Hemodynamics in off-pump surgery: normal versus compromised preoperative left ventricular function.

Objective: Off-pump coronary surgery (OPCABG), avoiding cardiopulmonary bypass and cardioplegic arrest, seems to be a better choice in patients with poor baseline cardiac function. Since cardiocirculatory collapse could be induced by heart displacement in this group of patients at high risk, a greater pathophysiologic understanding of the hemodynamic derangements occurring in such patients is needed.

Methods: Twenty-eight elective OPCABG patients were evaluated for hemodynamic changes induced by heart displacement, using arterial thermodilution to measure cardiac output and global end-diastolic volume. Hemodynamic parameters were recorded: at baseline; during proper exposure and stabilization of each vessel; and at the end of surgery. Patients were divided into two groups, according to baseline ejection fraction (EF): group A (EF>30%; N=16), group B (EF< or =30%; N=12).

Results: Heart displacement induced a significant drop in the cardiac and stroke index, with a lesser decrease of mean arterial pressure because of raised systemic vascular resistance. Preload, measured as global end diastolic volume, significantly decreased in group A, while it remained unchanged or increased in group B. Linear regression between the preload index and left ventricular stroke work was significant only in group A.

Conclusions: Patients with poor baseline cardiac function can well tolerate OPCABG. However, the pathophysiologic modifications underlying the hemodynamic changes are different compared to those in patients with good preoperative cardiac performance.