Factors influencing preoperative stress response in coronary artery bypass graft patients

BACKGROUND: In many studies investigating measures to attenuate the hemodynamic and humoral stress response during induction of anaesthesia, primary attention was paid to the period of endotracheal intubation since it has been shown that even short-lasting sympathetic cardiovascular stimulation may have detrimental effects on patients with coronary artery disease. The aim of this analysis was, however, to identify the influencing factors on high catecholamine levels before induction of anaesthesia. METHODS: Various potential risk factors that could impact the humoral stress response before induction of anaesthesia were recorded in 84 males undergoing coronary aortic bypass surgery, and were entered into a stepwise linear regression analysis. The plasma level of norepinephrine measured immediately after radial artery canulation was chosen as a surrogate marker for the humoral stress response, and it was used as the dependent variable in the regression model. Accordingly, the mean arterial blood pressure, heart rate and the calculated pressure-rate product were taken as parameters of the hemodynamic situation. RESULTS: Stepwise regression analysis revealed that the oral administration of low-dose clonidine (mean dose 1.75 μg.kg-1) on the morning of surgery was the only significant predictor (p = 0.004) of the high variation in preoperative norepinephrine plasma levels. This intervention decreased norepinephrine levels by more than 40% compared to no clonidine administration, from 1.26 to 0.75 nmol.l-1. There was no evidence for dose-responsiveness of clonidine. All other potential predictors were removed from the model as insignificant (p > 0.05). The use of beta-blocker, ace-inhibitors, ejection fraction, and body mass index were significant determinants for the hemodynamic situation (heart rate, mean arterial pressure, pressure rate product) of the patient during the pre-induction period. CONCLUSION: The oral administration of clonidine is the only significant predictor for the observed variation of norepinephrine levels during the preoperative period. Lack of significant dose responsiveness suggests that even a low dose of the drug can attenuate the preoperative stress response and thus is recommended in cardiovascular high risk patients.     

Gender differences in detecting coronary artery disease with dipyridamole stress myocardial perfusion imaging using 99m-Tc sestamibi gated SPECT

There are some specifics in the presentation of coronary artery disease (CAD) in women compared with men that may cause diagnostic pitfalls. The accuracy of noninvasive diagnostic testing in women tends to be lower than that in men. Stress myocardial perfusion imaging with 99m-Tc sestamibi gated SPECT is an accurate technique for detecting CAD. Only a few studies have compared dipyridamole stress imaging according to gender. The aim of the study was to compare the diagnostic value of dipyridamole myocardial perfusion imaging with 99m-Tc sestamibi gated SPECT in detecting CAD among patients of both sexes. We studied 62 consecutive patients (38 men, 24 women) using 99m-Tc sestamibi gated SPECT and dipyridamole stress to detect CAD. All the patients also underwent coronary angiography. Overall regional sensitivity was significantly lower in women compared with men (71.4% vs. 92.7%, p=0.039). There were no significant differences for detecting CAD in individual coronary arteries, although regional sensitivity in all three vascular territories was higher in men compared to women. The lowest sensitivity in women was found in the LAD territory (66.6%). Overall regional specificity in men and women was similar and did not reach statistical significance (88.7% vs. 94.7%). Significantly lower specificity in men was found only in the RCA territory (79.1%), compared with that in women (100%). Our results confirmed that there are certain gender differences in the diagnostic performance of dipyridamole stress myocardial perfusion imaging with 99-Tc sestamibi gated SPECT which are assigned to the characteristics of the female population. However, the diagnostic accuracy is also quite high in women, which makes this technique efficient enough in detecting CAD among this population.     

Predictors of postoperative atrial fibrillation after coronary artery bypass graft surgery

Objectives

The present study was aimed to identify the preoperative, intraoperative, and postoperative predictors of AF in a pure cohort of the patients with coronary artery disease who underwent CABG surgery.

Methods

Between November 2005 and May 2006, 302 consecutive patients were included in this prospective study. All the relevant clinical, electrocardiographic, echocardiographic, and laboratory data were gathered in the included patients and they were also monitored for development of post-CABG AF.

