Cardiac ablation and mapping 

STOP AF First trial

This study evaluates the safety and effectiveness of the Medtronic Arctic Front™ cryoablation system as an initial first-line rhythm control treatment.

Several healthcare professionals in white coats and scrubs sitting at a table with beverages and laptops discussing together

Study purpose and design

The STOP AF First trial1,2 is a prospective, multicenter, randomized study evaluating whether Arctic Front™ cryoballoon ablation is superior to antiarrhythmic drug (AAD) therapy as a first-line rhythm control treatment in patients with symptomatic paroxysmal atrial fibrillation (PAF).

A total of 225 drug-naïve patients (AAD for < 7 days) with symptomatic PAF aged 18–80 were enrolled at 24 centers in the United States. The Arctic Front Advance™ cryoballoon was used to establish pulmonary vein isolation (PVI) and the drug therapy arm received a class I or III AAD therapy.

Arctic Front cryoballoon encircled on a gray background

Key findings


Two circles, each with ten illustrated people inside — one circle has seven people highlighted and one has five people highlighted

74.6% freedom from acute procedural failure or atrial arrhythmia recurrence 12 months post-ablation.

By modified intention-to-treat analysis (which included all randomized patients who initiated therapy), freedom from primary efficacy failure was:

74.6% in the cryoballoon arm, 45.0% in the AAD arm (p < 0.001)


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Low complication rate. Primary safety events occurred in two subjects (estimated 12-month rate: 1.9%, 95% CI: 0.5–7.5%) in the cryoballoon arm. Since the upper bound of the 95% confidence interval was below the prespecified performance goal, the primary safety endpoint was met.

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Quality-of-life outcomes

A significant improvement (p < 0.01) in subjects’ quality of life was observed at 12 months for those in the ablation group as assessed with the AFEQT and EQ-5D questionnaires. Improvements in atrial fibrillation-specific quality of life at 12 months assessed using the AFEQT were larger with Arctic Front™ cryoballoon ablation versus AAD therapy.


A meta-analysis of three randomized controlled trials demonstrates cryoballoon ablation, compared to AADs, as an initial first-line therapy is associated with incremental benefits, including:

  • 39% relative reduction in the risk of atrial arrhythmia recurrence3
  • 8.32 points larger improvement in AFEQT score on average3
  • 29% relative reduction in healthcare utilization3
  • 62% relative reduction in hospitalization3

No significant difference in the rate of serious adverse events.


Watch the scientific exchange video.

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Log in to Medtronic Academy to view the video.

Learn more about the impact of Arctic Front™ cryoballoon ablation as initial treatment for atrial fibrillation featuring a discussion on a state-of-the-art review and meta-analysis demonstrating incremental benefits of Arctic Front™ cryoablation compared to AADs.

  • Jason Andrade, M.D.
  • Hugh Calkins, M.D.
  • Andrea Russo, M.D.
  • Jaret Tyler, M.D.

Endpoint definitions

Primary efficacy endpoint

Treatment success at 12 months

Treatment failure is defined as:

  • Acute procedural failure*
  • Any subsequent AF surgery or ablation in the left atrium (including those performed during the blanking period)
  • Any of the following after the 90-day blanking period:
    • Documented AF/AT/AFL
    • Cardioversion
    • Class I or III AAD use*

Primary safety endpoint

Composite of prespecified procedure- and system-related serious adverse events evaluated in the cryoballoon catheter ablation arm (prespecified performance goal: failure rate < 12%)

Primary safety events include:

  • Within 7 days:
    • Transient ischemic attack
    • Stroke
    • Major bleeding
    • Myocardial infarction
    • Vascular complication
  • Within 30 days:
    • Significant pericardial effusion
  • Within 12 months:
    • Symptomatic pulmonary vein stenosis
    • Atrial-esophageal fistula
    • Unresolved phrenic nerve injury at 12 months

Study population

Key inclusion criteria

  • A diagnosis of symptomatic PAF with the following documentation: 
    • Physician’s note indicating recurrent self-terminating AF or PAF
    • Any ECG-documented AF within 6 months prior to enrollment
  • Age 18–80

Key exclusion criteria

  • History of AF treatment with class I or III AAD, including sotalol, with the intention to prevent an AF recurrence. However, patients pretreated with above AAD for less than 7 days with the intention to convert an AF episode were allowed.
  • Prior left atrial ablation or left atrial surgical procedure
  • Prior persistent AF (continuous AF > 7 days)
  • Left atrial diameter > 5.0 cm
  • NYHA class III or IV congestive heart failure and/or known left ventricular ejection fraction (LVEF) less than 45%

Study recurrence monitoring



1 month

3 months

6 months

12 months

Patient-activated ambulatory ECG (TTM; weekly and when symptomatic    

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12-lead ECG

24-hour continuous ambulatory ECG




Educational resources on
Medtronic Academy

Access detailed product information, including spec sheets, videos, and presentations.


Treatment arm only.



Wazni OM, Dandamudi G, Sood N, et al. Cryoballoon ablation as initial therapy for atrial fibrillation. N Engl J Med. 2021;384(4):316–324.


Wazni OM, Dandamudi G, Sood N, et al. Cryoablation versus antiarrhythmic drug therapy as initial treatment for atrial fibrillation: impact on quality of life. J Am Coll Cardiol. 2021;77(18_Supplement_1):225–225.


Andrade JG, Wazni OM, Kuniss M, et al. Cryoballoon Ablation as Initial Treatment for Atrial Fibrillation: JACC State-of-the-Art Review. J Am Coll Cardiol. August 31, 2021;78(9):914–930.