Heart failure - where the heart struggles to pump enough blood around the body - affects millions of people every year.
There is a wide range of symptoms - from struggling to perform everyday tasks like getting dressed or gardening, to breathlessness whilst simply sitting still. Some patients experience chest pain.
Fitting a pacemaker can help to resynchronise the heart. But checking whether the pacemaker is working efficiently can be tricky. The ultrasound echo machine - which scans the chest - can only be used 6 weeks after the operation to implant the pacemaker, because of scarring and tenderness.
At London's Heart Hospital consultant cardiologist Dr Martin Thomas is pioneering the use of a new device called a Finometer.
It detects fluctuations in blood pressure and cardiac output per heartbeat via a probe attached to the patient's finger. This information can be used to tailor the pacemaker for each patient.
One patient, Reuben Naidu, had his first heart attack when he was just 33. Now in his 50s, his new pacemaker is adjusted by using the Finometer.
He's grateful that with Dr Thomas' team's help he can once again start to enjoy some of the pleasures of life - like good food and trips out.