Using Tc 99m PYP cardiac imaging may help diagnose and detect patients with heart failure

A retrospective cohort study found that using technetium 99m pyrophosphate (Tc 99m PYP) cardiac imaging helped detect and diagnose patients with transthyretin-related cardiac amyloidosis, a cause of heart failure with preserved ejection fraction.

The imaging technique also could accurately differentiate transthyretin-related cardiac amyloidosis from AL cardiac amyloidosis.

Lead researcher Adam Castano, MD, MS, of Columbia University Medical Center in New York, and colleagues published their results online in JAMA Cardiology on Aug. 24.

This analysis examined 171 patients who underwent evaluation for cardiac amyloidosis between Dec. 1, 2010, and Nov. 1, 2015, at three amyloid centers. The researchers evaluated patients from the Columbia University Center for Advanced Cardiac Care, the Boston University Amyloidosis Center and the Mayo Clinic.

Of the patients, 121 had transthyretin-related cardiac amyloidosis. The median age was 73 years old, and 86 percent of patients were males.

The researchers developed an algorithm to calculate a quantitative score and compare the concentration in the heart with a similar area in the opposite side of the chest. They measured Tc 99m PYP in the heart using a semiquantitative visual score and a quantitative heart to contralateral (H/CL) ratio.

The researchers said that Tc 99m PYP imaging demonstrated 91 percent sensitivity and 92 percent specificity for detecting transthyretin-related cardiac amyloidosis with an area under the curve of 0.960.

They added that univariable and multivariable Cox proportional hazards regression analyses showed that an H/CL ratio of 1.6 or greater predicted worse survival in patients with transthyretin-related cardiac amyloidosis.

During a five-year follow-up period, survival was significantly worse if patients had an H/CL ratio of 1.6 or greater compared with an H/CL ratio of less than 1.6, according to a Kaplan-Meier analysis.

“The visual score and the H/CL ratio in Tc 99m PYP planar cardiac imaging should be incorporated into diagnostic and prognostic algorithms for cardiac amyloidosis,” the researchers wrote.

The researchers mentioned a few potential limitations of the study, including referral bias and a high pretest probability for cardiac amyloidosis, which could have limited its generalizability to a broader population. They also said that echocardiography used in the study did not include strain-rate imaging. In addition, they could not determine the role of Tc 99m PYP cardiac imaging in genotype-positive but phenotype-negative individuals.

As of now, there are no effective treatments for transthyretin-related cardiac amyloidosis, but the researchers mentioned that there were several potential promising drugs being studied in phase 3 trials. Castano said in a news release that the researchers hoped to use Tc 99m PYP cardiac imaging to detect transthyretin-related cardiac amyloidosis before it develops into advanced heart failure and then use of the new therapies to treat the disease.

“This is a huge advance for patients with [transthyretin-related cardiac amyloidosis], which is under recognized and often misdiagnosed,” Castano said in a news 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.”