Extracellular volume quantification by dynamic equilibrium cardiac computed tomography in cardiac amyloidosis

Highlights

• Cardiac involvement determines outcome in amyloidosis.

• There is major unmet need for quantification of cardiac amyloid burden.

• Dynamic Equilibrium CT (DynEQ-CT) is a 5-minute contrast-enhanced CT scan.

• DynEQ-CT measures the extracellular volume fraction, which increases in amyloid.

• DynEQ-CT has major potential for diagnosis and quantification of cardiac amyloidosis.

Abstract

Background

Cardiac involvement determines outcome in patients with systemic amyloidosis. There is major unmet need for quantification of cardiac amyloid burden, which is currently only met in part through semi-quantitative bone scintigraphy or Cardiovascular Magnetic Resonance (CMR), which measures ECV_CMR. Other accessible tests are needed.

Objectives

To develop cardiac computed tomography to diagnose and quantify cardiac amyloidosis by measuring the myocardial Extracellular Volume, ECV_CT.

Methods

Twenty-six patients (21 male, 64 ± 14 years) with a biopsy-proven systemic amyloidosis (ATTR n = 18; AL n = 8) were compared with twenty-seven patients (19 male, 68 ± 8 years) with severe aortic stenosis (AS). All patients had undergone echocardiography, bone scintigraphy, NT-pro-BNP measurement and EQ-CMR. Dynamic Equilibrium CT (DynEQ-CT) was performed using a prospectively gated cardiac scan prior to and after (5 and 15 minutes) a standard Iodixanol (1 ml/kg) bolus to measure ECV_CT. ECV_CT was compared to the reference ECV_CMR and conventional amyloid measures: bone scintigraphy and clinical markers of cardiac amyloid severity (NT-pro-BNP, Troponin, LVEF, LV mass, LA and RA area).

Results

ECV_CT and ECV_CMR results were well correlated (r² = 0.85 vs r² = 0.74 for 5 and 15 minutes post bolus respectively). ECV_CT was higher in amyloidosis than AS (0.54 ± 0.11 vs 0.28 ± 0.04, p<0.001) with no overlap. ECV_CT tracked clinical markers of cardiac amyloid severity (NT-pro-BNP, Troponin, LVEF, LV mass, LA and RA area), and bone scintigraphy amyloid burden (p<0.001).

Conclusion

Dynamic Equilibrium CT, a 5 minute contrast-enhanced gated cardiac CT, has potential for non-invasive diagnosis and quantification of cardiac amyloidosis.