Perioperative myocardial infarction after coronary artery bypass surgery. Clinical significance and approach to risk stratification

Appraisal of Postoperative Outcomes of Volatile and Intravenous Anesthetics: A Network Meta-Analysis of Patients Undergoing Cardiac Surgery

OBJECTIVES

To determine the relative efficacy of specific regimens used as primary anesthetics, as well as the potential combination of volatile and intravenous anesthetics among patients undergoing cardiac, thoracic, and vascular surgery.

DESIGN

This frequentist, random-effects network meta-analysis was registered prospectively (CRD42022316328) and conducted according to the PRISMA-NMA framework. Literature searches were conducted up to April 1, 2022 across relevant databases. Risk of bias (RoB) and confidence of evidence were assessed by RoB-2 and CINeMA, respectively. Pooled treatment effects were compared with propofol monotherapy.

SETTING

Fifty-three randomized controlled trials (N = 8,085) were included, of which 46 trials (N = 6,604) enrolled patients undergoing cardiac surgery.

PARTICIPANTS

Trials enrolling adults (≥18) undergoing cardiac, thoracic, and vascular surgery, using the same induction regimens, and comparing volatile and/or total intravenous anesthesia for the maintenance of anesthesia. Given that the majority of trials focused on those undergoing cardiac surgery and the heterogeneity, analyses were restricted to this population.

MEASUREMENT AND MAIN RESULTS

Outcomes of interest included intensive care unit (ICU) length of stay (LOS), myocardial infarction, in-hospital and 30-day mortality, stroke, and delirium. Across 19 trials (N = 1,821; 9 arms; I2 = 64.5%), sevoflurane combined with propofol decreased ICU LOS (mean difference [MD] -18.26 hours; 95% CI -34.78 to -1.73 hours), whereas midazolam with propofol (MD 17.51 hours; 95% CI 2.78-32.25 hours) was associated with a significant increase in ICU LOS, when compared with propofol monotherapy. Among 27 trials (N = 4,080; 10 arms; I2 = 0%), midazolam was associated with significantly greater risk of myocardial infarction versus propofol (risk ratio 1.94; 95% CI 1.01-3.71). There were no significant differences across other outcomes.

CONCLUSION

In patients undergoing cardiac surgery, sevoflurane with propofol was associated with decreased ICU LOS compared with propofol monotherapy. Midazolam with propofol increased ICU LOS compared with propofol alone. The combined use of intravenous and volatile anesthetics should be explored further. Future trials in thoracic and vascular surgery are warranted.

A transient, closed-loop network of wireless, body-integrated devices for autonomous electrotherapy

Temporary postoperative cardiac pacing requires devices with percutaneous leads and external wired power and control systems. This hardware introduces risks for infection, limitations on patient mobility, and requirements for surgical extraction procedures. Bioresorbable pacemakers mitigate some of these disadvantages, but they demand pairing with external, wired systems and secondary mechanisms for control. We present a transient closed-loop system that combines a time-synchronized, wireless network of skin-integrated devices with an advanced bioresorbable pacemaker to control cardiac rhythms, track cardiopulmonary status, provide multihaptic feedback, and enable transient operation with minimal patient burden. The result provides a range of autonomous, rate-adaptive cardiac pacing capabilities, as demonstrated in rat, canine, and human heart studies. This work establishes an engineering framework for closed-loop temporary electrotherapy using wirelessly linked, body-integrated bioelectronic devices.

High-sensitivity cardiac troponin release after conventional and minimally invasive cardiac surgery

