Compartmentalizing chemomechanical transduction in the ejecting heart.
The efficiency of transferring the total energy generated by ventricular contraction (pressure-volume area, PVA) to external work (EW) and internal work (IW) and the myocardial oxygen consumption (MVO2) at zero PVA were determined during volume loading on right heart bypass before and after a 50% augmentation (CaCl2, 0.03 mEq/kg/min, n = 7) or depression (20 minutes of 37 degrees C ischemia with 30 minutes of reperfusion, n = 7) of the contractile state. An increased EW efficiency (64% +/- 7% vs. 81% +/- 6%, p less than 0.01) with reciprocally decreased IW efficiency (36% +/- 7% vs. 19% +/- 6%, p less than 0.01) occurs with calcium chloride-augmented contractility. A reversible ischemia and reperfusion insult has the converse effect on these relative efficiencies (EW, 73% +/- 4% vs. 49% +/- 4%; IW, 27% +/- 4% vs. 51% +/- 4%; each p less than 0.01). Calcium chloride increases the oxygen requirements of both basal metabolism (28 +/- 2 vs. 67 +/- 9 ml O2/beat/100 gm LV, p less than 0.01) and fiber shortening (11 +/- 5 vs. 62 +/- 11 ml O2/beat/100 gm LV, p less than 0.01). The postischemic heart has a decreased oxygen need for shortening (20 +/- 2 vs. 3 +/- 4 ml O2/beat/100 gm LV, p less than 0.01), paralleling the depressed inotropic state. This new model of compartmentalized chemomechanical transduction may allow specific modulation of the energetic derangements attendant to the surgically treated heart.
Krukenkamp
I B
IB
Department of Surgery, University of Illinois College of Medicine, Chicago.
Silverman
N A
NA
Levitsky
S
S
D000818:Animals; D001696:Biomechanical Phenomena; D001794:Blood Pressure; D001810:Blood Volume; D002122:Calcium Chloride / Q000494:pharmacology; D003327:Coronary Disease / Q000378:metabolism; D004285:Dogs; D004734:Energy Metabolism; D006321:Heart / Q000502:physiology*; D008955:Models, Cardiovascular; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects
D002122:Calcium Chloride