Pacemakers have existed in a very rudimentary form since the 19th century, when it was discovered that electrical impulses could be used to provoke a heartbeat. However, the devices that followed were large and bulky and had to be plugged into a mains current,putting the patient at risk of electrocution. It wasn't until 1960 that battery-powered implantable pacemakers came into use, having been invented four years previously.Electrical engineer Wilson Great batch was working on a heart-rhythm recorder when he added the wrong size of resistor to the circuitry. Rather than recording, he found that the device produced electrical pulses instead. He quickly realized that it could be used to regulate the electrical activity of the heart and guarantee a steady rhythm. Over the next two years, he succeeded in miniaturising the device and making it safe from bodily fluids.The first patient, a 77-year-old man, went on to live for a further 18 months.

a) Since when have pacemakers existed? b) What were the problems with the early machines? c) What can electrical impulses do to the heart? d) When working on a heart-rhythm recorder what did Wilson Great batch: i) do by mistake? ii) and what happened? e) When did the battery-powered implantable pacemakers come into use? What does a pacemaker consist of? If you have a pacemaker, what will happen if your heartbeat is abnormal? Describe the difference between a 'Double Lead' and a 'Single Lead' pacemaker. How old was the first patient who received a pacemaker when he died? Assuming he received it on his 77th Birthday.(1 mark)

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