Left Heart Catheterization Cannot Diagnose Pulmonary Embolism
A left heart catheterization (LHC) cannot and will not show a pulmonary embolism because it does not access the pulmonary arterial circulation where emboli are located. LHC is designed to visualize the left-sided cardiac chambers, coronary arteries, and aorta—none of which are involved in PE diagnosis.
Why LHC Cannot Detect PE
Anatomical Access Limitations
LHC accesses only the left heart and coronary arteries via retrograde approach through the aorta, completely bypassing the right heart and pulmonary circulation where emboli lodge 1.
Pulmonary emboli are located in the pulmonary arteries, which are part of the right-sided circulation and require venous access through the right atrium and right ventricle to visualize 1.
The correct procedure for direct PE visualization is pulmonary angiography, which requires catheterization through the venous system (femoral, jugular, or brachial vein) into the pulmonary trunk and pulmonary arteries using the Seldinger technique 1.
The Appropriate Catheter-Based Procedure for PE
Right Heart Catheterization with Pulmonary Angiography
Pulmonary angiography via right heart catheterization is the reference standard for PE diagnosis when non-invasive tests are indeterminate, with sensitivity of 98% and specificity of 95-98% 1.
The catheter must be advanced through the right ventricle into the pulmonary trunk to inject contrast directly into the pulmonary arteries for adequate visualization 1.
Direct angiographic signs of PE include complete vessel obstruction with concave contrast borders and intraluminal filling defects that have been validated over decades 1.
Current Clinical Role
Pulmonary angiography is now reserved for cases where CT angiography is negative but clinical suspicion remains high, as CT has largely replaced catheter-based angiography as first-line imaging 1.
Catheter-based procedures are primarily used for therapeutic intervention (thrombolysis, mechanical thrombectomy) rather than diagnosis in the modern era 2, 3, 4.
Modern Diagnostic Approach to PE
First-Line Imaging
CT pulmonary angiography (CTPA) is the recommended initial imaging modality for suspected PE, offering excellent spatial resolution and the ability to identify alternative diagnoses 1.
CTPA directly visualizes thrombi as filling defects in the pulmonary arteries and can assess right ventricular strain patterns 1.
Role of Echocardiography
Transthoracic echocardiography cannot definitively diagnose PE but can identify right ventricular dysfunction and pressure overload suggestive of hemodynamically significant PE 1.
In hemodynamically unstable patients with suspected massive PE, the absence of RV dysfunction on echo virtually excludes PE as the cause of shock 1.
Mobile right-heart thrombi detected on echo essentially confirm PE diagnosis and are associated with high early mortality, occurring in <4% of unselected PE patients 1.
Common Clinical Pitfall
The most critical error is confusing left heart catheterization with pulmonary angiography. If you suspect PE and are considering catheter-based diagnosis, you must specifically order pulmonary angiography with right heart catheterization—not a standard left heart catheterization performed for coronary or valvular assessment 1.