Instantaneous wave-free ratio

# Instantaneous Wave-Free Ratio

The Instantaneous Wave-Free Ratio (iFR) is a diagnostic tool used in the field of cardiology to assess the severity of coronary artery stenosis. It is a non-hyperemic pressure ratio that measures the pressure difference across a coronary artery lesion during a specific period of the cardiac cycle when the heart is at rest.

Background

Coronary artery disease is a condition characterized by the narrowing of the coronary arteries due to the buildup of atherosclerotic plaques. This can lead to reduced blood flow to the heart muscle and result in chest pain or myocardial infarction. Traditionally, the severity of coronary stenosis has been assessed using Fractional Flow Reserve (FFR), which requires the use of a hyperemic agent to induce maximum blood flow.

Principle

The iFR is calculated during the wave-free period of diastole, a phase in the cardiac cycle when the resistance in the microcirculation is naturally minimized. This allows for the assessment of the pressure gradient across a coronary lesion without the need for pharmacological agents. The iFR is expressed as a ratio of the distal coronary pressure to the aortic pressure.

Clinical Use

The iFR is used to guide percutaneous coronary intervention (PCI) decisions. It provides a physiological assessment of coronary stenosis, helping clinicians determine whether a particular lesion is likely to benefit from stenting. An iFR value below a certain threshold indicates that the lesion is hemodynamically significant and may require intervention.

Advantages

One of the main advantages of iFR over FFR is that it does not require the administration of hyperemic agents, which can cause discomfort and side effects in patients. This makes the procedure quicker and more comfortable for patients. Additionally, iFR can be measured more rapidly, reducing the overall time of the procedure.

Limitations

While iFR offers several advantages, it may not be suitable for all patients or lesions. Certain anatomical or physiological conditions may affect the accuracy of iFR measurements. Clinicians must consider these factors when interpreting iFR results.

Related Pages

• Fractional Flow Reserve
• Coronary Artery Disease
• Percutaneous Coronary Intervention
• Atherosclerosis

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