Mechanoenergetics characterizing oxygen wasting effect of caffeine in canine left ventricle

Toshiyuki Takasago, Yoichi Goto, Katsuya Hata, Akio Saeki, Takehiko Nishioka, Tad W. Taylor, Gentaro Iribe, Satoshi Mohri, Juichiro Shimizu, Junichi Araki, Hiroyuki Suga

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Caffeine causes a considerable O2 waste for positive inotropism in myocardium by complex pharmacological mechanisms. However, no quantitative study has yet characterized the mechanoenergetics of caffeine, particularly its O2 cost of contractility in the E(max)-PVA-VO2 framework. Here, E(max) is an index of ventricular contractility, PVA is a measure of total mechanical energy generated by ventricular contraction, and VO2 is O2 consumption of ventricular contraction. The E(max)-PVA-VO2 framework proved to be powerful in cardiac mechanoenergetics. We therefore studied the effects of intracoronary caffeine at concentrations lower than 1 mmol/l on left ventricular (LV) E(max) and VO2 for excitation-contraction (E-C) coupling in the excised cross-circulated canine heart. We enhanced LV E(max) by intracoronary infusion of caffeine after β-blockade with propranolol and compared this effect with that of calcium. We obtained the relation between LV VO2 and PVA with E(max) as a parameter. We then calculated the VO2 for the E-C coupling by subtracting VO2 under KCl arrest from the PVA- independent (or zero-PVA) VO2 and the O2 cost of E(max) as the slope of the E-C coupling VO2-E(max) relation. We found that this cost was 40% greater on average for caffeine than for calcium. This result, for the first time, characterized integratively cardiac mechanoenergetics of the O2 wasting effect of the complex inotropic mechanisms of intracoronary caffeine at concentrations lower than 1 mmol/l in a beating whole heart.

Original languageEnglish
Pages (from-to)257-265
Number of pages9
JournalJapanese journal of physiology
Volume50
Issue number2
DOIs
Publication statusPublished - Apr 2000

Keywords

  • Cardiac energetics
  • E(max)
  • Myocardial O consumption
  • PVA
  • Pressure-volume area

ASJC Scopus subject areas

  • Physiology

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