Functional remodelling and left ventricular dysfunction after repeated ischaemic episodes - A chronic experimental porcine model

This experimental study was set up to investigate left ventricular function and remodelling after repeated ischaemic episodes using magnetic resonance imaging (MRI). A significant reduction in mortality due to coronary heart, disease (CHD) has been explained by both a decline in the incidence of acut e myocardial infarction (AMI) and an improved post-AMI survival rate, sugge sting a change in the natural history of CHD. Experimental intracoronary mi croembolization can induce different ischaemic patterns and the functional impact of repeated ischaemic episodes different from occlusion of central e picardial arteries can be studied. In this study repeated intracoronary mic roembolizations were performed in 20 domestic pigs. After 129 d, MRT was pe rformed for assessment of left ventricular volume, mass and wall stress. Si x pigs underwent serial MRI at baseline, immediately after embolization and at the end of the observation period. Microembolizations induced acute myo cardial infarct expansion and increased left ventricular wall stress preced ing chronic remodelling. End systolic and end diastolic volumes increased f rom 15.1 +/- 2.7 cm(3) to 41.3 +/- 11.5 cm(3) (p < 0.002), and from 52.0 +/ - 6.7 cm(3) to 81.1 +/- 9.2 cm(3) (p < 0.0007), respectively. End systolic wall stress increased from and 17.5 +/- 2.7 to 29.7 +/- 6.2 N/m(2) (p < 0.0 01). Left ventricular filling pressures and cardiac index were unchanged. H istological examination revealed a diffuse pattern of perivascular fibrosis covering 12 +/- 3% of the left ventricular wall. This study demonstrates t hat repeated ischaemic episodes different from confined regional myocardial infarctions induce acute infarct expansion and chronic left ventricular re modelling in pigs. Serial assessment of absolute left ventricular volumes a nd mass is important during acute/chronic remodelling.