Myocardial perfusion and wall motion in infarction border zone: Assessmentby myocardial contrast echocardiography

Several mechanisms have been proposed to explain the decreased wall motion (WM) at the borders of myocardial infarction (MI), We used myocardial contr ast echocardiography (MCE) to Investigate the relation of perfusion to WM i n infarcted border zones (BZs) 6 weeks after MI in 5 sheep. After quantifyi ng the extent of WM abnormality and the perfusion defect, normal (NL), infa rcted, and BZs were defined. Peak intensity after contrast was measured in acoustic units (AU). Radiolabeled microspheres were injected to measure reg ional blood now. The heart was stained with 2,3,5-triphenyltetrazolium chlo ride (TTC). The perfusion defect on MCE was 33% +/- 7% of the total myocard ial area and correlated well with TTC (r = 0.92, P <.03). The BZ was 8% +/- 5% of the total myocardial area. Peak intensity after contrast was decreas ed in MI compared with BZ and NL (MI: 2.5 +/- 1.9 AU, BZ: 8.0 +/- 3.8 AU, P <.005; NL: 10.2 +/- 6.9 AU, P <.02) and comparable in NL and BZ. The blood flow measured by microspheres was not different in NL and BZ but was decre ased In MI (NL: 1.6 mL/g/min, st: 1.5 +/- 0.5 mL/g/min, MI: 0.7 +/- 0.5 mL/ g/min; P <.0001). In this model of chronic ovine MI, the BZ was small and i ts perfusion was preserved. These findings support the hypothesis that teth ering of normal myocardial segments explains the abnormal wall motion noted at the borders of MI.