Dynamic Behavior and Autonomic Regulation of Ectopic Atrial Pacemakers

Background—Heart rate (HR) variability reflects the neural regulation of normal pacemaker tissue, but the autonomic nervous regulation of abnormal atrial foci originating outside the sinus node has not been well characterized. We compared the HR variability of tachycardias originating from the ectopic foci and the sinus node. Methods and Results—R-R–interval variability was analyzed from 24-hour Holter recordings in 12 patients with incessant ectopic atrial tachycardia (average HR 107±14 bpm), 12 subjects with sinus tachycardia (average HR 106±9 bpm), and 24 age- and sex-matched subjects with normal sinus rhythm (average HR 72±8 bpm). Time- and frequency-domain HR variability measures, along with approximate entropy, short- and long-term correlation properties of R-R intervals (exponents α1 and α2), and power-law scaling (exponent β), were analyzed. Time- and frequency-domain measures of HR variability did not differ between subjects with ectopic and sinus tachycardia. Fractal scaling exponents and approx...