New imaging helps diagnose cardiac patients without a trip to the cath lab

Cape Cod Hospital now offers a new way to obtain images of the heart. This new process helps doctors diagnose patients with blocked heart arteries. It also helps patients with medium blockages decide if they really need an invasive heart procedure, called a cardiac catheterization.

The new process is called CT-FFR, which stands for computed tomography–fractional flow reserve. It is a non-invasive diagnostic test. CT-FFR is a high-tech computer simulation that takes a traditional CT scan of the heart and calculates how much pressure is lost as blood flows through narrowed arteries caused by cholesterol blockage. By using physics and math, it helps doctors see if a blockage is actually starving the heart of blood without needing to perform an invasive procedure to get this same information. It is also an alternative to other non-invasive diagnostic tests like nuclear stress tests, said Tendoh F. Timoh, MD, FACC, FSCMR, a cardiologist with Cape Cod Healthcare. These non-invasive diagnostic tests are the first step for doctors to diagnose blockages and determine if cardiac patients can be treated with medication or if they need further investigation and/or treatment using invasive procedures such as cardiac catheterization.

“I personally think CT-FFR is one of the best new technologies for the diagnosis and management of coronary artery disease,” Dr. Timoh said.

More Accurate and Easier

Dr. Timoh explained that CT-FFR is an improved and easier option for both patients and doctors.

Traditionally, non-invasive heart tests for blockages involve two main types:

• Physiologic (Stress) Testing: This non-invasive test looks at how the heart responds to exercise. Examples are stress echocardiography or nuclear stress testing. While these are good, they take a lot of time. Also, their accuracy is only moderate, and they can sometimes miss a problem that needs fixing.
• Anatomic Testing (CT Scan): This uses a CT scan to see the physical structure of the three main heart arteries and any potential blockages. It can find coronary plaque (buildup in the arteries). But its accuracy is also modest for finding blockages that are serious enough to need treatment.

If a non-invasive test is positive or unclear, patients are usually sent to the catheterization (cath) lab. There, an invasive procedure called cardiac catheterization is used to confirm the problem. This is the best way to diagnose serious heart disease. During this procedure, the patient is lightly sedated. A thin tube is put into a blood vessel and guided to the heart. Doctors inject a dye to see the blockage on an X-ray (an angiogram).

Sometimes, to assess moderate blockages, the doctor performs an invasive FFR measurement. To do this, the doctor guides a tiny, specialized wire into your heart artery to measure the blood pressure before and after a blockage. By comparing these numbers, the doctor can tell if the narrowing/blockage is actually restricting blood flow enough to require a stent, helping them avoid unnecessary treatments.

With continued advancements in anatomic testing, the CT scan can now obtain this FFR measurement, noninvasively. “This is a new milestone in non-invasive testing, as we can combine anatomic methods with information previously only available through the invasive cath lab,” Dr. Timoh said.

Benefits of CT-FFR

The CT-FFR process takes only a few minutes and is non-invasive. Patients are given medicine to control their heart rate and widen blood vessels for the best images. The CT scanner at Cape Cod Hospital is a high-quality, 256-slice scanner that can scan the whole heart in a single heartbeat, he said.

• How it works: If a major blockage is seen on the scan, the images are sent to a CT-FFR platform. AI and fluid dynamics measure the blood flow. This results in a CT-FFR value that shows the physiologic effect of the blockage.
• High Reliability: Dr. Timoh said CT-FFR is highly accurate and is less likely to miss a problem. It helps doctors find disease early.
• Cost-Effective: Researchers at the University of Virginia found that CT-FFR saves money by acting as a "gatekeeper" to reduce the number of invasive angiograms that aren't necessary.
• “If the scan is negative, it’s truly negative, so we don’t have to worry about the main heart arteries being blocked,” Dr. Timoh said.

If the scan is positive, CT-FFR accurately measures the blockage. This tells doctors if a patient needs to go to the cath lab. CT-FFR can also analyze the plaque to see if it is high-risk. High-risk plaque is more likely to rupture and cause a heart attack in the future. These patients with high-risk plaques must be treated more aggressively with medicine to lower their cholesterol.

The only drawback of CT-FFR is that for a suspected moderate blockage, there is a "gray zone" where the value is still uncertain. In this case, an invasive cardiac cath is still needed for confirmation. Dr. Timoh believes this gray zone will shrink as the AI modeling continues to improve.

CT-FFR is best for patients who have moderate heart risk or whose initial non-invasive tests are unclear. Patients with low risk can be treated with medicine. High-risk patients, such as those with persistent or intractable chest pain, are sent straight to the cath lab. CT-FFR helps doctors sort out the patients in the middle.

For both doctors and patients, CT-FFR is a welcome addition to the CT scan.

“It will tell you, do you have heart disease or not? It will help decide which patients with blockages will be better off with a cath lab procedure versus only medication. It will also help doctors know if they need to increase the medicine used to lower a patient's cholesterol,” he explained.