Eva L. Honkonen

Beneficial Effects of Ischemic Preconditioning on Right Ventricular Function After Coronary Artery Bypass Grafting

BACKGROUND Preservation of right ventricular myocardium is unsatisfactory in patients with critical stenosis or occlusion of the right coronary artery. The aim of this study was to investigate whether ischemic preconditioning (IP) improved the recovery of right ventricular function after coronary artery bypass grafting. METHODS Forty patients with three-vessel disease who had coronary artery bypass grafting were randomly assigned to the IP group (n = 20) or control group (n = 20). In the IP group, two cycles of two minutes of ischemia after three minutes of reperfusion were given before cross-clamping. Hemodynamic data were collected. Right ventricular ejection fraction was measured by thermodilution. RESULTS Right ventricular ejection fraction and right ventricular systolic volume index were decreased post-operatively (lowest value at 6 hours postoperatively). The changes in right ventricular ejection fraction were significantly milder in the IP group postoperatively (p = 0.012). The decrease in right ventricular systolic volume index postoperatively was also less in IP patients (p = 0.002). Fewer inotropic drugs were used in the IP group compared with controls. CONCLUSIONS Ischemic preconditioning had a myocardial protective effect on recovery of right ventricular contractility in patients who had coronary artery bypass grafting.

Ischaemic preconditioning has a beneficial effect on left ventricular haemodynamic function after a coronary artery biopass grafting operation.

OBJECTIVE Ischaemic preconditioning (IP) is the most effective procedure for endogenous myocardial protection. However, studies on the effects of IP in cardiac surgery are rare and controversial. The present aim was to investigate whether IP improves the haemodynamic recovery of CABG patients. DESIGN The study included 40 stable CABG patients with 3-vessel disease, randomized into an IP group (n = 20) and a control group (n = 20). In the IP group two cycles of 2-min ischaemia following 3-min reperfusion before cross-clamping were induced. The haemodynamics of the patients were followed-up to the first postoperative morning. RESULTS The cardiac index decreased at 1 and 6 h after surgery in the control group but increased in the IP group (-0.33 vs 0.09 l/min/m2, p = 0.02 and -0.15 vs 0.57 l/min/m2, p = 0.001, respectively). Depressions in the left ventricular stroke work index and the right ventricular stroke work index at 6 h after surgery were more severe in controls and were statistically significant (p = 0.049 and 0.007, respectively). Less inotropic support was used in the IP group. There were no differences in serum CK-MB, cardiac troponin I, myoglobin or lactate values between the two groups. CONCLUSION IP has a beneficial effect on left ventricular haemodynamic recovery after a CABG operation.

Protective effect of unstable angina in coronary artery bypass surgery

OBJECTIVE To test the hypothesis that recent ischaemic episodes in unstable cases have a protective effect on coronary artery bypass graft (CABG) patients. MATERIALS AND METHODS Twenty unstable patients with ischaemic episodes within 3 days before operation were compared with 20 stable patients. Haemodynamic data were monitored up to the first postoperative day. Biochemical markers were measured up to the second postoperative day. RESULTS The cardiac index decreased at 1 and 6 h after declamping in the stable group (89% and 97% of baseline) but increased in unstable patients (104% and 122%, p =0.038 and 0.036, respectively). The depression in the right ventricular stroke work index was significantly attenuated in the unstable group (58%, 67% and 83% in stable and 90%, 97% and 117% in unstable patients, p = 0.027, 0.010 and 0.049 at 1 and 6 h after declamping and 1st POD). The release of cardiac troponin I (CTnI) and CK-MB was significantly lower in the unstable group at 6 h after declamping (5.6 +/- 2.9 and 19.0 +/- 6.3 microg/l in unstable vs 17.4 +/- 9.6 and 25.8 +/- 12.3 microg/l in stable patients, p = 0.000 and 0.039, respectively). CONCLUSION Recent unstable angina before CABG might act as an ischaemic preconditioning stimulus and could improve haemodynamic function and cellular viability. Delayed preconditioning most likely causes this protective effect.Objective—To test the hypothesis that recent ischaemic episodes in unstable cases have a protective effect on coronary artery bypass graft (CABG) patients. Materials and methods —Twenty unstable patients with ischaemic episodes within 3 days before operation were compared with 20 stable patients. Haemodynamic data were monitored up to the first postoperative day. Biochemical markers were measured up to the second postoperative day. Results—The cardiac index decreased at 1 and 6 h after declamping in the stable group (89% and 97% of baseline) but increased in unstable patients (104% and 122%, p = 0.038 and 0.036, respectively). The depression in the right ventricular stroke work index was significantly attenuated in the unstable group (58%, 67% and 83% in stable and 90%, 97% and 117% in unstable patients, p = 0.027, 0.010 and 0.049 at 1 and 6 h after declamping and 1st POD). The release of cardiac troponin I (CTnI) and CK-MB was significantly lower in the unstable group at 6 h after declamping (5.6 2.9 and 19.0 6.3mg/l in unstable vs 17.4 9.6 and 25.8 12.3mg/l in stable patients, p = 0.000 and 0.039, respectively). Conclusion—Recent unstable angina before CABG might act as an ischaemic preconditioning stimulus and could improve haemodynamic function and cellular viability. Delayed preconditioning most likely causes this protective effect.

Effect of ischaemic preconditioning, cardiopulmonary bypass and myocardial ischaemic/reperfusion on free radical generation in CABG patients.

