A patient with a history of arrhythmia is found to have atrial amyloid deposition on autopsy. Do you know what peptide is associated with this finding?
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[02:14] Question of the Week
The autopsy of the patient with a history of arrhythmia revealed amyloid deposition in the atria but no other amyloid was found in the ventricles. Which of the following peptides is associated with amyloid deposition in the atria? And what is that peptide’s function?
(A) Calcitonin and reduction of blood calcium concentration
(B) Prolactin and gastric emptying
(C) Acetylcholine and positive chronotropy to sinoatrial node
(D) Immunoglobulin and cell-mediated immune response
(E) Atrial natriuretic peptide and vasodilation
[Related episode: Cardiac Electrophysiology—What is it?]
[03:15] Thought Process Behind the Correct Answer
The correct answer is E. An amyloid is a group of diverse extracellular proteins in variable amino acid sequences and they have common physical properties.
Amyloid deposition and the extracellular deposition of the fibrils are composed of the subunit of varied serum proteins that form beta-pleated sheet configurations that lead to the histologic changes seen in amyloidosis.
Isolated amyloidosis is found only in a single organ such as this cardiac amyloidosis. Alpha-atrial natriuretic peptide is responsible for deposition in this isolated cardiac amyloidosis. This is what’s responsible for amyloid deposition in part.
The incidence appears to be maybe part of the normal process of aging. In one autopsy series, 86% of the patients between the age of 81 and 90 had isolated atrial amyloidosis. It may lead to heart failure.
Although diuretics are commonly given to patients with heart failure due to cardiac amyloidosis, beta-blockers, calcium channel blockers, and ace inhibitors may be harmful.
[05:55] Understanding the Wrong Answer Choices
Calcitonin is associated with isolated amyloidosis of the thyroid. Prolactin is associated with lactation found in amyloidosis that is isolated to the pituitary gland.
Acetylcholine is the negative chronotropic sinoatrial node in the right vagus nerve.
The stimulation of the nerve decreases the firing of the SA nodes, increasing potassium and decreasing sodium and calcium movement to the cell.
Finally, immunoglobulin amyloid deposition is widespread and it’s the result of its light chain immunoglobulin deposition.
The point of the question was that isolated amyloidosis can affect many particular organs. This is different from more widespread amyloidosis related to immunoglobulin in terms of ideology and distribution.
[07:10] The Big Takeaway
Amyloid is not just that atrial natriuretic factor but you have to ask yourself where is it is as you’re reading this question. Is it in the parathyroid for prolactin or widespread for the immunoglobulin or is it in the atrium for the atrial natriuretic peptide?
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