Contractile, haemodynamic and neurohormonal abnormalities in heart failure.

Abstract

The biochemical abnormalities associated with heart failure include dysfunction of contractile proteins, functional impairment of energy-linked enzymes and disruption of cell membrane structure. The haemodynamic impairment resulting from cardiac dysfunction activates several neurohormonal systems, notably the renin-angiotensin-aldosterone system, sympatho-adrenal system and vasopressin release, whilst clinically important factors include an enlarged heart, increased systolic wall stress and an increased myocardial oxygen demand. An inverse relationship exists between systolic wall stress (afterload) and contractile function in heart failure. Moreover the increased systolic wall stress that occurs as a result of reduced cardiac output raises myocardial oxygen consumption, causing cardiac function to deteriorate still further. Diastolic abnormalities play an important role in hypertrophic disorders, in ventricular dilatation and in cases of myocardial ischaemia. The therapeutic objectives are therefore to decrease heart size, to reduce wall stress and oxygen demand, and to enhance diastolic distensibility.