Does perioperative myocardial ischemia lead to postoperative myocardial infarction?

To determine if a relationship exists between perioperative myocardial ischemia (ST segment depression greater than or equal to 0.1 mV) and postoperative myocardial infarction (PMI), nonparticipating observers recorded all ECG, hemodynamic, and other events between arrival of patients in the operating room and onset of cardiopulmonary bypass during 1,023 elective coronary artery bypass operations (CABG). The roles of preoperative patient characteristics, quality of the operation limited by disease as rated by the surgeon and duration of ischemic cardiac arrest as risk factors for PMI also were quantified. ECG ischemia occurred in 36.9% of all patients, with almost half the episodes occurring before induction of anesthesia. PMI was almost three times as frequent in patients with ischemia (6.9% vs. 2.5%) and was independent of when ischemia occurred. Ischemia was related significantly to tachycardia but not hypertension nor hypotension and was frequent in the absence of any hemodynamic abnormalities. The anesthesiologist whose patients had the highest rate of tachycardia and ischemia had the highest rate of PMI. Although neither single nor multiple preoperative patient characteristics related to PMI, suboptimal quality of operation and prolonged ischemic cardiac arrest increased the likelihood of PMI independent of the occurrence of myocardial ischemia. The authors conclude that perioperative myocardial ischemia is common in patients undergoing CABG, occurs randomly as well as in response to hemodynamic abnormalities, and is one of three independent risk factors the authors identified as related to PMI. PMI is unrelated to preoperative patient characteristics such as ejection fraction and left main coronary artery disease, and its frequency will relate primarily to perioperative management rather than patient selection.     

Intraoperative hemodynamic predictors of mortality, stroke, and myocardial infarction after coronary artery bypass surgery.

Evidence that intraoperative hemodynamic abnormalities influence outcome is limited. The purpose of this study was to determine whether intraoperative hemodynamic abnormalities were associated with mortality, stroke, or perioperative myocardial infarction (PMI) in a large cohort of patients undergoing coronary artery bypass grafting. Risk factors and outcomes were queried from a state-mandated cardiac surgery reporting system at two hospitals in New York, NY. Intraoperative hemodynamic abnormalities were derived from computerized anesthesia records by assessing the duration of exposure to moderate or severe extremes of hemodynamic variables. Multivariate logistic regression identified independent predictors of perioperative mortality, stroke, and PMI. Among 2149 patients, there were 50 mortalities, 51 strokes, and 85 PMIs. In the precardiopulmonary bypass (pre-CPB) period, pulmonary hypertension was a predictor of mortality (odds ratio [OR] 2.1, P = 0.029), and bradycardia and tachycardia were predictors of PMI (OR 2.9, P = 0.007 and OR 2.0, P = 0.028, respectively). During CPB, hypotension was a predictor of mortality (OR 1.3, P = 0.025). Post-CPB, tachycardia was a predictor of mortality (OR 3.1, P = 0.001), diastolic arterial hypertension was a predictor of stroke (OR 5.4, P = 0.012), and pulmonary hypertension was a predictor of PMI (OR 7.0, P < 0.001). Increased pulmonary arterial diastolic pressure post-CPB was a predictor of mortality (OR 1.2, P = 0.004), stroke (OR 3.9, P = 0.002), and PMI (OR 2.2, P = 0.001). Rapid intraoperative variations in blood pressure and heart rate were not independent predictors of these outcomes. These findings demonstrate the prognostic significance of intraoperative hemodynamic abnormalities, including data from pulmonary artery catheterization, to adverse postoperative outcomes. It is not known whether interventions to control these variables would improve outcome. IMPLICATIONS: Intraoperative hemodynamic abnormalities, including pulmonary hypertension, hypotension during cardiopulmonary bypass, and postcardiopulmonary bypass pulmonary diastolic hypertension, were independently associated with mortality, stroke, and perioperative myocardial infarction over and above the effects of other preoperative risk factors.     

Emergency re-revascularization with percutaneous coronary intervention, reoperation, or conservative treatment in patients with acute perioperative graft failure following coronary artery bypass surgery.

