Atrial Fibrillation Can Be A Family Affair
By Michael Lasalandra
Beth Israel Deaconess Medical Center Correspondent
Researchers are learning that
atrial fibrillation may have a genetic or familial component in as many as 30 percent of cases.
This condition -- irregular heartbeat episodes stemming from faulty electrical signals in the heart -- is said to afflict as many as 5.1 million Americans. Symptoms include shortness of breath, fatigue, chest discomfort, light-headedness and anxiety. If uncontrolled, the condition can lead to a debilitating or fatal blood clot or stroke.
"Increasingly, we are recognizing there is a strong family association with AF," said
Dr. Charles Haffajee, a cardiac electrophysiologist and director of device trials and the electrophysiology network at the
CardioVascular Institute at Beth Israel Deaconess Medical Center.
Recent studies suggest that up to 30 percent of all people with AF may have a history of the condition in their family. Most cases of atrial fibrillation are not caused by mutations in a single gene.
"More and more we are recognizing genetic predispositions in families with AF," said Dr. Haffajee. "It's not one gene. There are many genes that can carry risk. In a particular family, it may be one gene. The earlier in life that you suffer from AF, the more likely it is familial, especially when no heart disease is present."
Still, the treatment does not change, he noted. "We can't change your genes," he said.
However, if family members have been diagnosed with AF, then others in the family who may be having palpitations should be checked out. "We want to prevent you from having a stroke," he said.
The main thing is to make sure that if palpitations are occurring, tests are performed to see if AF is the cause. Then, patients who are diagnosed may need to go on a blood-thinner, usually Coumadin® or warfarin, to prevent blood clots that can lead to stroke, Dr. Haffajee said.
A big problem is that only about half of patients who are at risk of stroke are on Coumadin®, he said. And many who are on the drug are not taking the proper dose, as the drug is not easy to regulate. New blood thinners on the horizon may make that easier to deal with, he said.
But even if one has a gene linked to AF, it doesn't necessarily mean that person will suffer from the condition.
"You don't need a genetic analysis just because your father had AF," said Dr. Haffajee.
However, he noted that there is a lot of research being done in the field and that things may change.
For example, researchers at the Mayo Clinic reported in 2006 they had discovered a genetic mutation causing electrical activation of the heart muscle and AF. The finding provided new insight into a previously unrecognized mechanism for electrical instability in the human heart. The discovery was the first to identify a specific genetic mutation of the ion channel gene KCNA5 that leads to a disease called a channelopathy.
The Mayo study used genetic analysis to identify a mutation in the DNA of a sibling pair with AF in the absence of known risk factors for the disease. This genetic anomaly was not present in the individuals without AF.
The atrial fibrillation mutation occurred in the KCNA5 gene, which produces a key hart protein known as Kv1.5. Loss of Kv1.5 function made the atria -- the upper pumping chambers of the heart -- more vulnerable to stress-induced chaotic rhythms, and AF.
To validate the finding, the researchers reproduced the disease features at the molecular, cellular and organism levels and corrected the mutation, restoring the defective current.
In time, genetic research may identify what properties in a patient predispose him or her to AF. Once this has been determined, a personalized therapy can be developed for each patient based on their underlying genetic predisposition, according to Dr. Dan Roden of Vanderbilt University.