Postextrasystolic contractile decay always contains exponential and alternans components in canine heart

Juichiro Shimizu, Junichi Araki, Gentaro Iribe, Takeshi Imaoka, Satoshi Mohri, Kunihisa Kohno, Hiromi Matsubara, Tohru Ohe, Miyako Takaki, Hiroyuki Suga

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


In isolated, blood-perfused canine hearts, postextrasystolic potentiation (PESP) decays monotonically after a noncompensatory pause following a spontaneous extrasystole (ES). The monotonic PESP decay yields myocardial internal Ca2+ recirculation fraction (RF). We have found that after a compensatory pause (CP), PESP decays in alternans, consisting of an exponential and a sinusoidal decay component. We have proposed that this exponential component also yields RF. In the present study, we examined the reliability of this alternative method by widely changing the ES coupling interval (ESI), CP, and heart rate in the canine excised, cross-circulated left ventricle. We found that all PESP decays consisted of the sum of an exponential and a sinusoidal decay component of variable magnitudes whether a CP existed or not. Their decay constants as well as the calculated RF were independent of the ESI and CP. This confirmed the utility of our alternative RF determination method regardless of the ESI, CP, and heart rate. Direct experimental evidence of Ca2+ dynamics supportive of this alternative method, however, remains to be obtained.

Original languageEnglish
Pages (from-to)H225-H233
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Issue number1 48-1
Publication statusPublished - 2000


  • Cardiac contractility
  • Extrasystole
  • Mechanical alternans
  • Mechanical potentiation
  • Transient alternans

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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