Total Ca handling in canine mild Ca overload failing heart

Ju Mizuno, Junichi Araki, Gentaro Iribe, Masaki Maesako, Terumasa Morita, Katsumasa Miyaji, Takeshi Imaoka, Satoshi Mohri, Shunji Sano, Tohru Ohe, Masahisa Hirakawa, Hiroyuki Suga

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


We analyzed total Ca handling of the left ventricle (LV) in the mildly failing heart preparation induced by a temporary intracoronary Ca overloading intervention in eight excised and cross-circulated canine hearts. This Ca intervention consisted of interruption of coronary blood perfusion by Ca-free oxygenated Tyrode perfusion for 10 min followed by high-Ca (16 mmol/l) oxygenated Tyrode perfusion for 5 min. This intervention decreased the LV contractility index, E(max) (end-systolic maximum elastance), by 40% after restoration of the blood cross-circulation. We expected a Ca overload or paradox failing heart resembling the postischemic stunned heart and being characterized by an increased O2 cost of E(max). However, LV O2 consumption under mechanically unloading conditions decreased by 30% from control without increasing the O2 cost of E(max). To obtain a mechanistic view of this failing heart, we investigated cardiac total Ca handling by our integrative analysis method. In this method, we obtained the internal Ca recirculation fraction (RF) from the decay beat constant of the postextrasystolic potentiation following each sporadic spontaneous extrasystole in these failing LVs. We combined the RF with the decreased E(max) and the unchanged O2 cost of E(max) in our recently developed formula of total Ca handling. We found that these failing LVs had a slightly but significantly increased RF accompanied by either a slightly increased futile Ca cycling or a slightly decreased Ca reactivity of E(max) or both. Any of these three possible changes can account for the unchanged O2 cost of E(max). This result indicates that the present mildly failing heart has not yet fallen into a typical Ca overload or paradox by the temporary Ca overloading intervention.

Original languageEnglish
Pages (from-to)38-51
Number of pages14
JournalHeart and Vessels
Issue number1
Publication statusPublished - Oct 20 1999


  • Calcium paradox
  • Excitation-contraction coupling
  • Heart failure
  • Myocardial oxygen consumption
  • Ventricular contractility

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine


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