OBJECTIVE: Perioperative graft failure following coronary artery bypass grafting (CABG) results in acute myocardial ischemia/infarction (PMI), which may necessitate an acute secondary revascularization procedure to salvage myocardium, in order to preserve ventricular function and improve patient outcome. Whether acute percutaneous coronary (re)intervention (PCI), emergency reoperation, or conservative intensive care treatment should be applied, is currently unknown. METHODS: In order to identify the source of PMI and to pursue the appropriate re-revascularization strategy, coronary repeat angiography was emergently performed in 118 among 5427 consecutive isolated CABG patients with evidence of PMI. As a result, patients immediately underwent acute PCI (group 1), emergency reoperation (group 2), or were treated conservatively (group 3). Primary study endpoint was postoperative myocardial infarct size, as measured by peak cardiac troponin I (cTnI) serum levels. Secondary endpoints were perioperative left ventricular ejection fraction (LVEF%), assessed by transesophageal echocardiography, major adverse cardiac events, and short- and midterm mortality. RESULTS: Repeat coronary angiography revealed early perioperative bypass graft failure in 67 among 118 patients and 84 among 214 bypass grafts after CABG. The number and type of failing bypass grafts were comparable between groups 1 and 2, but significantly different to that of group 3 (P<0.007). Acute PCI was applied in 25 patients, redo-CABG in 15 patients, and conservative treatment in 27 patients. Procedural peak cTnI serum levels were significantly different between groups 1 and 2 (81+/-18 ng/ml vs 178+/-62 ng/ml; P<0.001). Global LVEF was reduced during the acute ischemic event when compared with preoperative values (P<0.01). Thereafter, LVEF improved during follow-up within each group (P<0.001), but did not differ between the three groups. In-hospital and 1-year mortality were 12.0% and 20.0% in group 1, 20.0% and 27% in group 2, and 14.8% and 18.5% in group 3, respectively (P=NS). CONCLUSIONS: Re-revascularization with emergency PCI may limit the extent of myocardial cellular damage compared with the surgical-based treatment strategy in patients with acute perioperative myocardial ischemia due to early graft failure following CABG.     

Perioperative myocardial ischemia in patients undergoing sternectomy shortly after coronary artery bypass grafting

Coronary revascularization reduces cardiac complications associated with noncardiac surgery in patients with severe coronary disease. However, patients undergoing emergency noncardiac surgery soon after coronary bypass operations may still be vulnerable to ischemic myocardial events. We prospectively evaluated the incidence of myocardial ischemia in 82 consecutive patents scheduled for sternectomy in the first (Group 1; 35 patients) or second (Group 2; 47 patients) week after coronary artery bypass graft (CABG) surgery. The interval between CABG surgery and sternectomy in Groups 1 and 2 was 6 days (range, 4-7 days) and 11 days (range, 8-14 days), respectively. Electrocardiographic (ECG) changes consistent with myocardial ischemia were assessed with a two-channel Holter system for 48 h. There were no between-group differences in updated Acute Physiology and Chronic Health Evaluation score, use of beta-blockers, or perioperative hemodynamic changes. The incidence of ECG changes consistent with myocardial ischemia was fivefold more frequent in Group 1 (22.85% versus 4.25%; P < 0.05). Of the ischemic patients in Group 1, 25% experienced a perioperative acute myocardial infarction (one was fatal). There were no infarcts in Group 2. Thus, patients appear to be prone to coronary events during sternectomy performed early after CABG surgery. Although the incidence of ischemia did not differ from that previously reported after CABG surgery alone, further investigation is required to determine whether the findings obtained in this high-risk population are generalizable to patients undergoing noncardiac surgery soon after uneventful CABG surgery. IMPLICATIONS: This study demonstrates an increased incidence of myocardial ischemia when sternectomy for mediastinitis is performed within one week of coronary artery bypass graft surgery, and this ischemia is associated with a 25% incidence of myocardial infarction.     

Nonrandomized Matched Pair Analysis of Intermittent Ischemic Arrest versus Potassium Crystalloid Cardioplegia during Myocardial Revascularization

The quest for the ideal method of myocardial preservation during coronary artery bypass graft (CABG) surgery continues at a rapid pace. Nevertheless, in the present clinical practice of cardiac surgery, the choice is chiefly between hypothermic intermittent ischemic arrest and hypothermic potassium cardioplegia. This study applies newer techniques in radionuclear cardiology, as well as more conventional enzymatic, electrocardiographic, and hemodynamic determinations, to the evaluation of the effectiveness of the previously mentioned modes of myocardial protection. Serial assessments are made preoperatively as well as during the first ten days postoperatively. We find that the perioperative incidence of myocardial damage and changes in left ventricular performance are almost identical using either method in patients with relatively normal preoperative left ventricular performance who do not have severe preoperative refractory ischemia or necrosis.     