Results

Postoperative AF occurred in 46 (15%) of patients. By univariate analysis, older age, P-wave abnormality in ECG, presence of mitral regurgitation, larger left atrium (LA), left main coronary artery involvement, failure to graft right coronary artery (RCA), and adrenergic use in ICU were significantly associated with occurrence of post-CABG AF (all P< 0.05). However, in the logistic regression model, age (OR: 1.067, 95%CI: 1.02-1.116, P=0.005), LA dimension (OR: 1.102, 95%CI: 1.017-1.1936, P=0.017), P-wave morphology (OR: 12.07, 95%CI: 3.35-48.22, P=0.0001), failure to graft RCA (OR: 3.57, 95%CI: 1.20-10.64, P=0.022), and postoperative adrenergic use (OR: 0.35, 95%CI: 0.13-0.93, P=0.036) remained independently predictive of postoperative AF.

Conclusion

The present study suggested that age, P-wave morphology, LA dimension, failure to graft right coronary artery, and postoperative adrenergic use were independent predictors of post-CABG AF. Therefore, clinical data, ECG and echocardiography may be useful in preoperative risk stratification of the surgical patients for the occurrence of post-CABG AF.     

Simultaneous off-pump coronary artery bypass grafting and ascending aortobifemoral bypass graft via ventral abdominal route

Aortoiliac disease often coexists with coronary artery disease. It is not uncommon to subject a patient to two separate interventions. We report two cases in which in simultaneous off-pump coronary artery bypass grafting was done with an ascending aortobifemoral bypass graft through the ventral abdominal route without any additional morbidity. Combining a technically simple method of limb bypass with an off-pump cardiac surgery is a promising procedure for revascularization of myocardium and lower limbs. We discuss the merits of combining an off-pump coronary artery bypass grafting procedure with a limb bypass.     

Biomechanical rationale of coronary artery bypass grafting of multivessel disease

The biomechanical model of human coronary arteries was modified for improving the quality of diagnosis and surgical treatment for coronary heart disease. The problem of hemodynamics in the left coronary artery with multivessel bed disease – 45% stenosis of the anterior descending branch and 75% stenosis of the circumflex branch – was particularly considered. Numerical simulation of the coronary arterial bypass of the main trunk was carried out to estimate the functional condition of the coronary arteries after restoring myocardial blood supply by surgery.     

Neurological complications of coronary artery bypass graft surgery: six month follow-up study.

As part of a major prospective study of the neurological complications of coronary artery bypass graft surgery patients were reviewed over six months to determine the clinical course and functional impact of early postoperative complications. One hundred and ninety one out of 312 (61%) patients had developed early postoperative disorders. At six months 165 of the 191 patients with early neurological complications were reviewed. Of the 165, 85 still had detectable neurological signs, but these were often minor and of little functional importance. Only 10 patients had neurological disability at six months, and this was major in only four patients, all of whom had suffered major perioperative stroke. No patient with non-disabling neurological complications in hospital became functionally impaired on returning home. Neurological disorders are not a major cause of failure to return to work by six months after coronary artery bypass surgery. Of 139 patients who were of working age and had not returned to work by six months, only four were prevented by neurological injury related to surgery. The long term prognosis for early neurological disorders after coronary artery bypass surgery is usually favourable, except in those patients who have sustained major perioperative stroke.     

Genome-wide assessment for genetic variants associated with ventricular dysfunction after primary coronary artery bypass graft surgery

Background

Postoperative ventricular dysfunction (VnD) occurs in 9–20% of coronary artery bypass graft (CABG) surgical patients and is associated with increased postoperative morbidity and mortality. Understanding genetic causes of postoperative VnD should enhance patient risk stratification and improve treatment and prevention strategies. We aimed to determine if genetic variants associate with occurrence of in-hospital VnD after CABG surgery.

Methods

A genome-wide association study identified single nucleotide polymorphisms (SNPs) associated with postoperative VnD in male subjects of European ancestry undergoing isolated primary CABG surgery with cardiopulmonary bypass. VnD was defined as the need for ≥2 inotropes or mechanical ventricular support after CABG surgery. Validated SNPs were assessed further in two replication CABG cohorts and meta-analysis was performed.

