Cryoballoon based therapy is an established therapy for the treatment of (paroxysmal) atrial fibrillation. However, with the rapid evolution in cryoablation technique and its increased effectiveness, the risk of complications increases. Therefore it is of utmost importance to define the optimal duration of cryoballoon ablation time.The objective of the study is to assess the optimal ablation duration using the second generation cryoballoon for isolation of pulmonary veins in the treatment of atrial fibrillation.

Rationale Cryoballoon based therapy is an established therapy for the treatment of (paroxysmal) atrial fibrillation. However, with the rapid evolution in cryoablation technique and its increased effectiveness, the risk of complications increases. Therefore it is of utmost importance to define the optimal duration of cryoballoon ablation time.

Objective To assess the optimal ablation duration using the second generation cryoballoon for isolation of pulmonary veins in the treatment of atrial fibrillation.

Study design The study is designed as a prospective multicentre randomized efficacy study.

Study population Patients 18-70 years of age with paroxysmal atrial fibrillation eligible for pulmonary vein isolation according to current international guidelines.

Intervention Patients will be randomized to 2 cycles of 1, 2 or 3 minutes of cryoballoon ablation after reaching the temperature "plateau phase".

Main study parameters/endpoints Acute success of pulmonary vein isolation.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

No additional risk is present as the procedure is common clinical practice, current cryoballoon application time is 3 minutes Shorter application times are not expected to add to the risk.

Inclusion Criteria:

• Paroxysmal atrial fibrillation eligible for pulmonary vein isolation according to current international guidelines.
• Age < 70 years.
• Willing and able to sign informed consent.
• Willing to and capable of following the requested study procedures.

Exclusion Criteria:

• Age < 18 years.
• Pregnancy
• Life or follow-up expectancy < 12 months.
• Previous PVI.
• Contrast allergy.
• Creatin clearance level < 60.
• Left ventricular ejection fraction < 40%
• Abnormal left atrium anatomy defined as number of PV's ≠ 4 or Left Atrium diameter >50mm (measured in the parasternal long axis, as assessed with transthoracic echocardiography) or >40 cc/m2 . This will lead to exclusion after inclusion but before randomisation.