Coefficient of R-R interval variations under deep breathing load in patients with wild-type transthyretin amyloid...

An autonomic nervous disorder is an important characteristic of cardiac amyloidosis; however, the prevalence of autonomic dysfunction in wild-type transthyretin amyloidosis (ATTR_wt) has not been established. Analysis of the R-R interval coefficient of variation (CVR-R) is a noninvasive method to measure parasympathetic activity. We aimed to assess autonomic dysfunction of ATTR_wt and determine the utility of CVR-R for the detection of ATTR_wt in other cardiac diseases.

This is a single-center, retrospective, case-control study. Fifty patients with heart failure (HF) were studied. The etiologies of HF were as follows: ATTR_wt, n = 10; previous myocardial infarction (MI), n = 20; and left ventricular hypertrophy (LVH) due to other disease processes (e.g., aortic stenosis), n = 20. We measured the CVR-R at rest (CVR-R_rest), CVR-R with deep breaths (CVR-R_breath), and the change rate (CVR-R_{diff rate)}. The relative change formula is as follows: CVR-R_{diff rate} = (CVR-R_breath - CVR-R_rest)/CVR-R_rest $$  100 (%).

There was no difference in the CVR-R_rest levels among the three groups. The CVR-R_{diff rate} levels in the ATTR_wt group were significantly lower (ATTR_wt: -8.77 [-43.8 to 10.9]; LVH: 67.4 [38.7 to 89.4]; MI: 83.7 [60.4 to 142.9]). Based on the receiver operative characteristic curve analysis to identify ATTR_wt in HF, the best cut-off value for the CVR-R_{diff rate} was 19.7 (area under the curve: 0.848).

Our data suggested autonomic dysfunction in patients with ATTR_wt. Measurement of the CVR-R in HF patients may be a convenient support tool for the detection of ATTR_wt.