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NewsletterLiterature Review Widespread coronary inflammation in unstable angina Buffon A, Biasucci L, Liuzzo G, et al, N
Engl J Med 200t; 347: 4-12.
Background: Unstable angina may be caused by inflammation within vulnerable coronary plaques. Activated leukocytes can be found in both the peripheral and coronary sinus blood of patients with unstable angina. It is not clear whether they are from the vascular bed of the stenosis causing the angina, or whether they result from more generalized inflammation. Methods: Neutrophil myeloperoxidase content was measured in cardiac, aortic, and femoral circulations of patients in 5 groups: 24 patients with unstable angina and stenosis in the left anterior descending artery; 9 with unstable angina and stenosis in the right coronary; 13 with chronic stable angina; 13 with variant angina and recurrent ischemia; and 6 control patients. Blood samples were taken from the femoral vein, the aorta, and the great cardiac vein, which drains only the left coronary artery. Results: Neutrophil activation causes reduction in myeloperoxidase content, thus negative numbers represent activation. In healthy patients, this number is close to zero. Both groups of patients with unstable angina had similar and lower myeloperoxidase content in their aortic blood (-3.9, left coronary stenosis and -5.5, right coronary stenosis) compared to the other 3 groups (P < 0.05). Neutrophil myeloperoxidase content in blood from the great cardiac vein was significantly decreased in patients with a left coronary lesion (-6.4) and in those with a right coronary lesion (- 6.6), but not in patients in the other 3 groups. Conclusions: Widespread activation of neutrophils was found both in the area of the stenosis causing the unstable angina, and in the area drained by a nonstenosed coronary artery in the case of patients with stenoses of the right coronary artery. This runs contrary to the concept that unstable coronary syndromes are caused by a single vulnerable plaque. Discussion: The authors cited numerous reports of postmortem examinations of patients who died from acute coronary syndromes, in which multiple fissured and thrombosed plaques were found. They suggested that this might be caused by a widespread inflammation of the endothelium, changing the interface between the blood and vessel walls, and also activating enzymes which would lyse plaque capsules. They also cited reports that inflammatory markers, including C-reactive protein and interleukin-6, are elevated in many patients (50-70 %) with acute coronary syndromes. However, fewer than half of all patients who have myocardial infarctions not preceded by unstable angina have elevations of these markers. This paper offers insight into the complex mechanisms that are associated with acute coronary syndromes. This might lead eventually to new therapies targeted to inflammation.
Improved outcomes in coronary artery bypass grafting with beating-heart techniques Mack M, Bachand D, Acuff T, Edgerton J, Prince
S, Dewey T, Magee M: J Thoracic and Cardiovascular Surgery 2002;124:598-606.
Outcome analyses of coronary artery bypass grafting without the use of cardiopulmonary bypass (OPCAB) have been based largely on retrospective data or non-randomized prospective data. Of the few prospective randomized studies that have been performed, no clear outcome benefit has been demonstrated with respect to stroke, heart attack, renal failure, or death. The benefits of OPCAB in retrospective studies include decreased blood loss, blood transfusion, mediastinal exploration for bleeding, mechanical ventilation, intensive care and hospital length of stay, and mortality. The data were often compared to concurrent data for patients undergoing CABG with CPB, or earlier data when OPCABG was not performed. Currently, there is little data supporting the absolute benefits of OPCABG over CABG with CPB. The article by Mack et al adds to this body of literature and provided another reason for reported benefits of OPCABG. Mack et al performed a retrospective study to assess the outcome of OPCAB compared to conventional CABG to address the following questions: 1) whether or not OPCAB can be safely and successfully incorporated into a busy cardiac surgical service, 2) whether or not surgical outcome can be improved, and 3) whether or not surgical technique contributes to the outcome. Retrospective data from 12,540 patients undergoing isolated CABG from 1995 to 2000 operated on by 32 surgeons obtained from the Society of Thoracic Surgeons (STS) database were analyzed. The data analyzed preoperative risk factors, operative variables, and postoperative outcomes using univariate and multivariate logistic regression to determine independent predictors of outcome. Data was analyzed in total, by year, and by surgeon. Outcome from 10 surgeons with data available from 1990 to 1995 when OPCABG was not used frequently was compared to their outcomes from 1995 to 2000 when OPCAB was used more frequently. Outcome from surgeons who performed OPCABG frequently was compared to