Venous activated clotting time after intra-arterial heparin: Effect of site of administration and timing of sampling

It is not known how the site of arterial administration of heparin and the timing of the activated clotting time (ACT) measurement affect the ACT during coronary interventions. We measured serial femoral venous ACTs after heparin was administered either via the angioplasty guiding catheter into the central aorta or peripherally via a sheath into the femoral artery. When heparin was administered into the central aorta, the ACT rose gradually and by 60 sec plateaued without further increase. When heparin was given into the femoral artery, the ACT displayed a marked “overshoot” early (20–270 sec after heparin) and did not plateau until sometime between 270 and 800 sec after heparin administration. We conclude that the site of administration and timing of venous sampling markedly affect the measured ACT during coronary interventions. Operators should be aware of these effects when assessing the accuracy of the ACT during coronary interventions. © 1996 Wiley‐Liss, Inc.