Pulmonary angiography is an imaging test that produces detailed pictures of the blood vessels in your lungs. A thin, flexible tube called a catheter is threaded through a vein and into the pulmonary arteries, where contrast dye is injected so the vessels show up clearly on X-ray. First described in 1964, it was long considered the gold standard for diagnosing blood clots in the lungs and other pulmonary artery problems.
Today, less invasive scans have largely replaced it for routine diagnosis. But it still plays an important role when those scans are inconclusive or when doctors need to treat a problem at the same time they identify it.
Why It’s Performed
The most common reason for pulmonary angiography has historically been detecting pulmonary embolism, a potentially life-threatening blood clot that blocks an artery in the lungs. Because the catheter sits directly inside the pulmonary arteries, the images it produces are exceptionally detailed.
Beyond blood clots, the procedure is used to evaluate several other conditions: chronic thromboembolic pulmonary hypertension (long-standing clots that raise pressure in the lung arteries), abnormal connections between arteries and veins in the lungs, narrowed or ballooning pulmonary arteries, and, less commonly, tumors within the pulmonary vessels. In many of these cases, the same catheter used for imaging can also deliver treatment, making the procedure both diagnostic and therapeutic in a single session.
How It Compares to a CT Scan
For most patients suspected of having a pulmonary embolism, doctors now order a CT pulmonary angiography (CTPA) instead. This is a specialized CT scan that also uses contrast dye but delivers it through a standard IV in the arm rather than a catheter threaded into the heart. It’s faster, less invasive, and widely available in emergency departments.
Conventional catheter-based pulmonary angiography is now typically reserved for situations where noninvasive imaging has been exhausted or when a catheter-based intervention is already planned. Early studies of CT angiography found its sensitivity for clots in the central lung arteries ranged from 74% to 81%, with specificity around 89% to 91%. For smaller clots deeper in the lung vessels, sensitivity dropped to about 68%. Modern CT scanners with thinner image slices have improved on those numbers considerably, which is a major reason the catheter-based approach has moved to the background for pure diagnosis.
Another noninvasive alternative is the ventilation-perfusion (V/Q) scan, which uses inhaled and injected radioactive tracers to compare airflow and blood flow in the lungs. It’s often chosen for patients who can’t receive iodine-based contrast dye. Magnetic resonance angiography (MRA) is a third option, though it’s used less frequently.
What Happens During the Procedure
You’ll be awake throughout, though you may receive a sedative to help you relax. The medical team monitors your heart rate, blood pressure, and oxygen levels continuously. A doctor selects an access site for the catheter, commonly a vein in the groin, neck, arm, or just below the collarbone. That area is numbed with a local anesthetic.
A small incision allows the catheter to enter the vein. Using real-time X-ray guidance (fluoroscopy), the doctor advances the catheter through the vein, into the right side of the heart, and out into the pulmonary arteries. Once positioned, iodine-based contrast dye is injected through the catheter. A rapid series of X-ray images captures the dye as it flows through the lung vessels, highlighting blockages, narrowing, or other abnormalities. Pressure readings inside the pulmonary arteries and blood oxygen samples can also be collected through the same catheter.
Preparing for the Test
Your medical team will typically ask about allergies (especially to iodine or contrast dye), current medications, and whether you might be pregnant. Blood tests to check kidney function and clotting ability are standard before any catheter-based procedure that involves contrast dye. Whether you need to fast beforehand varies by institution. Newer evidence from large studies of catheter-based angiography suggests that strict fasting may not be necessary for procedures done under local anesthesia and sedation, but many hospitals still follow traditional guidelines of no food for several hours prior. Follow whatever instructions your specific care team provides.
Risks and Complications
Pulmonary angiography is generally safe, but it is an invasive procedure that carries real risks. One large review from Henry Ford Hospital found an overall complication rate of 15%, with a mortality rate of 1.4%. Most complications are minor: temporary irregular heart rhythms as the catheter passes through the heart, bleeding or bruising at the puncture site, and allergic reactions to the contrast dye ranging from mild hives to more serious responses.
The iodine-based contrast dye poses a particular concern for people with reduced kidney function. The kidneys filter the dye out of the bloodstream, and in patients with fewer functioning kidney cells, each one bears a heavier load. The risk of contrast-induced kidney injury climbs steeply with worsening kidney function: roughly 5% when kidney filtration rates are normal or mildly reduced, around 10% to 15% with moderate impairment, and up to 30% in people with severe kidney disease. That risk is more than tenfold higher than in someone with healthy kidneys. Modern lower-concentration contrast agents have significantly reduced this risk compared to older formulas, and adequate hydration before and after the procedure helps protect the kidneys further.
Recovery After the Procedure
You’ll lie flat in a recovery area for one to two hours while staff monitor your vital signs and watch the catheter insertion site for bleeding. If the catheter went in through your groin, you’ll need to keep that leg straight during this period. A small weight or pressure bandage may be placed over the puncture site to prevent a hematoma, which is a pocket of blood collecting under the skin.
Pain at the insertion site is usually mild and manageable with over-the-counter medication. Once you’re home, check the puncture site several times a day for the first few days. Look for increased bleeding, swelling, warmth, color changes, or pain that worsens rather than improves. Most people return to normal activities within a day or two, though heavy lifting and strenuous exercise are typically discouraged for a short period to let the puncture site heal completely.
Its Evolving Role in Medicine
Conventional pulmonary angiography occupies a different place in medicine than it did a few decades ago. It’s no longer the first test ordered when a lung clot is suspected. Instead, its value has shifted toward interventional use: guiding catheter-based treatments that break up or remove clots, open narrowed arteries, or seal off abnormal vessel connections. In these scenarios, the diagnostic images and the therapy happen through the same catheter in the same session, which is something no noninvasive scan can offer.
For conditions like chronic thromboembolic pulmonary hypertension, where clots have scarred and permanently narrowed the lung arteries, catheter-based angiography remains essential both for mapping the disease and for performing balloon procedures that restore blood flow. It continues to serve as the definitive test when CT and V/Q results conflict or when the clinical picture doesn’t match the scan findings.