Nuclear Cardiac Study Now Available for Diagnosis of Suspected Cardiac Amyloidosis
Written by Keith Miller, MD, PhD, FACC
A new cardiac nuclear imaging study is now available at Bryan Heart for the evaluation of suspected cardiac amyloidosis. Technetium-labeled pyrophosphate (99mTc-pyrophosphate; 99mTc-PYP) localizes to myocardium infiltrated with amyloid fibrils composed of transthyretin, the basis of the most common form of cardiac amyloidosis. Combined with cardiac MRI, which Bryan Heart has offered for nearly 10 years, the 99mTc-PYP study affords the capability to definitively diagnose most cases of cardiac amyloidosis safely and non-invasively, without myocardial biopsy.
Once thought of as rare and without viable treatment options, cardiac amyloidosis (or amyloid cardiomyopathy) is now thought to be much more common than previously recognized. In addition, two recent developments have made it important to have an awareness of this condition and a working knowledge of when a diagnosis of cardiac amyloidosis should be considered. First, effective treatments are now available for the two major types of cardiac amyloidosis. Second, recent developments in cardiac imaging often make it possible to diagnose cardiac amyloidosis without requiring endocardial biopsy.
What is cardiac amyloidosis?
Cardiac amyloidosis is an infiltrative cardiomyopathy in which abnormal protein fibrils are deposited in the myocardium. It is increasingly recognized as a cause of heart failure in older patients, particularly with preserved ejection fraction.
Infiltrating protein fibrils come in one of two varieties:
- Immunoglobulin light chains (so-called AL-amyloidosis) which are composed of fragments of monoclonal light chains.
- Transthyretin, a liver-produced protein which can be mutated in a genetic form of amyloidosis or misfolded in a “wild-type” amyloid deposit. New treatments are available for this form of cardiac amyloid, making diagnosis of particular importance.
Amyloid cardiomyopathy should be considered in older persons who have:
- Been hospitalized for heart failure
- Elevated troponin levels
- Levels of NT-proBNP that are out of proportion to the clinical context
Patients typically present with preserved ejection fraction heart failure, often have symptoms of right-sided (e.g., leg edema and ascites) heart failure in addition to left-sided heart failure, and may have unexplained atrial arrhythmias or conduction system disease. In addition, patients may exhibit symptoms of involvement of other organs such as bilateral carpal tunnel syndrome, biceps tendon rupture, and peripheral neuropathy.
Echocardiography is usually the first imaging modality, and typical findings include increased LV wall thickness and significant diastolic dysfunction, biatrial enlargement, and a characteristic granular sparkling appearance of the myocardial wall. A summary of diagnostic clues to ATTR-CM can be found in the table below. Also see the diagnostic algorithm for patients with suspected cardiac amyloidosis.
If you have questions or would like a patient evaluated for cardiac amyloidosis, please contact Bryan Heart at 402-483-3333.
Circulation: Heart Failure; Vol. 12, No. 9; 4 Sept 2019; Expert Consensus Recommendations for the Suspicion and Diagnosis of Transthyretin Cardiac Amyloidosis; Mathew S. Maurer, Sabahat Bokhari, Thibaud Damy, Sharmila Dorbala, Brian M. Drachman, Marianna Fontana, Martha Grogan, Arnt V. Kristen, Isabelle Lousada, Jose Nativi-Nicolau, Candida Cristina Quarta, Claudio Rapezzi, Frederick L. Ruberg, Ronald Witteles, Giampaolo Merlini https://www.ahajournals.org/doi/10.1161/CIRCHEARTFAILURE.119.006075