New data show that defibrillators programmed to wait longer to deliver therapy are safe for secondary prevention ICD patients


Medtronic has announced the results from the first prospective randomised clinical trial to show that Medtronic implantable cardioverter defibrillators (ICDs) can safely extend detection times before triggering therapy in secondary prevention patients. The results of the PainFree SST sub-study, unveiled as a late-breaking presentation at the Heart Rhythm Society’s 35th Annual Scientific Sessions (7–10 May; San Francisco, USA), demonstrate that physicians can choose to programme ICDs with delayed detection interval settings without compromising safety for high-risk patients.

Previous studies of prolonged interval detection have focused on primary prevention patients, who have not experienced an episode of sudden cardiac arrest but are at risk. Secondary prevention patients are at higher risk for a deadly irregular heart rhythm, having already experienced an episode of sudden cardiac arrest.

“The results of this study are important for secondary prevention patients, who often are treated with more aggressive ICD programming to address arrhythmic events as quickly as possible,” says Laurence D Sterns, cardiologist at Royal Jubilee Hospital in Victoria, British Columbia, Canada. “Previous studies have demonstrated that devices programmed to wait longer to deliver therapy do not increase the risk of fainting episodes among primary prevention patients, and now we know the same strategy can be safely used in more patients, even patients at increased risk based on their disease progression.”

Patients in the PainFree SST trial received Medtronic Protecta ICDs with SmartShock Technology, an exclusive shock reduction algorithm that enables the devices to better differentiate between dangerous and harmless heart rhythms. Secondary prevention participants were randomised into two groups: an extended interval detection group (30/40 intervals) and a standard interval detection group (18/24 intervals).

The study found that longer detection intervals did not significantly increase the risk of fainting episodes among secondary prevention patients after one-year of follow-up, establishing the safety of this programming strategy among higher-risk patients. The number of patients with syncope events within 24 hours of a device-detected arrhythmic event was similar between groups. Patients programmed to receive standard interval detection were 98% free of arrhythmic fainting episodes, compared to 96.9% of patients programmed to receive prolonged interval detection.

The study results also revealed that the portion of patients receiving inappropriate shocks, or unnecessary therapy delivered in response to benign arrhythmias or electrical noise sensed by the device, was low and not different between groups. After one year, only 1% of patients in the standard detection group and 1.3% of patients in the extended interval detection received inappropriate shocks. These results further demonstrate the efficacy of Medtronic ICDs with SmartShock Technology to deliver life-saving therapy only when appropriate.