Effects and Significance of Premature Beats on Fractal Correlation Properties of R‐R Interval Dynamics

Background: Premature beats (PBs) have been considered as artifacts producing a bias in the traditional analysis of heart rate (HR) variability. We assessed the effects and significance of PBs on fractal scaling exponents in healthy subjects and patients with a recent myocardial infarction (AMI). Methods: Artificial PBs were first generated into a time series of pure sinus beats in 20 healthy subjects and 20 post‐AMI patients. Thereafter, a case‐control approach was used to compare the prognostic significance of edited and nonedited fractal scaling exponents in a random elderly population and in a post‐AMI population. Detrended fluctuation analysis (DFA) was used to measure the short‐term (α₁) and long‐term (α₂) fractal scaling exponents. Results: Artificial PBs caused a more pronounced reduction of α₁ value among the post‐AMI patients than the healthy subjects, for example, if >0.25% of the beats were premature a >25% decrease in the α₁ was observed in post‐AMI patients, but 4% of the premature beats were needed to cause a 25% reduction in α₁ in healthy subjects. Both edited (1.01 ± 0.31 vs 1.19 ± 0.27, P < 0.01) and unedited α₁ (0.71 ± 0.33 vs 0.89 ± 0.36, P < 0.05) differed between the patients who died (n = 42) and those who survived (n = 42) after an AMI. In the general population, only unedited α₁ differed significantly between survivors and those who died (0.96 ± 0.19 vs 0.83 ± 0.27, P < 0.05). Conclusions: Unedited premature beats result in an increase in the randomness of short‐term R‐R interval dynamics, particularly in post‐AMI patients. Premature beats must not necessarily be edited when fractal analysis is used for risk stratification.