Long-term oral sildenafil improved left ventricular function and reduced infarction size after LAD occlusion. Sildenafil was given continuously for 4 weeks in the drinking water (3 mg/kg/day) (n = 8/group). Top: The LVEF was measured before MI (basal), and at 1 and 4 weeks. UT: untreated control; S: sildenafil. Middle: representative micrographs (4 X) for the histochemical detection of collagen by Picrosirius red in paraffin-embedded sections. Bottom: quantitative image analysis of infarction area. Statistical differences are stated for untreated versus basal, and sildenafil versus untreated; *p < 0.05; ***p < 0.005.