Hello, my name is Jan Griffin. I am a heart failure cardiologist at the Medical University of South Carolina, and today I'm going to be speaking about diagnostic testing for amyloidosis. These are our learning objectives. We are going to recognize findings suggestive of amyloidosis and select appropriate testing for diagnosis of amyloidosis. So diagnosis of amyloidosis can be challenging due to a number of other reasons for increased wall thickness on echocardiograms, such as hypertrophic cardiomyopathy, aortic stenosis, and hypertensive heart disease, to name a few. There are many diagnostic algorithms available. I like this one published in 2022 and the heart failure guidelines. So you start off with a suspicion for cardiac amyloidosis, and this may be based on history, electrocardiogram, echocardiogram, cardiac MRI, and the first thing you need to do is rule out the presence of a monoclonal light chain. If there is no monoclonal light chain present, you can proceed with non-biopsy diagnosis of cardiac amyloidosis using a PYP scan. However, if there is a monoclonal light chain present, then you need to consult hematology or oncology and consider biopsy of the heart or another organ. If there is no amyloid detected on an extracardiac biopsy, it must be noted that that does not rule out amyloidosis and you must biopsy the affected organ, in this case being the heart. And if you do detect amyloid on the heart biopsy, then you need to determine which type of amyloid is present, and this is done by using mass spectrometry. So the first test that you are likely going to pursue is an electrocardiogram when you see these patients in the outpatient or inpatient setting. Classical low voltage is found in as little as 25-40% of patients with cardiac amyloidosis. A more accurate parameter is voltage-to-mass ratio. There are several ways to calculate voltage-to-mass ratio, one being using the total QRS score divided by the LV mass index. This was found to be reasonably sensitive between 81-87% and specific somewhere between 79-82% to differentiate cardiac amyloidosis from hypertrophic cardiomyopathy or hypertensive heart disease. Other findings that you may see in an electrocardiogram are atrial fibrillation or flutter, and these are seen in over 50% of people with ATTR cardiac amyloidosis. Conduction delay including atrioventricular block for first or second degree AV block is seen in over 50% with ATTR, and intraventricular conduction delay. Pseudo-infarct pattern may also be seen on ECG, and this is where there are two or more contiguous Q waves in the absence of obstructive CAD, left bundle branch block, or LV wall motion abnormalities. The next test that you are likely going to pursue is an echocardiogram, and this is an essential part of the screening process for amyloidosis. It is the initial screening test of choice in those for whom you have a suspicion of cardiac amyloid, but it is insufficient as an independent diagnostic test, and it cannot differentiate between AL and ATTR cardiac amyloidosis. Here are some of the high-yield echo findings, some of the red flags that are seen on echo, and these should raise suspicion for cardiac amyloidosis in the appropriate clinical context. Most importantly, and the first thing that will likely draw your attention, is increased LV wall thickness. This is generally greater than 12 mm and should be in the absence of abnormal loading conditions. You may also see increased relative wall thickness, and this cut-off is greater than 0.42. Other findings you might see on 2D imaging are interatrial septal thickening, RV hypertrophy, pericardial effusion, diffuse valve thickening, biatrial enlargement, and a preserved ejection fraction with low stroke volume index. When you're looking at Doppler imaging, you may find reduced tissue Doppler, so looking at S', E' and A' velocities, all under 5 cm per second, and this is known as the 5-5-5 sign. You may see a restrictive transmitral Doppler filling pattern, and you will see the mitral inflow demonstrates a high E wave velocity with small A wave velocity, with an E to A ratio greater than 2. You will likely see diastolic dysfunction greater than or equal to grade 2, and a reduced TAPSE. And finally, when you're looking at speckle tracking strain imaging, you may see this typical apical sparing pattern, also known as the cherry-on-top appearance. There may be low flow, low gradient, severe aortic stenosis, and you may also see impaired left atrial strain. So here are some of the echo images that I have just referred to. Here on the left, you can appreciate the pulse wave Doppler demonstrating a restrictive pattern, so high E wave, low A wave velocity. And on the bottom right here, this is myocardial speckle tracking imaging, and this shows the typical apical sparing pattern. Here you see the longitudinal strain in