Non-ischemic Cardiomyopathies - Cases

1351525 - Stump The Guidelines? A Rare Cause of Cardiac Amyloidosis Detected by CMR

Thursday, January 26, 2023

4:08 PM – 4:14 PM

Location: Sandpiper

Presenting Author(s)

Jeremy A. Slivnick, MD

Assistant Professor
University of Chicago Medicine
Chicago, Illinois, United States

Primary Author(s)

Jeremy A. Slivnick, MD

Assistant Professor
University of Chicago Medicine
Chicago, Illinois, United States

Co-Author(s)

JK

Jung Kwon, MD

Resident Physician
University of Chicago Medicine, Illinois, United States
NS

Nitasha Sarswat, MD

Assistant Professor
University of Chicago Medicine, United States
AH

Aliya Husain, MD

Professor
University of Chicago Medicine, United States
Amit R. Patel, MD

Professor
University of Virginia Health System
Charlottesville, Virginia, United States

Disclosure(s):

Jeremy A. Slivnick, MD: No financial relationships to disclose

Description of Clinical Presentation: A 73-year-old male with a history of membranoproliferative glomerulonephritis (MPGN) complicated by kidney failure requiring renal transplantation was evaluated for new onset cardiomyopathy. An echocardiogram at this time showed moderate concentric left ventricular hypertrophy (LVH), significantly progressed from a previous exam one year prior. Right ventricular (RV) systolic function was noted to be mildly reduced. A technetium pyrophosphate scan (Tc-PyP) scan was obtained which was negative for transthyretin cardiac amyloidosis (ATTR-CA) with grade 0 uptake and comprehensive light chain analysis did not reveal a monoclonal protein (Figure 1, Top Panel).

Diagnostic Techniques and Their Most Important Findings: Given the patient’s rapid, unexplained LVH, a cardiac magnetic resonance (CMR) was obtained. Cine imaging demonstrated moderate LVH with normal systolic function (Figure 2A). Pre-contrast T1 relaxation times were elevated at 1,137 ms (Figure 2B) Following gadolinium administration, inversion time (TI) scout was notable for abnormal gadolinium kinetics with simultaneous nulling of blood pool and myocardium (Figure 2C). There was diffuse, striking subendocardial to near-transmural late gadolinium enhancement (LGE) most prominently involving the basal myocardium, findings highly suggestive of CA (Figure 2D, solid arrows). Given the high clinical concern for CA, a Tc-PyP was repeated six months later which was again negative for ATTR-CA (Figure 1, Bottom Panel). Given the discordant imaging findings, an endomyocardial biopsy was performed which identified amyloid fibrils on Congo Red staining (Figure 3, solid arrows). Mass spectrometry was consistent with Serum amyloid A (SAA) subtype. A diagnosis of AA-CA was made.

Learning Points from this Case: AA-CA is a rare form of cardiac amyloidosis caused by deposition of SAA protein—an acute phase reactant—in the myocardium. This disorder is most commonly observed in patients with longstanding chronic inflammatory conditions such as rheumatoid arthritis or vasculitis¹. Renal dysfunction is a key feature of AA-CA and is present in high as 97% of cases¹. In our patient’s case, his MPGN and renal dysfunction were felt to be the most likely triggers. AA-CA can be diagnosed non-invasively with ¹²³I-labeled serum amyloidosis protein nuclear scan or with tissue biopsy; inflammatory markers do not play a clear role in the diagnosis of AA-CA. Treatment is typically with immunosuppression aimed at stabilizing the chronic inflammatory disorder¹. Current guidelines recommend screening for CA with a combination of Tc-PyP and comprehensive light chain analysis which unfortunately have low sensitivity for detection of AA-CA². This case highlights the importance of having a low threshold to pursue further testing including invasive tissue biopsy when typical CA CMR features are present even in the absence of confirmatory non-invasive testing. Furthermore, CMR can provide value in cases of negative Tc-PyP and light chain biomarkers when clinical suspicion is particularly high.