Temporal organization of atrial activity and irregular ventricular rhythm during spontaneous atrial fibrillation: an in vivo study in the horse.
Abstract: Atrial fibrillation (AF) is common in healthy horses. We studied the temporal organization of AF to test the hypothesis that the arrhythmia is governed by a high degree of periodicity and therefore is not random in the horse. Further, we surmised that concealed conduction of AF impulses in the AV node results in an inverse relationship between AF frequency and ventricular frequency. Results: Fast Fourier transform (FFT) analysis of atrial activity was done on signal-averaged ECGs (n = 11) and atrial electrograms (n = 3) of horses with AF at control (C), after quinidine sulfate (22 mg/kg by mouth every 2 hours) at 50% time to conversion (T50), and immediately before conversion (T90) to sinus rhythm. FFT always revealed a single dominant frequency peak. The mean dominant frequency decreased until conversion (C = 6.84 +/- 0.85 Hz, T50 = 4.87 +/- 1.5 Hz, T90 = 3.41 +/- 1.18 Hz; P < 0.001). Mean AA intervals (n = 500) gradually increased after quinidine. Mean RR intervals (n = 500), standard deviation of the mean (SDM), Poincaré plots, and serial autocorrelograms (SACs) of 500 RR intervals were measured at C and T90 to determine the ventricular response to AF and quinidine-induced changes in the variability of the ventricular response. Mean RR interval and SDM were reduced after quinidine (C = 1431 +/- 266 msec and 695 +/- 23 msec; T90 = 974 +/- 116 msec and 273 +/- 158 msec, respectively; P < 0.01). Poincaré plots and SAC at C and at T90 revealed a significant correlation of consecutive RR intervals typical of a system with a deterministic behavior. At T90, the variability of RR intervals was reduced and the overall periodicity of RR intervals was increased after quinidine administration. Conclusions: In the horse, AF is a complex arrhythmia characterized by a high degree of underlying periodicity. The inverse AA-to-RR interval relationship and reduced variability of RR intervals after quinidine suggest that the ventricular response during AF results from rate-dependent concealment of AF wavelets bombarding the AV node, which nevertheless results in a significant degree of short-term predictability of beat-to-beat changes in RR intervals.
Publication Date: 2000-08-02 PubMed ID: 10921795DOI: 10.1111/j.1540-8167.2000.tb00049.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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This research article studies the behavior of atrial fibrillation or irregular heart rhythm in horses. The researchers postulate that the disorder is non-random and governed by a constant pattern. The research also examines the impact of the antiarrhythmic drug, quinidine sulfate, on atrial fibrillation.
Understanding Atrial Fibrillation in Horses
- The study aimed to understand the activity of atrial fibrillation in horses by determining its pattern or randomness. The researchers also hypothesized an inverse relationship between the frequency of atrial fibrillation and ventricular frequency caused by the hidden conduction of AF pulses in the AV node (atrioventricular node which affects the heart’s rhythm) of a horse’s heart.
- By using Fast Fourier Transform analysis on signal-averaged ECGs and atrial electrograms, they discovered a single dominant peak frequency repeatedly occurring. The mean dominant frequency decreased up to the point of conversion of the atrial rhythm, showing a systemic pattern and non-randomness.
Impact of Quinidine Sulfate on AF
- Quinidine sulfate, a drug used to treat heart arrhythmia, was administered to the horses to observe its impact on AF and ventricular activity. This part addressed the second focus of the study which was to understand how this drug could potentially inverse atrial and ventricular rhythm frequencies.
- The drug was observed to influence both atrial and ventricular rhythms. After quinidine administration, the intervals between atrial activities gradually increased while the intervals between ventricular activities (RR intervals) significantly were reduced, verifying their initial hypothesis.
- The behavior of the simultaneous variability and periodicity in ventricular rhythm was determined using Poincaré plots and serial autocorrelograms. These revealed deterministic behavior proving the claim of heart rhythm being subjected to inherent cycles.
Summarizing the Research Finding
- In conclusion, atrial fibrillation in horses is a complex arrhythmia that does not act randomly and is primarily governed by an identifiable pattern of frequency cycles.
- The administration of quinidine sulfate further reversed the frequency cycles of atrial and ventricular activities – strengthening the suggestion that the ventricular response during AF occurs from the rate-dependent behavior of AF pulses in the AV node. This also implies that there could be a degree of predictability in beat-to-beat changes in RR intervals.
Cite This Article
APA
Gelzer AR, Moïse NS, Vaidya D, Wagner KA, Jalife J.
(2000).
Temporal organization of atrial activity and irregular ventricular rhythm during spontaneous atrial fibrillation: an in vivo study in the horse.
J Cardiovasc Electrophysiol, 11(7), 773-784.
https://doi.org/10.1111/j.1540-8167.2000.tb00049.x Publication
Researcher Affiliations
- Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA. gelzer@vet.upenn.edu
MeSH Terms
- Animals
- Atrial Fibrillation / physiopathology
- Atrial Fibrillation / veterinary
- Electrocardiography
- Heart Conduction System / physiopathology
- Horse Diseases / physiopathology
- Horses
- Quinidine / therapeutic use
Grant Funding
- P01-HL39707 / NHLBI NIH HHS
- R01-HL60843 / NHLBI NIH HHS
Citations
This article has been cited 5 times.- Kuroda T, Minamijima Y, Kinman CK, Takahashi Y, Ebisuda Y, Inoue K, Ishikawa H, Mita H, Tamura N, Nukada T, Toutain PL, Ohta M. Rational quinidine dosage regimen for atrial fibrillation in Thoroughbred racehorses based on population pharmacokinetics. Front Vet Sci 2024;11:1454342.
- Fender AC, Dobrev D. Recent highlights on the mechanistic basis of cardiovascular remodeling from the International Journal of Cardiology Heart & Vasculature. Int J Cardiol Heart Vasc 2023 Aug;47:101248.
- Kjeldsen ST, Nissen SD, Buhl R, Hopster-Iversen C. Paroxysmal Atrial Fibrillation in Horses: Pathophysiology, Diagnostics and Clinical Aspects. Animals (Basel) 2022 Mar 10;12(6).
- Buhl R, Carstensen H, Hesselkilde EZ, Klein BZ, Hougaard KM, Ravn KB, Loft-Andersen AV, Fenner MF, Pipper C, Jespersen T. Effect of induced chronic atrial fibrillation on exercise performance in Standardbred trotters. J Vet Intern Med 2018 Jul;32(4):1410-1419.
- January CT, Wann LS, Alpert JS, Calkins H, Cigarroa JE, Cleveland JC Jr, Conti JB, Ellinor PT, Ezekowitz MD, Field ME, Murray KT, Sacco RL, Stevenson WG, Tchou PJ, Tracy CM, Yancy CW. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the Heart Rhythm Society. Circulation 2014 Dec 2;130(23):e199-267.
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