Former US vice-president, who recently had a heart transplant, worried that electronic pulse to cardiac device might kill him

The former United States vice-president Dick Cheney was so fearful of assassination by terrorists sending an electronic shock to his implanted heart defibrillator that he ordered doctors to fit a new device without a wi-fi capability.

The extraordinary admission comes in the 72-year-old's new book Heart: An American Medical Odyssey, in which he also reveals that two months after his 2001 inauguration he prepared a letter of resignation to President George W Bush that he carried with him almost constantly, which he could hand over if he felt his health deteriorating.

Cheney, a fiercely loyal deputy during both terms of Bush's administration, has suffered five heart attacks since the age of 37 and had a heart transplant last year. In an interview to support his book on the CBS show 60 Minutes, due to air on Sunday night, he describes his current health as "a miracle".

But it is Cheney's fear of assassination that will provide a major talking point from the interview and book, which was written in conjunction with his longtime cardiologist, Dr Jonathan Reiner.

A fictional vice-president in the hit US television drama Homeland was murdered by terrorists sending an electronic signal to his pacemaker, in an episode several years after Cheney had his device fitted, in June 2001. It was an alarming plotline, he said.

"I was aware of the danger that existed, I found it credible because I knew from the experience we had and the necessity for adjusting my own device that it was an accurate portrayal of what was possible," he said in the CBS interview.

Reiner said Cheney asked him in 2007 to remove the defibrillator and replace it with one that had no wireless capability.

"It seemed to be a bad idea for the vice-president of the United States to have a device that maybe somebody in the next hotel room or downstairs might be able to hack into," he said.

Cheney said his resignation letter was written as a precaution early in 2001, weeks after Bush took office and as he recuperated from an angioplasty to reopen an artery that surgeons had worked on four months previously.

"Basically what I did was I resigned the United States vice-presidency effective March 28th 2001," Cheney said, adding that Bush "was a little surprised but he thought it was a good idea."

The letter remained in an envelope with him throughout his terms of office and he said he was thankful never to have to deliver it.

Cheney insists his health issues never interfered with his decision making during his lengthy career in Washington politics, which began in 1968 as an aide to a Wisconsin congressman and saw him become chief of staff to President Gerald Ford as a chain-smoking 34-year-old in 1975. Even during the most stressful period of his time as vice-president, the terrorist attacks on the United States in September 2001 and their aftermath, he said his condition did not affect his thinking.

"No, not at all. I was as good as I could be given that I was 60-something years old at that point and a heart patient," he said. "I didn't think about my health. I was thinking about the problem we were dealing with."

Reiner, however, said he feared that Cheney would become another victim of the fateful day, revealing that tests on the morning of September 11 showed that the vice-president had hyperkalaemia, an elevated level of potassium in the bloodstream that can lead to cardiac arrest.

"Oh, great, the vice-president is going to die tonight from hyperkalaemia," Reiner said he recalled thinking as he watched a television round-up of the day's events.

Ultimately, Cheney said, a heart transplant last year saved his life, 20 months after he was fitted with a ventricular assist device that regulated his heartbeat as he waited. He said it transformed him from a sallow and very sick man who could walk only with a cane to a more robust and healthy character today. "I feel fantastic," he said.

Medical advances had helped him, he said, along with a little luck along the way. In the interview he tells of how Reiner once likened him to somebody who gets up late for work and drives to work with every set of traffic lights turning green just as he approached them.

"That's a pretty good description," Cheney said.