Reduction of "no-reflow" phenomenon by intra-aortic balloon counterpulsation in a randomized magnetic resonance imaging experimental study.
OBJECTIVE
Intra-aortic balloon counterpulsation (IABC) can improve post-myocardial infarction (MI) outcomes, but the mechanisms of such effect remain unclear. We hypothesized that IABC augmentation reduces the extent of microvascular obstruction after acute infarction.


BACKGROUND
Microvascular obstruction or "no-reflow" (MO) has been shown to negatively influence left ventricular (LV) remodeling after myocardial infarction (MI).


METHODS
Seventeen dogs underwent 90 min of coronary artery occlusion followed by reperfusion. Animals were then randomized to either IABC (n = 9) or control (n = 8); IABC augmentation was performed for 24 h after MI. Microvascular obstruction and infarct size by first-pass and delayed contrast-enhanced magnetic resonance imaging (MRI) were measured at 1 and 24 h after reperfusion and compared with postmortem infarct size and MO by microspheres.


RESULTS
Microvascular obstruction by MRI, expressed as percent LV mass, decreased significantly in IABC (4.9 +/- 2.2% to 3.6 +/- 1.5%) and increased in controls (3.4 +/- 0.5% to 4.9 +/- 1.1% from 1 to 24 h, respectively; p < 0.001). Similar results were found for MO defined by microspheres. In the control group, MO increased significantly, during 24 h of study (from 8.8 +/- 1.7% to 43.2 +/- 11.1% of infarcted myocardium; p < 0.05), whereas not important change was observed in the IABC group (from 21.3 +/- 7.1% to 25.8 +/- 14.7%; p < 0.05 vs. control at 24 h). Infarct size, measured by MRI, increased in both groups (13.2 +/- 1.8 to 15.5 +/- 2.1 from 1 to 24 h, respectively; p < 0.05).


CONCLUSIONS
Intra-aortic balloon counterpulsation augmentation performed after reperfusion improves myocardial perfusion at the tissue level, and reduces the extent of no-reflow caused by microvascular obstruction.
Amado
Luciano C
LC
Department of Medicine, Division of Cardiology, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21287-6568, USA.
Kraitchman
Dara L
DL
Gerber
Bernhard L
BL
Castillo
Ernesto
E
Boston
Raymond C
RC
Grayzel
Joseph
J
Lima
João A C
JA
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D004396:Coloring Agents; D003326:Coronary Circulation / Q000502:physiology*; D015908:Counterpulsation; D004195:Disease Models, Animal; D004285:Dogs; D007423:Intra-Aortic Balloon Pumping; D008279:Magnetic Resonance Imaging; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D015425:Myocardial Reperfusion; D011859:Radiography; D013778:Tetrazolium Salts; D016896:Treatment Outcome
D004396:Coloring Agents; D013778:Tetrazolium Salts; C009591:triphenyltetrazolium