Fractional Flow Reserve (FFR)

Simply put: while a conventional angiogram shows how a vessel looks, FFR demonstrates how that vessel functions.

How Does FFR Work?

Precision Sensor: An ultra-thin guidewire equipped with a miniature pressure sensor at its distal tip is introduced into the target coronary artery.
Pressure Measurement: The wire is navigated across the stenosis (narrowing) to measure the blood pressure both proximal to (before) and distal to (after) the lesion.
Ratio Calculation:
Step 1: An ultra-thin guidewire with a miniature pressure sensor is placed inside the artery.
Step 2: The wire measures the blood pressure at two points: before the narrowing (Proximal Pressure) and after the narrowing (Distal Pressure).
Step 3: A short-acting drug (usually Adenosine) is given to maximize blood flow through the heart.
Step 4: The system calculates the final ratio using a simple formula.

An FFR score of 1.0 means perfect, unrestricted blood flow. Any drop below 1.0 indicates the percentage of blood flow lost due to the blockage (e.g., an FFR of 0.70 means only 70% of normal blood pressure is reaching the rest of the heart).

Understanding the Results: Clinical Interpretation

The numerical value obtained from the FFR measurement directly guides the physician’s therapeutic strategy:

0.80 and Above: Blood flow is hemodynamically sufficient. Even if the vessel visually appears stenotic on an angiogram, it does not restrict adequate myocardial perfusion. Consequently, stent placement (angioplasty) is generally unnecessary, and optimal medical therapy is sufficient.
0.75 to 0.80: This represents a clinical “gray zone”; therapeutic decisions are personalized based on the patient’s specific symptoms and clinical history.
Below 0.75: Blood flow across the stenosis is restricted by 25% or more. This degree of ischemia carries significant clinical risk and definitively requires revascularization via percutaneous coronary intervention (stenting) or coronary artery bypass graft (CABG) surgery.

Why is FFR Critical? (Clinical Efficacy)

In standard coronary angiography, certain lesions appear “borderline” or intermediate (50% to 70% stenosis). Relying solely on visual morphology can leave the interventionist uncertain about whether to deploy a stent.

Prevents Unnecessary Interventions: FFR occasionally reveals that a lesion appearing severely narrowed visually actually maintains excellent functional blood flow. This spares the patient from the unnecessary deployment of a foreign body (stent).
Identifies Hidden Risks: Conversely, FFR can prove that a visually mild stenosis is actually causing severe hemodynamic restriction, establishing a definitive, evidence-based indication for revascularization to prevent adverse cardiac events.