间断缺血心停搏在冠脉搭桥术中的应用

１９９２～１９９３年间为１８０例冠脉病变的病人施行冠脉搭桥术，全部病人均采用核甙抑制剂利多氟嗪预处理和低温（２８℃）间断缺血心停搏进行术中心肌保护。平均每例病人作冠状动脉端吻合３～４个，每个吻合口用９分钟，主动脉阻断累加时间约２５分钟，体外循环时间９０分钟，术后医院死亡率１．６％（３／１８０），无术后心梗发生。作者认为，冠脉搭桥术的术中心肌保护可采用核甙抑制剂和间断缺血心停搏方法，而不用心肌停搏液。     

The Efficacy of Medical Stabilization Prior to Myocardial Revascularization in Early Refractory Postinfarction Angina

The timing of coronary artery bypass graft (CABG) surgery in patients with persistent, severe myocardial ischemia after an acute myocardial infarction is controversial. Based on the previous disappointing clinical experience with urgent surgery, a period of medical stabilization (mean ten days, range two to 28) prior to surgery was employed in a prospective nonrandomized clinical trial. The frequent use of intravenous nitroglycerin and intra-aortic balloon pumping was important in allowing preoperative clinical stabilization in these patients who were refractory to conventional medical therapy. The combined medical-surgical treatment protocol was associated with no early or late mortality in 20 patients who suffered preoperative myocardial infarction and demonstrated refractory post-infarction angina. Although these patients were considered to be high-risk surgical candidates, the incidence of perioperative myocardial damage in this selected group was comparable with that observed in patients undergoing elective CABG surgery at this institution without recent preoperative myocardial infarction. In order to determine the hemodynamic effectiveness of this selected patient management process, perioperative changes in left ventricular performance were determined by multigated cardiac blood pool imaging. Computer-based analysis of this radionuclide-related data allowed the accurate determination of ejection fraction (EF). Those patients with preoperative subendocardial infarction (N = 12) had no decrease in global EF 24 hours after operation and significant increases in EF seven days and eight months after operation. This pattern is analogous to that observed in patients without preoperative myocardial necrosis undergoing elective CABG surgery at this institution. Those patients with recent preoperative transmural myocardial infarction (N = 8) showed a decrease in EF 24 hours after operation, but recovered to preoperative levels seven days and eight months after operation. There was, however, no increase in EF in this subgroup of patients. On the basis of this study, the authors tentatively recommend a concerted effort at preoperative medical stabilization prior to CABG surgery in patients with persistent refractory myocardial ischemia soon after acute myocardial necrosis. A prospective, randomized study comparing urgent and delayed surgery, as well as nonsurgical treatment, will be necessary to define more precisely optimal management of this subgroup of cardiac patients.     

Automated, continuous ST segment analysis in the ECG as a monitor of myocardial ischemia during aortocoronary bypass surgery

Patients with coronary artery disease (CAD) who are subjected to cardiac and major noncardiac surgical procedures have a high incidence of perioperative myocardial ischemia. Earlier studies in patients undergoing coronary artery bypass graft surgery (CABG) indicated the frequency of postoperative myocardial infarction to be directly proportional to the incidence and severity of pre-bypass myocardial ischemia. METHODS. We investigated the incidence of pre-bypass ischemia in 50 patients undergoing elective CABG using an automated ST segment monitoring system (Marquette 7010). Analyzing leads I, II, and V5, this device measures ST segment deviations 60 ms after the J-point. Occurrence of myocardial ischemia was defined as follows: new ST segment deviations larger than 1 mm = 0.1 mV that lasted for more than at least 10 consecutive heartbeats. RESULTS. In 19 out of 50 patients (38%) we found 96 episodes of myocardial ischemia in the pre-bypass period; 47% of all ischemic episodes were associated with significant hemodynamic changes, e.g., tachycardia, hypertension, or hypotension. The incidence of ischemia was different between population sub-groups: patients with a previous infarction had a lower incidence of ischemia (35%) than patients without infarction (44%). Patients with preoperative left ventricular end diastolic pressure (LVEDP) less than 15 mm Hg had a lower incidence of ischemia (29%) than patients with LVEDP greater than 15 mm Hg (50%). Patients treated preoperatively with beta-blockers showed a significantly lower incidence of ischemia (9%) when compared to untreated patients (46%, p less than 0.05). No difference was found between patients with or without unstable angina pectoris or between patients of NYHA classes II, III, or IV. Postoperative myocardial infarction occurred in 2 patients, both with evidence of pre-bypass myocardial ischemia. CONCLUSION. Our study confirms that automated ST segment analysis is able to detect myocardial ischemia similarly to that documented in previous studies using conventional ECG lead analysis.     

