In a study presented at the 1998 American Heart Association meetings in November, the UCSF researchers showed for the first time that Ibutilide can safely and effectively stop atrial fibrillation in patients with WPW. Atrial fibrillation was induced in the controlled environment of UCSF Stanford Health Care's electrophysiology (EP) labs during EP study in 14 patients with WPW. Intravenous Ibutilide stopped the atrial fibrillation within twenty minutes of the infusion in 13 of the 14 patients.
In a second ongoing prospective study, the researchers are examining the mechanisms of how Ibutilide works. To date, eighteen WPW patients ranging in age from 4 to 75 years old have been given Ibutilide during EP study. The researchers have identified Ibutilide's effects on conduction over the abnormal accessory pathway.
Ibutilide has previously been shown to effectively stop atrial fibrillation in adults only. The UCSF studies have included children as well, including Shannon Koehler, a boy with WPW. Koehler was given Ibutilide when he was nine years old and developed atrial fibrillation during an EP study. The Ibutilide allowed the electrophysiologists to continue their work and safely eliminate Koehler's two accessory connections.
Normally, electrical impulses flow in a controlled rhythm from the upper chambers of the heart (atria) to the lower chambers (ventricles), causing the heart to contract and pump blood at a steady pace. The accessory pathway found in WPW patients allows electrical impulses to return back to atria rapidly and acts as a "short circuit," which can lead to tachycardia or atrial fibrillation.