On Monday, Vice President Dick Cheney went to see his doctor about a cold and was told that he had an irregular heart rhythm and needed an electric shock to try to make his heart rhythm regular again. Fortunately, it worked.
Two questions come to mind: is this unusual? And how worrisome is it, given that the vice president has had heart problems for many years?
Doctors know that what happened to Vice President Cheney is actually a pretty common scenario. A patient comes in for some symptom unrelated to the heart, or perhaps just a general checkup. While taking the patient's pulse and listening to the heart, the doctor detects an irregular heart rhythm, gets an EKG, and discovers that the patient has a particular kind of irregular heart rhythm—or "arrhythmia"—called atrial fibrillation.
What is atrial fibrillation? Normally, the heart's upper chambers (the atria) pump about 60 to 90 times a minute at rest, with a regular rhythm. With atrial fibrillation, the atria beat much faster, and the rhythm is irregular. (Instead of "pump … pump … pump … pump," the heart goes "pump … pump …… pump pump … … pump.")
Atrial fibrillation affects some 2.2 million Americans, many of them elderly. About one out of every 10 people over the age of 80 experiences atrial fibrillation. Atrial fibrillation is not necessarily a sign of serious heart disease. Indeed, President George H.W. Bush had a brief episode of atrial fibrillation in 1991, at a time when he had an overactive thyroid but no underlying heart disease.
Atrial fibrillation does not always cause symptoms. A person may become aware of it only when his or her pulse is checked by a clinician or an EKG is performed, as news stories indicate happened with Vice President Cheney yesterday. More commonly, people with atrial fibrillation feel a fluttering sensation in the chest or an awareness that the heart is racing. Other symptoms include shortness of breath, dizziness or a lightheaded feeling, weakness, fatigue and sometimes chest pain.
Today doctors have many ways to treat atrial fibrillation. The first decision is whether to restore the heart rhythm to a normal pattern, called sinus rhythm, or to let the patient stay in atrial fibrillation using medications to slow the heart rate to about 80 beats per minute.
Vice President Cheney and his doctors opted for the quickest way to get his heart rhythm back to sinus rhythm. His heart doctors arranged for him to be sedated and then used an electrical impulse that short-circuits the atrial fibrillation, giving the heart a chance to right itself. Doctors call this electrical cardioversion.
In general, atrial fibrillation is not a dangerous rhythm. But it does increase the risk of stroke. When the heart's left atrium fibrillates, it doesn't pump blood effectively. As a result, blood pools inside this chamber. Tiny clots—some no bigger than a pencil tip—may form in this stagnant blood. If a clot breaks loose, it can travel through the lower chamber of the heart and out to the other parts of the body. Even a tiny clot can cause a major stroke if it travels to the brain.
To prevent clots from forming in the atria, patients take an anticlotting medication such as warfarin (Coumadin). Even for patients who get cardioverted back to normal sinus rhythm, doctors usually want them to take warfarin for a few weeks prior to the procedure. Since Mr. Cheney was cardioverted right away, he probably was already taking warfarin or an alternative anticlotting drug.
How worrisome is this arrhythmia, given the vice president's past heart disease? Cheney undeniably has very serious heart disease: his coronary arteries were narrowed enough to give him his first heart attack when he was in his 30s. He's had a total of four heart attacks, which have injured a lot of his heart muscle. So he has both injured arteries feeding the heart muscle, and injured heart muscle.
The past heart muscle injury has caused his heart to periodically develop the most dangerous type of arrhythmia: ventricular arrhythmias. Unlike atrial fibrillation, ventricular arrhythmias involve the heart's two lower chambers, the ones that do most of the work of pumping blood around the body. Some ventricular arrhythmias can cause sudden death. For this reason, the vice president has an implantable defibrillator that detects when a ventricular arrhythmia occurs and shocks the heart back into a normal rhythm. Such devices have been widely available just for the past decade, and have been life-saving for many people.
Neither the brief period of atrial fibrillation nor the small shock given to restore normal rhythm will damage the vice president's heart. The atrial fibrillation may return again—it often does—but if it is caught and treated early should not cause major problems. Most of the treatments are effective. Like the implantable defibrillator used to prevent death in case the vice president suffers from the more dangerous ventricular arrhythmia, they are among the many major medical advances made during our lifetime that now allow patients like Cheney with serious heart problems to live longer and fuller lives.