冠状动脉旁路移植术患者术后早期运动耐量改善的影响因素

目的　探讨冠状动脉旁路移植术 (CABG)患者术后早期运动耐量改善的影响因素 ,以提高手术疗效。方法　随机选择 30例行 CABG患者 ,术前和术后 1～ 3个月进行平板运动试验 (TET) ,以手术前后运动功量的差值为应变量 ,各项临床指标与手术情况为自变量 ,进行 L ogistic多元回归分析。　结果　无手术死亡。术后运动功量等运动耐量指标及心肌缺血指标有明显改善 (P<0 .0 0 1) ,术前左心功能、心肌梗死史、心绞痛、高血压和乳内动脉 (IMA)移植是影响手术疗效的主要因素。　结论　 CABG能显著提高运动耐量 ,改善心肌缺血 ,了解并重视这些影响因素将有助于更好地选择手术病例 ,预测手术疗效。     

Is the pressure rate quotient a predictor or indicator of myocardial ischemia as measured by ST-segment changes in patients undergoing coronary artery bypass surgery?

Perioperative myocardial ischemia is associated with an increased risk of perioperative myocardial infarction (PMI). Several attempts have been made to define intraoperative hemodynamic predictors of myocardial ischemia. In a canine preparation with coronary stenosis, a pressure rate quotient (PRQ = mean arterial pressure/heart rate) less than one (PRQ less than 1) indicated subendocardial myocardial ischemia. The authors tested this hypothesis in patients undergoing elective coronary artery bypass graft operation (CABG), using electrocardiogram (ECG) ST-segment changes (leads II/V5) to diagnose myocardial ischemia. Sixty (n = 60) patients having CABG surgery were prospectively studied before initiation of cardiopulmonary bypass. Calibrated ECG leads II and V5 (diagnostic mode) were monitored continuously and recorded with the use of a Hewlett-Packard computer ST-segment analyzer. In addition, arterial and pulmonary artery pressures were monitored. Ischemia was defined as new-onset ST deviation (greater than or equal to 1 mm from the baseline ECG). ECG and hemodynamic data were stored at 2-min intervals for subsequent computer analysis. Serial creatinine phosphokinase (CPK) X MB (%) determinations and 12-lead ECGs were collected for the initial 3 postoperative days. Of the 3,463 intervals (2 min) available for study, 3,322 (96%) were satisfactorily recorded for 60 patients. Ischemia occurred during 65 intervals in 9 patients (9 of 60), of which only 34% (22 of 65) were associated with a PRQ less than 1 (P less than 0.01). In contrast, there were 466 intervals during which PRQ was less than 1, but without ECG evidence of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Results of Treatment Methods in Cardiac Arrest Following Coronary Artery Bypass Grafting

Abstract   Background and aim of the study: Emergency re-revascularization and invasive/noninvasive interventions in intensive care unit (ICU) are two main treatment methods in cardiac arrest following coronary artery bypass grafting (CABG). We evaluated the short- and long-term consequences of these two methods and discussed the indications for re-revascularization. Methods: Between 1998 and 2004, a total of 148 CABG patients, who were complicated with cardiac arrest, were treated with emergency re-revascularization (n = 36, group R) and ICU procedures (n = 112, group ICU). Re-revascularizations are mostly blind operations depending on clinical/hemodynamic criteria. These are: no response to resuscitation, recurrent tachycardia/fibrillation, and severe hemodynamic instability after resuscitation. Re-angiography could only be performed in 3.3% of the patients. Event-free survival of the groups was calculated by the Kaplan-Meier method. Events are: death, recurrent angina, myocardial infarction, functional capacity, and reintervention. Results: Seventy percent of patients, who were complicated with cardiac arrest, had perioperative myocardial infarction (PMI). This rate was significantly higher in group R (p = 0.013). The major finding in group R was graft occlusion (91.6%). During in-hospital period, no difference was observed in mortality rates between the two groups. However, hemodynamic stabilization time (p = 0.012), duration of hospitalization (p = 0.00006), and mechanical support use (p = 0.003) significantly decreased by re-revascularization. During the mean 37.1 ± 25.1 months of follow-up period, long-term mortality (p = 0.03) and event-free survival (p = 0.029) rates were significantly in favor of group R. Conclusion: Better short- and long-term results were observed in the re-revascularization group.     

