To test for oxygen wasting by norepinephrine (NE) without relying on normalization by measures of performance such as the pressure-volume area, myocardial oxygen consumption (MV̇O2) was determined for isovolumic beats at five different left ventricular (LV) end-diastolic volumes (EDV) in nine isolated cross-perfused canine hearts in each of three states: a basal anesthetic state (B); after depression with halothane (H); and after adding NE to increase contractility back to the B state (H + NE). The end-diastolic and peak systolic pressure-volume lines were identical for B and H + NE. The R2 for a linear regression of MV̇O2 per beat for B vs. H + NE for beats originating at the same EDV and developing similar (within 10%) peak isovolumic pressures for all hearts was 0.85. The slope and intercept were 0.83 and 0.01, which are significantly less than one (P < 0.001) and greater than zero (P < 0.001), respectively. These data suggest that NE increases both the economy of pressure development as well as activation energy of an isovolumically contracting LV.
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Issue number||3 32-3|
|State||Published - Jan 1 1992|
- efficiency of pressure development
- myocardial oxygen consumption
- oxygen wasting