Conventional Pulmonary Angiography When CTPA Is Not Tolerated
Conventional (catheter-based) pulmonary angiography can be considered when CTPA cannot be performed or is not tolerated, though it is rarely used as a first-line test and should be reserved for specific clinical scenarios where non-invasive testing remains inconclusive or unavailable. 1
Current Role of Conventional Pulmonary Angiography
The advent of CTPA has rendered conventional pulmonary angiography largely obsolete for routine PE diagnosis. 2 However, specific indications remain:
- Pulmonary angiography is the method of choice when non-invasive tests are either inconclusive or not available. 1
- It may be indicated in rare situations of extremely high bleeding risk (e.g., after neurosurgery) combined with an abnormal high-probability lung scan. 1
- It can be considered in patients with relative contraindications to thrombolytic or heparin therapy where definitive diagnosis is essential. 1
Safety Profile
Modern pulmonary angiography is considerably safer than historically perceived:
- Current risk of fatal complications is approximately 0.1% and serious non-fatal complications approximately 1.5%. 1
- This represents a 50% reduction in fatal and fourfold reduction in non-fatal complications compared to earlier decades. 1
Contraindications and Limitations
No absolute contraindications exist for pulmonary angiography, though several relative contraindications should be considered: 1
- Allergy to iodine-containing contrast agents 1
- Impaired renal function 1
- Left bundle branch block 1
- Severe congestive heart failure 1
- Severe thrombocytopenia 1
The general condition of the patient is the primary deciding factor, as demonstrated by studies showing pulmonary angiography could not be performed in 10-20% of scheduled patients due to clinical instability. 1
Alternative Strategies When CTPA Is Contraindicated
Before proceeding to invasive angiography, consider these alternatives:
- Ventilation-perfusion (V/Q) scintigraphy is an acceptable alternative imaging modality when CTPA cannot be performed. 3
- Lower-extremity compression ultrasonography should be performed in stable patients with CTPA contraindications. 3
- Detection of proximal deep vein thrombosis on ultrasound is sufficient to initiate anticoagulation without further imaging. 3
- MRA pulmonary arteries can identify emboli in central and segmental arteries, though it was technically inadequate in 25% of patients in the PIOPED III trial. 4
Appropriateness Ratings
According to ACR guidelines, conventional pulmonary angiography receives low appropriateness ratings in most clinical scenarios:
- Rating of 1 (usually not appropriate) for low/intermediate probability PE 5
- Rating of 3 (usually not appropriate) for intermediate/high probability PE 5
- Rating of 4 (may be appropriate) in pregnant patients, used rarely for clarification or catheter-directed intervention 5
Common Pitfalls
- Do not assume conventional angiography is the "gold standard" for subsegmental clot, where interobserver disagreement occurs in up to one-third of cases with sensitivity and positive predictive values of only 87-88%. 2
- Do not overlook that the overall accuracy of catheter pulmonary angiography is likely inferior to CTPA. 4
- Do not perform invasive angiography when V/Q scanning or lower extremity ultrasound could provide sufficient diagnostic information. 3
- Recognize that few centers maintain expertise in selective angiography and catheter fragmentation techniques. 2
Clinical Decision Algorithm
When CTPA is not tolerated or contraindicated:
- First, perform lower extremity compression ultrasound - if positive for proximal DVT, initiate anticoagulation without further imaging 3
- Second, consider V/Q scintigraphy - acceptable alternative with established diagnostic utility 3
- Third, evaluate MRA if available - though limited by technical inadequacy rate and longer study duration 4
- Reserve conventional pulmonary angiography for cases where: