Fractional flow reserve

Fractional Flow Reserve (FFR) is a diagnostic technique used in cardiology to measure the pressure differences across a coronary artery stenosis (narrowing) to assess the likelihood that the stenosis impedes oxygen delivery to the heart muscle (myocardial ischemia). This technique is instrumental in guiding decisions on the need for angioplasty or stenting in patients with coronary artery disease (CAD).

Overview

Fractional Flow Reserve is calculated during a cardiac catheterization procedure by measuring the blood pressure before and after a coronary artery stenosis using a specialized pressure wire. The FFR value is the ratio of the maximum achievable blood flow in a diseased coronary artery to the maximum achievable flow in a hypothetical normal coronary artery. An FFR of 1.0 is considered normal, indicating that the coronary artery can deliver blood as well as a normal artery would. An FFR of 0.80 or less is typically considered indicative of myocardial ischemia, suggesting that the stenosis may warrant revascularization.

Procedure

The FFR measurement is performed in the catheterization laboratory. The procedure involves threading a guide catheter into the coronary artery. A pressure wire is then advanced through the catheter and placed beyond the stenosis. Blood pressure is measured both before and after the stenosis while the patient is given a medication to induce hyperemia (increased blood flow), ensuring that the measurement reflects the coronary artery's capacity to deliver blood under conditions of high demand. The FFR is calculated by dividing the pressure downstream of the stenosis by the pressure upstream.

Clinical Significance

FFR-guided percutaneous coronary intervention (PCI) has been shown to improve patient outcomes compared to traditional angiography alone. By accurately identifying which lesions are responsible for ischemia, FFR allows for more targeted and appropriate use of interventions like stenting, potentially reducing the risk of unnecessary procedures and improving clinical outcomes.

Advantages

• Accuracy: FFR provides a more precise assessment of the physiological impact of a coronary artery stenosis than angiography.
• Outcome Improvement: Studies have shown that FFR-guided PCI can lead to better patient outcomes, including reduced rates of death, myocardial infarction, and the need for urgent revascularization.
• Cost-Effectiveness: By avoiding unnecessary stenting, FFR-guided treatment strategies can be more cost-effective for managing patients with CAD.

Limitations

• Invasive Procedure: FFR measurement requires cardiac catheterization, an invasive procedure that carries inherent risks, though they are relatively low.
• Hyperemic Agents: The need for pharmacological induction of hyperemia can introduce variability in the measurement and may not be suitable for all patients.
• Interpretation: The interpretation of FFR values can be influenced by various factors, including the presence of microvascular disease or the accuracy of the pressure measurements.

Conclusion

Fractional Flow Reserve has emerged as a critical tool in the management of coronary artery disease, enabling more precise and personalized treatment decisions. By focusing interventions on lesions that genuinely impair myocardial perfusion, FFR-guided strategies can improve patient outcomes and offer a more efficient use of healthcare resources.