Selective coronary microembolization in sheep produced a stable model of chronic severe ischemic heart failure with persistent hemodynamic impairment and a 170% increase in left ventricular collagen.
A sheep model of chronic ischemic heart failure demonstrates that stable severe HF involves complex interactions among hemodynamic load, neurohumoral activation, extracellular matrix remodeling, and myocyte apoptosis.
The mandatory use of pharmacotherapy in human heart failure (HF) impedes further study of natural history and remodeling mechanisms. We created a sheep model of chronic, severe, ischemic HF left ventricular (LV) ejection fraction (LVEF) <35% stable over 4 wk by selective coronary microembolization under general anesthesia and followed hemodynamic, energetic, neurohumoral, structural, and cellular responses over 6 mo. Thirty-eight sheep were induced into HF (58% success), with 23 sheep followed for 6 mo (21 sheep with sufficient data for analysis) after the LVEF stabilized (median of 3 embolizations). Early doubling of LV end-diastolic pressure persisted, as did increases in LV end-diastolic volume, LV wall stress, and LV wall thinning. Contractile impairment (LV end-systolic elastance, LV preload recruitable stroke work, and dobutamine-responsive contractile reserve) and diastolic dysfunction also remained stable. Cardiac mechanical energy efficiency did not recover. Plasma atrial natriuretic peptide levels remained elevated, but rises in plasma aldosterone and renin activity were transient. Collagen content increased 170%, the type I-to-III phenotype ratio doubled in the LV, but right ventricular collagen remained unaltered. Fas ligand cytokine levels correlated with expression of both caspase-3 and -2, suggesting a link in the apoptotic "death cascade." Caspase-3 activity also bore a close relationship to LV meridional wall stress calculated from echocardiographic and intraventricular pressure measurements. We concluded that the stability of chronic untreated severe ischemic HF depends on the recruitment of myocardial remodeling mechanisms that involve an interaction among hemodynamic load, contractile efficiency/energetics, neurohumoral activation, response of the extracellular matrix, wall stress, and the myocyte apoptotic pathway.
Huang et al. (2004) studied chronic severe ischemic heart failure (n=38). selective coronary microembolization was evaluated on hemodynamic, energetic, neurohumoral, structural, and cellular responses. Selective coronary microembolization in sheep produced a stable model of chronic severe ischemic heart failure with persistent hemodynamic impairment and a 170% increase in left ventricular collagen.