Kate Johnson

June 09, 2015

BALTIMORE — Myocardial scintigraphy, which is molecular imaging of the heart, can be used to predict major adverse cardiac events (MACE) in patients with transthyretin-type amyloidosis, according to results from a new study.

When the procedure is performed routinely with the bone radiotracer technetium-99m hydroxymethylene diphosphonate (99mTc-HMDP) as a part of the diagnostic work for transthyretin-type cardiac amyloidosis, it could "potentially save lives" by prompting a complete cardiac work-up in at-risk patients, said lead investigator Axel Van Der Gucht, MD, from Henri Mondor Hospital in Créteil, France.

"To our knowledge, this is the first report showing the prognostic value of 99mTc-HMDP myocardial scintigraphy in patients with transthyretin-type amyloidosis," Dr Van Der Gucht told Medscape Medical News.

Positive findings indicate the need for "a more attentive clinical and preclinical follow-up, including electrocardiography, transthoracic echocardiogram, and biological tests," he explained.

Dr Van Der Gucht and his colleagues evaluated 55 patients diagnosed with transthyretin-type amyloidosis who underwent both whole-body and cardiac 99mTc-HMDP scintigraphy.

He presented the results here at the Society of Nuclear Medicine and Molecular Imaging 2015 Annual Meeting.

The myocardial uptake of 99mTc-HMDP and the heart-to-skull retention ratio were used to diagnose cardiac amyloidosis. The reserachers confirmed the diagnosis with endomyocardial and extracardiac biopsy or, in the absence of biopsy, transthoracic echocardiogram or cardiac MRI.

Major Cardiac Adverse Events

The composite primary end point of the study was major cardiac adverse events — including death, heart failure, atrial fibrillation, and conduction disturbances — at 6 months.

Of the 55 study participants, 21 were diagnosed with wild-type transthyretin cardiac amyloidosis and 26 were diagnosed with mutated transthyretin cardiac amyloidosis.

In terms of the primary end point, "patients with a high heart-to-skull ratio of imaging agent retention had a worse prognosis," Dr Van Der Gucht reported.

The 6-month MACE-free survival rate was better in patients who had a heart-to-skull retention ratio below 1.94 than in those who had a higher ratio (95% vs 60%; P = .025).

When this prognostic information was combined with New York Heart Association class, patients could be stratified by MACE-free survival, with prognostic groups ranging from 44% to 100%%, he explained.

 
I believe that this model needs to be validated in a larger number of patients.
 

"This study is important because, currently, no prospectively validated and consistent model system exists that can reliably prognosticate patients with transthyretin-type amyloid cardiomyopathy," said Taimur Sher, MD, from the Mayo Clinic in Jacksonville, Florida.

Having said that, given the small sample size, I believe that this model needs to be validated in a larger number of patients," he told Medscape Medical News.

Diagnosis is "often delayed because of nonspecific presenting symptoms and failure to recognize early signs of amyloid heart disease on routine cardiac imaging," according to Dr Sher, who published a recent review on cardiac amyloidosis (Future Cardiol. 2014;10:131-146).

The researchers have demonstrated that the combination of 99mTc-HMDP myocardial scintigraphy and clinical variables is predictive of MACE, Dr Sher explained. "Advancements in cardiac imaging and proteomics are expected to positively impact our ability to diagnose, prognosticate, and treat cardiac amyloidosis," he added.

Dr Van Der Gucht and Dr Sher have disclosed no relevant financial relationships.

Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2015 Annual Meeting: Abstract 27. Presented June 7, 2015.

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