Myocardial metabolism before and after valve replacement for aortic stenosis.
OBJECTIVE
Post ischemic disturbances of myocardial metabolism that may contribute to postoperative heart failure and are accessible to metabolic treatment have been identified early after coronary surgery. Knowledge derived from these studies may not be applicable to other patient groups. Therefore we studied myocardial energy metabolism in patients operated for isolated aortic stenosis.


METHODS
Twenty patients undergoing isolated aortic valve replacement (AVR) because of aortic stenosis without significant regurgitation were studied before and immediately after surgery. Myocardial uptake of oxygen and energy substrates was assessed with coronary sinus catheter technique.


RESULTS
Free fatty acids (FFA) were the main source of myocardial energy before and after AVR. A significant uptake of lactate was only recorded preoperatively. A significant uptake of glutamate of the same magnitude as previously described in coronary patients was found pre- and postoperatively. Postoperatively a relative decrease of myocardial oxygen extraction ratio (P<0.001) and oxygen consumption (P=0.14) by approximately 20% was observed.


CONCLUSIONS
Preoperative and postoperative metabolic adaptation with substantial uptake of glutamate, previously claimed to be due to chronic or repetitive ischemia, was demonstrated. The results indicate that oxidative metabolism had not fully recovered when the procedure was completed. However, the potentially unfavorable postoperative metabolic state with predominant reliance on FFA as energy source was out-balanced by the unloading effect of AVR with a reduction in myocardial oxygen extraction.
Vanky
F B
FB
Department of Cardiothoracic Surgery, Linköping Heart Center, University Hospital, Linköping, Sweden.
Hakanson
E
E
Szabó
Z
Z
Jorfeldt
L
L
Svedjeholm
R
R
D000368:Aged; D000596:Amino Acids / Q000378:metabolism; D001024:Aortic Valve Stenosis / Q000378:metabolism / Q000503:physiopathology / Q000601:surgery*; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D004734:Energy Metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005260:Female; D005990:Glycerol / Q000378:metabolism; D019918:Heart Valve Prosthesis Implantation; D006439:Hemodynamics; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D011182:Postoperative Care; D011300:Preoperative Care; D016896:Treatment Outcome
D000596:Amino Acids; D015415:Biomarkers; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D019344:Lactic Acid; D005990:Glycerol; D010100:Oxygen