11-07-2014, 01:44 PM
The correct answer is C. 28% chose this.
Low voltages on an ECG can be due to an increase in the distance between the heart and ECG leads due to pericardiac effusions, large body habitus, infiltration of the heart muscle with proteins, or metabolic abnormalities. Amyloidosis has immunofluoresecence when stained with Congo-red, and the presence of amyloid proteins in his subcutaneous tissues makes the findings on this ECG a sign of an infiltrative cardiomyopathy. One of the most common causes of restrictive/infiltrative cardiomyopathy is cardiac amyloidosis due to AL amyloidosis (light chain amyloid). Patients with cardiac amyloid typically present with right heart failure. Amyloidosis is also associated with atrioventricular conduction delay. Presyncope and orthostasis are common in cardiac amyloidosis due to autonomic dysfunction and arrhythmias. Other findings of cardiac amyloid include low-voltage QRS on ECG, ventricular wall thickening, and other physical signs of a restrictive cardiomyopathy.
A is not correct. 61% chose this.
A amyloid produces a systemic type of amyloidosis that is almost never associated with cardiac amyloidosis, and therefore would not lead to ECG changes. A amyloid is associated with a number of rheumatologic diseases including rheumatoid arthritis and ankylosing spondylitis.
B is not correct. 3% chose this.
Kerato-epithelin is a protein associated with the development of localized corneal amyloid. It would not result in ECG changes
D is not correct. 2% chose this.
Medin, if mutated, can deposit in the aortic wall and is found in people >60 years old. It does not lead to cardiac amyloidosis and therefore would not generate these ECG findings.
E is not correct. 6% chose this.
Transthyretin is a protein produced by the liver that can mutate and result in amyloidosis. It is associated with both neurologic and cardiac amyloidosis, but transthyretin-caused amyloidosis is less common than that caused by light chain immunoglobulins. Transthyretin can cause isolated cardiac amyloidosis in African-Americans, but this man is white.