Apolipoprotein A-IV Cardiac Amyloidosis

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  Visual Summary. Contemporary Nonbiopsy Algorithms Focused on ATTR and AL Amyloidosis May Lead to False Reassurance When Testing Is Negative or False Attribution When Monoclonal Gammopathy Is Present When clinical suspicion is high or findings are discordant, endomyocardial biopsy with mass spectrometry is essential for definitive amyloid typing. AL = light-chain amyloidosis; ApoA-IV = apolipoprotein A-IV; CMR = cardiac magnetic resonance imaging; ECG = electrocardiogram; LV = left ventricular; MGUS = monoclonal gammopathy of undetermined significance; PYP = pyrophosphate.

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  Figure 1. Electrocardiogram of Patient 1 This electrocardiogram demonstrates a first-degree atrioventricular block and a pseudo-infarct pattern. This tracing was obtained at a paper speed of 25 mm/s and at a voltage calibration of 10 mm/mV.

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  Figure 2. Echocardiogram and Longitudinal Strain Pattern of Patient 1 (A) Parasternal long-axis still image view demonstrating moderate concentric left ventricular thickening. (B) Speckle-tracking longitudinal strain imaging shows markedly reduced peak-systolic global longitudinal strain (−9.5%) with apical sparing (apical longitudinal strain: 15.6%), corresponding to an apical-to-basal strain ratio of 2.26, a characteristic pattern associated with cardiac amyloidosis.

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  Figure 3. Cardiac Magnetic Resonance Imaging of Patient 1 (A) Short-axis cine images demonstrating concentric left ventricular wall thickening. (B) Short-axis late gadolinium enhancement (LGE) image showing diffuse circumferential near-transmural enhancement throughout the left ventricle. (C) Four-chamber long-axis cine image confirming increased left ventricular wall thickness. (D) Four-chamber long-axis LGE image demonstrating diffuse near-transmural enhancement in a noncoronary distribution. The diffuse near-transmural pattern of enhancement in a nonischemic distribution, together with concentric hypertrophy, is characteristic of an infiltrative cardiomyopathy.

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  Figure 4. Representative Images of Apolipoprotein A-IV Amyloidosis Patient 1. (A) Nodular amorphous material was seen throughout the myocardium. (B) The material was fluorescent on a Thioflavin S stain and (C) stained blue-gray on a Masson Trichrome, in contrast to the collagen which stained a royal blue. Patient 2. (D) A solitary, large amyloid nodule was seen adjacent to the myocardium. (E) It displayed apple green birefringence upon polarization of the Congo Red stain. (F) No amyloid material was seen within the myocardium, as noted on this negative Congo Red stain showing only collagen (white) birefringence. (Original magnifications: A to E = 200×, B = 400×, F = 100×).

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  Figure 5. Electrocardiogram of Patient 2 This electrocardiogram demonstrates a first-degree atrioventricular block with a nonspecific intraventricular conduction defect with a QRS duration of 160 ms. This tracing was obtained at a paper speed of 25 mm/s and at a voltage calibration of 10 mm/mV.

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  Figure 6. Echocardiogram and Longitudinal Strain Pattern of Patient 2 (A) Parasternal long-axis still image view demonstrating moderate concentric left ventricular thickening. (B) Speckle-tracking longitudinal strain imaging shows markedly reduced peak-systolic global longitudinal strain (−6.0%). Segmental analysis shows more pronounced impairment in the anterolateral segments compared with the inferior and septal walls. This distribution is atypical for cardiac amyloidosis, which characteristically demonstrates relative apical sparing.