Reperfusion Injury-Related Intramyocardial Hemorrhage

Abstract

Myocardial reperfusion injury is defined as the death of cardiomyocytes as a direct result of one or more events initiated by reperfusion. These events could be inflammation, oxidative stress, calcium overload, neurohumoral activation, cytotoxicity of anaerobic metabolites, etc. Intramyocardial hemorrhage as a consequence of ischemia–reperfusion injury during acute myocardial infarction and subsequently is frequent and portends worse prognosis. Animal studies have demonstrated that intramyocardial hemorrhage does not occur with ST-elevation myocardial infarction unless myocardium is reperfused with blood. Magnetic resonance imaging is the technique of choice for its detection but has limited availability in emergencies and is expensive. Echocardiography can be used for indirect myocardial tissue characterization. Echocardiography coupled with myocardial contrast imaging is increasingly being used for detecting hemorrhage in infarcted segments. In the presence of wall motion abnormality, increased segmental echogenicity, significantly increased wall thickness underlying hypermobile endocardium, and neocavitations within the myocardium are the characteristic features. Occasionally, extensive wall splitting and formation of pseudotumor due to large hematoma are the striking features of intramyocardial hemorrhage. Intramyocardial hemorrhage in acute myocardial infarction can occur during early phase, following reperfusion and during remodeling process. There is no definite echocardiographic imaging method to assess reperfusion hemorrhage in vivo, but signal-void cavity-like or cystic appearance within the myocardium in the setting of myocardial infarction is highly suggestive. Detecting hypointense area of hemorrhage could be complicated by low-intensity echoes emanating from the normal myocardium. Echocardiography should be performed in every patient before and after reperfusion therapy and serially till discharge. There are no studies comparing the diagnostic yield of echocardiography compared to magnetic resonance imaging. Those with obvious myocardial hematoma need special attention with regard to antiremodeling agents, dual antiplatelet therapy, and possibly surgery. A majority of patients with significant intramural hemorrhage end up having reduced left ventricular function, adverse remodeling, true or pseudo-aneurysms, and even heart failure although spontaneous resorption has also been reported.