CT Angiogram of the Chest (for blood clot)

What it is

A pulmonary embolism is a clot, usually formed in a leg vein, that has travelled to the lungs and lodged in an artery there. Nothing about the chest on a plain scan shows it. What does show it is timing: contrast is pushed rapidly into an arm vein, and the scanner fires during the few seconds when that dye is filling the pulmonary arteries and nothing else. The arteries become a bright branching tree, and a clot shows up as a dark plug where the brightness stops. Because the whole chest is imaged anyway, the same scan frequently turns up a different explanation for the symptoms — a collapsed lung, pneumonia, or something wrong with the aorta.

Why it is done

• To confirm or exclude a pulmonary embolism in someone with sudden breathlessness, chest pain that is worse on breathing in, or an unexplained fast heart rate
• To look for another cause of the same symptoms when the clot question is settled
• To reassess a patient already treated for a clot whose condition has changed
• To examine the chest arteries when a problem with the aorta or the pulmonary vessels is suspected

What to expect

This is almost always an unplanned, urgent scan. An IV goes into an arm — a larger one than usual, because the dye has to be delivered fast by a pump — and the injection brings the familiar wave of warmth and metallic taste. Patients are asked to hold their breath for a handful of seconds, which is the hardest part when breathing is already difficult. The scan itself is over in well under a minute. A radiologist reads it quickly, because treatment decisions wait on the result.

Questions worth asking

• In an emergency department this arrives with a facility fee, a physician fee and a separate radiology reading. Can I have the charges itemized so I can check each one's network status?
• Blood tests are usually drawn alongside this scan. Are those billed by the hospital lab or by an outside lab that will send its own invoice?
• If the scan is negative and I am sent home, is the visit still billed at the emergency level it was opened at?
• If a follow-up scan is suggested weeks later to check the clot has resolved, could that be done at an outpatient center at a lower price?