Diagnosing Inherited Arrhythmias
MADISON - Gene mutations lurk in secret, sometimes taking decades to reveal. When they trigger, the consequences for patients can be lethal—sudden, unexplained cardiac death in otherwise apparently healthy young people.
While inherited arrhythmias are somewhat rare—experts estimate that only one in 5,000 individuals has the most common form of the disease—they can carry a strong, traceable genetic component. In other words, if a person has an inherited arrhythmia, chances are good his or her relatives are at risk as well.
Tracking that genetic component and diagnosing arrhythmias before tragedy strikes is the main reason UW Health cardiologists Craig January, MD, PhD
and Kathleen Maginot, MD
have created the Inherited Arrhythmias Clinic at University of Wisconsin Hospital and Clinics. Once every week, Dr. Maginot, a pediatric cardiologist, and Dr. January, an adult cardiologist, become "genetic detectives."
"Traditional clinical electrophysiologists and cardiologists, particularly in the adult world, don't think about genetics the way we think about genetics," says January.
The UW Health Inherited Arrhythmias Clinic
is geared specifically toward the identification and treatment of the genetic-based mutations that predispose family members to arrhythmia-related deaths. Maginot and January hone in on the tiniest details of individual family histories, looking for clues and hints.
"It's not just asking a patient, 'Has there been a sudden death?'" says Dr. January, who has been studying inherited arrhythmias for much of his career.
"It's the way you ask it. We usually spend an hour with patients just trying to get their entire family history. It's a huge time commitment."
Today, geneticists have identified at least 10 inherited arrhythmia syndromes, and at least a dozen specific genes linked to their formation. The most well-known is long QT syndrome, a condition in which a cellular defect disrupts the heart's electrical rhythm, causing syncope, seizures, and even sudden death. With certain arrhythmias, a patient's electrocardiogram can appear normal, making the diagnosis trickier.
"These are usually younger patients who are really time bombs waiting to happen," say Drs. Maginot and January. "You can also have the gene mutation and not be affected clinically. Some people can live a normal life and never have an episode. Or you can have a one-month-old infant die from it. There's a huge spectrum."
Dr. January likens long QT syndrome and other inherited arrhythmias to the proverbial iceberg—what was once thought to be a condition affecting adolescents and young adults has been traced back to infants and forward to an older population. In fact, some cases of Sudden Infant Death Syndrome (SIDS) are likely due to long QT syndrome.
Inherited arrhythmia patients are commonly treated with medications and lifestyle changes, such as restrictions from competitive sports or avoiding certain over-the-counter and prescription medicines that can potentially trigger arrhythmias in vulnerable patients. An implantable cardioverter-defibrillator (ICD) may be necessary to detect a life-threatening arrhythmia and provide a shock to treat it.
"Years ago, we had no idea that some people who died carried the diagnosis of long QT syndrome," says Dr. Maginot. "It's exciting that we can identify these children and young adults early and make a difference in their lives."
Date Published: 02/29/2008