Overview of Fractional Flow Reserve
Doctors use a process called angiography to get a clear picture of your coronary anatomy (the blood vessels supplying your heart). This helps them see how much narrowing, also called stenosis, plaque, or a blockage, is present in your coronary artery. The blockage can cause the inside of your coronary vessels to look irregular, and doctors measure the size of this irregularity based on a percentage. This percentage helps the doctors understand how much of your artery is blocked. They classify the blockage as mild, moderate, or severe.
Figuring out how to treat moderate blockages in coronary artery disease can be tricky for heart doctors or interventional cardiologists. They can use a method known as angioplasty and stenting to help increase blood flow to your heart and reduce chest pain. However, sometimes it’s not clear whether these methods are the best choice. This is where something called Fractional Flow Reserve (FFR) comes in.
The FFR is another tool that can help doctors identify those tricky moderate blockages. It’s a procedure that measures the blood pressure and flow through a specific part of the coronary artery. If FFR shows that the blood flow isn’t seriously blocked, the blockage does not need to be treated with angioplasty or stenting. Instead, the doctor can safely treat the patient with medications.
A doctor can do FFR during a coronary angiogram or a cardiac catheterization, which are both standard ways to examine your heart and blood vessels. The FFR has proven to be a helpful way to evaluate “intermediate” blockages and to determine whether angioplasty or stenting is required.
How is Fractional Flow Reserve performed
FFR, or Fractional flow reserve, is a procedure that’s part of a heart test called a diagnostic cardiac catheterization. This test lets your doctor determine if any of your heart’s arteries are blocked. To do this, your doctor will use a special piece of equipment called a guide catheter, and a special wire, to measure the blood pressure on both sides of the blockage in the artery. One side is called the ‘proximal’ side – or the side before the blockage – and the other side is called the ‘distal’ side – or the side after the blockage. Your doctor can use a type of x-ray to help properly place the special wire.
Now, to get the most accurate FFR measurement, your doctor needs to make sure that the blood is flowing through your heart’s arteries as fast as it can – this is called maximal hyperemia. This can be achieved by using a special drug that is usually given through an IV. This drug is called adenosine.
To calculate the FFR, your doctor will divide the blood pressure on the ‘distal’ side (after the blockage) by the blood pressure on the ‘proximal’ side (before the blockage). In a perfect situation where there are no blockages, this ratio would be 1. But if there is a blockage, the ratio would be less than 1. For instance, if the FFR value is 0.80, it means that the blood flow in the affected artery is 80% of what it would be if the artery was completely clear.
This FFR value helps your doctor determine the severity of the blockage, and decide the best course of treatment. If the FFR is less than 0.75, the blockage is severe and is restricting blood flow, making a surgical procedure to clear the blockage necessary. If the FFR is higher than 0.80, the blood is flowing reasonably well despite the blockage, and your doctor may decide to manage the condition with medicines. If the FFR falls in between (from 0.75 to 0.80), the best treatment method isn’t clear and further evaluation is required.
What Else Should I Know About Fractional Flow Reserve?
Coronary artery disease (CAD), a condition where the blood vessels that supply blood to the heart narrow down, is one of the top causes of death in the United States. It’s responsible for about one out of every four deaths each year.
One common treatment for this is coronary revascularization, a procedure to restore the blood flow to the heart. This process is especially helpful in reducing symptoms and the risk of heart attacks and death in acute coronary syndromes (ACS), a medical term for situations where the blood supplied to the heart muscle is suddenly blocked. However, the use of this procedure for stable CAD, when the disease is not progressing or changing, is not as straightforward.
Determining when to use coronary revascularization has relied heavily on visual inspections of the heart’s blood vessels using a procedure called angiography. During this, the patient’s symptoms, medical history, the visual appearance of the blood vessels in the heart, and the choice between other treatment options like Coronary Artery Bypass Grafting (CABG), a type of surgery, are considered. However, since this decision-making process involves a lot of judgment on the part of the doctor, there have been potential cases of misuse.
To overcome these issues, trials have been conducted to develop guidelines, ensuring that the procedure is used appropriately. These guidelines, known as Appropriate Use Criteria (AUC), aim to make sure that the right treatment is provided to the right patient at the right time, and for the right reasons.
In the early 1990s, FFR, a technique used to determine the severity of narrowing of the heart’s arteries, was developed. An important trial in 2001 demonstrated that it was safe to delay coronary revascularization if the FFR was above 0.75, indicating moderate blockage. However, its use was not widespread for various reasons.
In 2007, a study called COURAGE found no added benefit of routinely performing coronary revascularization in patients with stable CAD compared to giving them optimal medications alone. This finding, along with the issue of inappropriate stenting (placing a small mesh tube to keep the artery open), and the establishment of guidelines, have given renewed importance to the use of FFR.
