Large-magnitude, transient, bradycardic events in rabbits.
We propose that heart period sequences are organized similarly to sentences, with a lexicon of recurrent, similarly shaped words. These words should fulfill four criteria: universality, nonrandomness, central statistical tendencies, and specific associated physiology. Here we describe a large-magnitude, transient bradycardia (LMTB) and assess whether it constitutes a word. LMTBs were seen in 11 of 12 adult female rabbits. All shape parameters were different than those of the beat-randomized and phase-randomized surrogate sequences (P < 0.05-0.001). LMTBs were 8. 4 +/- 2.9 beats and 2.64 +/- 0.87 s long and were characterized by bradycardia of 77 +/- 49 ms over 1.09 +/- 0.49 s with a recovery to baseline over 1.56 +/- 0.61 s. The LMTBs had a slower recovery than onset in 9 of 11 rabbits and were highly peaked in 10 of 11 rabbits (P < 0.05). Scalar, magnitude, and shape parameters had values with central statistical tendencies. About 76% of LMTBs were accompanied by hypotension (mean -6.1 +/- 3.9 mmHg) that lagged 2 beats behind the onset of the bradycardia and that correlated with the bradycardia (-10.5 +/- 4.1 ms/mmHg). Thus transient bradycardic events are a distinct "word" in the lexicon of heart rate variability.
Cardiovascular Research Group, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
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Roach
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Thakore
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Sheldon
D000818:Animals; D001919:Bradycardia / Q000503:physiopathology*; D005260:Female; D006339:Heart Rate; D008954:Models, Biological; D011817:Rabbits; D013997:Time Factors