Temporal endothelin dynamics of the myocardial interstitium and systemic circulation in cardiopulmonary bypass

Objective: Increased systemic levels of the bioactive peptide endothelin 1 during and after cardioplegic arrest and cardiopulmonary bypass have been well documented. However, endothelin 1 is synthesized locally, and therefore myocardial endothelin 1 production during and after cardiopulmonary bypass remains unknown. Methods: Pigs (n = 11) were instrumented for cardiopulmonary bypass, and cardioplegic arrest was initiated. Myocardial interstitial and systemic arterial levels of endothelin 1 were measured before cardiopulmonary bypass, throughout bypass and cardioplegic arrest (90 minutes), and up to 90 minutes after separation from bypass. Myocardial interstitial endothelin 1 was determined by microdialysis and radioimmunoassay. Results: Baseline myocardial endothelin 1 levels were higher than systemic endothelin 1 levels (25.6 ± 6.7 vs 8.3 ± 1.1 fmol/mL, P < .05). With the onset of bypass, myocardial endothelin 1 increased by 327% ± 92% from baseline (P < .05), which preceded the increase in systemic endothelin 1 levels. Conclusion: Myocardial compartmentalization of endothelin 1 exists in vivo. Cardiopulmonary bypass and cardioplegic arrest induce temporal differences in endothelin 1 levels within the myocardial interstitium and systemic circulation, which, in turn, may influence left ventricular function in the postbypass period.