What ACT target is recommended during most left-sided EP procedures?

• A. ACT < 250 seconds
• B. ACT > 300 seconds (commonly 300–350 s)
• C. ACT around 600 seconds
• D. ACT is not used

Answer: (B)

Anticoagulation management with activated clotting time is essential during left‑sided EP procedures because catheters in the left heart and the transseptal puncture create a high risk for thrombus formation. ACT is used to gauge the effect of heparin in real time and guide dosing so you keep the blood sufficiently anticoagulated without tipping into excessive bleeding.

The recommended target is to maintain ACT above about 300 seconds, usually in the 300–350 second range. This level provides effective protection against thrombus formation on catheter surfaces and endocardial tissue during ablation, while avoiding the high bleeding risk that comes with much higher ACT values. An ACT well below this (around 250 seconds or less) leaves the door open for clots and potential embolic events. Conversely, aiming for very high ACT (around 600 seconds) substantially increases bleeding risk, which can lead to complications like access-site bleeding or pericardial bleeding. In practice, after a heparin bolus, the infusion is titrated to keep ACT in the roughly 300–350 second range with continuous monitoring throughout the procedure.