A Patient with a Pulmonary Embolism Is Being Treated with a Heparin

A patient with a pulmonary embolism is being treated with a heparin infusion. What diagnostic finding suggests to the nurse that treatment is effective?

A) The patients PT is within reference ranges.
B) Arterial blood sampling tests positive for the presence of factor XIII.
C) The patients platelet level is below $100,000 / \mathrm{mm}^{3}$ .
D) The patients activated partial thromboplastin time (aPTT) is 1.5 to 2.5 times the control value.