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| Learning Labs: Electrophysiology |
Long QT Syndrome and the Resting Membrane Potential:
From Microscopic to Macroscopic
A case of near SUDDEN DEATH in a teenager
Kara, a 14 year-old girl with a history of seizures, was finishing her first lap at spring track practice when she slowed down and fell to the ground. Her friends and the track coach had seen her have seizures before and assumed this was another. However, Kara did not recover within seconds to minutes, as she had on previous occasions, and she began to turn blue. Luckily, a maintenance man had seen her collapse from across the field and called 911. The Fire Department ambulance arrived within minutes and found Kara unresponsive, not breathing and without a pulse. They hooked their defibrillator up to her chest and found she was in ventricular fibrillation - a chaotic heart beat that so disturbs the contraction of the heart that no blood is pumped. Kara required two cardiac shocks from the defibrillator and intravenous epinephrine and other drugs to get her heart going again. After 20 minutes of resuscitation she still had not taken a breath on her own. The medics were pessimistic about her recovering from this cardiac arrest as they loaded her into the ambulance for transport to the hospital. Just as they lifted her, Kara took a gasping breath - a sign that she might recover after all. Knowing Kara faced a long recovery period requiring sophisticated care at a major medical center, her medical condition was stabilized, and, while still in a coma, she was transported to Maine Medical Center. |
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How a case of near sudden death is evaluated
Sudden death strikes without warning as result of an irregular heartbeat. It usually occurs in someone who appears to be healthy and is often fatal. While Kara had been diagnosed with epilepsy at age 8, epilepsy is only rarely associated with sudden death. In addition, Kara's collapse was associated with ventricular fibrillation which is a very unusual abnormal rhythm of the heart in a teenager. Her physicians focused on the causes of ventricular fibrillation as they sought the reason for Kara's collapse. By examining her electrocardiogram, or ECG (which measures the electrical activity of the beating heart), they discovered Kara had a prolonged interval during many of her heart beats between the beginning of the Q-wave and the end of the T-wave. This suggested she had a problem called Long QT syndrome (LQTS). It also suggested that she may not have had epilepsy in the first place, and all of her seizures may have been caused by other, less severe, episodes of ventricular fibrillation. |
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Electrophysiology Labs at ScienceWorks for ME provide hands-on experience with understanding the electrical activity of cells. Computer simulations of recordings from excitable cells offered by ScienceWorks for ME can be used to illustrate the principles behind the resting membrane potential and the action potential. |
Photographs and diagrams reprinted with permission.
To schedule a visit for your biology class, contact by e-mail
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Electrophysiology Labs at ScienceWorks for ME
Links about Long QT syndrome
Key to the diagnosis of Long QT syndrome |
