The long term adaptive mechanisms involve myocardial hypertrophy and remodeling which occurs slowly over weeks to months.
The capacity of these adaptive mechanisms meant to sustain cardiac performance is not infinite and over a period of time maladaption sets in. Short term effects are mainly adaptive and occur in acute heart failure whereas long term effects are mainly deleterious and occur in chronic heart failure. For example, salt and water retention augments preload as short-term effect but causes pulmonary congestion and edema in the long term. Vasoconstriction helps to maintain blood pressure and perfusion of vital organs but it aggravates pump dysfunction by increasing afterload. Sympathetic stimulation increases heart rate and stroke volume but also increases energy expenditure. Hypertrophy helps to unload individual muscle fibers but leads to death of cardiac cells and cardiomyopathy of overload.
Sympathetic Activity
In heart failure there is adrenergic activation and parasympathetic withdrawal. This results in increase in myocardial contractility, tachycardia, sodium retention, renin release and generalized vasoconstriction.