5.3 Catheter Shapes & Angiographic Projections

Selective coronary angiography depends on two skills working together: seating the correct catheter shape at the ostium and imaging the vessel in projections that separate overlapping branches. Foreshortening—a stenosis hidden because the beam shoots down the length of the vessel—is one of the most common sources of angiographic error. The RCIS exam tests both catheter nomenclature and projection vocabulary extensively.

Diagnostic Catheter Shapes

Judkins Catheters (JL and JR)

Judkins Left (JL) catheters engage the left coronary artery (LCA). Size selection depends on aortic root width and height:

Judkins Right (JR) catheters engage the RCA:

JR catheters sit in the right sinus; the tip points toward the RCA ostium. Excessive counterclockwise torque can cause deep engagement and RCA dissection.

Amplatz Catheters (AL and AR)

Amplatz Left (AL) and Amplatz Right (AR) catheters use a secondary curve that hooks the ostium from the opposite sinus. They are useful when:

• Judkins catheters fail to engage
• The aortic root is dilated or aneurysmal
• Coronary takeoff is anomalous
• Graft cannulation requires a different approach angle

AL catheters engage the LCA from the contralateral (right) sinus with an upward hook. AR catheters engage the RCA similarly. Caution: Amplatz catheters can "jump" out or deeply engage when pulled back—operators must stabilize before injection.

Multipurpose (MP) Catheter

The multipurpose (MP) catheter is a versatile shape used for:

• Left ventriculography (alternative to pigtail in some labs)
• Aortic root/aortography
• Graft cannulation (SVG, occasionally native vessels)
• Coronary engagement when Judkins/Amplatz fail

The MP tip is angled and can be shaped for selective work; it is less ostium-specific than JL/JR.

Internal Mammary (IM) Catheter

The internal mammary (IM) catheter is designed to cannulate LIMA and RIMA grafts post-CABG. The gentle curve follows the subclavian–mammary path. Identifying patent mammary graft supply to the LAD is a key post-bypass angiographic goal.

Pigtail Catheter

The pigtail catheter has a looped, non-traumatic tip and is the standard choice for:

• Left ventriculography — positioned across the aortic valve in the LV
• Aortography — positioned in the ascending aorta or aortic root

The pigtail distributes contrast evenly and reduces endocardial trauma compared with straight-tip catheters.

Catheter Quick-Reference Table

Angiographic Projections

Fluoroscopic projections describe C-arm position relative to the patient. Standard terminology combines:

1. RAO or LAO — right or left anterior oblique rotation
2. Cranial or caudal — angulation toward the head or feet

Primary Projection Families

The Spider View

The spider view (approximately LAO 45–60° / cranial 15–30°, exact angles vary by lab) is the single most important LCA projection on the RCIS exam. It:

• Separates the LAD (appears to drop down) from the LCx (appears to go left)
• Opens the LM bifurcation for ostial and bifurcation stenosis assessment
• Reduces overlap of diagonal and OM branches

Without a spider-equivalent cranial LAO view, LM and proximal LAD lesions are frequently foreshortened and underestimated.

RCA Projection Essentials

Always acquire at least two orthogonal views of any stenosis before reporting severity.

Practical RCIS Tips

• Confirm catheter type and French size on the sterile field before the case starts
• Learn each physician's default projections but know the anatomic rationale so you can suggest additional views
• When the physician asks for "cranial LAO," move C-arm to LAO first, then add cranial angulation
• Document projection angles in the report when significant findings depend on a specific view
• For post-CABG cases, have IM and MP catheters available before the case begins