| Popis: |
The failing heart is unable to provide some organs, notably the brain and the myocardium, with the amount of blood flow they require. To this myocardial inadequacy and resulting "circulatory insufficient" the body reacts by setting in action compensatory mechanisms which are "intracardiac" first (Starling's heterometric regulation, ventricular hypertrophy), then neurohormonal, with the activation of vasoconstrictor systems (noradrenergic system, renin-angiotensin-aldosterone system, arginine-vasopressin system) counterbalanced by the activation of vasodilator systems (vasodilator prostaglandins, atrial natriuretic factor and kinins). However, the vasoconstrictor systems outweigh the vasodilator systems. They create an excessive arterial and venous vasoconstriction, together with water-and-salt retention, which leads to an increase of left ventricular work during both systole and diastole and to a gradual worsening of the heart failure. The present-day treatment of heart failure aims at reducing the water-and-salt retention and at restoring the balance between the vasoconstrictor and vasodilator systems. |
