Early metoprolol administration before coronary reperfusion results in increased myocardial salvage: analysis of ischemic myocardium at risk using cardiac magnetic resonance.
BACKGROUND
Beta-blockers improve clinical outcome when administered early after acute myocardial infarction. However, whether beta-blockers actually reduce the myocardial infarction size is still in dispute. Cardiac magnetic resonance imaging can accurately depict the left ventricular (LV) ischemic myocardium at risk (T2-weighted hyperintense region) early after myocardial infarction, as well as the extent of necrosis (delayed gadolinium enhancement). The aim of this study was to determine whether early administration of metoprolol could increase myocardial salvage, measured as the difference between the extent of myocardium at risk and myocardial necrosis.


RESULTS
Twelve Yorkshire pigs underwent a 90-minute left anterior descending coronary occlusion, followed by reperfusion. They were randomized to metoprolol (7.5 mg during myocardial infarction) or placebo. Global and regional LV function, extent of myocardium at risk, and myocardial necrosis were quantified by cardiac magnetic resonance imaging studies performed 4 and 22 days after reperfusion in 10 survivors. Despite similar extent of myocardium at risk in metoprolol- and placebo-treated pigs (30.9% of LV versus 30.6%; P=NS), metoprolol resulted in 5-fold-larger salvaged myocardium (32.4% versus 6.2% of myocardium at risk; P=0.015). The LV ejection fraction significantly improved in metoprolol-treated pigs between days 4 and 22 (37.2% versus 43.0%; P=0.037), whereas it remained unchanged in pigs treated with placebo (35.1% versus 35.0%; P=NS). The extent of myocardial salvage was related directly to LV ejection fraction improvement (P=0.031) and regional LV wall motion recovery (P=0.039) at day 22.


CONCLUSIONS
Early metoprolol administration during acute coronary occlusion increases myocardial salvage. The extent of myocardial salvage, measured as the difference between myocardium at risk and myocardial necrosis, was associated with regional and global LV motion improvement.
Ibanez
Borja
B
Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY 10029, USA.
Prat-González
Susanna
S
Speidl
Walter S
WS
Vilahur
Gemma
G
Pinero
Antonio
A
Cimmino
Giovanni
G
García
Mario J
MJ
Fuster
Valentin
V
Sanz
Javier
J
Badimon
Juan J
JJ
D000818:Animals; D008279:Magnetic Resonance Imaging; D008790:Metoprolol / Q000627:therapeutic use*; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000473:pathology; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000473:pathology / Q000517:prevention & control*; D015425:Myocardial Reperfusion; D009336:Necrosis; D013318:Stroke Volume; D013552:Swine
D008790:Metoprolol