After cardiac surgery, a certain degree of myocardial injury is common. The arbitrarily proposed biomarker cut-off point in the Third Universal Definition for diagnosing coronary artery bypass grafting (CABG)–related perioperative myocardial infarction (PMI) is controversial and unvalidated for non-CABG surgery. Minimally invasive cardiac surgery is often thought to be associated with less myocardial damage compared to conventional surgical approaches. We conducted a real-life prospective study with serial sampling of high-sensitivity cardiac troponin T (hs-cTnT) in patients undergoing conventional and minimally invasive cardiac surgery. Four different types of cardiac surgery were performed in 400 patients (February 2014–January 2015): CABG, aortic valve replacement, minimally invasive mitral/tricuspid valve surgery through the HeartPort (HP) technique and combined CABG/valve surgery. Each group was further subdivided for comparison between the different surgical techniques. Blood samples were collected consecutively at intensive care unit (ICU) admission and 3, 6, 9, 12, 18, 24 and 48 h thereafter. The hs-cTnT values by peak timepoint differed significantly depending on the surgical approach. The overall peak timepoint for hs-cTnT occurred 6 h after ICU admission. The combined surgery and multiple-valve HP groups had the highest values (medians of 1067.5 (744.9–1455) ng/L and 1166 (743.7–2470) ng/L, respectively). The peak hs-cTnT values for patients developing PMI showed high variability. Differentiation between cardiac surgery–related necrosis and PMI remains challenging. This study emphasizes the importance of a clinically reliable biomarker cut-off value in addition to electrocardiography and echocardiography to optimize PMI diagnosis.

Perioperative myocardial infarction diagnosis after coronary artery bypass grafting surgery using coupled electrocardiographic changes and cardiac troponin I

Purpose

Perioperative myocardial infarction (PMI) is one of the most common causes of prolonged intensive care unit (ICU) and hospital stay after coronary artery bypass grafting (CABG) and is associated with poor prognosis and increases postoperative mortality due to the lack of accurate diagnostic methods. This study examines the association between electrocardiography (ECG) ischemic changes and cardiac troponin I concentration.

Methods

In this cross-sectional study, the ECG of 100 patients was recorded before and 24 h after the surgery. The cardiac troponin I concentration was measured 24 h after the termination of the surgery.

Results

The average concentration of troponin I was 6.79 μg/L in the no-ECG-changes group, 11.69 μg/L in the ST depression group, 11.26 μg/L in the ST elevation group, and 27.54 μg/L in the new Q wave group. The mean troponin concentration was significantly higher in the ECG-changes group compared to no-ECG-changes group. Comparing the ECG-changes together showed significant differences between the new Q wave and the other changes. ST elevation and ST depression were not statistically significant.

Conclusion

The three ECG-changes groups had a higher risk of PMI after their CABG. The risk of PMI was at its highest value in the new Q wave group and at its lowest in the no-ECG-changes group.

High-sensitivity troponin T release profile in off-pump coronary artery bypass grafting patients with normal postoperative course

BACKGROUND

The aim of the study was to investigate the high-sensitivity troponin T (hs-TnT) release profile in off-pump coronary artery bypass grafting (OPCABG) patients with normal postoperative course.

METHODS

From January 2015 to October 2016, 398 consecutive OPCABG patients who had normal postoperative courses were enrolled. Blood samples for hs-TnT were collected at several time points and the comparisons among different time points grouped by various factors were further analyzed.

RESULTS

There were 317 male and 81 female patients, with a median age of 64. For 66.1% of the patients, peak hs-TnT occurred at the 24th hour after OPCABG, regardless of the groups divided by different factors. In total, the hs-TnT values were much higher in male group (P = 0.035), in patients who need 5 or more bypass grafts (P = 0.035) and in patients with high-risk EuroSCORE II assessment (P = 0.013). However, we failed to find any significant differences between different age groups (P = 0.129) or among different coronary heart disease classifications (P = 0.191).

CONCLUSIONS

The hs-TnT values were affected by various factors and culminated around the first 24 h following OPCABG. It may provide some useful information for future clinical studies of myocardial biomarkers after OPCABG.

Alpha-2 adrenergic agonists for the prevention of cardiac complications among adults undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may help prevent postoperative cardiac complications.

OBJECTIVES

To determine the efficacy and safety of α-2 adrenergic agonists for reducing mortality and cardiac complications in adults undergoing cardiac surgery and non-cardiac surgery.

SEARCH METHODS

We searched CENTRAL (2017, Issue 4), MEDLINE (1950 to April Week 4, 2017), Embase (1980 to May 2017), the Science Citation Index, clinical trial registries, and reference lists of included articles.

