| Sumario: | INTRODUCTION: Studies assessing heart rate (HR) behavior after premature beats have focused on HR responses to ventricular premature beats (VBPs), but there is less information of HR behavior after atrial premature beats (APBs). METHODS AND RESULTS: HR turbulence after VPBs and APBs was first measured in response to ambient APBs and VPBs occurring during 24-hour ambulatory ECG recordings in 29 subjects without structural heart disease, and in response to programmed atrial (AE) and ventricular extrastimuli (VE) in 6 subjects undergoing electrophysiologic (EP) examination. Turbulence onset (TO) was more negative (-2.3 +/- 3.2% vs -0.9 +/- 2.8%, P < 0.01) and turbulence slope (TS) was steeper (11 +/- 11 vs 5.1 +/- 4.1 msec/R-R interval, P < 0.05) after VPBs than APBs. Compared to VPBs, the acceleration of HR after APBs was delayed by one beat, and APBs were associated with a short R-R interval preceding the APB, resulting in a blunted TO. Studies of patients undergoing an EP test confirmed the one-beat delay of HR acceleration and the blunted TO after programmed AE compared to VE (P < 0.05). TO and TS after VPBs were related to baroreflex sensitivity. TO also was related to 24-hour standard deviation of N-N intervals (SDNN). However, the TO or TS following APBs was not related to either SDNN or baroreflex sensitivity. CONCLUSION: HR behavior is different in response to APBs and VBPs among subjects without structural heart disease. Different definitions and calculation formulas should be used in the analysis of HR turbulence after APBs and VPBs.
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