Little Liam King was only 5 days old when he became the youngest patient ever to receive a pacemaker to regulate his heart rate. Depending on which version of the story you read, his parents were told he'd only live 15 minutes, 15 days, or 15 months without the surgery. I'll be looking for the story to be published in one of the medical journals to find out which.
Liam was born with a heart defect which affected the electrical system in his heart. This is called heart block. The heart's electrical system is supposed to coordinate the contractions which pump blood through the heart. In heart block, the blood vessels are often normal, but the electrical signals don't get to the right place to cause the ventricles (lower chambers) of the heart to contract. There are 3 types of heart block.
First Degree -- the signal gets through, but not as fast as is typical. This type of heart block usually does not require any treatment.
Second Degree -- Most of the signals get through, but there is an occasional missed beat. Depending on the frequency, this type may cause enough symptoms to require a pacemaker.
Third Degree -- also known as complete AV block. This is the type baby Liam has. No signals get through to the ventricles. The ventricles have their own electrical signal which will cause them to beat at a slow rhythm, but which may not provide enough blood flow - especially for a baby. Individuals with third degree block are at risk of sudden cardiac death and will need an implanted pacemaker.
The images of baby Liam on the icWales site show just how large the pacemaker is in comparison to this fairly small infant. It covers about half of his abdomen. As he grows, the pacemaker will have to be periodically replaced and repositioned. He seems to have done very well in his hospital stay. He was delivered 6 weeks before his due date and released from the hospital only a little over 4 weeks after his birth. There are more than a few 34 week preemies who would still be hospitalized even without the cardiac complications and surgery.
Update: See the comments - Liam's dad dropped by to let me know they were actually told he might only survive 15 minutes. Amazing how differently the various news sites reported this.