Myocardial infarction causes death of myocardial cells, which reduces cardiac muscle mass and contractility. 2 Diastolic dysfunction occurs when the left ventricle becomes very stiff and resists relaxation and proper filling. This stiffness causes high pressures within the ventricles, preventing them from filling with sufficient blood volume. Other causes include valvular stenosis, pericardial disease, obesity and diabetes, which cause declines in myocardial compliance. The three components of SV are preload, afterload, and the contractile state of the heart.
Contractility is the inherent ability of the myocardial cell to contract.
The Frank-Starling principle states that changes in preload can alter the force of myocardial contraction, increasing contractility as preload increases. In systolic dysfunction, the greater the increase in afterload the greater the reduction in SV, thus an inverse relationship exists. Changes which cause heart failure result in a decrease in CO, activating several endogenous neurohormonal systems. Plasma norepinephrine levels are elevated in CHF and correlate with the degree of failure. Decreased renal perfusion also stimulates renin production.