The importance of defining left ventricular area at risk in vivo during acute XXXX : an experimental evaluation with myocardial contrast two-dimensional echocardiography.

@entity235 @entity1563 @entity1188 @entity583 @entity65
Because the left ventricular "area at risk" is the most important determinant of ultimate @entity1188 size, it would be useful to know the size of the area at risk during acute @entity583 to make therapeutic decisions. We therefore performed a series of experiments in four groups of @entity235 . In group I @entity235 (n = 15) we attempted to determine whether current methods of assessing left ventricular function during acute @entity583 reflect the true size of the area at risk. At each of two to five sequential stages, a more proximal @entity1563 was performed to produce a larger area at risk until @entity65 occurred. At each stage, the area at risk (measured by myocardial contrast echocardiography), hemodynamic variables, and left ventricular ejection fraction (LVEF) were measured. Hemodynamic variables became abnormal when the area at risk was large (25% to 40% of the left ventricle), whereas LVEF became abnormal when the area at risk was of moderate size (18%). When cardiac output and LVEF were normalized to baseline values, a close inverse relationship was noted between these variables and area at risk. In contrast, there was a poor relationship between normalized mean arterial pressure and area at risk (r = .42). In group II @entity235 (n = 9) the area at risk was measured serially over 6 hr after @entity1563 . The size of the area at risk remained unchanged regardless of the transmural extent of the ultimate @entity1188 . The circumferential endocardial extent of the area at risk closely predicted the circumferential endocardial extent of the @entity1188 at 6 hr in eight of nine @entity235 that developed an @entity1188 . Group III @entity235 (n = 7) underwent the same protocol as group II @entity235 , but the duration of occlusion was 3 hr. The circumferential endocardial extent of the area at risk closely predicted the circumferential endocardial extent of the @entity1188 . Group IV @entity235 (n = 5) underwent subtotal @entity1563 . Although regional wall motion abnormalities were noted in this group, no area at risk could be defined. We conclude that although a close inverse relationship is noted between normalized cardiac output and area at risk, the absolute values for cardiac output and other hemodynamic variables become abnormal only when the area at risk is large (25% to 40%); measurement of LVEF may provide a better assessment of the size of the area at risk than hemodynamic variables.(ABSTRACT TRUNCATED AT 400 WORDS)
