Exploring the complexity: the interplay between the angiotensin-converting enzyme insertion/deletion polymorphism and the sympathetic response to hemodialysis

Patients on hemodialysis (HD) are at increased risk for arrhythmias and sudden cardiac death. Autonomic nervous system (ANS) dysfunction seems to participate in the arrhythmogenic process. Genetic factors have an impact on ANS modulation, but the specific role of the insertion/deletion (I/D) polymorphism in the gene for angiotensin-converting enzyme (ACE) has not been investigated. Since the D allele increases gene expression, it is a candidate polymorphism to interact with the ANS. The aim of the present study was to compare the behavior of heart rate variability (HRV) during HD, as a surrogate for ANS response to stressors, between the ACE genotypes. In a sample of patients with chronic kidney disease I/D ACE genotypes were assessed with PCR and HRV was measured before, in the second hour, and after a HD session. HRV parameters in the time and frequency domains were analyzed by repeated-measures mixed models according to the time of measurement and ACE polymorphism. HRV parameters in the frequency domain presented significantly different variations during the HD session between patients with or without the D allele. Only patients with the II genotype presented an increase in low-frequency normalized units and in the low frequency-to-high frequency ratio throughout HD. Patients with the II genotype seemed to have a more physiological response to the volemic and electrolytic changes that occur during HD, with greater sympathetic activation than patients with ID and DD genotypes. NEW & NOTEWORTHY Adding to the effort to understand the complexity of cardiovascular system regulation, we have found that the autonomic nervous system response to the acute volume removal during hemodialysis may be different between angiotensin-converting enzyme insertion/deletion polymorphisms. To our knowledge, this is the first time that this specific interaction was analyzed during a volume removal intervention.