14th International Congress
THE "NEW FRONTIERS"
OF ARRHYTHMIAS 2000

Jan. 29 - Feb. 5, 2000
Marilleva, Trento, Italy

RT-213

Noninvasive estimation of atrial fibrillatory rate as an index of atrial refractoriness. Short and long-term intra-individual variability following physiological and pharmacological interventions

S. Bertil Olsson, M.Ph. Ingemansson, C.-J. Lindholm, C. Meurling, M. Stridh, L. Sörnmo.
Depts of Cardiology and Applied Electronics, Lund University, Lund, Sweden

Abstract

Atrial fibrillation (AF) is perpetuated by reexcitations occurring close to the actual local refractory period, allowing an indirect assessment of refractoriness by studying the fibrillatory cycle length. Using a computerbased suppression of QRST and power-frequency analysis of the remaining fibrillatory signal, we have identified the dominating atrial cycle length (DACL) in patients with different types of AF, studied its spontaneous spatial and temporal variability and explored the effect of different autonomic interventions.

There is an intraindividual spatial dispersion of endocardially recorded DACL but no differences between values extracted from precordial leads. During resting conditions, DACL recorded in V1 ranges between 120 and 180 ms, the longest values found in patients with AF of recent onset and the shortest in those with longlasting AF without conversion success.

Stimulation by either limb of the autonomic nervous system shortens the DACL. The magnitude of vagally induced shortening of DACL during rest is however minimal in patients with CAF. The magnitude of change of DACL during physiological conditions is related to its absolute value. Thus, DACL variability is minimal in patients with values at the lower end of its entire range whilst those with high values exhibit changes in the order of 20%.

Estimation of DACL permits a continuos and noninvasive mode of following changes of a measure of atrial refractoriness (and/or conduction velocity) during AF. The exact mechanism behind the spontaneous short-term variations of DACL remains to be further explored as well as the role of its spatial dispersion in endocardial leads.

Key Words