What is heart failure?
Heart failure (HF) can be caused by any heart condition where the heart’s pumping ability becomes impaired, either because of an abnormality in cardiac structure or function. This results in inadequate perfusion- the inability of the heart to supply adequate oxygenated blood flow to fulfil the body’s needs (the workload).
HF can be acute or chronic. Acute HF develops rapidly (over hours or days). Chronic HF develops over month or years and is a long-term condition usually associated with the heart undergoing adaptive response to changes caused by disease because of this it will be the focus of the essay.
There are two types of failure, which either cause the left ventricle to:
- become thickened and stiff, impairing its ability to fill with blood (Diastolic HF) or - become enlarged and weak, impairing its ability to pump blood to the rest of the body (Systolic HF)
HF can affect any person and over 550,000 new causes are reported each year in the USA. It is more common in more economically developed countries associated with the main cause being chronic artery disease. CAD is caused by atherosclerosis- a build-up of plaque (which is a fatty-deposit of cholesterol and cellular waste.) Rates of smoking, saturated fat (and cholesterol) intake and sedentary lifestyles are all of which are causes of CAD, with higher rates in MEDC’s. Hospitalisations from are over 1.1m/year, more than all types of cancer combined. It costs $37bn per year (2009) and its prevalence in the US is high at 5.7m -2% 40-59, increasing to 10 % >80  since the heart becomes weaker more vulnerable to failure with age. But it can also affect young children, particularly those with genetic heart diseases.
Causes of Chronic HF 
The (primary) cause of HF is coronary artery disease. Plaque builds-up lining the artery, narrowing the lumen reducing the oxygenated blood flow to some areas of the myocardium. Myocardial infarction can occur if the plaque ruptures resulting in a blood clot, completely blocking the flow of blood to an area of the muscle, reducing its pumping ability and can often result in permanent damage where cells left deoxygenated may die. This can cause dysrhythmia and stop the heart contracting efficiently.
Other causes also directly affect the heart. Myocarditis, by viral infection damages the heart muscle; valve disorders like regurgitate valves lead to a volume overload in the left side so the heart progressively dilates; drug induced failures from substances like cocaine, alcohol or even chemotherapy, can damage the myocardium; hypertension can also put excess strain on the heart making it work harder. Other factors like genetic disease could also cause HF. For example, hyperopic cardiomyopathy caused by a mutation of cardiomyocytes; restrictive diseases like amyloidosis/sarcoidosis; or sickle cell- by which the sickle shaped red blood cells carry less oxygen meaning the heart works harder to oxygenate the body.
Conditions like kidney failure that do not directly affect the heart may also cause HF. This puts strain on the heart as excess fluid is retained in the bloodstream increasing the volume the heart has to pump.
Ventricular remodelling- systolic/diastolic dysfunctions
A Systolic dysfunction can be caused by arrhythmias resulting in an accumulation of blood the left ventricle. This accumulation of blood causes pressure called preload, if too high it cause the ventricle to dilate (remodel). Accumulating blood and pressure can also affect the structure of cordiomyocytes. These are responsible for the contraction of the heart, through micro fibrils with distinct repeating units called sarcomeres; which could be stretched enough so that the myosin and actin filaments within are pulled apart. This makes it more difficult for them to overlap, reducing the strength of contraction resulting in a lower ejection function.
One cause of HF is long term