The pain does not radiate and increases on inspiration

[Shabir.]

A 42-year-old woman presents to the hospital with the sudden onset of shortness of breath associated with chest pain. The pain does not radiate and increases on inspiration. On physical examination, blood pressure is 110/80 mm Hg, pulse is 116/min, and respirations are 22/min. She is 125 pounds. An EKG reveals sinus tachycardia at 120 beats per minute, and the chest x-ray is normal. Baseline prothrombin time (PT) is 12 seconds, and the partial thromboplastin time (PTT) is 28 seconds. The patient is bolused with 5,000 units of heparin and then started on a drip of 1,000 units per hour. The V/Q scan gives a high probability for a pulmonary embolus.

Six hours later, the repeat PT is 12.5 seconds, and the PTT is 30 seconds. She is rebolused with 5,000 units of heparin, and the drip is raised to 1,100 units per hour. Six hours later, the PT is 12.4 seconds, and the PTT is 31 seconds.

What is the most likely reason for this scenario?

(A) Lupus anticoagulant
(B) Anticardiolipin antibodies
(C) Factor V mutation
(D) Antithrombin III deficiency
(E) Protein S deficiency

[clark]

D as heparin works on antithrombin 111 but no change in ptt