The says more than a million people are living with heart failure - and around 7.6 million have a heart or circulatory disease causing an average of 480 deaths each day, or one every three minutes. But knowing signs can mean you get an early diagnosis which can help keep the problem and its symptoms under control.

cardiothoracic surgeon at London's St Bartholomew's Hospital says if you experience any of the subtle signs below, particularly more than one at the same time, speak to your GP.

FATIGUE: Feeling tired due to late nights, stress or social commitments is one thing, but if extreme fatigue has kicked in for no obvious reason, it may be the early stages of heart failure. In a Usually, fatigue should improve with a little rest. If not, it may be a sign something is wrong.

SWELLING: As well as pain in the legs, ankles and feet - there are various reasons behind lower limb swelling, including blood pressure medication, inactivity, pregnancy and even tight clothing. But Mr Aktuerk says if your swelling doesn't go down, even after resting your legs, it may be a worry as your heart is struggling to pump blood effectively.

Dr Rosie Godeseth, a cardiologist and Associate Medical Director at adds: "Speak to a doctor if swelling persists or is accompanied by symptoms like dizziness and shortness of breath."

Pain or cramping in your calves when you walk can also be caused by lack of blood to the leg. The British Heart Foundation says this is a marker of peripheral arterial disease, caused by a build-up of fatty deposits in arteries so that less blood can get through.

RAPID WEIGHT GAIN: If the scales are going up or your clothes feel tighter, even despite efforts to lose weight, it could signal a heart problem. Dr Godeseth explains: "When the heart isn't effectively pumping, it can lead to reduced blood flow in the kidneys. These organs regulate fluid and sodium balance, so they respond to the reduced blood flow by retaining fluid and sodium."

Mr Aktuerk says fluid can also build up in other areas. He adds: "A sudden and unexplained increase in weight, especially if accompanied by other symptoms listed here, could be a telling sign."

SHORTNESS OF BREATH: Getting breathless more easily, especially lying down or after mild exertion, is a concern. Mr Aktuerk says: "As the heart weakens it can't pump blood effectively to the lungs, causing a build-up of fluid, which can manifest in a shortness of breath. Another sign is using more pillows at night and getting breathless climbing one or two flights of stairs."

PERSISTENT COUGH: Wheezing and a cough that won't go away and is often worse at night and pink or blood-tinged mucus, should not be ignored, according to Dr Godeseth. "This occurs after heart failure causes a fluid build-up in the lungs, so speak to a doctor if you have had a cough for more than three weeks."