SELECTION CRITERIA

We included randomized controlled trials that compared α-2 adrenergic agonists (i.e. clonidine, dexmedetomidine or mivazerol) against placebo or non-α-2 adrenergic agonists. Included trials had to evaluate the efficacy and safety of α-2 adrenergic agonists for preventing perioperative mortality or cardiac complications (or both), or measure one or more relevant outcomes (i.e. death, myocardial infarction, heart failure, acute stroke, supraventricular tachyarrhythmia and myocardial ischaemia).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials. We evaluated included studies using the Cochrane 'Risk of bias' tool, and the quality of the evidence underlying pooled treatment effects using GRADE methodology. Given the clinical heterogeneity between cardiac and non-cardiac surgery, we analysed these subgroups separately. We expressed treatment effects as pooled risk ratios (RR) with 95% confidence intervals (CI).

MAIN RESULTS

We included 47 trials with 17,039 participants. Of these studies, 24 trials only included participants undergoing cardiac surgery, 23 only included participants undergoing non-cardiac surgery and eight only included participants undergoing vascular surgery. The α-2 adrenergic agonist studied was clonidine in 21 trials, dexmedetomidine in 24 trials and mivazerol in two trials.In non-cardiac surgery, there was high quality evidence that α-2 adrenergic agonists led to a similar risk of all-cause mortality compared with control groups (1.3% with α-2 adrenergic agonists versus 1.7% with control; RR 0.80, 95% CI 0.61 to 1.04; participants = 14,081; studies = 16). Additionally, the risk of cardiac mortality was similar between treatment groups (0.8% with α-2 adrenergic agonists versus 1.0% with control; RR 0.86, 95% CI 0.60 to 1.23; participants = 12,525; studies = 5, high quality evidence). The risk of myocardial infarction was probably similar between treatment groups (RR 0.94, 95% CI 0.69 to 1.27; participants = 13,907; studies = 12, moderate quality evidence). There was no associated effect on the risk of stroke (RR 0.93, 95% CI 0.55 to 1.56; participants = 11,542; studies = 7; high quality evidence). Conversely, α-2 adrenergic agonists probably increase the risks of clinically significant bradycardia (RR 1.59, 95% CI 1.18 to 2.13; participants = 14,035; studies = 16) and hypotension (RR 1.24, 95% CI 1.03 to 1.48; participants = 13,738; studies = 15), based on moderate quality evidence.There was insufficient evidence to determine the effect of α-2 adrenergic agonists on all-cause mortality in cardiac surgery (RR 0.52, 95% CI 0.26 to 1.04; participants = 1947; studies = 16) and myocardial infarction (RR 1.01, 95% CI 0.43 to 2.40; participants = 782; studies = 8), based on moderate quality evidence. There was one cardiac death in the clonidine arm of a study of 22 participants. Based on very limited data, α-2 adrenergic agonists may have reduced the risk of stroke (RR 0.37, 95% CI 0.15 to 0.93; participants = 1175; studies = 7; outcome events = 18; low quality evidence). Conversely, α-2 adrenergic agonists increased the risk of bradycardia from 6.4% to 12.0% (RR 1.88, 95% CI 1.35 to 2.62; participants = 1477; studies = 10; moderate quality evidence), but their effect on hypotension was uncertain (RR 1.19, 95% CI 0.87 to 1.64; participants = 1413; studies = 9; low quality evidence).These results were qualitatively unchanged in subgroup analyses and sensitivity analyses.

AUTHORS' CONCLUSIONS

Our review concludes that prophylactic α-2 adrenergic agonists generally do not prevent perioperative death or major cardiac complications. For non-cardiac surgery, there is moderate-to-high quality evidence that these agents do not prevent death, myocardial infarction or stroke. Conversely, there is moderate quality evidence that these agents have important adverse effects, namely increased risks of hypotension and bradycardia. For cardiac surgery, there is moderate quality evidence that α-2 adrenergic agonists have no effect on the risk of mortality or myocardial infarction, and that they increase the risk of bradycardia. The quality of evidence was inadequate to draw conclusions regarding the effects of alpha-2 agonists on stroke or hypotension during cardiac surgery.

Heart-Type Fatty Acid Binding Protein and Ischemia-Modified Albumin for Detection of Myocardial Infarction After Coronary Artery Bypass Graft Surgery

BACKGROUND

Heart-type fatty acid binding protein (hFABP) and ischemia-modified albumin (IMA) have been put forward as novel biomarkers to detect myocardial injury shortly after onset of ischemia. We compared hFABP and IMA with cardiac troponin I (cTnI) for speed and reliability in the diagnosis of perioperative myocardial infarction (PMI) after coronary artery bypass graft surgery (CABG).

