21.11.08 17:57 Age: 10 yrs

A new era for intermittent coronary sinus occlusion

Intermittent pressure eleveation of the coronary venous system as method to protect ischemic myocardium.

Background: Beating heart surgery leaves myocardial areas underperfused and rendered ischemic during brief coronary artery occlusions. This effect of controlled myocardial ischemia counteracts positive trends in OPCAB patients. In a recent meta-analysis in experimental myocardial infarction, intermittent coronary sinus occlusion (ICSO) proved valid to salvage ischemic myocardium by 30%. Furthermore this beneficial effect was closely related to the achieved coronary sinus pressure during intermittent occlusions. Moreover there was evidence that this beneficial effect can be optimised, using coronary venous pressure data.

We have developed a coronary venous pressure controlled closed loop system that auto regulates and optimises redistribution of venous flow towards deprived myocardium (PICSO). The aim of this study was to evaluate optimisation criteria investigating coronary venous flow data during PICSO. Methods: Intermittent coronary sinus occlusion was performed in 12 adult anesthetized sheep during occlusion of the LAD. In addition to coronary sinus pressure (CSP) recordings a Transonic flow probe was placed around the great cardiac vein adjacent to the site of LAD occlusion. Venous flow measurements in the GCV via continuous wave Doppler sonography were performed.

Result: During CS occlusion and in accordance to the pressure rise in the venous circulation a negative (retrograde) GCV flow directed towards the ischemic myocardium occurred. After reopening of the CS a tremendous flow increase in the opposite direction (antegrade flow) was observed. A significant difference in both flow directions could be detected in favour of the antegrade flow (p < 0.007). Our experimental studies provide evidence of retrograde flow into the ischemic zone which occurs in association with intermittent coronary sinus occlusion. Comparison between different cycles was performed with ANOVA, followed by Tukey`s post hoc test for comparison between all cycle groups.

Antegrade , as well retrograde flow differences between various cycles can be considered significant (p<0.00). These results confirm our assumptions that certain cycles improve GCV flow more than others, which might be an important proposal for optimal cycle length.

Conclusion: These experimental data support the notion that transient pressure elevation in the coronary venous system recruits collateral flow towards ischemic myocardium. Optimal timing significantly improves the effectiveness of the method. Because of the ease of this intervention, PICSO is capable to protect myocardial performance during beating heart surgery.

W. Mohl MD PhD, B. Syeda MD, G. Weigel MD, P. Pichler MD, I. Kajgana MSc, L. Kharboot MSc. F. Rattay PhD Department of Cardiothoracic Surgery University of Vienna Vienna Austria