the basal and the MYG segments of the LV are more severely impaired than the strain in the apical segments, and then this gives you your bullseye pattern of this cherry-on-top appearance. A cutoff value of 1 can differentiate cardiac amyloidosis from other left ventricular hypertrophy phenotypes with a good sensitivity and specificity. Here we see the parasternal long axis view, 4-chamber view, and the short axis view, and you can really here appreciate increased wall thickening, which is characteristic of ATTR cardiac amyloidosis. Cardiac MRI provides high-resolution imaging with an ability to characterize tissue and provides a functional assessment, particularly if echo images are poor. It can assist in differentiating between cardiac amyloid and other cardiac processes with increased wall thickness, and it may assist in early detection in those with systemic amyloidosis. On cardiac MRI, you will often see diffuse subendocardial or transmural late gadolinium enhancement. You may see increased myocardial native T1 and extracellular volume expansion, looking for a value greater than 40%. T2 mapping can assess myocardial edema, and you may see nulling of the myocardium before or at the same inversion time as blood pool. It is important to remember that cardiac MRI cannot differentiate between AL and ATTR amyloidosis. In patients with biopsy-proven systemic amyloid, however, the cardiac MRI features that are noted here can be used along with structural findings of increased wall thickness and myocardial mass to diagnose cardiac involvement, but you must have biopsy-proven extracardiac disease. The use of cardiac MRI is evolving, and it is used to detect and quantify disease burden. So late gadolinium enhancement detects areas of fibrosis. The administration of contrast and extracellular volume measurement enables us to isolate the signal from the extracellular space, providing an estimate of the amyloid deposits. The hypothesis of ECV being a surrogate measure of the amyloid burden within the myocardium and the degree of amyloid deposition in the myocardium being one of the major drivers of survival in these patients. Native T1 is a measure of myocardial relaxation, and it's influenced by extracellular and intracellular compartments. And you can see here on the cardiac MRI images, on the right, you see very clearly this transmural late gadolinium enhancement. It's very obvious. In the middle, subendocardial late gadolinium enhancement, a little less obvious, a little more subtle. And then when you have no late gadolinium enhancement at all here on the left. Cardiac biomarkers are useful for raising suspicion. They are not specific, but values are often higher in the compensated state than an average HF-PEF patient. And they are crucial for the staging of disease, as I'm going to show you on the next slide. NT-proBNP is highly sensitive. It is not specific, but it is a marker of cardiac involvement in patients with biopsy-proven AL amyloidosis. And lower than the 97.5th percentile for normal subjects virtually excludes significant AL cardiac amyloidosis. You see increased levels of NT-proBNP in AL amyloidosis with preclinical cardiac involvement, who may have an apparently normal echo. And this is due to the known toxic effects of the light chains. NT-proBNP levels tend to be lowest in patients with variant ATTR cardiac amyloidosis and highest in those with AL cardiac amyloidosis. And NT-proBNP is recommended as a screening tool in pre-symptomatic variant TTR carriers with a predominant cardiac phenotype mutation. And typically, it's recommended to start screening with this about 10 years prior to the predicted age of onset. So as I mentioned, these cardiac biomarkers can be used for staging and prognosis. And here are three staging systems that are in use. The first here, the Mayo staging system, is used for patients with wild-type ATTR cardiac amyloidosis. They use troponin T and NT-proBNP with the cutoffs shown here to classify patients as stage 1, stage 2, or stage 3. And you can see the median survival end months here on the chart. The UK NAC system can be used for patients with either wild-type or variant ATTR cardiac amyloidosis. And this staging system uses EGFR cutoff of 45 and NT-proBNP cutoff of 3,000. And then more recently, the Columbia score, again, can be used in patients with wild-type or variant ATTR. And this builds on the UK NAC or the Mayo staging system by adding the daily furosemide equivalent dose and the NYHA class, grading people as stage 1 to stage 3, with median survival of 91 months at stage 1, 36 or 39 at stage 2, and 20 at stage 3. And the Columbia score then provides incremental value over and above the UK NAC and the Mayo risk scores. So it is imperative, as I mentioned earlier, that we rule out AL amyloidosis. And we do this by checking serum and urine