METHODS

In all, 210 consecutive patients undergoing isolated CABG with cardiopulmonary bypass were enrolled in a prospective study. Blood samples were taken perioperatively and throughout the first 72 hours after surgery; clinical data and events were recorded. In cohort A, serum concentrations of hFABP and cTnI were measured using a combined quantitative bedside assay. In cohort B, IMA and cTnI serum concentrations were measured using an albumin cobalt binding test. Perioperative myocardial infarction was defined using a cTnI cutoff of greater than 10.5 ng/mL occurring within 24 hours of CABG or new electrocardiographic changes.

RESULTS

In cohort A, 14 patients were identified with PMI (group 1), whereas 94 had no PMI and served as controls (group 2). Both hFABP and cTnI were increased in group 1 as compared with group 2 (p < 0.001). Although cTnI did not differ before 12 hours, hFABP diverged much earlier, at 1 hour postoperatively (p < 0.001). An hFABP concentration of 20 μg/mL at 1 hour detected PMI with an area under the curve of 77.1%. In cohort B, 18 patients were identified with PMI (group 3), and 84 patients served as controls (group 4). No difference in cTnI values could be observed between the groups until 12 hours postoperatively. Ischemia-modified albumin failed to differentiate at any postoperative time point; the low discriminative power of IMA was confirmed with an area under the curve of 53.3% at 1 hour, 48.5% at 6 hours, and 39.3% at 12 hours postoperatively.

CONCLUSIONS

Heart-type fatty acid binding protein is a sensitive and rapid biomarker that detected PMI reliably at 1 hour after CABG, much earlier than cTnI. The diagnostic value of IMA for detection of PMI appears to be very limited in this setting.

High-Sensitivity Troponin Release Profile After Cardiac Surgery

BACKGROUND

Postoperative serum troponin levels and perioperative myocardial infarction (MI) rates correlate with mortality and morbidity following cardiac surgery. The objective of this study was to document the release profile of high sensitivity troponin T (hsTnT) following different cardiac operations.

METHODS

Patients undergoing one of five different isolated cardiac surgical procedures (eligible preoperative hsTnT <29ng/L, serum creatinine < 0.2mmol/L) were recruited prospectively. Serum hsTnT was measured at 0, 4, 6, 8, 10, 12, 24 and 72hours after the first surgical insult to myocardium, together with daily electrocardiographs.

RESULTS

There were 10 patients in the on-pump coronary artery bypass group and 5 each in the remaining groups (off-pump coronary artery bypass, open aortic valve replacement, transcutaneous aortic valve implantation and mitral valve replacement). Five additional patients were excluded due to perioperative MI or renal failure. Median [range] of peak hsTnT was 241[99-566], 64[50-136], 353[307-902], 115[112-275], and 918[604-1166] ng/L, respectively. Operations with the lowest peak hsTnT values peaked earliest (four hours) while those with highest values peaked latest (eight hours).

CONCLUSION

After cardiac surgery, the hsTnT profile peaks four to eight hours after the initial surgical insult. The magnitude and timing of the peak correlates to the expected degree of surgically-induced myocardial injury.

Acute coronary angiography after coronary artery bypass grafting

OBJECTIVES

Coronary angiography is the golden standard when myocardial ischemia after CABG occurs. We summarize our experience of acute coronary angiography after CABG.

DESIGN

All 4446 patients (mean age 68 ± 9 years, 22% women) who underwent CABG 2007 to 2012 were included in this retrospective observational study. Incidence, indications, findings, measures of acute angiography after CABG was assessed. Outcome variables were compared between patients who underwent angiography and those who did not.

RESULTS

Eighty-seven patients (2%) underwent acute coronary angiography. Patients undergoing angiography had ECG changes (92%), echocardiographic alterations (48%), hemodynamic instability (28%), angina (15%), and/or arrhythmia (13%). Positive findings were detected in 69% of the cases. Only ECG changes as indication for angiography had a moderate association with positive findings, but the precision increased if other sign(s) of ischemia were present. Thirty-day mortality (7% versus 2%, p = 0.002) was higher and long-term-cumulative survival lower (77% versus 87% at five years, p = 0.043) in angiography patients.

