medwireNews: Technetium 99m pyrophosphate (Tc 99m PYP) planar cardiac imaging accurately differentiates transthyretin (ATTR) cardiac amyloidosis from other amyloid conditions and may also predict survival, US researchers report.
This finding is “clinically important because treatments for this form of heart failure [ATTR cardiac amyloidosis] differ from other cardiomyopathies (including the avoidance of digitalis, calcium channel blockers, and high-dose beta-blockade)”, Adam Castano (Columbia University Medical Center, New York) and colleagues explain.
The researchers retrospectively assessed Tc 99m PYP cardiac imaging data for 171 patients (86% men, median age 73 years) who underwent evaluation for cardiac amyloidosis at three amyloid centres in the USA. Of these patients, 121 had ATTR cardiac amyloidosis, 34 had light-chain-related (AL) amyloidosis and 16 had nonamyloid heart failure with preserved ejection fraction (HFpEF).
As reported in JAMA Cardiology, patients with ATTR cardiac amyloidosis had a significantly higher quantitative heart to contralateral (H/CL) imaging ratio than patients with AL amyloidosis and HFpEF, at a median of 1.73 vs 1.16. This finding is “consistent with previously published single-center data”, the researchers remark.
And when the team used a combined H/CL cutoff of 1.5 or greater for centers that used a 1-hour incubation and 1.3 or greater for those with a 3-hour incubation time, the overall sensitivity and specificity for detection of ATTR cardiac amyloidosis were 91% and 92%, respectively.
During 1 year of follow-up, 33 (19.3%) patients died. The researchers found that those with an H/CL ratio of 1.6 or greater had a significant 3.9-fold increased risk of death, which increased to 7.9-fold upon multivariate adjustment, compared with patients who had an H/CL ratio below 1.6.
Furthermore, Kaplan-Meier survival analysis showed that patients with an H/CL ratio of 1.6 or above had significantly worse 5-year survival, at approximately 35%, than those with a lower ratio, at approximately 70%.
Castano and co-authors also note that patients with a high H/CL ratio had a significantly thicker interventricular septal wall, a lower stroke volume index and a lower myocardial contraction fraction, which is “suggestive of more advanced disease”.
They conclude: “[D]etection of ATTR cardiac amyloidosis using Tc 99m PYP in vulnerable individuals may be important not only for diagnosis and prognostication, but also for early identification of the disease.
“The recognition of cardiac amyloidosis before overt HFpEF symptoms ensue may be a key therapeutic goal given that the majority of the emerging agents are designed to prevent further amyloid deposition with no direct effect on deposited amyloid”, they say.
By Laura Cowen
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