Spider View for Proximal First Diagonal Branch Visualization
The spider view (steep LAO caudal projection) is NOT the optimal choice for visualizing a very proximal first diagonal branch origin; instead, a right lateral projection with cranial angulation (90-120° RAO with 30° cranial) is superior for this specific anatomy. 1
Why the Spider View Has Limitations for Proximal Diagonal Origins
The spider view, while excellent for left main coronary artery (LM) evaluation and bifurcation disease, is specifically designed to visualize the LM body and its bifurcation into the LAD and left circumflex (LCx). 2, 3 However, this projection has significant drawbacks for proximal diagonal branch visualization:
Anatomic overlap: The proximal first diagonal branch originates from the LAD in the region where the vessel courses anteriorly in the interventricular groove, and standard projections including the spider view often result in overlap between the LAD and diagonal branches, obscuring the true origin and severity of any stenosis. 1
High radiation exposure: The spider view (typically 70° LAO with 30° caudal angulation) carries high X-ray exposure for both operator and patient, which is a significant limitation. 2, 3
The Superior Alternative: Right Lateral with Cranial Angulation
The right lateral projection (90-120° RAO) with 30° cranial angulation is the optimal view for proximal first diagonal branch origins, as reported by the American Heart Association:
This projection exposes the origins and proximal segments of the LAD in 89% of angiograms with strong inter-observer agreement (PABAK 0.86). 1
The cranial angulation specifically separates the diagonal branch from the LAD body, eliminating the overlap that occurs in standard projections. 1
Clinical Reasoning for View Selection
When selecting angiographic projections for diagonal branch evaluation, consider:
Proximal diagonal branches require views that separate them from the LAD body—the right lateral with cranial angulation achieves this separation effectively. 1
The spider view remains valuable for left main bifurcation assessment and guiding percutaneous coronary interventions on LM disease, but should not be relied upon for proximal diagonal branch origins. 2, 3
Common Pitfalls to Avoid
Do not assume the spider view is universally optimal for all left coronary system anatomy—it is specifically designed for LM evaluation, not diagonal branch origins. 2, 3
Avoid relying on a single projection—if the right lateral with cranial angulation does not adequately visualize the diagonal origin, consider complementary views rather than defaulting to the spider view. 1
Be aware of radiation exposure—the spider view's high radiation burden makes it less desirable when alternative projections can provide superior visualization. 3