What is a PYP scan for ATTR-CM?
Fact-checked by An early and accurate diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM) is vital for promptly starting treatments that can help slow disease progression. Technetium-99m pyrophosphate scans — more simply called PYP scans — are a specialized type of noninvasive heart imaging that plays a key role in the diagnostic process.
ATTR-CM is a type of cardiac amyloidosis, a group of heart diseases that occur when abnormal protein clumps, called amyloid deposits, accumulate in the heart. In ATTR-CM, these deposits contain a protein called transthyretin (TTR).
In the past, invasive heart muscle biopsies were required to diagnose ATTR-CM. Now, most ATTR-CM diagnoses can be achieved with PYP scans and other noninvasive tests.
Why a PYP scan is important
PYP scans are an important step in the diagnostic process for most people with ATTR-CM. These scans allow visualization of TTR amyloid deposits in the heart, a hallmark of the disease.
When a person first experiences ATTR-CM symptoms, they’ll usually undergo general heart health tests to identify cardiac issues that might be consistent with ATTR-CM, as well as blood or urine tests to exclude other types of cardiac amyloidosis.
However, none of these heart health tests for amyloidosis can definitively establish the presence of TTR deposits. As such, doctors will usually then order a PYP scan to detect ATTR-CM.
A positive PYP scan result is highly indicative of ATTR-CM and helps rule out light-chain (AL) amyloidosis, another type of cardiac amyloidosis that requires a different treatment approach. For many, the test can confirm an ATTR-CM diagnosis without the need for more invasive and riskier biopsies.
Doctors can also use the results from this noninvasive heart scan to determine the extent of amyloid buildup in the heart, helping them better understand the patient’s prognosis and care needs and to develop a tailored treatment plan as early as possible.
How does a PYP scan for ATTR-CM work?
A PYP scan is a cardiac amyloidosis test that relies on radioactive tracer molecules and a specialized camera to visualize amyloid deposits in the heart.
A commonly used tracer, technetium-99m pyrophosphate (Tc99m PYP), gives the scan its name. However, other tracer molecules can be used for the test, including Tc99m hydroxymethylene diphosphonate (used in the U.S. and elsewhere) and Tc99m diphosphonate, which is more commonly used in Europe. These tracers contain very small amounts of radioactive material.
When injected into the body, the tracers bind to amyloid deposits and bone due to their specific calcium and mineral composition. The tracers bind more strongly to deposits containing TTR than to amyloid deposits that are associated with other forms of cardiac amyloidosis.
PYP scans are a type of scintigraphy, or gamma scan, which uses specialized cameras sensitive to radiation to visualize the tracer. If the tracer accumulates in the heart, it suggests the presence of cardiac TTR amyloid deposits.
What to expect during the scan
The entire process of a PYP scan may take up to three or four hours. During that time, you can expect to:
- receive an intravenous (into-the-vein) injection of the radioactive tracer, usually in the arm
- wait one to three hours while the tracer moves through the body, with the exact time depending on the specific tracer
- lie on your back on the scanner bed with your hands above your head for 30 to 45 minutes, staying still while the camera moves around and takes pictures
Unlike MRIs, PYP scans aren’t usually noisy, but they do require patients to lie very still in an enclosed space.
There are no major safety risks with the procedure, so you’ll usually be able to leave immediately after the scan and resume your usual activities.
Risks and safety
A PYP scan is a safe heart amyloidosis test with fewer risks than invasive biopsies. Some people may feel minor discomfort from the injection or from lying still on the scanner bed.
Although the tracer contains radioactive material, the radiation exposure is very low, comparable to the background radiation most people absorb in a year. Most of the tracer is excreted in urine or stool, while the rest is eliminated over time.
Interpreting PYP scan results
Healthcare providers typically report PYP scan results as positive, negative, or inconclusive for ATTR-CM.
This is determined with a visual grading system, called the Perugini scale, that rates the amount of tracer in the heart muscle relative to nearby bones, resulting in one of four grades:
- grade 0: very little or no tracer in the heart; normal uptake in the bones
- grade 1: some tracer in the heart, but still lower than in the bones
- grade 2: similar concentration of tracer in the heart and bones
- grade 3: higher concentration of tracer in the heart than in the bones
Grades 2 and 3 correspond to a positive result, grade 1 is inconclusive, and grade 0 is negative.
Alongside blood and urine test results excluding AL amyloidosis, a positive PYP result is usually sufficient to confirm an ATTR-CM diagnosis. A negative result suggests that ATTR-CM is unlikely, although false negatives are possible. In inconclusive cases, biopsies, cardiac MRIs, or other follow-up tests may be necessary.
Questions to ask your doctor before or after a PYP scan
Before the PYP procedure, you may want to talk with your healthcare providers about:
- what to expect during a PYP scan at their specific medical center
- how the scan fits in with the rest of the diagnostic process
- if there are special instructions to follow on the day of the test
- any concerns you have about heart amyloidosis imaging and its risks
If you are claustrophobic or have trouble lying still, it’s a good idea to let your doctors know in advance. They may prescribe a mild sedative to make you more comfortable during the procedure.
People who are pregnant, might be pregnant, or are breastfeeding should also alert their healthcare team before the scan.
After the scan, a few things to ask your healthcare team include:
- how and when the test results will be interpreted
- what follow-up steps are necessary for the diagnosis, including the potential need for genetic testing or counseling
- guidance about tracking symptoms
- the process of developing a care plan for ATTR-CM
Amyloidosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
