Cardiologists say Vice President Dick Cheney's episode of irregular heart rhythm will not likely affect his immediate health — but the condition could point to a worsening of his continuing heart problems.
Cheney's doctor detected his irregular heartbeat, technically known as atrial fibrillation, Monday morning when the vice president visited because of concerns over a lingering cough, believed to be from a cold.
The diagnosis was enough to send Cheney to George Washington University Hospital for a treatment called cardioversion, which is designed to shock the heart back into a normal rhythm. The procedure, which took place Monday afternoon and requires briefly placing the patient under general anesthetic, "went smoothly and without complication," according to a statement issued by Cheney's office.
"The Vice President has returned home and will resume his normal schedule tomorrow at the White House," Monday's statement reads.
Doctors agree that the irregular heartbeat poses little additional threat to Cheney's health.
"Atrial fibrillation, by itself, is not a very serious heart rhythm problem," says Dr. Doug Zipes, director emeritus of the cardiology division of the Indiana University School of Medicine.
Additionally, the cardioversion procedure did not likely put him in further danger.
"It's a very, very low risk procedure," says Dr. Kim Eagle, clinical director of the University of Michigan's cardiovascular center. "Almost always, we are able to effectively restore a patient's heart rhythm to a normal heart rhythm."
Still, cardiologists say the finding is not good news for Cheney.
"It is something that, if he was my patient, I would wish he didn't have," Zipes says. "Individuals with his heart disease history with atrial fibrillation do not do as well with their condition than those without atrial fibrillation."
Indeed, the irregular rhythm represents the latest link in a chain of heart problems for the vice president, a progression that began in 1978 with his first heart attack, which occurred when Cheney was 37.
Since then, the 66-year-old Cheney has weathered three more heart attacks — one in 1984, one in 1988, and one in 2000. He underwent quadruple bypass surgery in 1988, sustained two angioplasties on the blocked artery responsible for his fourth heart attack, and had an implantable cardioverter defibrillator, or ICD, installed in 2001, to regulate his heartbeat.
Some worry that this history could mean the vice president's heart troubles are getting worse.
"Development of atrial fibrillation is generally a negative event," says Dr. Sanjeev Saksena, director of the Cardiovascular Institute and arrhythmia service for Atlantic Health, adding that the condition has negative implications for the ventricles — the two lower chambers of the heart.
"It would imply that his ventrical function deteriorated, and the [atrial fibrillation] could further worsen it and cause more limitations in his exercise capacities and ability to function, and can, in turn, provoke further worsening of heart function," Saksena says.
Despite these concerns, the cardioversion Cheney underwent likely improved his condition — at least for the time being. Initial success rates for the procedure are high, with 75 percent to 93 percent of patients experiencing a normal heart rhythm afterward.
But for many patients, the effects of the treatment are only temporary; anywhere from one-quarter to one-half of patients relapse within a month of a successful procedure, and 70 percent to 90 percent experience atrial fibrillation again within a year.
And the treatment can be an uncomfortable one. Dr. David Haines, chief of cardiovascular medicine at Beaumont Hospital in Royal Oak, Mich., notes that the electric shock Cheney received through his chest is "the same shock as a person in cardiac arrest gets. A person in atrial fibrillation gets it to restore normal electrical activity."
Cardioversion carries risks of its own, though they are slight. Doctors likely treated Cheney with anticoagulants before the procedure — if he was not on them already — to lessen the chances that the procedure would have dislodged clots, which could have then travel through the bloodstream and led to stroke. Doctors likely also performed imaging tests of his heart to ensure that no clots were present.
"We know that individuals with atrial fibrillation are predisposed to clots and stroke," Zipes says, adding that doctors likely looked to anticoagulants, such as coumadin, to minimize these risks. The other potential problem, Zipes notes, is "the fast heart rate associated with atrial fibrillation.
"This is even more important to patients with defibrillators," he says. "Shocks can be delivered inappropriately because of the increased heart rate associated with atrial fibrillation."
Zipes says this increased heart rate is usually treated with drugs intended to slow the patient's heart rate. But he says that, more important than the immediate consequences, are the implications with regard to Cheney's overall heart health.
"The fact that he came in with a lingering cough, apparently from a cold, certainly could, instead, be a lingering cough from progressive heart failure," Zipes says.
The ABC News Medical Unit contributed to this report.