What Cardiac Catheterization Actually Measures
A cardiac catheterization (heart cath) is the gold standard for directly measuring pressures inside your heart chambers and visualizing your coronary arteries. Unlike non-invasive tests such as echocardiograms or stress tests, catheterization provides definitive anatomic and hemodynamic data that drives surgical decision-making.
Coronary Angiography: Your Artery Roadmap
The most common reason for catheterization is coronary angiography — injecting contrast dye to visualize blockages. Your report will describe:
- Vessel involved — LAD (left anterior descending), LCx (left circumflex), RCA (right coronary artery), left main
- Percent stenosis — The degree of narrowing (e.g., 70%, 90%, 100% occluded)
- Dominance — Whether your RCA or LCx supplies the PDA (posterior descending artery)
- TIMI flow — A 0–3 scale measuring how well blood flows past a blockage
A stenosis of =70% in a major epicardial vessel (or =50% in the left main) is generally considered hemodynamically significant and may warrant intervention.
Hemodynamic Data: Pressures and Gradients
Beyond angiography, catheterization measures intracardiac pressures that reveal how well your heart is functioning:
- LVEDP (left ventricular end-diastolic pressure) — Elevated values (>15–18 mmHg) suggest heart failure or diastolic dysfunction
- Pulmonary artery pressure — Elevated PA pressures may indicate pulmonary hypertension, a critical factor in surgical risk
- Valve gradients — The pressure difference across a stenotic valve (e.g., a mean gradient >40 mmHg suggests severe aortic stenosis)
- Cardiac output — How much blood your heart pumps per minute, measured by thermodilution or the Fick method
The SYNTAX Score: Quantifying Complexity
For patients with multi-vessel coronary artery disease, cardiologists calculate a SYNTAX score from the angiogram. This score (0–100) quantifies the complexity of your coronary anatomy and helps guide the CABG vs. PCI decision:
- Low (0–22) — PCI and CABG have similar outcomes
- Intermediate (23–32) — Heart Team discussion recommended
- High (=33) — CABG generally preferred based on trial data
Why Interpretation Varies — and Why It Matters
The same angiogram can be read differently by different cardiologists. Studies have shown inter-observer variability of 10–20% in visual stenosis estimation. This is why fractional flow reserve (FFR) — measuring actual pressure differences across a lesion — has become increasingly important for borderline lesions.
More importantly, the decision about what to do with your catheterization findings depends on integrating the anatomic data with your symptoms, functional status, medical history, and risk profile. A 70% LAD stenosis in an asymptomatic diabetic patient with preserved ejection fraction is a fundamentally different clinical scenario than the same lesion in a symptomatic patient with reduced EF.
Getting an Independent Review
If your catheterization results have led to a recommendation for cardiac surgery, an independent review of the actual images — not just the report — can provide clarity. At WhiteGloveMD, our Heart Team reviews your angiographic images alongside your complete clinical profile to ensure the proposed treatment aligns with current evidence and your individual anatomy.