CONCLUSIONS

Acute angiography is a rare event after CABG. Postoperative myocardial ischemia leading to acute coronary angiography is associated with increased short-term and long-term mortality.

Minimally invasive cardiac surgery: A systematic review and meta-analysis

BACKGROUND

Minimally invasive (MI) cardiac surgery was introduced to reduce problems associated with a full sternotomy. This meta-analysis aimed to investigate the effects of minimally invasive cardiac surgery on a range of clinical outcomes.

METHODS

To identify potential studies (randomised/prospective clinical trials) systematic searches were carried out. The search strategy included the concepts of "minimally invasive" OR "MIDCAB" AND "coronary artery bypass grafting" OR "cardiac surgery". This was followed by a meta-analysis investigating cross-clamp time, cardiopulmonary bypass (CPB) time, operation time, ventilation time, intensive care unit (ICU) stay, hospital stay, incidence of myocardial infarction and of stroke/neurologic complications.

RESULTS

Eight studies (9 intervention groups), totalling 596 participants were analysed. MI cardiac surgery was associated with a shorter ICU stay mean difference (MD) -0.7days (95% confidence interval (CI) -1.23 to -0.18, p=0.009) and longer cross-clamp MD 6.7min (95% CI 1.24 to 12.17, p=0.02), CPB MD 26.68min (95% CI 10.31 to 43.05, p=0.001), and operation times MD 55.03min (95% CI 22.76 to 87.31, p=0.0008). However no differences were found in the ventilation time MD -3.94h (95% CI -8.09 to 0.21, p=0.06), length of hospital stay MD -1.14days (95% CI -3.11 to 0.83, p=0.26) and in the incidence of myocardial infarction odds ratio (OR) 1.97 (95% CI 0.49 to 7.9, p=0.34) or stroke/neurologic complications OR 0.67 (95% CI 0.11 to 4.05, p=0.66).

CONCLUSIONS

Minimally invasive cardiac surgery is as safe as conventional surgery and could reduce costs due to a shorter period spent in ICU.

Leucocyte-depleting arterial line filtration does not reduce myocardial injury assessed by Troponin T during routine coronary artery bypass grafting using crossclamp fibrillation

Introduction: Leucocyte filtration can reduce inflammation and end-organ damage. The aim of this study was to test the cardioprotective effect of systemic leucocyte filtration during cardiopulmonary bypass (CPB) for coronary revascularization.

Methods: Sixty patients scheduled for elective coronary artery bypass grafting were prospectively randomised to receive either a test leucocyte-depleting (LD) filter or a control standard arterial line filter in the CPB circuit. Myocardial injury was determined by serum Troponin T concentration up to 72 h postoperatively. In addition, perioperative neutrophil counts, serum elastase and electrocardiograms (ECGs) were evaluated.

Results: There was a peak of Troponin T release at 6 h in both groups. There was no difference between LD or control group Troponin T at any time point. No difference in neutrophil count was found. A greater rise in neutrophil elastase occurred in the LD group during CPB and 10 min post CPB (376 and 496 versus 108 and 228 mcg/L, p <0.001).

Conclusions: LD arterial line filters did not confer any cardioprotective effect as measured by Troponin T in elective coronary revascularization cases.

Effect of Aortic Cross-Clamp Time on Myocardial Infarction after Coronary Bypass Surgery

Univariate and multivariate statistical analyses were applied to 1200 consecutive patients undergoing first-time myocardial revascularization. Forty-three patients (3.6%) developed evidence of myocardial infarction as judged by serial electrocardiograms and release of enzymes. Out of 23 preoperative and intraoperative potential risk factors for perioperative myocardial infarction, multivariate regression analysis revealed that duration of aortic cross-clamping was a powerful continuous variable risk factor. The relative risk increased twofold at 44 minutes compared to 17 minutes, approached three times the risk at 53 minutes, and reached more than six times the risk after 84 minutes of aortic cross-clamping. Two other independent predictors for perioperative myocardial infarction were identified: the presence of preoperative arterial hypertension and significant (> 75%) left main coronary artery stenosis. Left ventricular impairment, gender, age, severity of angina, and the number of distal anastomoses were not identified as risk factors for perioperative myocardial infarction. Our data indicate that the incidence of perioperative myocardial infarction may be reduced by consistent efforts to minimize aortic cross-clamp time without compromising the adequacy of myocardial revascularization.

