Heart failure is the result of long-term cardiovascular disease, acute cardiac trauma, or idiopathic (unknown) diagnosis. In each instance, there is a reduction in the ability of the heart to increase cardiac output when there is an increase in cardiovascular demand from exercise or physical activity.
Typically, the reduction in cardiac output is a result of impaired stroke volume (amount of blood pumped in each beat) due to poor ventricular filling and/or poor ejection of blood.
Heart failure with reduced ejection fraction (the percentage of blood leaving your heart each time it contracts) is typically the result of an impaired ability of the heart to contract as a result of coronary artery disease/myocardial infarction/transient myocardial ischemia, chronic volume overload due to valve functional impairments or dilated cardiomyopathies. In addition, it might be the result of increased afterload stemming from hypertension or aortic stenosis.
Heart failure with preserved ejection fraction is also possible and is the result of impaired ventricular filling stemming from left ventricular hypertrophy, myocardial fibrosis, transient myocardial ischemia, or pericardial constriction.
In each instance, there is a remodeling of the heart to try to improve ejection fraction by increasing the size of the ventricle and/or the thickness of the walls of the heart. However, this concentric hypertrophy over the long term does not improve function.
The result is an impairment in heart function that gets worse with time ultimately leading to the need for heart transplantation.