Extracardiac Biopsy Sensitivity in Transthyretin Amyloidosis Cardiomyopathy Patients With Positive Tc-Labeled Pyrophosphate Scintigraphy Findings.

BACKGROUND

The accurate sensitivity of amyloid deposition in extracardiac tissue (subcutaneous tissue and gastrointestinal tract) has not been evaluated in transthyretin amyloidosis cardiomyopathy (ATTR-CM) patients. This study aimed to evaluate the sensitivity of amyloid deposition in obtained endomyocardial and extracardiac biopsies.

METHODS AND RESULTS

This study retrospectively evaluated 175 consecutive ATTR-CM patients (wild-type [ATTRwt]: 134, hereditary [ATTRv]: 41) who had positive findings on Tc-labeled pyrophosphate (Tc-PYP) scintigraphy and underwent tissue biopsy of at least one organ (subcutaneous tissue, gastrointestinal tract, and endomyocardium). Amyloid deposition was observed in the subcutaneous tissue of 57/150 patients (38%), gastrointestinal tract of 80/131 patients (61%), and endomyocardium of 108/109 patients (99%). Compared to patients with ATTRv, ATTRwt had significantly lower sensitivity in subcutaneous tissue (73% vs. 25%, P<0.01) and tended to be lower in the gastrointestinal tract (74% vs. 57%, P=0.08) biopsies. Among 124 patients who underwent both subcutaneous tissue and gastrointestinal tract biopsies, amyloid was detected in at least 1 specimen in 91 (73%) patients. The sensitivity of the combination of extracardiac biopsies was 66% and 94% in ATTRwt-CM and ATTRv-CM, respectively. Multivariate analysis reveals that ATTRv was the only significant predictor of amyloid deposition in the subcutaneous tissue.

CONCLUSIONS

Subcutaneous tissue and gastrointestinal tract biopsy sensitivity are inadequate, especially in patients with ATTRwt; however, the combination of these extracardiac biopsies contributes to increased sensitivity in patients with positive Tc-PYP scintigraphy findings.