Prognostic importance of postbypass regional wall-motion abnormalities in patients undergoing coronary artery bypass graft surgery. SPI Research Group

Regional wall motion abnormalities (RWMA) detected by intraoperative transesophageal echocardiography (TEE) are thought to be sensitive markers of myocardial ischemia. To assess the prognostic significance of RWMA as compared with other less costly technologies such as electrocardiography (ECG) and hemodynamic measurements [blood pressure (BP) and pulmonary artery (PA) pressure], 50 patients were prospectively studied who were undergoing elective coronary artery bypass graft (CABG) surgery using continuous TEE, ECG (Holter), and hemodynamic measurements during the prebypass, postbypass, and early postoperative intensive care unit (ICU) periods (first 4 h). Echocardiographic and ECG evidence of ischemia was characterized during each of these three periods and related to adverse clinical outcomes (postoperative myocardial infarction, ventricular failure, and cardiac death). Clinicians were blinded to the TEE and ECG information. The prevalence of myocardial ischemia during the perioperative periods was as follows: prebypass, 20% (TEE) versus 7% (ECG); postbypass, 36% (TEE) versus 25% (ECG); ICU 25% (TEE) versus 16% (ECG). Neither prebypass TEE ischemia nor ECG ischemia occurring in any of the three periods predicted adverse outcome. In contrast, postbypass TEE ischemia was predictive of outcome: six of 18 patients with postbypass TEE ischemia had adverse outcomes versus 0 of 32 without TEE ischemia (P = 0.001). Seventy-three percent of the echocardiographic ischemic episodes occurred without acute change (+/- 20% of control) in heart rate, BP, or PA pressure. The authors conclude that: 1) prebypass myocardial ischemia was relatively uncommon, 2) the incidence of ECG and TEE ischemia was highest in the postbypass period, and 3) postbypass RWMA were related to adverse clinical outcome.     

围术期心肌梗塞的诊疗进展

迄今越来越多的存在心脏高危疾病的患者进行各种手术治疗．由此产生的围术期心肌梗塞（PMI）日益受到关注。依据导致PMI的病理生理机制可以将PMI分为两种类型;1型为围术期出现急性冠脉综合征．2型则是由于在稳定的冠脉病变的基础上（在围手术期间）出现过长时间供氧与耗氧的不平衡而发生的。在围术期对心肌缺血细致严密的监护、在保证血压的基础上严格的控制心率,降低心输出置及预防心脏失代偿的发生,对PMI的预防具有积极的意义。而冠脉血管的外科干预治疗并不是推荐的预防PMI的治疗手段,常规的抗血栓治疗可能加重围术期出血。     

Scintigraphic demonstration of myocardial perfusion and ischaemia associated with coronary artery bypass grafting

OBJECTIVES: To assess if myocardial perfusion scintigraphy (MPS) at rest can be of value in elucidating myocardial perfusion, ischaemia and perioperative myocardial infarction (PMI) associated with coronary artery bypass graft (CABG) surgery. DESIGN: This was a prospective randomized study of patients undergoing elective CABG. Forty-eight patients in the control group underwent serial ECG recordings and measurements of CK-MB and cTnT. Fifty-four patients in the study group were additionally examined with MPS preoperatively and 2-4 days and 6 weeks postoperatively. RESULTS: The study showed a highly significant (p < 0.001) improvement in myocardial radionuclide uptake from preoperatively to 2-4 days postoperatively. Judged from ECG and enzymatic changes, two control patients and one study patient only had PMI and no additional cases of PMI were demonstrated by MPS. CONCLUSION: MPS at rest showed that CABG significantly improved myocardial perfusion, by demonstrating an increase in radionuclide uptake. In diagnosing PMI, we found that MPS provided no additional information beyond cardiac biochemical markers and ECG changes.     

