Electrophysiology test may predict SCD risk
Investigators induce VT in CAD patients
Electrophysiology studies can help predict who is at risk for sudden cardiac death (SCD) and guide treatment to prevent a significant number of those deaths, researchers report. Information on their study was presented in May at the 20th annual scientific session of the North American Society of Pacing and Electrophysiology (NASPE) in Toronto.
Investigators for the Multicenter Unsustained Tachycardia Trial (MUSTT) evaluated more than 2,200 patients believed to be at high risk for SCD. Electrophysiology studies were conducted to determine whether sustained ventricular tachycardia (VT) could be induced in certain patients with coronary artery disease (CAD). Key results:
• Patients in whom VT could be induced were 1.4 times more likely to subsequently die than those in whom VT could not be induced.
• Among patients in whom VT could be induced, deaths were reduced by 27% in those who received therapy compared with those who received no therapy.
• Among patients who received therapy, deaths were reduced by 74% in patients treated with a defibrillator compared with patients treated with antiarrhythmic drugs.
• At five years, 32% of patients in whom sustained VT could be induced had died, compared with 24% of those who could not be induced.
Patients evaluated in MUSTT had a history of CAD combined with depressed function of the left ventricle of the heart and a history of spontaneous nonsustained VT. In patients in whom sustained VT could be induced, half were initially treated with antiarrhythmic drugs and half received no therapy. If electrophysiology studies showed that the initial drug therapy was not effective in preventing VT, patients received other drug therapies or were given a defibrillator. Of 2,202 patients enrolled in the study, sustained VT was induced in 767. Of these, a total of 704 were randomized, with 353 receiving standard drug therapy and 351 receiving no therapy. A total of 161 patients went on to receive defibrillator therapy.
Azimilide shows promise for PSVT and SCD
At the same meeting, a study was presented that showed that azimilide, an investigational antiarrhythmic drug manufactured by Procter & Gamble Pharmaceuticals, significantly reduced the risk of recurrence in patients with symptomatic paroxysmal supraventricular tachycardia (PSVT).
"For years, radio frequency ablation has been the standard of care. However, noninvasive drug therapy is preferred by many physicians and patients," said Richard Page, MD, a lead study investigator from the University of Texas Southwestern Medical Center in Dallas. "Azimilide showed potential as a valuable addition to the range of drug therapies currently available to treat PSVT." (See the news brief on ablation in Cost Management in Cardiac Care, June 1999, p. 70.)
The studies showed that patients on placebo had a 135% greater risk of a symptomatic arrhythmia recurrence vs. patients treated with azimilide. On average, patients on azimilide were 60% more likely to be free of a symptomatic occurrence on any given day as compared to patients on placebo.
More than 130 patients were treated with once-daily oral doses of 100 mg, 75 mg, or 35 mg of azimilide or placebo and tracked over six to nine months. The 100 mg dose was found to have statistically significant and clinically important antiarrhythmic effects.
Azimilide is generally well tolerated, the most commonly reported side effect being headache. It is the first antiarrhythmic agent found to effectively block both the slow and fast potassium channels in the heart, and it significantly prolongs the symptomatic recurrence of atrial fibrillation. Azimilide is also being studied to understand its potential role in the prevention of SCD in high-risk patients after a heart attack.
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