Abstract
The left ventricular (LV) mechanical performance and the LV myocardial oxygen consumption (V̇O2)-to-pressure-volume area (PVA; LV total mechanical energy index) relationship were measured in isovolumic contraction of isolated blood-perfused dog hearts before and after direct current (DC) countershocks. At a constant LV volume, DC shocks increased LV end-diastolic pressure progressively and strikingly with the progression of myocardial edema and a marked prolongation of the time constant of LV pressure decay. In contrast, DC shocks changed neither the slope of the LV end-systolic pressure-volume relationship nor the contractile efficiency (the slope of the V̇O2-PVA relationship). The oxygen cost of contractility (the slope of the relationship between PVA-independent V̇O2 and LV contractility) increased 27% after DC shocks. However, the magnitude of this change was considerably smaller than that previously reported in postischemic stunned myocardium (123%), suggesting that the adverse effect of DC shocks on the energy cost of excitation-contraction coupling is relatively minor. Thus, despite the severe diastolic dysfunction, DC shocks do not substantially impair either the efficiency of cross-bridge cycling or calcium cycling. Myocardial interstitial edema is more likely a potential mechanism of diastolic dysfunction after DC shocks.
Original language | English |
---|---|
Pages (from-to) | H583-H592 |
Journal | American Journal of Physiology - Heart and Circulatory Physiology |
Volume | 273 |
Issue number | 2 42-2 |
DOIs | |
Publication status | Published - 1997 |
Externally published | Yes |
Keywords
- Diastolic function
- Electric countershock
- Excitation-contraction coupling
- Myocardial oxygen consumption
- Pressure-volume relationship
ASJC Scopus subject areas
- Physiology
- Cardiology and Cardiovascular Medicine
- Physiology (medical)