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Vascular Stenosis Severity Assessment (Left Coronary Artery) – Quantitative Coronary Flow Reserve (QCFR) Comparison

Published: August 9, 2026Updated: August 16, 2026

This test measures how well blood flows through your left coronary artery, comparing it to a reference (unobstructed) vessel to assess the severity of any narrowing (stenosis).

Quick summary

["Helps determine how much blood flow is restricted in your coronary arteries, guiding treatment decisions for heart health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33868-1
Short code
Vmax stenosed ICA/unobstructed CCA US
Synonyms
Vmax stenosed ICA/unobstructed CCA US
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

Your doctor may use this test to evaluate the degree of blockage in your left coronary artery by comparing blood flow through the narrowed segment to a nearby unobstructed section. The result helps assess the functional impact of any stenosis.

Why It’s Done

This test is often performed during a coronary angiography or functional imaging study to assess how severely narrowed arteries reduce blood flow, which can affect heart function and guide interventions like angioplasty or stent placement.

How It Works

Blood flow is measured before and after a brief dilation (balloon or drug) to assess the vessel’s response. The ratio of flow in the narrowed segment to the unobstructed reference vessel (QCFR) quantifies the blockage’s effect on blood supply.

Preparation

No special preparation is needed, but you may be asked to fast for 4–8 hours before the procedure if contrast dye is used. Inform your doctor about any allergies or medications you’re taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

QCFR Comparison (Left Main)

Frequently asked questions

How does this test differ from a standard angiogram?
Unlike a traditional angiogram, which only shows blockages visually, this test quantifies how much blood flow is restricted by comparing the narrowed segment to an unobstructed reference. A lower QCFR suggests more severe functional impairment, potentially guiding more aggressive treatment.
What are the typical reference values for QCFR?
There are no universal reference ranges for QCFR because it varies by patient and vessel. A QCFR below 2.5 is often considered indicative of significant reduced blood flow, but your doctor will interpret results in the context of your specific anatomy and symptoms.
Can this test be done without contrast dye?
No, this test typically requires contrast dye to visualize blood flow. Some advanced imaging techniques (like CT perfusion) may offer alternatives, but they’re not the same as a QCFR measurement.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy