Paroxysmal atrial fibrillation describes AF that comes and goes, but usually stops spontaneously with the heart rhythm returning to normal. Persistent AF goes on for seven days or longer, while long-standing persistent AF is when symptoms have lasted over a year but the patient is still adopting a rhythm control strategy.6,14

Permanent AF is used to describe the condition when the patient and doctor accept that heart rhythm cannot be restored and no further attempts to restore or maintain heart rhythm will be attempted.14

Heart failure severity is normally classified as one of four stages:11 
Class 1 – no symptoms during normal physical activity 
Class 2 – symptoms only appear with physical activity 
Class 3 – symptoms appear with minor physical activity 
Class 4 – symptoms such as shortness of breath are present when resting and any physical activity causes discomfort.

Ejection fraction, the measure of how much blood the left ventricle pumps out each contraction, is normally 50-70 per cent. Heart failure with reduced ejection fraction is when the ejection fraction is below 40 per cent. When it is above 75 per cent this may indicate hypertrophic cardiomyopathy.9,15

About half of heart failure is classified as heart failure with preserved ejection fraction (HFpEF) with the ejection fraction at 50 per cent or more but symptoms are present. The principal cause is impaired left ventricular relaxation (rather than contraction) possibly due to muscle stiffening, although contraction may also be affected.9,15,16