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(ABC NEWS) -- When Claire Ives was seven months pregnantwith her third child, she used a handheld device to listen to her unborn son'sheartbeat. As she turned the machine on, she thought something hadmalfunctioned.

"I thought I wasn't listening right orsomething," Ives, a nurse in London, told ABCNews.com. "I didn't believe his[heart] rate could be that fast."

Ives' son had a heart rate of about 300 beats per minute, nearly double thenormal 160.

After doctors were alerted to the baby's elevated heart rate, Ives deliveredher son, Edward Ives, five weeks early via emergency cesarean at the UniversityCollege London Hospital.

Edward Ives was born with supraventricular tachycardia (SVT)and was given a fivepercent chance of survival. SVT is caused by improper electrical impulses in theheart that leads to an irregular rapid heartbeat heart, which then can lead toheart failure or affect internal organs. When the heart beats too quickly, itcan't fill up properly and then distribute blood to vital organs correctly.

"I just thought he was going to die," said Ives.

A few hours after Edward was born, his heart started to race again. Doctorsattempted to reset his heart rate by shocking his heart and giving him differentmedications, but when that failed they were left without many options except onethey had never tried for SVT: They would lower Edward's body temperature toprotect his vital organs and slow his heart rate.

"We'd gone through all the usual maneuvers that usually work in babies,giving drugs ... trying to shock the heart, the baby and get [a healthy heart rateback]," said Dr. Nicola Robertson, who works in the neonatal unit at theUniversity College London Hospital.

Over a period of hours the doctors used a cold gel blanket to lower Edward'sbody temperature to approximately 91 degrees, which both protected his organsand slowed the electrical circuit in his heart. Unfortunately, over the nextday, as Edward was warmed up, his heart began to race again. So the team againcooled his body temperature, three days after they had initially lowered it.

"That was one of the worst nights," recalled Ives. "I asked one of the nursesif he was going to die and she said he might."

Ives was sent out of the room when the doctors again attempted to slow hisheart rate down by not only cooling but administering medication. Eventuallythey came to tell her that his heart rate had slowed, although he would againneed to be warmed up to see if his heart rate was stable.

"It was really strange highs and lows because he was doing extremely poorly,"said Ives. "But, oh, thank God! It worked."

Doctors then began the slow process of warming Edward, this time going at aslower rate as they carefully raised his temperature only half a degree every 12hours. This time his heart rate remained stable.

It wasn't until 10 days after giving birth that Claire Ives was able to holdher son. A month later she and her husband, Phillip Ives, were able to bringEdward home to join his two older siblings.

Now a healthy six-month old, Edward has an excellent prognosis and isunlikely to need further hospitalizations for SVT although he is being closelymonitored to see if the irregular heartbeat returns.

"It's made me appreciate all the small things about my children," said ClaireIves, who is planning to run a half-marathonto raise awareness about neonatal SVT. "It's the best thingever to bring him home."

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