NATALIE ALLEN, CNN ANCHOR: Some people are asking if the stress of campaigning for his son could have caused Bush's irregular heartbeat. CNN medical correspondent Holly Firfer takes an in-depth look at what triggers the condition and the risks involved when it develops.</s>HOLLY FIRFER, CNN MEDICAL CORRESPONDENT (voice-over): Atrial fibrillation is one of the most common forms of an irregular heartbeat. It happens when the upper chamber of the heart stops beating normally and starts to quiver or speed up. The lower chamber, which beats in rhythm with the upper chamber, gets confused and the heart starts to pump too quickly.</s>DR. STEVE MANOUKIAN, CARDIOLOGIST: In general, when someone goes into atrial fibrillation, they tend not to feel well. It's unusual for them to pass out.</s>FIRFER: The heart feels like it's racing, there may be shortness of breath, dizziness, sweating, chest pains and even faintness during a-fib.</s>MANOUKIAN: For some people, atrial fibrillation can be a one- time occurrence. For other people it can be recurrent.</s>FIRFER: But it can be chronic. Preexisting conditions such as high blood pressure, weak heart muscles and leaky valves can cause atrial fibrillation.</s>MANOUKIAN: Patients who have thyroid disease or hyperthyroidism have an over stimulation of their heart, and it causes, under stress, the heart to potentially go into this atrial fibrillation rhythm.</s>FIRFER: If chronic atrial fibrillation is left untreated, blood cannot flow through the chambers of the heart evenly. Clots can form and travel throughout the body, putting the patient at risk of stroke or heart failure. Doctors can apply an electric shock to the heart to regulate the heartbeat, a procedure called cardioversion, or use drug therapy. In some patients, a pacemaker may be used to maintain a normal heartbeat. In any case, if atrial fibrillation is caught early, it does not have to be life-threatening. Holly Firfer, CNN.
Heart Fibrillation: An In-Depth Look at the Triggers and the Risks