Protection of evolving myocardial infarction and failed PTCA

The use of controlled reperfusion strategies in cardiac surgery to minimize ischaemia/reperfusion damage

Ischaemia and reperfusion occur during almost every cardiac operation, and one of the key elements to achieve a successful operation is to counteract the detrimental effects of induced ischaemia and reperfusion during the operation. The cardiac surgeon is in a unique position to protect the heart before ischaemia is induced and to avoid further damage during the reperfusion period. The surgeon can alter the composition of the reperfusate and the conditions of reperfusion so that the ischaemia/reperfusion injury is minimal, even after very complex procedures that require long aortic cross-clamp periods. This in turn allows him to perform a near-perfect surgical repair of the underlying disease without the pressure of time. The vast knowledge gained in this field over the years has led to application in other organs, such as the limbs (acute limb ischaemia), lungs (lung transplantation), kidney and liver (kidney and liver transplantation), and more recently even for the brain [acute cerebral artery occlusion (stroke)] and the whole body (cardiopulmonary resuscitation). Further improvements in reperfusion strategies will allow salvage of tissue and even whole body after ischaemic periods thought previously to be irreversibly damaged.

Off-Pump Coronary Artery Bypass for Emergency Myocardial Revascularization

Emergency coronary artery bypass is associated with increased operative mortality. The objective of this study was to evaluate the efficiency and safety of off-pump emergency coronary artery bypass, and to compare the outcome with that of the conventional on-pump procedure. Data of 79 patients who underwent emergency isolated coronary artery bypass were reviewed retrospectively; 45 had off-pump coronary bypass and 34 had conventional surgery. In the off-pump group, mean ejection fraction was significantly lower (28% ± 9% vs. 39% ± 10%), and there were fewer grafts per patient (1.8 ± 0.7 vs. 3.2 ± 0.8). Early mortality was higher in the conventional surgery group (14.7% vs. 8.9%), but late mortality was similar in both groups. Patients who had on-pump surgery had lower rates of recurrent angina (16% vs. 34%) and symptoms of heart failure (20% vs. 51%). Re-hospitalization was more common in off-pump patients, but cardiac re-interventions were similar. There was no significant difference in 5-year survival rates. The results of off-pump coronary bypass were better than the preoperative predicted EuroSCORE, thus it was concluded that patients treated on an emergency basis should have an off-pump revascularization procedure.

Emergency Coronary Artery Bypass Grafting Can Be Performed Safely Without Cardiopulmonary Bypass in Selected Patients

BACKGROUND

Patients requiring emergency surgical revascularization are often not considered for off-pump coronary artery bypass grafting (OPCAB).

METHODS

From 1996 to 2003, 614 patients underwent emergency coronary artery bypass grafting (Society of Thoracic Surgeons definition) at an academic institution. Forty-four (7%) of these procedures were performed without cardiopulmonary bypass, while 570 were conventional coronary artery bypass procedures with cardiopulmonary bypass (CABG/CPB). Data were collected prospectively into a computerized database and reviewed retrospectively.

RESULTS

Though a greater proportion of CABG/CPB patients had critical left main stenosis (15.9% vs 38.3%, p = 0.005), other preoperative risk factors were similar between groups. Completeness of revascularization (No. distal anastomoses/No. diseased vessel systems) was significantly greater in the CABG/CPB group (1.51 +/- 0.03 vs 1.25 +/- 0.07, p = 0.003). There were no differences among individual complication rates (death, cardiac reoperation, postoperative myocardial infarction, permanent cerebral vascular accident, deep sternal wound infection, renal failure requiring hemodialysis, and respiratory failure requiring reintubation). However, the combined incidence of these endpoints was significantly lower in the OPCAB group (6.8% vs 21.1%, p = 0.038). OPCAB patients received fewer blood transfusions (65.9% vs 84.9%, p = 0.004) and had a significantly shorter intensive care unit stay (1.47 vs 3.20 days, p = 0.016). In-hospital mortality (0% vs 6.3%, p = 0.168) and mean postoperative length of stay (5.48 vs 7.03 days, p = 0.414) favored OPCAB, but did not reach statistical significance.

CONCLUSIONS

Off-pump coronary artery bypass can be performed safely and effectively and should be considered in selected patients with acceptable hemodynamics undergoing emergency coronary revascularization.

Leukocyte-depleted continuous blood cardioplegia for coronary artery bypass grafting

Many cardiac surgeries are performed with blood cardioplegia. However, some studies suggest that activated neutrophils form blood cardioplegia can cause reperfusion injury. In this study we assessed myocardial protection using a leukocyte-depleted cardioplegic solution. Patients undergoing elective coronary artery bypass grafting (CABG) with continuous blood cardioplegia were divided into two groups: the LD group, which received leukocyte-depleted blood cardioplegia (n = 11); and the control group, which received nonfiltered blood cardioplegia (n = 11). IL-6, IL-8, CK-MB, and troponin T were measured in the coronary sinus blood immediately after the release of the aortic cross-clamp. Cytokine concentrations were also measured upon the patient's return to the ICU. The total dopamine and dobutamine doses, hemodynamic measurements after surgery, and the leukocyte filtration rate were also measured. During antegrade cardioplegia infusion, leukocytes were almost completely removed (filtration rate: 85.8+/-4.0%). However, during terminal warm cardioplegia, leukocyte removal decreased (filtration rate: 39.9+/-7.8%). Immediately after the release of the aortic cross-clamp, plasma CK-MB and troponin T concentrations were significantly lower in the LD group (17.7+/-1.9 U/l and 0.017+/-0.002 ng/ml, respectively) than in the control group (30.3+/-3.6 U/l and 0.072+/-0.029 ng/ml, respectively). The IL-6 and IL-8 concentrations were similar in the LD group and the control group. After the return to the ICU, the CK-MB and troponin T concentrations were similar in the two groups. No significant differences were found in the total doses of dopamine or dobutamine after surgery in the two groups (99+/-77 vs 101+/-128 microg/kg/min). No significant differences were found in the hemodynamic parameters after surgery in the two groups. In patients undergoing CABG with continuous blood cardioplegia, leukocyte-depleted blood cardioplegic solution may attenuate reperfusion injury.

Leukocyte depletion of blood cardioplegia attenuates reperfusion injury

BACKGROUND

Leukocytes are associated with myocardial injury during reperfusion after ischemia. Short periods of leukocyte depletion during reperfusion result in persistent attenuation of postischemic myocardial dysfunction.

METHODS

Leukocyte depletion was examined in a canine model of regional myocardial ischemia and reperfusion. The extracorporeal circuit and cardioplegia circuits underwent leukocyte depletion by mechanical filtration. Animals were instrumented for baseline global function before 90-minute occlusion of the left anterior descending coronary artery. Global function during ischemia and at 5, 30, 60, and 90 minutes after a 60-minute cardioplegic arrest using continuous blood cardioplegia was assessed in leukocyte-depleted (n = 9) and control (n = 10) groups.

RESULTS

No significant difference between groups was seen for systemic leukocyte counts, global function, or water content. Endothelial function was significantly protected as assessed by response to both calcium ionophore (endothelial-dependent, receptor-independent relaxation: leukocyte-depleted, 72% +/- 19% of endothelin-induced constriction versus control, 46% +/- 14%; p < 0.05) and acetylcholine (endothelial-dependent, receptor-dependent relaxation: leukocyte-depleted, 83% +/- 11% versus control, 44% +/- 15%; p < 0.05).

CONCLUSIONS

Leukocyte-mediated endothelial reperfusion injury can be attenuated by leukocyte depletion during reperfusion.