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Imaging modality distinguishes amyloid-related HF from other conditions
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A cardiac imaging test can enable amyloid-related HF to be identified, according to findings published in JAMA Cardiology.
“This is a huge advance for patients with [transthyretin-related cardiac amyloidosis], which is underrecognized and often misdiagnosed,” researcher Adam Castano, MD, MS, a cardiology fellow at Columbia University Medical Center, said in a press release. “This test will spare certain patients from having to undergo a biopsy in order to get a definitive diagnosis. Many people with [transthyretin-related cardiac amyloidosis]are frail and elderly, so being able to avoid a biopsy, even when it can be done with a less-invasive catheter-based procedure, is a significant step forward.”
In the retrospective, multicenter study, the researchers evaluated 229 patients from three U.S. amyloid centers undergoing assessment for cardiac amyloidosis, including via technetium 99m pyrophosphate (Tc 99m PYP), between December 2010 and November 2015.
After applying exclusion criteria, the researchers included 171 patients (86% men; median age, 73 years; range, 65-79) in the study. Of these, 121 had transthyretin-related cardiac amyloidosis (ATTR-CA), 34 had light chain-related amyloidosis and 16 had nonamyloid HF with preserved ejection fraction (HFpEF).
All patients underwent a single Tc 99m PYP cardiac scan read by nuclear cardiologists and radiologists as part of a routine amyloid assessment.
The researchers evaluated Tc 99m PYP cardiac retention using a semiquantitative visual score (range, 0 [no uptake] to 3 [uptake greater than bone]). Additionally, Tc 99m PYP cardiac retention was assessed through a quantitative heart to contralateral (H/CL) ratio of blood counts in a region of interest over the heart, divided by backward counts in an identical size region over the contralateral chest, including ribs, soft tissue and blood pool. The researchers defined a visual score of 2 or higher, or an H/CL ratio of 1.5 or greater, as indicative of ATTR-CA. The primary outcome was time to death after Tc 99m PYP cardiac scan.
Castano and colleagues found that a semiquantitative visual score of 2 or higher was significantly more prevalent among the patients with ATTR-CA vs. those with another condition (ATTR-CA, 87.6%; others, 12%; P < .001).
Consistent with previously published single-center data, those with ATTR-CA also had a greater H/CL ratio (median value, 1.74; interquartile range, 1.53-1.98 vs. 1.16; interquartile range, 1.02-1.30; P < .001), the researchers wrote.
An analysis of Tc99m PYP uptake by clinical disease state revealed that patients with NYHA class I or class II symptoms had no difference in H/CL ratio vs. patients with NYHA class III or class IV symptoms (I or II, median H/CL ratio, 1.51; interquartile range, 1.2-1.83; III or IV, median H/CL ratio, 1.6; interquartile range, 1.33-1.88; P = .82).
The overall sensitivity for detecting ATTR-CA using a semiquantitative visual score of 2 or higher was 88%, and the overall specificity was also 88% with an area under the curve of 0.943 (95% CI, 0.902-0.977). In a quantitative analysis of myocardial Tc 99m PYP uptake, which involved combining an H/CL ratio of at least 1.5 (for centers using a 1-hour incubation) and an H/CL ratio of at least 1.3 (for when 3-hour incubation was used), the overall sensitivity was 91% and the overall specificity was 92%, with an area under the curve of 0.96 (95% CI, 0.93-0.981).
Thirty-three patients (19.3%) died during the study period. Among the subtypes evaluated, probability of death was 32.4% for patients with light-chain related amyloidosis, 26.4% for patients with ATTR-CA and 6.3% for patients with HFpEF.
Although a visual score of 3 vs. 2 was not associated with death (P = .22), H/CL ratio of at least 1.6 conferred elevated risk for death compared with H/CL ratio of less than 1.6 (HR = 3.911; 95% CI, 1.155-13.247) and the trend remained at 5 years (log-rank P = .02), the researchers wrote. – by Jennifer Byrne
Disclosure: Castano reports being funded by a fellowship sponsored in part by Merck. Please see the full study for a list of the other researchers’ relevant disclosures.
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