The Relationship Between Immediate Outcome After Cardiac Surgery, Homogeneous Cardioplegia Delivery, and Ejection Fraction

¹ From the Department of Medicine, Brigham Hospital, Boston
² From the Departments of Anesthesia and Critical Care, and Surgery, the University of Chicago
³ From the Department of Medicine, The University of Illinois, Chicago
⁴ Chicago Medical School

Background: Optimal myocardial protection during cardiac surgery with ischemic arrest is predicated on among other variables, homogeneous cardioplegia distribution. Contrast echocardiography has been shown to provide information regarding the intramyocardial distribution of cardioplegia solution. To test the hypothesis that information regarding cardioplegia distribution derived from contrast echocardiography may be associated with immediate clinical outcome after cardiac surgery, data from 21 patients were examined retrospectively.

Methods: Contrast-enhanced cardioplegia distribution patterns of the left ventricle short axis view obtained with transesophageal echocardiography were examined off-line by four observers blinded to clinical outcome. Contrast effect was scored for eight equally divided myocardial segments (0=no contrast, l=nonuniform contrast, 2=uniform contrast, 3=excessive contrast). The scores were then averaged between segments and between observers to generate an antegrade, a retrograde, and a combined global contrast score for each patient.

Results: Seventeen patients were separated from bypass without difficulty (group A) and 4 patients required sustained inotropic therapy or an intra-aortic balloon pump to facilitate separation from bypass (group B). As would be expected, group A patients had a higher average preoperative ejection fraction than did group B patients (60 percent ± 14 vs 31 percent ± 7, p<0.01). In group A, however, for 4 of 17 patients (23 percent), low preoperative ejection fraction was not predictive of postoperative exogenous circulatory support requirements. Group A patients also had significantly higher antegrade (1.6 vs 1.2, p<0.02), retrograde (1.7 vs 1.1, p<0.02), and combined global contrast scores (1.7 vs 1.1, p<0.01) than did group B patients. All patients with low preoperative ejection fraction and low intraoperative contrast scores required exogenous support to separate from cardiopulmonary bypass.

Conclusion: Contrast echocardiography makes possible an evaluation of the intensity and distribution of contrast-enhanced cardioplegia delivery and we believe the efficacy of intraoperative myocardial protection. Although low preoperative ejection fraction is a known predictor of poor immediate postoperative outcome following cardiac surgery, not all patients with low preoperative ejection fractions require inotropic support postoperatively. Our results suggest that monitoring cardioplegia distribution with contrast echocardiography may offer insight for better patient stratification based on intraoperative myocardial protection in patients with low ejection fraction. We believe a more extensive evaluation of this relationship should be pursued in a prospective manner.

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