Antitachycardia pacing associated with better survival versus shock treatment

10 March 2010

MedWire News: Shock treatment of ventricular arrhythmia (VA) episodes in patients with implantable cardioverter defibrillators (ICDs) is associated with poorer survival than antitachycardia pacing (ATP) termination, indicates a meta-analysis of four trials.

The study found that patients with VA episodes and shocks have higher mortality, with around a 20% increase in mortality per shocked episode, than patients with neither VA episodes nor shocks, or those with VA treated with ATP only. Furthermore, the greater the number of VA episodes and shocks the higher their mortality.

The study include a total of 2135 patients enrolled in the PainFREE Rx, PainFREE Rx II, EMPIRIC, and PREPARE trials.

As reported in the journal Heart Rhythm, a total of 5376 spontaneous episodes were analyzed, of which 3934 were adjudicated VA.

Of these, most were potentially ATP-terminable ventricular tachycardia (VT; 58.2%) or fast ventricular tachycardia (FVT; 37.4%). As VT and ventricular fibrillation were treated by a single therapy type (ATP and shocks, respectively) the effect of therapy type could not be studied, whereas FVT was treated by primary shocks in 32% of episodes and by ATP only in 68%, allowing episode and therapy effects to be uncoupled.

Overall, 138 patients died over a mean of 10.8 months of follow-up. Older age, worse New York Heart Association class, and coronary artery disease were associated with increased mortality whereas remote myocardial infarction (more than 6 months previously) and beta-blocker use were associated with reduced mortality. Adjudicated VA episodes that received at least one shock were also independently predictive of death, at a hazard ratio of 1.2 per shocked episode.

ATP-terminated FVT did not increased episode mortality risk, whereas each shocked FVT was associated with a HR of 1.32 (p<0.0001).

Survival rates were highest among patients with no VA or ATP-only treated VA, at 93.8% and 94.7%, respectively, and lowest for shocked patients, at 88.4%.

“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,” commented lead author Michael O’Sweeney (Brigham and Women’s Hospital, Boston, Massachusetts, USA).

“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.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

Heart Rhythm; 7: 353-360