You are here :

Data from the STOP AF (Sustained Treatment of Paroxysmal Atrial Fibrillation) clinical trial shows superiority over anti-arrhythmic drugs

STOP-AF is the first and largest, randomized, controlled clinical trial assessing the effectiveness and safety of the Medtronic Arctic Front® Cardiac CryoAblation Catheter System when used to treat patients with drug refractory paroxysmal atrial fibrillation (PAF). Outcomes on all patients were assessed through 12-months of follow-up.
Initial Study Results

The clinical study initial results were presented at the American College of Cardiology Late Breaking Clinical Trial on March 15, 2010.

All primary safety and effectiveness endpoints were met.

- Primary Effectiveness End Point: Treatment Success
o Treatment Success = 69.9 percent for cryoablation patients vs. 7.3 percent for AF drug patients
o Treatment success was defined as Acute Procedural Success (APS) and freedom from Chronic Treatment Failure (CTF)
o APS was defined as demonstration of electrical isolation in three or more pulmonary veins at the conclusion of the first cryoablation procedure. 98.2 percent of cryoablation patients achieved APS.
o CTF was defined as the occurrence of detectable AF after a 90-day blanking period. CTF also included the occurrence of an AF intervention other than a cryo reablation during the blanked follow up period, or the use of a non-protocol AF drug anytime through the 12-month follow up.

- Primary Safety End Points: Cryoablation Procedure Events (CPEs) in cryoablation group and Major Atrial Fibrillation Events (MAFEs) in both study groups
o Both primary safety outcomes were met
o Cryoablation patients with one or more Cryoablation Procedure Events (CPEs) was 3.1 percent with a one-sided 95 percent upper confidence bound of 6.3 percent, which was significantly less than the 14.8 percent pre-specified upper confidence bound (p < 0.001).
o 96.9 percent of cryoablation patients were free from MAFEs, compared to 91.5 percent of AF drug patients (p < 0.001, non-inferiority).

Medtronic Arctic Front Cardiac CryoAblation Catheter System
The Medtronic Arctic Front Cardiac CryoAblation Catheter System is an ablation system that uses cryoablation, or freezing technology. A coolant is released into the catheter’s balloon to freeze and ablate the tissue; freezing helps the balloon maintain contact with the tissue. The Medtronic Arctic Front Cardiac CryoAblation Catheter System is designed to be used with fluoroscopy and does not require the use of complex, three dimensional electroanatomical mapping systems.

The technologies used in the STOP AF trial include:
- The Arctic Front Cryocatheter, which inflates and fills with coolant to ablate the tissue where the pulmonary veins enter the left atrium;
- The FlexCath® Steerable Sheath, which helps deliver and position the cryocatheter in the left atrium;
- The Freezor® MAX Cardiac CryoAblation Catheter, which is a single‐point catheter used to provide additional ablations, as needed; and
- The CryoConsole, which houses the coolant, electrical and mechanical components that run the catheters during a cryoablation procedure.

To date, more than 9000 patients have been treated worldwide with the Arctic Front cryocatheter. The Arctic Front® Cardiac CryoAblation Catheter System is commercially available for use in Europe and certain other countries outside the United States and is under investigational use in the United States.

The STOP AF study was sponsored by Medtronic CryoCath LP. The Principal Investigator was Dr. Douglas Packer of the Mayo Clinic in Rochester, Minnesota.