Vasodilator therapy utilizing nitroprusside and nitroglycerin after coronary artery surgery

The hemodynamic effects of combined therapy utilizing sodium nitroprusside (SNP) and nitroglycerin (TNG) were compared with those of TNG therapy in patients who underwent coronary artery bypass grafting (CABG). Of 58 patients who received catecholamine infusion to maintain hemodynamics after CABG, 17 had perioperative myocardial infarction (PMI (+) cases) and the other 41 had not PMI (PMI (-) cases). 26 of 41 patients (PMI (-) cases) received nitroglycerin therapy (NTG group) and the other 15 patients received combined therapy (SNP + NTG group). 11 of 17 patients (PMI (+) cases) received NTG therapy and the other 6 patients received combined therapy. The hemodynamic valuables, which were studied, were as follows; cardiac index, stroke volume index, left ventricular stroke work index, systemic vascular resistance index, pulmonary vascular resistance index, and deep core temperature. SNP + TNG group revealed significantly lower systemic vascular resistance index and pulmonary vascular resistance index than TNG group in PMI (-) cases. In PMI (+) cases, SNP + TNG group revealed significantly higher cardiac index, stroke volume index, left ventricular stroke work index, and significantly lower pulmonary vascular resistance index than TNG group. These findings demonstrate that combined therapy can obtain more secure vasodilation than TNG therapy.     

Perioperative myocardial ischemia: importance of the preoperative ischemic pattern

Previous studies investigating the incidence of myocardial ischemia in patients undergoing coronary-artery bypass grafting (CABG) surgery have not considered the potential significance of the preoperative ischemic pattern in the development of intra- and postoperative myocardial ischemia and infarction. Accordingly, the authors compared the frequency and severity of pre-, intra-, and postoperative ischemic episodes (ST-segment depression greater than or equal to 0.1 mV or elevation greater than or equal to 0.2 mV) in 50 men with severe coronary artery disease scheduled for elective CABG. All subjects were monitored by continuous electrocardiography (ECG) (Holter monitor) for 2 preoperative days, intraoperatively, and 2 postoperative days (total monitoring time = 4,363 h). Routine anti-anginal medications were continued until the morning of surgery, and the anesthetic management of the patient was not controlled. During the preoperative period, 42% of the patients had ECG ischemic episodes, 87% of which were clinically silent. Only 18% developed intraoperative ischemia. Postoperatively, the incidence increased to 40%. The number of ischemic episodes/hour (epis/h) of monitoring among the three monitoring periods was similar (0.09 +/- 0.12 epis/h preoperatively, 0.11 +/- 0.20 epis/h intraoperatively, and 0.05 +/- 0.08 epis/h postoperatively; P = NS). The median duration of ischemic episodes was similar pre- and intraoperatively (16 vs. 18.5 min, P = NS), but greater postoperatively (41 min, P less than 0.05). Seventy-six per cent of the perioperative ECG ischemia occurred without acute change (+/- 20% of control) in blood pressure or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)     

On- and off-pump coronary surgery and perioperative myocardial infarction: an issue between incomplete and extensive revascularization.

OBJECTIVE: Complete myocardial revascularization is the standard for coronary artery bypass grafting. It has been shown, however, that off-pump coronary bypass surgery (OPCAB) may reduce completeness of revascularization without affecting perioperative myocardial infarction rates. We evaluated the influence of OPCAB on major postoperative events in a large consecutive cohort of patients, with special emphasis on risk factors for perioperative myocardial infarction. METHODS: From 1995 to 2004, 5935 patients underwent isolated coronary bypass surgery; of these, 4623 (77.9%) and 1312 (22.1%) underwent on-pump coronary surgery (CABG) and OPCAB, respectively. Patients undergoing OPCAB were matched to patients undergoing CABG by propensity score; logistic regression analysis models were used to study predictors of perioperative myocardial infarction. RESULTS: In matched pairs, postoperative mortality, myocardial infarction, stroke, and atrial fibrillation were similar between groups, while reoperation for bleeding, time on ventilator and red blood cell use were lower in patients undergoing OPCAB. The number of distal anastomoses was lower in patients undergoing OPCAB (2.2+/-0.80 in OPCAB vs 2.9+/-0.86 in CABG, p<0.001), as well as complete revascularization rates (61.9% in OPCAB vs 90.0% in CABG, p<0.001). Multivariate analyses, performed on preoperative and intraoperative variables, showed that both incomplete revascularization and increasing numbers of distal anastomoses (even when controlling for completeness of revascularization) were significant predictors of perioperative myocardial infarction, while CABG/OPCAB strategy did not influence it. CONCLUSIONS: The choice of surgical technique did not influence the occurrence of major perioperative complications and of myocardial infarction, which is negatively affected by incomplete or too extensive revascularization strategies.     

