The investigators aim to test the thrombotic potential of various heart chambers including left atrium, left atrial appendage, right atrium and peripheral veins. Blood samples will be taken from the different chambers in 50 patients admitted for standard pulmonary vein ablation and compared to patients without atrial fibrillation admitted for left sided supra ventricular tachycardia or mitral clip. Thrombin generation parameters will be assessed by the calibrated automated thrombogram.

Atrial fibrillation is the most common arrhythmia, there is a strong correlation between atrial fibrillation and embolic stroke. In order to lower the risk for embolic stroke anticoagulation is recommended for patients with CHADS-VASC score equal or above 2. The mechanism for thrombus formation in the left atrium is thought to be caused by various factors 1. blood stasis due to the loss of atrial kick 2. endothelial dysfunction 3. blood hemostatic alteration leading to procoagulant state.

Previous studies demonstrated increased thrombin generation in the left atrium in patients with atrial fibrillation, when compared to other heart chambers and when compared to control group in patients with structurally normal heart.

In recent years calibrated automated thrombogram (CAT) is considered a good indicator for total thrombotic activity in hypercoagulable states.

In the current study the investigators aim to test the thrombotic potential of various heart chambers including left atrium, left atrial appendage, right atrium and peripheral veins. Blood samples will be taken from the different chambers in 50 patients admitted for standard pulmonary vein ablation without changing the course of the procedure. Thrombin generation parameters will be assessed by the calibrated automated thrombogram. A control group composed of 50 patients admitted for standard left sided supra ventricular tachycardia ablation or patients admitted to mitral clip procedure without the presence of atrial fibrillation.

In addition demographic data,CHADS-VASC score, atrial fibrillation burden, echocardiographic and cardiac CT parameters will be collected.

Inclusion Criteria:

• Age above 18
• Pulmonary vein ablation, SVT ablation or mitral clip.
• Informed consent

Exclusion Criteria:

• Left atrial thrombus
• Pregnancy
• Active malignancy
• Thrombophilia
• Anticoagulants 24 hours before procedure
• Active infectious disease
• Chronic kidney disease (eGFR<30)

Study group:Participants with atrial fibrillation admitted to pulmonary vein ablation Control group: Participant without atrial fibrillation admitted to left sided SVT ablation or Mitral clip.