During LA ablation in patients with mechanical valves, what ACT target is recommended during the procedure?

• A. ACT > 200 seconds
• B. ACT > 400 seconds
• C. ACT > 300 seconds
• D. ACT > 500 seconds

Answer: (C)

Maintaining adequate anticoagulation during left atrial ablation in patients with mechanical valves is essential because catheter manipulation and transseptal access can provoke thrombus formation on the prosthesis or in the atrium. Activated clotting time (ACT) guides real-time heparin dosing to keep blood moderately anticoagulated throughout the procedure.

A target ACT just above 300 seconds provides enough protection against thromboembolism without pushing bleeding risk too high. Too low a target (e.g., around 200 seconds) leaves a higher risk of clot formation on the valve or catheters, while aiming for very high ACT (400–500 seconds) increases bleeding, especially with transseptal puncture and catheter manipulation. Thus, ACT > 300 seconds is the best balance for LA ablation in patients with mechanical valves.