Systematic review of ATTR: cardiac amyloidosis, survival, and effects of treatment

Introduction and methods

Background

In transthyretin-mediated (ATTR) amyloidosis, instability of the TTR protein due to genetic or degenerative factors may lead to deposition of TTR monomers in vital organs such as the heart [1]. Currently, systematic evidence on the prevalence and clinical outcomes of this disease is lacking.

Aim of the study

The study aim was 3-fold: (1) to better understand the prevalence of cardiac amyloidosis in various patient subgroups, (2) to provide survival estimates for wild-type ATTR (wtATTR) and different hereditary ATTR (hATTR) genotypes, and (3) to explore the effects of novel ATTR therapeutics on the natural course of disease.

Methods

The authors performed a systematic review of the literature published in MEDLINE before 31 December 2021 to investigate the prevalence of cardiac amyloidosis and all-cause mortality (at 1, 2, and 5 years) in ATTR patients. A total of 62 studies (n=277,882 patients) reporting the prevalence of cardiac amyloidosis were identified. Data on ATTR mortality were extracted from 95 studies (n=18,238 ATTR patients). Subgroup analyses were performed for ATTR subtype, hATTR genotypes, and treatment subgroups.

Main results

Cardiac amyloidosis

• The prevalence of cardiac amyloidosis was high in patients with clinical suspicion of this condition (1 7%–71%) and carriers of TTR mutations (3%–85%).
• The prevalence was also high among patients with unexplained LV hypertrophy or a hypertrophic cardiomyopathy phenotype (2%–34%), patients with HFpEF (14%–29%), and elderly with aortic stenosis (13%).
• Statistical heterogeneity between studies was high (I²=98%; P<0.0001).

Clinical outcomes

• Compared with patients with hATTR, patients with wtATTR were older (mean age: 67.1 vs. 77.1 years; Q=42.1; P=7 × 10⁻¹⁰) and more frequently male (Q=88.9; P=5 × 10⁻²⁰ ).
• The pooled estimate of 2-year survival for the natural disease course was 73.3% (95%CI: 70.9%–75.7%), although this varied between countries (61%–85%; Q=68.56; P=3.5 × 10⁻⁹ ). Statistical heterogeneity between studies was high (I²=97% ; P<0.01) and was not eliminated by country or continent subgroup analysis.
• The pooled estimated 2-year survival was 70.4% (95%CI: 66.9%–73.9%) for non-subtyped ATTR, 76.0% (95%CI: 73.0%–78.9%) for wtATTR, and 77.2% (95%CI: 74.0%–80.4%) for hATTR.
• Despite wtATTR patients being older, the wtATTR subtype was independently associated with higher survival rates compared with the hATTR subtype at 1 year (z=2.291; P=0.022) and 2 years (z=2.650; P=0.008) in meta-regression analysis adjusted for age, sex, and study sample size.
• All-cause mortality at 2 and 5 years was higher among patients with “cardiac” hATTR mutations (i.e., Val122Ile and Thr60Ala) and lower among patients with Val30Met mutations compared with wtATTR patients (both P=10⁻¹⁵).

Effect of treatment

• Compared with the natural disease course (i.e., patients receiving supportive standard of care or symptomatic treatment for HF), survival was higher in patients treated with novel ATTR therapeutics (tafamidis or patisiran) at both 2 years (72.4%; 95%CI: 69.8%–74.9% vs. 79.9%; 95%CI: 74.4%–85.3%; P<0.05) and 5 years (45.8%; 95%CI: 41.5%–50.1% vs. 64.0%; 95%CI: 50.1%–78.0%; P<0.05).

Conclusion

References

Find this article online at Eur J Heart Fail.