Dynamic and differential changes in myocardial and plasma endothelin in patients undergoing cardiopulmonary bypass.
OBJECTIVE
The bioactive peptide endothelin modulates left ventricular function by changing afterload, coronary vascular tone, and myocardial contractility. However, whether increased plasma endothelin levels observed in patients during and after coronary revascularization and cardiopulmonary bypass reflect actual myocardial interstitial levels are unknown.


METHODS
A microdialysis probe (outer diameter: 0.77 mm; length: 4 mm) was placed in the left ventricular apical midmyocardium in 20 patients and myocardial interstitial fluid was collected (2.5 microL/min) at baseline and up to 30 minutes after cardiopulmonary bypass. Myocardial interstitial and systemic arterial endothelin were measured by radioimmunoassay.


RESULTS
Baseline myocardial interstitial endothelin was over 6-fold higher than plasma (20.11 +/- 2.07 vs 3.19 +/- 0.25 fmol/mL, P < .05). Plasma endothelin increased by 23% +/- 12% at 60 minutes of cardiopulmonary bypass whereas myocardial interstitial endothelin increased by 105% +/- 24%, P < .05), and this change was higher than in the plasma ( P < .05). Although no further change in plasma endothelin occurred during cardiopulmonary bypass, myocardial interstitial levels increased further after crossclamp removal (400% +/- 75%) and remained significantly higher than plasma at separation from cardiopulmonary bypass.


CONCLUSIONS
The unique findings of this study were 2-fold: First, significant compartmentalization of endothelin exists within the human myocardium. Second, a significantly higher and temporally disparate change in myocardial interstitial endothelin occurs during and after cardiopulmonary bypass when compared with systemic levels. These dynamic changes in myocardial endothelin likely influence coronary vascular tone and contractility.
Multani
M Marlina
MM
Medical University of South Carolina, Charleston 29425, USA.
Ikonomidis
John S
JS
Kim
Peter Y
PY
Miller
Elizabeth A
EA
Payne
Kim J
KJ
Mukherjee
Rupak
R
Dorman
B Hugh
BH
Spinale
Francis G
FG
D000368:Aged; D002315:Cardiopulmonary Bypass; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000097:blood / Q000601:surgery*; D019332:Endothelin-1 / Q000032:analysis* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D017551:Microdialysis; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000737:chemistry*; D011184:Postoperative Period; D018487:Ventricular Dysfunction, Left / Q000097:blood
D019332:Endothelin-1