TTR (Transthyretin) Stabilizers Are Associated With Improved Survival in Patients With TTR Cardiac Amyloidosis

Abstract

Background: TTR (transthyretin) cardiac amyloidosis is caused by dissociation of TTR into monomers, which misassemble into amyloid fibrils. TTR stabilizers act at the dimer-dimer interface to prevent dissociation. We investigated differences in survival among patients with TTR cardiac amyloidosis on stabilizer medications compared with those not on stabilizers.

Methods and results: A retrospective study of patients with TTR cardiac amyloidosis presenting to a single center was conducted. Baseline characteristics were compared between those treated with stabilizers and those not treated with stabilizers. Cox proportional hazards modeling assessed for univariate predictors of the composite outcome of death or orthotopic heart transplant (OHT). Multivariable Cox proportional hazards assessed whether stabilizer treatment was independently associated with improved death or OHT after controlling for significant univariate predictors. One hundred twenty patients (mean age, 75±8, 88% male) were included: 29 patients who received stabilizers and 91 patients who did not. Stabilizer use was associated with a lower risk of the combined end point of death or OHT (hazard ratio, 0.32; 95% confidence interval, 0.18-0.58; P<0.0001). Subjects treated with stabilizers were more likely to be of White race (93% versus 55%; P<0.001), classified as New York Heart Association classes I and II (79% versus 38%; P=0.002), less likely to have a mutation (10% versus 36%; P=0.010), have lower troponin I (median 0.06 versus 0.12 ng/mL; P=0.002), and higher left ventricular ejection fraction (49% versus 40%; P=0.011), suggesting earlier stage of disease. In multivariable Cox analysis, the association between stabilizer and death or OHT persisted when adjusted for all noncollinear univariate predictors with P<0.05 (hazard ratio, 0.37; 95% confidence interval, 0.19-0.75; P=0.003).

Conclusions: TTR stabilizers are associated with decreased death and OHT in TTR cardiac amyloidosis. These results need to be confirmed by ongoing randomized clinical trials.

Keywords: amyloidosis; male; mutation; retrospective study; transthyretin; troponin I.

Figure 1

Study Population and Breakdown by Treatment Strategy

Figure 2

Kaplan-Meier Analysis Among 120 Patients with TTR-CA Over the 1.9 Year Median Follow-up for the Outcome of Death or OHT, Stratified by use of Stabilizer