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President George W. Bush’s recent heart problems may have been much more serious than previously thought.

In August, the 67-year-old former president underwent a procedure to have a stent inserted, after a routine stress test discovered a blockage in one of his arteries. But now, the National Journal quoted a source close to the president, saying the blockage was actually quite severe.

"He was more than 95 percent occluded," an authoritative source told the National Journal. "With a blockage like that in a main artery you're supposed to die. He was pretty lucky they caught it."

A few weeks after Bush's surgery, Fox News Medical A Team member, Dr. Marc Siegel, also noted that the blockage was very severe.

“Doctors who have stated that his cardiac work-up was unnecessary are doing what bad TV experts do all the time — speculating wildly without enough information," Siegel wrote in an op-ed for USA Today. "In Bush's case they are completely wrong.”

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    According to Dr. Kevin Campbell, a cardiologist for the University of North Carolina, such a high amount of plaque buildup in the artery would have almost certainly led to a heart attack if doctors had not caught the blockage.

    “It’s a ticking time bomb,” Campbell, who did not treat the president, told FoxNews.com. “All that has to happen is that plaque has to rupture and completely block up the blood vessel.  When you have a blockage like he did…he most certainly would have had a heart attack in his lifetime if he hadn’t had that (procedure) done.”

    The news of Bush’s blocked artery came as somewhat of a surprise, since the former president is known to exercise regularly and is considered to be in great shape. However, Campbell said other factors may have led to the blockage.

    “Genetics does play a part,” Campbell said.  “Even though you can be the healthiest person in the world, you still may have high cholesterol or you may have a family history of heart disease.  He’s doing everything right in overcoming any genetic predisposition, but a lot of heredity goes into it.”

    According to Freddy Ford, a spokesman for the office of George W. Bush, the procedure was performed successfully without complication.

    “He is grateful to the skilled medical professionals who have cared for him. He thanks his family, friends, and fellow citizens for their prayers and well wishes. And he encourages us all to get our regular check-ups," Ford said in a written statement.

    During a stent procedure, a small mesh tube is inserted in the blocked artery through the use of a catheter.  Once inside, a balloon located within the stent expands, smashing the plaque against the walls of the artery and clearing out the blockage.  The stent then remains in the blood vessel and acts somewhat like scaffolding, keeping the artery open and restoring blood flow.

    Campbell said that Bush’s case is a great example of how routine testing can save a person’s life.

    “His doctors understood they needed to fix it before a heart attack, and that’s great preventative medicine,” Campbell said.