Myocardial perfusion and wall motion in infarction border zone: assessment by 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 contrast echocardiography (MCE) to investigate the relation of perfusion to WM in infarcted border zones (BZs) 6 weeks after MI in 5 sheep. After quantifying the extent of WM abnormality and the perfusion defect, normal (NL), infarcted, and BZs were defined. Peak intensity after contrast was measured in acoustic units (AU). Radiolabeled microspheres were injected to measure regional blood flow. The heart was stained with 2,3, 5-triphenyltetrazolium chloride (TTC). The perfusion defect on MCE was 33% +/- 7% of the total myocardial 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 decreased 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 decreased in MI (NL: 1.6 mL/g/min, BZ: 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 its perfusion was preserved. These findings support the hypothesis that tethering of normal myocardial segments explains the abnormal wall motion noted at the borders of MI.