Basic Research in Cardiology

, Volume 94, Issue 4, pp 284–293

Load dependence of left ventricular contraction and relaxation.¶Effects of caffeine

  • A.F. Leite-Moreira
  • J. Correia-Pinto
  • T.C. Gillebert
Original contribution

DOI: 10.1007/s003950050154

Cite this article as:
Leite-Moreira, A., Correia-Pinto, J. & Gillebert, T. Basic Res Cardiol (1999) 94: 284. doi:10.1007/s003950050154

Abstract

Objective: Load dependence of left ventricular (LV) contraction and relaxation was investigated at baseline and after alteration of intracellular calcium handling by caffeine. Methods: Afterload was increased by aortic clamp occlusions (n = 281) in anesthetized open-chest dogs (n = 7). Control and first heartbeat after the intervention were considered for analysis. Results: Caffeine (50 mg/kg, iv) had no inotropic effect. The systolic LV pressure (LVP), developed in response to aortic occlusion, decreased as ejection proceeded and this pressure generating capacity was not affected by caffeine. Late-systolic aortic occlusions induced premature onset and accelerated rate of initial LVP fall at baseline and similarly after caffeine. Graded diastolic aortic occlusions induced systolic LVP elevations of various magnitudes. Smaller LVP elevations prolonged ejection and accelerated LVP fall, while larger elevations had opposite effects. The transition from acceleration to deceleration was observed at 83.1 ± 1.1 % of peak isovolumetric LVP at baseline and at lower loads, at 77.6 ± 1.2 %, after caffeine (p < 0.01). Isovolumetric heartbeats prolonged the time constant τ by 238 ± 70 % at baseline and only by 155 ± 44 % after caffeine (p < 0.01). The relaxation-systolic pressure relation, which describes afterload dependence of relaxation, was also modified by caffeine. Conclusions: Caffeine affected LV relaxation without altering contractility. As a consequence contraction-relaxation coupling was modified by caffeine. These results might help to understand load dependence of relaxation in conditions where intracellular calcium handling is altered.

Key words Calcium (cellular) – contractile function – diastole – heart failure – sarcoplasmic reticulum (function)

Copyright information

© Steinkopff Verlag 1999

Authors and Affiliations

  • A.F. Leite-Moreira
    • 1
  • J. Correia-Pinto
    • 1
  • T.C. Gillebert
    • 2
  1. 1.Laboratory of Physiology, Faculty of Medicine, Alameda Professor Hernâni Monteiro, P-4200 Porto, Portugal, E.mail: amoreira@med.up.ptPT
  2. 2.Department of Cardiology, University of Antwerp, Wilrijkstraat, 10, B-2650 Antwerp, BelgiumBE