MedicalResearch.com Interview with:
Adam Castano, M.D., M.S.
Division of Cardiology
Columbia University Medical Center
New York Presbyterian Hospital
MedicalResearch.com: What is the background for this study?
Response: Transthyretin cardiac amyloidosis (ATTR-CA) is an increasingly recognized cause of heart failure with preserved ejection fraction (HFpEF). Traditionally, the gold standard for diagnosis has required an endomyocardial biopsy coupled with either immunohistochemistry or mass spectroscopy. These specialized tests are only performed at centers with experienced satff, do not yield prognostically useful information, may be inadvisable for frail older adults, and often present logistical challenges that lead to delayed care.
Fortunately, single center studies have demonstrated excellent diagnostic accuracy using technetium 99m pyrophosphate (Tc99mPYP) cardiac imaging for noninvasively detecting ATTR-CA and differentiating it from another major type of cardiac amyloidosis called light chain (AL). But the diagnostic accuracy of this technique in a multicenter study and the association of Tc99mPYP myocardial uptake with survival were not known prior to this study.
Therefore, we assessed in a multicenter study Tc99mPYP cardiac imaging as a diagnostic tool and its association with survival. We conducted a retrospective cohort study of 229 patients evaluated at 3 academic specialty centers for cardiac amyloidosis and also underwent Tc99mPYP cardiac imaging. We measured retention of Tc99mPYP in the heart using a semiquantitative visual score (range 0-3) and a more quantitative heart-to-contralateral (H/CL) ratio calculated as total counts in a region of interest over the heart divided by background counts in an identical size region of interest over the contralateral chest. The outcome measured was time to death after Tc99mPYP imaging.
MedicalResearch.com: What are the main findings?
Response: The main finding was that among 171 patients with biopsy proven diagnoses (121 with ATTR and 50 with non ATTR [34 AL, 16 HFpEF]), Tc99mPYP imaging was an excellent test with 91% sensitivity and 92% specificity for detecting ATTR-CA. In other words, 99mTcPYP was excellent both at diagnosing and ruling out ATTR-CA. In addition, we found that among patients who scanned positive for ATTR-CA, a H/CL ratio of 1.6 or greater predicted worse survival.
MedicalResearch.com: What should readers take away from your report?
Response: Tc99mPYP may be incorporated into diagnostic testing algorithms for patient with suspected cardiac amyloidosis. In patients for whom there is a high clinical suspicion of cardiac amyloidosis, Tc99mPYP may be of diagnostic and prognostic importance.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Tc99mPYP appears to be useful for noninvasively diagnosing and prognosticating ATTR-CA in patients who present to specialty amyloid centers but its application in patients who may have early ATTR-CA disease is not known. Future studies are needed to test whether patients diagnosed with ATTR-CA but who do not yet demonstrate advanced symptoms have detectable myocardial uptake of 99mTcPYP.
MedicalResearch.com: Is there anything else you would like to add?
Response: Our study corroborates data from another important study that demonstrated that 99mTcPYP along with 2 other radioisotopes commonly used in Europe can be used to diagnose ATTR-CA without the need for an invasive biopsy in patients who have been ruled out for AL cardiac amyloidosis from blood testing. The future application of 99mTcPYP scanning may enable easier and earlier diagnosis of ATTR-CA and holds promise to be used as a screening tool in at risk populations.
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