The transcatheter edge to edge mitral valve repair (TEER) and left atrial appendage closure (LAAC) are the interventional cardiology procedures that require periprocedural anticoagulation with unfractionated heparin (UFH). The UFH is administered either before or immediately after transseptal puncture, at the discretion of the operator

The aim of the study is to establish the optimal timing of initiation of periprocedural anticoagulation in patients undergoing structural heart interventions requiring transseptal puncture (TEER and LAAC), Patients who undergo TEER implantation or LAAC procedure will be randomized to two groups:

1. Early UFH administration. The iv. bolus of UFH (100Units/kg) will be given after obtained femoral vein access and at least 5 minutes prior to the start of the TSP.
2. Late UFH administration. The iv. bolus of UFH (100Units/kg) will be given immediately after TSP, defined as the introduction of transseptal sheath into the left atrium.

Inclusion Criteria:

1. Age above 18 years
2. Planned TEER procedure or left atrial appendage closure
3. The patient is willing to sign informed consent and comply will all study procedure

Exclusion Criteria:

1. Women who are pregnant or breastfeeding and those women of childbearing potential who do not agree to use at least two contraceptive measures (oral contraception, mechanical contraception, approved contraceptive implants, intrauterine device, tubal ligation). The criterion does not apply to women who have been postmenopausal for at least 2 years prior to study enrollment (defined as at least one year without menstrual periods) or underwent surgical sterilization procedure. All eligible women who are younger than 55 years must have negative pregnancy test within 24 hours prior to randomization.

2. Congenital or acquire bleeding disorders (i.e.diagnosed thrombophilia, bleeding diathesis, thrombocyopenia with platelet count <50 thousand/ml, INR elevated >1.5 in the last test prior to randomization)

3. INR > 1.5 within 24 hours prior to the procedure in patients chronically treated with vitamin K antagonists. (applies to the last INR value prior to randomization)

4. Last dose of new oral anticoagulant < 48 hours prior to the procedure (assessed at randomization)

5. Last dose of low molecular weight heparin <12 hours prior to the procedure (assessed at randomization)

6. Contraindications to MR imaging (i.e. claustrophobia, ferromagnetic intraocular foreign boddies, ferromagnetic metalic prostheses)

7. Implanted cardiac devices for electrotherapy if:

   • device has epicardial leads
   • left disconnected leads or non-functional or damaged devices
   • device implanted within abdominal wall
   • the patient is pacemaker dependant (lack of escape rhytm >30/min)
   • the device was implanted or exchanged within 6 weeks prior to the MR examination
   • device mulfunction identified during the control performed prior to the MR examination, that in the opinion of electrophysiologist team may impact the safety of MR imaging
   • low voltage of the device battery - the battery on the examination day should have at least 20% of the voltage value between the nominal value and elective replacement indicator (ERI) value, or the expected battery life calculated by the device should equal or exceed one year.

to be defined

IPD sharing will be considered after study completion and publication of the results.

to be defined

The study will be conducted by blinded and unblinded staff. The participants, investigators, care provider and outcome assessors will be blinded. However, in every center the dedicated unblinded study nurse will randomize the patient and prepare two syringes either with saline or UFH. The syringes will be labeled with number 1 and number 2 and will be provided to the anestesiologist taking care of patient during the procedure. The injection from syringe nr 1 will be administered after obtaining the venous access and 5 minutes before the start of TSP. The injection from syringe nr 2 will be administered after TSP defined as introduction of trans-septal sheath into the left atrium. The unblinding nurse responsible for the randomization procedure and preparation of syringe nr 1 and syringe nr 2 and will be not involved in any other procedures or care of the patients enrolled into the study.