RT-174
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The role of fluctuations in
heart rate and ectopic beat frequency in the onset of paroxysmal atrial fibrillation
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Johan E.P. Waktare, Katerina
Hnatkova, Francis D. Murgatroyd, Xiaohua Guo, A. John Camm, Marek Malik.
St. Georges Hospital Medical School, London, UK
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Abstract
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Introduction. The method by which
atrial fibrillation (AF) is initiated may have important therapeutic implications. This
study sought to examine this question in a population of patients with clinically relevant
paroxysmal AF through the use of Holter recordings.
Methods and Results. All episodes of atrial fibrillation of at least
30 sec duration with 2 mins of preceding noise free sinus rhythm were identified on
24-hour Holter recordings from patients recruited to pharmacotherapy trials for PAF. This
2 min period, divided into 30 sec segments, was utilised for analysis. All tachograms were
inspected and the cardiac rhythm (rate, change in rate, ectopics, etc.) analysed to
determine patterns of AF onset. There were 231 qualifying episodes from 33 Holter
recordings (19 patients). No consistent pattern of AF onset was visible from the
tachograms, with individual patients exhibiting wide variations in heart rhythm behaviour.
Ectopics increased from 0.67 to 3.26 per 30 sec (p = 3.25 ¥ 10-18), but mean
heart rate did not change: 64.9 ± 11.6 vs 64.3 ± 11.6 bpm (p = ns). AF was most
frequently preceded by two normal duration cycles followed by a short cycle (54%), with
three normal duration cycles being the second most common finding (11%).
Conclusion. Prior to the onset of PAF, atrial ectopics increase in
frequency and the heart rate is usually slow. Beyond this, there is no consistent pattern
of beats or reproducible dynamic change in cardiac rhythm in an unselected population with
clinically relevant PAF.
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Key Words
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RR interval, repolarization, heterogeneity,
variability
paroxysmal AF, Holter ECG, Laser Holter System, atrial refractory period, CRAFT trial,
autonomic nervous system, macro-reentrant basis, atrial ectopic activity, non-electrical
trigger factors, OA
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