Relation of the contractile reserve of hibernating myocardium to myocardial structure in humans

Background-Although dobutamine echocardiography (DE) is widely used to asse ss myocardial viability in humans, little is known about the relation betwe en contractile reserve and myocardial structure. Methods ana Results-We evaluated 20 patients with coronary disease (64+/-13 years old, ejection fraction 28+/-7.5%) with DE (up to 40 mu g.kg(-1).min( -1)), rest-redistribution Tl-201 single photon emission CT, and quantitativ e angiography before bypass surgery. During surgery, patients underwent tra nsmural myocardial biopsies (n=37) guided by transesophageal echocardiograp hy to determine the extent of interstitial fibrosis and intracellular and i nterstitial proteins by histopathology and immunohistochemistry. Among the 37 segments biopsied, 16 recovered function as assessed 2 to 3 months later . Segments with postoperative functional recovery had more wall thickening at low-dose DE (28% versus 3%, P<0.001), higher thallium uptake (69% versus 48%, P=0.03), and less interstitial fibrosis (2% versus 28%, P<0.001), Qua ntitative angiographic parameters did not predict recovery of function. Seg ments with DE viability (contractile reserve and/or ischemia) had less fibr osis (2.7% versus 28%, P<0.001), less vimentin and fibronectin (both P<0.01 ), more glycogen (P=0.016), and higher thallium uptake (64% versus 35.5%, P <0.055 than those without viability. Viable segments by both DE and thalliu m had less fibrosis (1%) than those viable by 1 of the 2 techniques (9%) or not viable by both (28%, P=0.005). Thickening at low-dose DE correlated we ll with the extent of interstitial fibrosis (r=-0.83, P<0.01). Conclusions-Contractile reserve during DE correlates inversely with the ext ent of interstitial fibrosis and the amount of fibronectin and vimentin and directly with rest-redistribution thallium uptake.