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10 May 1999
UCSF CARDIOLOGISTS ARE REVOLUTIONIZING TREATMENT FOR ATRIAL FIBRILLATION
Although many heart arrhythmias have been curable for over a decade, atrial fibrillation, the most common heart rhythm disturbance in the United States, has until recently been relegated to largely ineffective treatments with undesirable side effects. Now new knowledge of what causes atrial fibrillation (AF) is revolutionizing the way cardiologists treat this abnormal rhythm estimated to effect more than two million Americans.
Atrial fibrillation is an irregular rhythm of the heart caused by erratic electrical impulses that interfere with the heart’s normal timing of contractions. Cardiologists have thought that numerous irregular impulses similar to small eddies swirl around the upper chambers of the heart and cause AF. Only recently have heart rhythm specialists begun to recognize that in many patients, there is a single point of electrical firing causing the irregular beats.
“Think of dropping pebbles onto a smooth pond,” said Michael D. Lesh, MD, associate professor of medicine and director of the University of California San Francisco’s Atrial Arrhythmia Center, part of UCSF Stanford Health Care. “If you drop them fast enough, the surface of the pond will be quite turbulent. But if you remove the source of the pebbles, the turbulence stops.”
To remove the focus of the abnormal impulse, a research team at UCSF led by Lesh is applying a decade-old technique in a new way. UCSF electrophysiologists have been successfully eradicating other kinds of heart arrhythmias with a procedure called radiofrequency catheter ablation for the past ten years, but have only started using the procedure to treat AF since 1998. Catheter ablation, a technique pioneered at the UCSF Electrophysiology section department, uses a pinpoint of heat inside the heart to burn, or ablate, the source of turbulence leading to AF.
“This is a great example of how advances in our understanding of the cause of a disease can lead to new and better forms of therapy,” said William Grossman, MD, professor of medicine and chief of cardiology at UCSF.
Although catheter ablation for this particular heart rhythm disturbance is still considered investigational, its potential to offer enormous relief plus its rising success rate has already placed it in high demand. While AF is not typically life threatening, it often causes palpitations, weakness, fatigue, chest pain, and shortness of breath, significantly reducing a person’s quality of life. The most serious potential complication is the increased risk of stroke, necessitating the use of blood-thinning medications which can lead to problems of excessive bleeding, Lesh said. Because of the frequency of AF, researchers have been trying to understand its causes for more than a century.
“This is a fantastic time to be in this field,” said Kyoko Hattori, RN, BSN, clinical nurse coordinator of the UCSF Atrial Arrhythmia Center. “For the first time in history there’s a potential cure for atrial fibrillation, not just a treatment that gives partial relief.”
Lesh and his associates at UCSF have treated over 50 patients suffering from atrial fibrillation using catheter ablation, including Patricia Snyder, MD, who had been suffering from this arrhythmia for 21 years before having the procedure. “It has been quite exhilarating, redesigning my life to include biking, wind surfing, and a glass of rich, red wine while watching the sunset,” she wrote in a letter of appreciation. “I have truly been reborn thanks to your efforts.” Snyder had the procedure almost a year ago and has not experienced a single episode of palpitations since, said Peter Guerra, MD, a senior electrophysiology fellow at UCSF and a member of Lesh’s team.
In a proper functioning heart, the upper chambers beat first followed a split second later by the lower chambers, all coordinated by electrical impulses emitted between 60 to 100 beats per minute. With AF, numerous irregular impulses cause the upper chambers to beat up to 350 times per minute and override the normal rhythm. This causes the upper chambers to beat so rapidly they quiver, or fibrillate, said Lesh. Some of these abnormal signals pass to the lower chambers and cause irregular pumping in the ventricles. The overall result is uncontrolled heartbeats which lead to characteristic symptoms such as fatigue and palpitations.
“It is our understanding that at least some, if not all, atrial fibrillation is initiated by an abnormal trigger that sets off the arrhythmia,” said Lesh. “If we target this point of origin and eliminate it, the arrhythmia will stop.”
Cardiologists guide small tubes into a patient’s heart and deliver a pinpoint amount of radio wave energy that abolishes a pea-size piece of heart tissue. If successful, ablation destroys the abnormal electrical circuits and a regular heartbeat is restored.
Despite some encouraging results, the current procedure is only about 50 percent successful, Lesh said. Some people with AF have more than one location in the atrium that sends out abnormal impulses, and finding and eliminating multiple sites is not practical. Another problem is that the abnormal impulse may not fire during the procedure, making it impossible to locate. A new catheter designed by Lesh that uses sound waves rather than radio waves to locate the impulse may end these limitations. If successful, the catheter could reduce the procedure time from the five or more hours it now takes to perhaps an hour or less, said Lesh. Clinical trials of the new catheter should begin later this year.
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