When you're given the diagnosis of heart failure, naturally you're a bit concerned! The word "failure" is quite extreme, when really it just means that the heart isn't working as well as it used to - which is a large spectrum. So, perhaps we should really call it "reduced heart efficiency" - but I guess it doesn't have the same ring to it.

Understanding heart failure relies on understanding the structure of the heart (please read our general overview and come back!). 

When the heart's muscle contracts, pumping blood out of the ventricles, interestingly it doesn't squeeze all of the blood out. In fact, just over a third remains in the ventricles after the aortic and pulmonary valves shut. Why? Pressures...efficiency...who knows...who cares - the important thing to know is that a healthy heart pumps roughly 55-60% of the blood out of the ventricles on each beat. We call this percentage the ejection fraction. 

In the vast majority of cases, a patient with heart failure will have a lower ejection fraction than they used to. Perhaps the muscle aiding the emptying of the ventricle has weakened with age, or secondary to a heart attack in the past - whatever the reason, the pump isn't as good anymore. 

This leads to two main problems. Firstly, less blood is being pumped around the body/to the lungs on each beat. And secondly, all that extra blood sitting in the ventricles causes a back flow of pressure - like a dam on a river or a build up of cars in a traffic jam. The ventricle acts as a stubborn night-club bouncer, not letting anymore blood in. As a result, long queues form and too much blood pools in areas it shouldn't. 

If the left ventricle is weaker, blood will pool there. This increases pressure in the left atrium above and in the lung vasculature. The extra pressure in the lungs vessels means that fluid leaks into the airways - we call this pulmonary oedema (Pulmonary-Lung, Oedema-Fluid).
This will lead to shortness of breath, particularly when lying flat - imagine tipping a half-empty bottle of water sideways (the water spreads over a larger surface area like a big, wet blanket). This is why patients with heart failure may notice themselves sleeping with three pillows. 

If the right ventricle is weaker, blood will pool there. This increases pressure in the right atrium above. The venous system cannot overcome the pressure ahead when trying to return blood from all around the body to the heart. As a result, gravity deposits the excess fluid in the legs/feet, causing them to swell. 

Lots of people have both left and right-sided heart failure together (as, ultimately, one system relies on the other) - meaning they will have both the shortness of breath and the leg swelling. 

To diagnose heart failure, your doctor will order an echocardiogram. An ultrasound probe will be used to record your heart's pumping action and interpret its efficiency. 

Once confirmed, further tests may happen to uncover the cause of the heart failure in the hopes of reversing it. Some medications will be started, such as beta blockers (Bisoprolol, Metoprolol, etc.) and ACE inhibitors or ARBs (common blood pressure meds) - these medications have been proven to improve outcomes in ejection fraction reduced heart failure. 

The main focus of heart failure treatment is fluid management. If the heart can't keep up with the demand of circulating fluid, we aim to reduce it. We may as well, it's not like the extra fluid sitting in your lungs or feet are doing any good anyway. And more importantly, it'll have you feeling a whole lot better. 
To reduce your fluid levels, we have two weapons in our arsenal. A fluid restriction of 1.5L a day, and a diuretic medication (Furosemide being the most common) that tricks the kidneys producing more pee. We will be led by your symptoms, and your weight in terms of the dose. 

If you've gained 3kg of weight in three days, it's unlikely to be the fault of the cookie jar in such a short period of time. Likely, excess fluid is reaccumulating and you need to increase your diuretic dose or reduce your fluid intake. This will improve your breathing and keep the cankles at bay!

Heart failure treatment is a fluid issue. The heart's pumping efficiency is reduced, so we have to reduce the workload to match its ability. It's that simple.