QFR Versus FFR in Intermediate Coronary Stenosis: An Author’s Response

FAVOR III Europe Trial Offers Critical Insights into IVC Filter Complications

The FAVOR III Europe trial, a significant undertaking in cardiovascular research, has brought forth crucial data concerning inferior vena cava (IVC) filters and their associated thrombotic complications. This large-scale study offers valuable perspectives for clinicians managing patients at risk of pulmonary embolism (PE).

Inferior vena cava (IVC) filters are devices designed to capture blood clots. These filters are implanted in the IVC to prevent perhaps life-threatening pulmonary embolisms. Though, their use is not without risks, including the growth of thrombotic events within the filter itself.

Understanding these risks

What are the key limitations of FFR as a physiological assessment tool?

Understanding the Challenge of Intermediate Lesions

Intermediate coronary stenosis – lesions falling within the 40-70% diameter stenosis range – present a critically important clinical dilemma. determining the true hemodynamic significance of these lesions is crucial for guiding revascularization strategies and improving patient outcomes. Traditionally, Fractional Flow Reserve (FFR) has been the gold standard. However, Quantitative Flow Ratio (QFR) is emerging as a compelling choice, and increasingly, a preferred method in many centers. This article addresses key considerations and nuances in choosing between QFR and FFR for evaluating these challenging lesions.We’ll delve into the technical aspects, clinical evidence, and practical implications for cardiologists.

FFR: The Established Standard

for years, FFR has been the cornerstone of physiological assessment of coronary artery disease.

How FFR Works: FFR measures the pressure gradient across a coronary stenosis during maximal hyperemia,induced by adenosine administration. A value ≤ 0.80 generally indicates hemodynamic significance, suggesting the lesion is likely to benefit from revascularization.

Strengths of FFR: Extensive clinical trials (e.g., FAME, DEFER) have demonstrated FFR’s ability to improve outcomes by guiding percutaneous coronary intervention (PCI). It’s a well-validated and widely adopted technique.

limitations of FFR:

Adenosine administration can cause side effects like chest discomfort, dyspnea, and arrhythmias.

FFR is angle-dependent, meaning the measurement can be influenced by catheter positioning.

Requires specialized equipment and trained personnel.

Hyperemic response variability exists between patients.

QFR: A Novel Approach to Physiological Assessment

QFR represents a significant advancement in coronary physiology. It utilizes computational fluid dynamics (CFD) based on routine angiographic images to assess the impact of a stenosis on blood flow.

How QFR Works: QFR derives a non-hyperemic, index-based measurement of the flow-limiting potential of a stenosis. It analyzes the angiogram in multiple planes to create a 3D reconstruction of the coronary artery and calculates the ratio of distal to proximal flow. A QFR value ≤ 0.80 suggests hemodynamic significance.

Advantages of QFR:

No Hyperemia Required: Eliminates the need for adenosine administration and its associated side effects. This is particularly beneficial for patients with contraindications to adenosine (e.g., severe COPD, high-grade AV block).

Angle Independence: QFR is less susceptible to angle-dependent errors compared to FFR, providing more consistent and reliable measurements.

Faster Procedure Time: QFR analysis can be performed more quickly than FFR, possibly reducing procedure time and cost.

Integration with Angiography: QFR seamlessly integrates with standard angiography workflows.

Current evidence Supporting QFR: Recent studies, including the FAVOR III trial, have shown non-inferiority of QFR compared to FFR in guiding PCI for intermediate coronary lesions. Furthermore, some data suggests QFR may offer improved diagnostic accuracy in certain scenarios, such as diffuse disease.

QFR vs. FFR: A Head-to-Head Comparison

| Feature | FFR | QFR |

|—|—|—|

| Hyperemia | Required (Adenosine) | Not Required |

| Angle Dependence | Yes | No |

| Procedure Time | Longer | Shorter |

| Equipment | Specialized pressure wire | Software integrated with angiography system |

| Cost | Higher | Lower (potentially) |

| Clinical Validation | Extensive | Growing, with promising results |

| Patient Comfort | Lower (due to adenosine) | Higher |

Clinical Scenarios: When to Choose QFR or FFR

The choice between QFR and FFR shoudl be individualized based on patient characteristics and clinical context.

QFR is particularly well-suited for:

Patients with contraindications to adenosine.

Patients with diffuse coronary artery disease.

Situations where rapid assessment is critical.

labs aiming to reduce adenosine-related complications.

FFR may be preferred in:

Patients where a hyperemic response is robust and reliable.

Centers with extensive experience and established FFR protocols.

Complex lesions where additional physiological information beyond flow limitation is desired.

The Role of Advanced Imaging: IVUS and OCT

Intravascular Ultrasound (IVUS) and Optical Coherence Tomography (OCT) provide detailed anatomical information about coronary lesions.While not direct substitutes for physiological assessment, they can complement both FFR and QFR.

IVUS/OCT and QFR/FFR Synergy: Combining anatomical data from IVUS/OCT with physiological data from QFR/FFR can provide a more comprehensive understanding of lesion severity and guide optimal stent sizing and deployment.

* Discordance resolution: In cases where QFR or FFR results are discordant with angiographic findings or clinical presentation, IVUS/OCT can help identify underlying