Results

Over 100 SNPs were associated with VnD (P<10⁻⁴), with one SNP (rs17691914) encoded at 3p22.3 reaching genome-wide significance (P_{additive model} = 2.14×10⁻⁸). Meta-analysis of validation and replication study data for 17 SNPs identified three SNPs associated with increased risk for developing postoperative VnD after adjusting for clinical risk factors. These SNPs are located at 3p22.3 (rs17691914, OR_{additive model} = 2.01, P = 0.0002), 3p14.2 (rs17061085, OR_{additive model} = 1.70, P = 0.0001) and 11q23.2 (rs12279572, OR_{recessive model} = 2.19, P = 0.001).

Conclusions

No SNPs were consistently associated with strong risk (OR_{additive model}>2.1) of developing in-hospital VnD after CABG surgery. However, three genetic loci identified by meta-analysis were more modestly associated with development of postoperative VnD. Studies of larger cohorts to assess these loci as well as to define other genetic mechanisms and related biology that link genetic variants to postoperative ventricular dysfunction are warranted.     

Changes in plasma atrial natriuretic peptide--immunoreactivity in patients undergoing coronary artery bypass graft placements

Plasma atrial natriuretic peptide immunoreactivity (IrANP) was measured before, during, and after cardiopulmonary bypass for coronary artery bypass graft placement. Eight subjects scheduled for elective operation had in the premedicated preoperative state slightly elevated IrANP compared to controls. Neither induction of anesthesia with a high dose narcotic/non-depolarising relaxant/diazepam technique nor cardiopulmonary bypass changed IrANP significantly. Mixed venous and arterial IrANP increased immediately after discontinuing bypass, and remained elevated 1 h later. Because ANPs affect peripheral resistance as well as urinary sodium loss, the post-bypass elevations in these peptides may contribute to cardiovascular and diuretic effects after cardiopulmonary bypass.     

Release of pro-inflammatory mediators during myocardial ischemia/reperfusion in coronary artery bypass graft surgery

Inflammation has been reported to play an important role in cardiac surgery under cardiopulmonary bypass due to systemic endotoxemia. In order to develop strategies against this injury in future we studied the combined effect of a number of inflammatory mediators in myocardial ischemia/reperfusion. Coronary sinus blood samples of ten patients undergoing coronary artery bypass graft surgery (CABG) were obtained at three time intervals (1) before onset of bypass (2) 30 min after cross clamp, and (3) 10 min after removal of cross clamp. The samples were subjected to evaluate levels of nitric oxide byproducts (nitrite and nitrate and citrulline), inflammatory cytokines (interleukin-2, interferon- and interleukin-6), adhesion molecules, (CD62L and CD54), ratio of cell surface markers (CD4/CD8 and TCR/) cell activation markers (CD69 and HLA DR) and second messengers (protein kinase C, inositol 1,4,5 triphosphate and intracellular calcium levels). Ischemia and further reperfusion resulted in significant rise in nitrite and nitrate levels (p < 0.001), interleukin-6 (p < 0.01), CD62L (p < 0.001), CD69 (p < 0.05), protein kinase C (p < 0.001) and intracellular calcium (p < 0.001). A fall in CD4/CD8 ratio was observed on reperfusion. These changes during CABG show that ischemia/reperfusion leads to a release of an array of pro-inflammatory mediators of tissue injury, which could lead to pathophysiological changes. Hence the study suggests the need of some protective therapies against these inflammatory markers.     

Cardiac PET-CT: advanced hybrid imaging for the detection of coronary artery disease

Hybrid imaging of positron emission tomography (PET) together with computed tomography (CT) is rapidly emerging. In cardiology, this new advanced hybrid imaging modality allows quantification of cardiac perfusion in combination with assessment of coronary anatomy within a single scanning session of less than 45 minutes. The near-simultaneous anatomical evaluation of coronary arteries using CT and corresponding functional status using PET provides a wealth of complementary information in patients who are being evaluated for (suspected) coronary artery disease, and could help guide clinical patient management in a novel manner. Clinical experience gained with this recently introduced advanced hybrid imaging tool, however, is still limited and its implementation into daily clinical practice remains largely unchartered territory. This review discusses principles of perfusion PET, its diagnostic accuracy, and potential clinical applications of cardiac PET-CT in patients with ischaemic heart disease. (Neth Heart J 2010;18:90–8.)