Coupling interval from slow to tachycardiac pacing decides sustained alternans pattern.
We discovered that the coupling beat interval from a slow to a tachycardiac pacing period considerably affected the pattern of the beat-to-beat alternation of the tachycardia-induced sustained contractile alternans. We analyzed the relationship between the coupling interval and the pattern and amplitude of the alternans in the isovolumic left ventricle of canine blood-perfused hearts. The alternans pattern and amplitude varied transiently over the first 30-50 beats and became gradually stable over the first minute in all 12 hearts. We discovered that stable alternans, even under the same tachycardiac pacing, had three different strong-weak beat patterns depending on the coupling interval. A relatively short coupling interval produced a representative sustained alternans of the strong and weak beats. A relatively long coupling interval produced a similar sustained alternans but in a reversed order of even- and odd-numbered beats counted from the coupling interval. However, sustained alternans disappeared after 1-3 specific coupling intervals. We conclude that ventricular pacing rate does not solely determine the pattern and amplitude of sustained contractile alternans induced by tachycardia.
Suzuki
S
S
Department of Physiology II, Okayama University Medical School, Okayama 700-8558, Japan.
Araki
J
J
Doi
Y
Y
Fujinaka
W
W
Minami
H
H
Iribe
G
G
Mohri
S
S
Shimizu
J
J
Hirakawa
M
M
Suga
H
H
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002304:Cardiac Pacing, Artificial; D002306:Cardiac Volume / Q000502:physiology; D004285:Dogs; D006321:Heart / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013610:Tachycardia / Q000503:physiopathology*; D017725:Ventricular Pressure / Q000502:physiology
D002118:Calcium