Do you prefer using unfractionated heparin or low molecular weight heparin in stable patients presenting with NSTE ACS awaiting primary PCI (assuming normal renal function)?

I advocate for the use of LMWH. I see a surprising number of patients on unfractionated heparin with PTTs indicating either homeopathic (<35s) or supratherapeutic (>120s) levels of anticoagulation. The 2025 ACC/AHA Guideline for the Management of Patients With Acute Coronary Syndromes summarizes clinical trial and meta-analysis data, which show no significant difference in death, MI, or major bleeding between UFH and LMWH in NSTE-ACS patients undergoing PCI.

Unfractionated heparin, with its much shorter T 1/2, is preferred to enoxaparin (T 1/2 12 odd hours), even in the era of transradial procedures (as opposed to transfemoral cases with higher bleed risk).