those who performed OPCABG infrequently. Of the 12,540 CABG operations, only 1,915 (15%) were performed without CPB. The frequency of OPCABG increased from 1995 (1.2% of total) to 2000 (34% of total). Approximately 40% of the OPCABG cases in 1995 and 1996 were single vessel arterial grafts performed through a lateral thoracotomy. A sternotomy approach was used more frequently in the latter part of the study with the introduction of new surgical techniques, which facilitated the performance of bypass grafting to the lateral and posterior portions of the heart. Selection of the surgical approach was at the discretion of the surgeon. The predicted STS mortality for OPCABG patients was 3.13% compared to 2.80% for CABG with CPB. Patients undergoing OPCABG were more likely female, had a greater incidence of lung and renal disease, and had previous bypass surgery. Patients undergoing CABG with CPB were more likely to have been smokers, had a previous myocardial infarction, had cardiogenic shock, required resuscitation more frequently, and were more likely to have three vessel and left main coronary artery disease. Patients undergoing CABG with CPB had more bypasses performed, and had fewer single vessel bypasses (30% vs. 2.8%). Mortality was greater for CABG with CPB (3.5%) when compared to OPCABG (1.9%). Multiple logistic regression analysis showed the use of CPB was an independent predictor of mortality. Separate analyses for each procedure showed a number of variables to be predictors of outcome for the respected procedures. Other data showed reductions in blood transfusion, reoperation, prolonged ventilation, renal failure, atrial fibrillation, and hospital stay for patients undergoing OPCABG when compared to CABG using CPB. Outcome according to surgeon was different. Surgeons who were "high adopters" of OPCABG had a lower mortality from 1990 to 1995 compared to surgeons who were eventually "low adopters" of OPCABG. The "high adopters" continued to have a lower mortality from 1995 to 2000. Furthermore, "high adopters" reported its lowest mortality in 2000 while the "low adopters" reported a mortality approximately 5 times higher. Finally, there was an overall decrease in mortality in 1999 and 2000. The authors concluded that OPCABG was safely incorporated into surgical practice, however "adoption rate" varied from surgeon to surgeon. A significant learning curve was not found. The lower mortality found for patients undergoing OPCABG, was explained, in part, by differences in outcomes for individual surgeons. The overall increased use of OPCABG may have contributed also to the decrease in mortality of CABG patients over the last two years of the study. This study, although retrospective, is important because it examined additional variables that may explain differences in outcome between OPCABG and CABG withCPB. The authors concluded that surgeons with lower mortalities prior to the use of OPCABG tended to be high adopters of OPCABG and continued to have lower mortality compared to the low adopters. In other words, the lower complications reported for OPCABG may be due to the surgeon's ability rather than the avoidance of CPB. The authors also concluded that the overall reduction in mortality for the entire surgical group in the 1999 and 2000 likely reflected the increased adoption of OPCABG. This conclusion is premature for several reasons. The two groups were not equally matched. Patients undergoing CABG with CPB may have had more significant coronary artery disease, had fewer single vessel bypasses, had a greater numbers of bypasses per patient performed, had a greater incidence of preoperative infarction, and had a greater incidence of preoperative hemodynamic instability. The data also did not compare demographic data and surgical procedure from year to year, and therefore it is not possible to compare outcomes from one year to another. This is important because of changes in medical therapy, in opinion regarding the timing of surgical procedures, in preoperative preparation, in postoperative medical management, and in surgical technique. For example, certain patients with greater perceived operative risk or hemodynamic instability may not have been offered OPCABG. These include patients with diastolic dysfunction, heart failure, technically difficult bypasses (calcified, narrowed, and/or intramyocardial coronary arteries). Finally, this study relied entirely on the STS database and risk assessment scales which may not have included all risk factors for prediction of outcome. For example, the database did not capture the presence of left ventricular diastolic dysfunction or right ventricular dysfunction. In summary, this article is important because it addressed the contribution of surgical ability to help explain differences in outcome between OPCABG and CABG with CPB. With this in mind and the lack of supportive data from a well designed randomized prospective study, it is still not entirely clear whether OPCABG offers significant benefits over CABG with CPB. Table of Contents:
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