Inflammatory marker comparison between patients with acute coronary syndrome undergoing on-pump versus off-pump coronary artery bypass graft surgery

Abstract

The World Health Organization (WHO) has warned in 2005 that: “Coronary heart disease is now one of the leading causes of death worldwide. It is on the rise and has become a true pandemic that respects no borders” (WHO, 2005). The Heart and Stroke Foundation of South Africa more specifically estimates that approximately 33 (thirty‐three) people per day will die of a heart attack in South Africa. Despite the already high death toll resulting from AIDS in South Africa, death from a chronic disease, also including heart disease, will increase from 565 deaths per day in the year 2000, to 666 deaths per day by 2010 (Steyn, 2007).

Acute coronary syndrome (ACS) is an ‘umbrella term’ describing a heterogeneous spectrum of clinical symptoms compatible with acute myocardial ischaemia (Monaco, Mathur, Martin, 2005; ACC/AHA, 2007) and an ongoing inflammatory process resulting from atherosclerosis. ACS can either be treated medically (pharmacological treatment), by percutaneous coronary intervention (PCI), or by performing coronary artery bypass graft (CABG) surgery either through on‐pump or offpump CABG surgery. By treating the ACS patient by means of CABG surgery, an inflammatory response is further triggered on top of the already existing inflammation resulting from atherosclerosis. This leads to a systemic inflammatory response (SIR), which may eventually lead to systemic inflammatory response syndrome (SIRS). This study focuses on the inflammatory response initiated by the CABG technique applied during the revascularisation of the ACS patient. Many past studies compared on‐pump and off‐pump CABG surgery, arguing not only the advantages and disadvantages of these surgeries, but also the outcomes regarding SIRS. Both types of surgery are associated with an inflammatory response resulting from tissue trauma and the use of the extracorporeal circulation (EC) in CABG surgery (Quaniers, Leruth, Albert, Limet, Defraigne, 2006).

This non‐randomised, observational study primarily aimed to assess and compare the pre‐ and the post‐operative inflammatory markers between (n=60) patients with ACS undergoing either on‐pump CABG (n=30) or off‐pump CABG surgery (n=30). A secondary objective was to ascertain whether a correlation exists between the pre‐operative risk factors, the surgical procedure and the pre‐ and post‐operative inflammatory markers. Three inflammatory markers ‐ full blood count (FBC), procalcitonin (PCT) and C‐reactive protein (CRP) ‐ were analysed employing normal routine laboratory analysis. Interleukin‐6 (IL‐6) and tumour necrosis factor alpha (TNF‐α) were analysed using an enzyme amplified sensitivity immunoassay (EASI) method. The inflammatory markers were analysed pre‐operatively (baseline) and post‐operatively and at different time intervals (24, 48, 72, 96 and 120 hours post‐operatively).

Pre‐operatively, all the leucocytes were already elevated in both CABG groups, as could be expected in patients with ACS resulting from the already existing atherosclerotic process and the consequent pre‐operative existing inflammatory response. A significant pre‐operative difference was moreover detected in respect of the lymphocytes between the two CABG groups (p=0.03024). A significant post‐operative difference was also detected between the two CABG groups. The following significantly elevated levels were detected in the on‐pump CABG surgical group: for WCC at 24 hours (p=0.00761), 48 hours (p=0.01520) and 72 hours (p=0.00004); for neutrophils at 24 hours (p=0.17422), 96 hours (p=0.18611) and 120 hours (p=0.12872); for lymphocytes at 48 hours (p=0.04829) and at 96 hours (p=0.01982); and, for PCT at 24 hours (p=0.00811), 48 hours (p=0.00966) and 72 hours (p=0.01823) . However, measurable values of IL‐6 levels were found to be higher in the off‐pump CABG surgical group, with significant differences manifesting between the two CABG groups at 96 hours (p=0.05352) and 120 hours (p=0.09729). No differences between the two groups could be demonstrated for eosinophils, basophils, monocytes, CRP and TNF‐α.

In conclusion: despite the demonstrable inflammatory responses in both CABG groups, no difference in clinical outcomes was observed. The inflammatory responses evoked by on‐pump and off‐pump CABG procedures will, for some time to come, remain an area of interest for future research, but they are certainly not the only factors to have a bearing on surgical outcomes. The impact of intraoperative events needs to be elucidated further ‐ and in more detail ‐ in order to attempt to determine the relationship of these events on the extent of inflammatory responses and clinical outcomes, irrespective of whether the procedure is performed with or without cardiopulmonary bypass.