physiopathology*; D015203:Reproducibility of Results; D014055:Tomography, Emission-Computed; D016896:Treatment Outcome; D016277:Ventricular Function, Left / Q000502:physiology*