Structural myocardial changes after coronary artery surgery

Abstract

Background: Postoperative contractile dysfunction or 'myocardial stunning' has been described after coronary artery bypass grafting (CABG). In the present study we sought to determine if and to what extent clinical, structural and histochemical evidence of myocardial changes associated with stunning could be found in patients after CABG and cold crystalloid cardioplegia.

Materials and methods: Left ventricular (LV) biopsies were obtained from CABG patients (n = 10) prior to and at the end of cardiopulmonary bypass (CPB). These biopsies were immunostained for the inducible heat-shock protein 70 (HSP-70i), intercellular adhesion molecule-1 (ICAM-1) and actin. ATP was measured by bioluminescence.

Results: Biopsies pre-CPB showed no evidence of myocardial damage as HSP-70i was absent and a regular actin cross-striation pattern and only constitutive ICAM-1-expression were present. After CPB we found significantly increased HSP-70i and ICAM-1 levels as well as a deranged actin cross-striation pattern with a widening of actin bands. ATP levels declined from 10 mmol L-1 pre-CPB to 4.9 mmol L-1 after CPB. Correspondingly, coronary sinus effluent showed a significant lactate production. Although, cardiac function determined by transoesophageal echocardiography did not deteriorate, significant inotropic support was necessary to maintain cardiac output.

Conclusions: Our results present clinical and structural evidence of 'myocardial stunning' after CABG and cold crystalloid cardioplegia. Increased HSP-70i and ICAM-1 expression, as well as a deranged actin cross-striation pattern, might be structural markers to determine 'myocardial stunning' in clinical settings.