OBJECTIVE To investigate the free radicals (FR) generation after ischaemic preconditioning and cardiopulmonary bypass and during reperfusion in CABG patients, and the role of ischaemic preconditioning. METHODS Forty-three CABG patients were randomised into an ischaemic preconditioning and a control group. The protocol for ischaemic preconditioning was two cycles of 2-min ischaemia followed by 3-min reperfusion. Free radicals were measured using electron spin resonance spectroscopy. Global and right heart functions were collected. RESULTS The free radicals generation in coronary sinus blood in the ischaemic preconditioning group was 9.7 and 16.6% after the ischaemic preconditioning protocol and 10 min after declamping, 6.8 and 13.3% in the controls. The free radicals in arterial samples were, respectively, 21, 14, 10 and 9% at 10 min, 1, 2 and 24 h after reperfusion. Cardiac index (CI) and right ventricular ejection fraction (RVEF) were improved by ischaemic preconditioning. CONCLUSION Both ischaemic preconditioning and cardiopulmonary bypass induced free radicals generation. Although ischaemic preconditioning had no effect on free radicals generation after the operation, it protected against postoperative stunning.

Dopexamine unloads the impaired right ventricle better than iloprost, a prostacyclin analog, after coronary artery surgery

OBJECTIVE To evaluate the ventricle-unloading properties of dopexamine and iloprost and to compare their effects on right ventricular (RV) function and oxygen transport in patients with low RV ejection fraction (RVEF) after cardiac surgery. DESIGN A prospective, randomized, double-blind, cross-over, clinical study. SETTING University hospital. PARTICIPANTS Twenty patients with proximal total stenosis of the right coronary artery studied immediately after coronary artery surgery. INTERVENTIONS Treatment drugs were administered in a random order in doses equipotent with respect to cardiac output response. Infusion rates were increased stepwise to induce a 25% increase in cardiac index. A washout period of 60 minutes was allowed between treatments. MEASUREMENTS AND MAIN RESULTS Central hemodynamics, RV function assessed by the EF (fast-response thermodilution), end-systolic and end-diastolic volumes, and systemic oxygenation were measured before and after the first drug, after the washout period, and after the second drug. Central filling pressures remained constant during treatments. Both drugs decreased pulmonary vascular resistance index, but iloprost was more effective (p < 0.05). Iloprost decreased mean arterial and pulmonary artery pressure, which were unaffected by dopexamine. Dopexamine increased EF significantly more than iloprost (p < 0.001). End-systolic volume index decreased subsequent to dopexamine only (p < 0.001). Iloprost increased intrapulmonary shunt more than dopexamine (p < 0.001). Changes in oxygen delivery, consumption, and extraction were similar. CONCLUSION The findings suggest that dopexamine is more effective than iloprost for support and unloading of the postoperatively disturbed RV in terms of RVEF and end-systolic volume. The reduction of pulmonary vascular resistance after administration of iloprost without a decrease in end-systolic volume might not be considered a reduction of RV afterload. Iloprost increases the pulmonary shunt fraction, however, more than dopexamine, indicating a more prominent vasodilator effect.

Combined Antegrade-Retrograde Blood Cardioplegia does not Protect Right Ventricle Better than Either Technique Alone in Patients with Occluded Right Coronary Artery

To study the hypothesis that combined antegrade-retrograde delivery of cardioplegia might overcome the limitations in myocardial protection of either technique alone, we compared the distribution of the different cardioplegic approaches by assessing myocardial cooling and evaluated the effects on right ventricular (RV) function in elective coronary artery bypass grafting (CABG) patients with occluded right coronary artery (RCA). In a randomized trial, 15 patients received exclusively antegrade (ante group), 14 patients received exclusively retrograde (retro group) and 15 patients received combined, alternating antegrade-retrograde (combi group) cold blood cardioplegia. Myocardial temperatures were measured at four sites in the heart. Right ventricular function was assessed by determining the ejection fraction (fast-response thermodilution) and preload-related RV stroke work in repeated measurements. Myocardial cooling was similarly uneven and the posterior wall of the RV remained above 20 degrees C after all three methods of delivering hypothermic (5-7 degrees C) cardioplegia. The RV ejection fraction and preload-related (right atrial pressure) RV stroke work decreased postoperatively similarly in all groups. The results suggest that combined antegrade-retrograde cold blood cardioplegia could not provide more homogeneous myocardial cooling or better RV recovery than either technique alone in three-vessel-diseased CABG patients with occluded RCA.

Preceding unstable angina affects inflammatory response and hemodynamics after coronary artery bypass surgery

The authors set out to investigate the inflammatory response and its impact on the hemodynamic function in stable and unstable coronary artery bypass (CABG) patients. Nineteen stable and twenty unstable patients were included in this prospective study. Serum IL-6, IL-8, TNF-α, and IL-10 were measured before, during and after cardiopulmonary bypass (CPB). Hemodynamic data was also collected. TNF-α was detected more often in unstable patients than in stable patients before (p=0.03) and after CPB (p<0.01). TNF-α response after CPB was evident (p=0.03). Serum IL-6 and IL-8 level were significantly increased after 10 minutes of CPB, reaching the peak value at 6 hours after declamping. IL-10 level reached the highest, 6.8 × the baseline at 6 hours after declamping in the unstable, but 3.3 × of baseline on the first post-operative day (POD) in the stable patients (p=0.04). CI was better preserved in unstable patients (p=0.04). Serum TNF-α was more likely to be found in patients with recent unstable episodes. CPB induces a release of serum IL-6, IL-8 and IL-10. Recent unstable angina seems to modify the cytokine response and hemodynamic outcome.