immunofixation electrophoresis and the serum free light chain ratio. The serum free light chain ratio and serum immunofixation has a 99% sensitivity for ruling out AL amyloidosis. Again, I want to stress that it is imperative that immunofixation be performed as electrophoresis is not sufficient to rule out AL amyloid. There are suggested normal reference ranges for serum free light chains in patients with CKD. The reason for this is that free light chains are filtered by the glomeruli. And renal dysfunction can lead to increased serum free light chain concentrations. And it affects the kappa and lambda light chains differently. So when you're making a diagnosis of AL cardiac amyloid, it is definitely more challenging in patients with chronic kidney disease. And if there is any question, you should always speak with your hematology oncology colleagues. Here on the chart are some suggested wider reference ranges for normal kappa lambda ratio in people with CKD stages 1 to 5. All of the aforementioned studies simply just raise suspicion for ATTR cardiac amyloidosis. And none are adequate as a diagnostic test. So there are three bone AVID radio tracers available. And in the United States, we generally use pyrophosphate or PYP. Any grade 2 or 3 uptake on a PYP scan is used to diagnose ATTR cardiac amyloidosis. It has 100% positive predictor value for ATTR cardiac amyloidosis in the absence of a monoclonal protein on serum and urine immunofixation and in the presence of a normal serum free light chain ratio. You should remember that perigine grade 1 may be seen in other subtypes such as AL, amyloid A, or apolipoprotein A1. And that is not diagnostic for ATTR cardiac amyloidosis. Here is an image of a PYP scan in somebody with grade 3 uptake. You can see here very clearly that the uptake in the myocardium is much greater than that of the surrounding ribs or bone. And here then is the SPECT imaging confirmation of the myocardial uptake. And this is showing the absence of blood pool. So this is a positive scan for ATTR cardiac amyloidosis. You can see false positive or false negative scans with PYP. And outlined here in this chart are some of the causes of false positive and false negative that you should be aware of. So based on the work of Gilmore and colleagues at the UK National Amyloidosis Centre, the non-biopsy diagnosis of TTR amyloid is positive if patients have unexplained heart failure or are carriers of a pathogenic TTR mutation. They must have echo or cardiac MRI findings consistent with or suggestive of cardiac amyloidosis. They must have either grade 2 or 3 uptake on scintigraphy. And there must not be a monoclonal protein present on serum or urine immunofixation with a normal free light chain ratio. If all of these are present, then the patient satisfies the non-biopsy diagnostic criteria for ATTR cardiac amyloidosis. It should be noted that AL amyloidosis can result in grade 1 uptake or a higher grade of uptake on bone scintigraphy. And we know that the sensitivity and specificity of grade 2 or 3 cardiac uptake on scintigraphy for diagnosing cardiac ATTR as opposed to cardiac AL amyloidosis in patients who had a monoclonal protein was only 92 and 91% respectively. So any patient who has a monoclonal protein present on immunofixation in whom you have a suspicion for cardiac amyloidosis who also has uptake on bone scintigraphy must undergo additional testing. And this includes histologic diagnosis and amyloid typing. So in other words, they must undergo a biopsy. Here on the slide, you can see an endomyocardial biopsy from a patient with cardiac amyloidosis. Again, we see just staining positive for cardiac amyloid. It does not differentiate between AL or ATTR. And this biopsy specimen must be sent for mass spectrometry to differentiate the type of amyloidosis present. Although amyloid can be identified on extracardiac tissue, the sensitivity is variable. The sensitivity of FATPAD and bone marrow biopsy is amyloid type dependent, as you can see here on the slide. So although extracardiac biopsies may be useful, a negative result must not be interpreted as inconclusive. And if you continue to have suspicion for amyloidosis affecting the heart, you must perform an endomyocardial biopsy. So in summary, echo and cardiac MRI are not diagnostic for cardiac amyloidosis. Non-biopsy diagnosis of ATTR cardiac amyloid can only be performed if there is grade 2 or grade 3 uptake on bone syntagraphy in the absence of a monoclonal protein in serum and urine immunofixation and in the presence of a normal free light chain ratio. A negative FATPAD or bone marrow biopsy does not rule out AL amyloidosis if there is a high clinical suspicion. And please beware of false positive or negative PYP scans. Thank you very much.

amyloidosis diagnosis

transthyretin amyloid

cardiac MRI

echocardiograms

biomarkers