MIBG Scans Prove Valuable in Determining Familial Amyloid Polyneuropathy Patients’ Outcomes, Study Shows

An imaging technique that uses tiny amounts of radioactive chemicals can help doctors predict the outcomes of cases of familial amyloid polyneuropathy, according to a Portuguese study.

The research also demonstrated that a liver transplant can stabilize FAP patients’ heart conditions.

The University of Lisbon study was published in the journal Revista Portuguesa de Cardiologia. Its was “Progression of myocardial sympathetic denervation assessed by ¹²³I-MIBG imaging in familial amyloid polyneuropathy and the effect of liver transplantation,”

FAP is a neurodegenerative disease, but can also affect the heart and kidneys.

It stems from deposits of faulty amyloid protein components known as peptides in the heart and other organs. An amyloid-peptide buildup in the heart can impair cardiac innervation — the brain’s ability to send nerve signals that control heartbeats.

Doctors use an imaging technique called myocardial scintigraphy to determine whether cardiac innervation is normal or impaired. The radioactive element used in the imaging is iodine-123, also known as metaiodobenzylguanidine, or MIBG. So doctors call it MIBG scintigraphy.

In previous studies, imaging has detected impaired innervation in early stages of FAP.

Previous studies have also linked poorer patient prognosis and an increase in their risk of dying to a heart-lung innervation ratio. The heart-to-mediastinum ratio compares the innervation the heart receives with the innervation that the main component of the lungs, the mediastinum, receives. Doctors use the ratio to predict heart failure.

The main way to treat a person with FAP is a liver transplant, which slows the progression of the disease. While the operation stops the progression of neurological problems, amyloid deposits can continue building in the heart, leading to cardiac complications.

Until the Lisbon research, no study had used MIBG scans to track FAP patients’ deterioration in cardiac innervation. Tracking the deterioration helped the team identify changes in the H/M ratio, which they could then use to predict patient outcomes.

In addition, few previous studies had looked at a liver transplant’s impact on cardiac innervation.

The Lisbon researchers followed 232 FAP patients an average of 4 1/2 years. Once a year they checked patients’ hearts and used MIBG imaging to determine their H/M ratios.

A key finding was that deterioration of cardiac innervation occurs slowly before FAP symptoms show up, but accelerate once symptoms appear.

Another important finding was that the first MIBG scan was a strong predictor of patients’ outcome and risk of death. Since deterioration in cardiac innervation occurs very slowly, however, subsequent MIBG scans had little effect on patients’ prognosis.

Researchers also discovered that deterioration in cardiac innervation stabilized after a liver transplant. While a transplant failed to improve cardiac innervation, it did not worsen after the operation.

By providing researchers with H/M ratios, the study showed that MIBG scintigraphy is a valuable tool for predicting FAP patient outcomes. It also showed that a liver transplant stabilizes cardiac innervation.

The research team emphasized that the earlier a liver transplant is done, the earlier that deterioration of cardiac innervation can be stopped.