Lactate release during reperfusion predicts low cardiac output syndrome after coronary bypass surgery

Background. Cardioplegic arrest induces anaerobic myocardial metabolism with a net production of lactate from glycolysis. However, persistent lactate release during reperfusion suggests a delayed recovery of normal aerobic metabolism and may lead to depressed myocardial function necessitating inotropic or intraaortic balloon pump support (low output syndrome [LOS]). We examined the relation between perioperative myocardial metabolism and postoperative clinical outcomes in patients undergoing isolated coronary artery bypass surgery (CABG).

Methods. We reviewed 623 patients who were enrolled in clinical studies evaluating perioperative myocardial metabolism between 1983 and 1996. Arterial and coronary sinus blood samples were obtained intraoperatively to assess myocardial metabolism. Clinical data regarding patient demographics and postoperative outcomes were prospectively collected and entered into our institutional database.

Results. Low output syndrome developed in 36 patients (5.8%). Myocardial lactate release was higher in these patients compared with those who did not develop postoperative LOS. Advanced age and poor preoperative left ventricular function were independent predictors of lactate release during reperfusion. Persistent lactate release after 5 minutes of reperfusion was the only independent predictor of postoperative LOS in this low-risk population.

Conclusions. Persistent lactate release during reperfusion occurs in a significant proportion of low-risk patients undergoing isolated CABG and is an independent predictor of postoperative low cardiac output syndrome. Persistent lactate release during reperfusion suggests a delayed recovery of aerobic myocardial metabolism and may be related to intraoperative misadventure or inadequate myocardial protection. Myocardial lactate release may be useful as an alternative end-point in clinical trials evaluating perioperative myocardial protection.     

Scintigraphic demonstration of myocardial perfusion and ischaemia associated with coronary artery bypass grafting

Objectives. To assess if myocardial perfusion scintigraphy (MPS) at rest can be of value in elucidating myocardial perfusion, ischaemia and perioperative myocardial infarction (PMI) associated with coronary artery bypass graft (CABG) surgery. Design. This was a prospective randomized study of patients undergoing elective CABG. Forty-eight patients in the control group underwent serial ECG recordings and measurements of CK-MB and cTnT. Fifty-four patients in the study group were additionally examined with MPS preoperatively and 2–4 days and 6 weeks postoperatively. Results. The study showed a highly significant (p?<?0.001) improvement in myocardial radionuclide uptake from preoperatively to 2–4 days postoperatively. Judged from ECG and enzymatic changes, two control patients and one study patient only had PMI and no additional cases of PMI were demonstrated by MPS. Conclusion. MPS at rest showed that CABG significantly improved myocardial perfusion, by demonstrating an increase in radionuclide uptake. In diagnosing PMI, we found that MPS provided no additional information beyond cardiac biochemical markers and ECG changes.     

Nonocclusive mesenteric ischemia after off-pump coronary artery bypass surgery: a word of caution

We present a series of five cases of off-pump coronary artery bypass surgery complicated with fatal nonocclusive mesenteric ischemia. We review a total of 489 patients aged 65 and older (mean age 74.9 +/- 3.2 years) who underwent off-pump coronary artery bypass surgery. The diagnosis of nonocclusive mesenteric ischemia was confirmed by computed tomography-angiography and/or selective angiography of the superior mesenteric artery, or intraoperatively. Three patients underwent laparotomy with bowel resection. In two cases, resection of bowel was not feasible. Of the possible predisposing factors, we found that four of the patients (two preoperative and two perioperative) had received epinephrine and two had an intra-aortic balloon counter pulsation due to acute myocardial infarction and cardiogenic shock. All patients were over 65 years of age, and all had acute anterior wall myocardial infarction and hemodynamic instability or post-myocardial infarction unstable angina. Nonocclusive mesenteric ischemia is a difficult clinical entity to recognize, has no clear-cut effective management, has a poor prognosis as a result of low cardiac output, and can be aggravated by off-pump coronary artery bypass grafting.