WASHINGTON, DC — March 1, 2010 – Analysis of ICD patients enrolled in four different trials found patients with life-threatening ventricular arrhythmias (VA) treated only with antitachycardia pacing (ATP) have higher survival rates than VA patients who experienced at least one shock-treated episode. According to research published in the March edition of the HeartRhythm Journal , the official journal of the Heart Rhythm Society, 80.2% of VA episodes were successfully treated with ATP-only therapy from an ICD.
The multi-trial analysis evaluated 2,135 patients enrolled in four trials incorporating ATP to reduce shocks; trials included PainFREE Rx, PainFREE Rx II, EMPIRIC and PREPARE. All patients had ICDs implanted less than four weeks prior to enrollment and device programming was standardized in each study with some differences between studies. The completely unique data set of this research method compared the effects of ATP therapy versus shock therapy in ICD patients. Previous studies focused primarily on the effects of shocks only.
In the 2,135 patients enrolled, a total of 3,934 VA episodes were treated and 1,339 were fast ventricular tachycardia (FVT) episodes. FVT was the only type of VA episode treated with both ATP and shocks; therefore, the only type of VA available to compare mortality effects of ATP and shock therapies for similar VA type. More than 82% of the FVT episodes were terminated using ATP and did not increase VA episode mortality risk; whereas, shocked FVT increased mortality risk by 32%.
“While there is absolutely no doubt that ICD shocks for lethal VA prolong life, this experiment does introduce the possibility that electrical therapy type may influence mortality risk in some ICD patients,” said lead author, Michael O. Sweeney, M.D., Cardiac Arrhythmia Service, Brigham and Women’s Hospital in Boston, Mass. “Historically, near-total reliance on shocks for terminating VA probably underestimated the survival benefit of ICDs and we should consider changes in device programming as well as additional treatment strategies to reduce shocked VA episode burden.”
Life-saving shocks contain an inherent paradox. Shock strengths sufficient to terminate life-threatening VA, like ventricular fibrillation (VF), cause myocardial damage, whereas weaker shocks cause less damage but do not terminate VF. ICD shocks for life-threatening VA clearly prolong life in most patients; however, strategies to minimize shocks with ATP, shorten shocked episode durations, and reduce VA episode burden through drugs and catheter ablation may further improve survival in ICD patients.
“There are several readily available strategies to reduce VA episode and shock therapy burden overall, and increasing the use of these strategies may improve long-term survival in ICD patients,” said Dr. Sweeney.