Increased sympathetic nervous system output: 

• Compensatory: Positive chronotropic and Ionotropic effect. Sympathetic venoconstriction decreases capacitance of venous system and increase venous return to heart.

• Decompensatory: Excess is deleterious: Increasing myocardial oxygen requirement, increasing peripheral vascular resistance.

Starling curve shifts: Heart attempts to compensate for low cardiac output either by dilatation (to increase end diastolic pressure) or hypertrophy  (increased oxygen demand). The Starling curve is shifted downward to right and has a flattened contour in the patient with decreased cardiac contractility. Compliance refers to pressure required to fill ventricle to a certain volume. In CHF the ventricles become stiff (Non-compliant) requiring a higher LVEDP to achieve diastolic filling adequate to maintain cardiac output.

Rennin angiotensin system: Decreased renal perfusion leads to salt and water retention. Elevation of LVEDP.