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Medtronic has unveiled results from the PainFree SST clinical trial evaluating its Protecta implantable cardioverter defibrillators (ICDs) with SmartShock technology, a shock reduction algorithm that enables the devices to better differentiate between dangerous and harmless heart rhythms.

Data from the PainFree SST study demonstrated that defibrillators programmed to wait longer to deliver therapy are safe for secondary prevention ICD patients with Medtronic SmartShock technology.

PainFree SST clinical trial is a prospective, randomised clinical trial that involved 2,790 patients at 126 international centres. Patients in the multi-centre trial received the Protecta ICDs with SmartShock technology.

Of the 2,790 patients, 786 had a secondary prevention indication and 705 consented to interval detection randomization. At baseline, 32% of the patients had atrial fibrillation and 33% had a history of syncope.

Secondary prevention participants were randomised into two groups, comprising an extended interval detection group and a standard interval detection group.

The sub-study results were assessed using a primary endpoint of one year of freedom from arrhythmic syncope, and secondary endpoints included time to first all-cause syncope, appropriate therapy and inappropriate shock.

According to Medtronic, the PainFree SST clinical trial 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 the extended interval detection and standard interval detection groups.

"We know the same strategy can be safely used in more patients, even patients at increased risk based on their disease progression."

Patients programmed to receive standard interval detection were 98% free of arrhythmic fainting episodes, compared with 96.9% of patients programmed to receive prolonged interval detection.

In addition, the study showed 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.

Only 1% of patients in the standard detection group and 1.3% of patients in the extended interval detection received inappropriate shocks after one-year.

Royal Jubilee Hospital in Victoria, Canada, cardiologist Dr Laurence Sterns said that 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.

"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," Dr Sterns said.

Medtronic claims that the PainFree SST clinical trial results further demonstrate the efficacy of its ICDs with SmartShock Technology to deliver life-saving therapy only when appropriate.

Image: Medtronic’s Protecta XT DR ICD with SmartShock technology. Photo: courtesy of Medtronic Inc.