Comparison of different techniques to identify cardiac involvement in immunoglobulin light chain (AL) amyloidosis

We retrospectively reviewed the utility of N-terminal prohormone of brain natriuretic peptide (NT-proBNP) and transthoracic echocardiogram (TTE) in diagnosing cardiac involvement in patients with biopsy-proven systemic immunoglobulin light chain amyloidosis seen at the Mayo Clinic between 1 January 2006 and 30 December 2015. We analyzed 2 cohorts: patients undergoing endomyocardial biopsy for suspicion of cardiac involvement (cohort 1) and patients who had serum NT-proBNP and comprehensive echocardiographic evaluation at diagnosis (cohort 2). Of 179 patients undergoing endomyocardial biopsy (cohort 1), 173 (97%) had evidence of amyloid deposition, with 159 having NT-proBNP performed at the time of the procedure. The NT-proBNP was elevated (>300 pg/mL) in all 159 patients (sensitivity, 100%; median NT-proBNP, 4917 pg/mL; range, 355-69 541). The left ventricular ejection fraction, interventricular septal thickness, and strain rate were abnormal in 89/168 (53%), 102/64 (61%) and 92/95 (97%), respectively. Among cohort 2 (n = 342), 259 (76%) had an elevated NT-proBNP, of whom 237 (92%) had an abnormality detected on TTE. Of 83 patients with normal NT-proBNP <300 pg/mL, 27 (33%) had an abnormality on TTE (all with borderline strain rate −18% to −15%). Only 5/27 patients were considered to have possible early cardiac involvement and none had any other diagnostic or classical features of amyloidosis on TTE. The combination of NT-proBNP and comprehensive echocardiographic evaluation can diagnose cardiac amyloidosis negating the need for endomyocardial biopsy. A negative NT-proBNP rules out clinically meaningful cardiac involvement and may obviate the routine use of TTE in patients with a low clinical suspicion of cardiac amyloidosis.