Plasma levels of growth differentiation factor-15 are associated with myocardial injury in patients undergoing off-pump coronary artery bypass grafting

Growth differentiation factor-15 (GDF-15) has recently emerged as a risk predictor in patients with cardiovascular diseases. We therefore aimed to investigate the role of GDF-15 in the occurrence of cardiac injury during off-pump coronary artery bypass grafting (OPCAB). 55 consecutive patients with coronary artery diseases were recruited in this prospective, observational study. All patients were operated for OPCAB surgery. Serial blood samples were collected preoperatively, 12 hours and 36 hours after surgery. GDF-15, together with C-reactive protein, cardiac troponin I, creatine kinase MB and N-terminal pro B-type natriuretic peptide levels in plasma were measured at each time-point. GDF-15 levels increased significantly at 12 hours after surgery, attaining nearly 2.5 times the baseline levels (p < 0.001). Postoperative GDF-15 levels correlated positively with cTnI (p = 0.003) and EuroSCORE II (p = 0.013). According to the ROC curves, postoperative plasma GDF-15 was found to be the best biomarker to predict perioperative cardiac injury, compared with cTnI, CK-MB and EuroSCORE II. Circulating GDF-15 is a promising novel biomarker for identifying perioperative myocardial injury in patients undergoing OPCAB.

Early detection of asymptomatic bypass graft abnormalities using a cardiac troponin I ratio following coronary artery bypass surgery

BACKGROUND

We sought to identify the best cardiac Troponin I (cTnI) ratio to detect asymptomatic graft or anastomoses anomalies after myocardial revascularization.

METHODS

Patients with a rising cTnI profile, based on measurements at 6 and 12 hours (cTnI 12 hours : 6 hours ratio >1) after the last anastomosis in off-pump surgery or after cardiopulmonary bypass in on-pump surgery, underwent a coronary angiogram, despite an uncomplicated postoperative course and absence of electrocardiogram changes. The optimal threshold value for the ratio was determined using a receiving operator characteristic (ROC) curve.

RESULTS

From April 2005 to May 2011, among 1693 patients undergoing isolated coronary artery bypass graft (CABG), 29 (1.7%) had a cTnI ratio >1 and underwent postoperative angiography. Twenty abnormalities were observed in 16 patients (55%). In the anastomoses, there were four occlusions and four stenosis. In the grafts, there were 12 stenosis: two of the Y graft anastomosis, two dissections, five hematomas and three kinking. TIMI flow grade based on results of the Thrombolysis In Myocardial Infarction trial was 3 in six patients, 1 in five, and 0 in five. In the 16 patients with lesions, the cTnI ratio was 2.1 ± 1.4 versus 1.4 ± 0.3 in patients with no lesions (p = 0.09). A ratio of 1.3 (p = 0.003) was determined by ROC curve analysis as having the greatest discriminant capacity, with associated sensitivity of 87.5% and specificity of 62%.

CONCLUSION

A cTnI 12 hours : 6 hours ratio >1.3 may be indicative of these abnormalities. Early identification of these anomalies may avoid adverse outcomes.

Perioperative myocardial infarction in patients undergoing myocardial revascularization surgery

INTRODUCTION

Perioperative myocardial infarction adversely affects the prognosis of patients undergoing coronary artery bypass graft and its diagnosis was hampered by numerous difficulties, because the pathophysiology is different from the traditional instability atherosclerotic and the clinical difficulty to be characterized.

OBJECTIVE

To identify the frequency of perioperative myocardial infarction and its outcome in patients undergoing coronary artery bypass graft.

METHODS

Retrospective cohort study performed in a tertiary hospital specialized in cardiology, from May 01, 2011 to April 30, 2012, which included all records containing coronary artery bypass graft records. To confirm the diagnosis of perioperative myocardial infarction criteria, the Third Universal Definition of Myocardial Infarction was used.

RESULTS

We analyzed 116 cases. Perioperative myocardial infarction was diagnosed in 28 patients (24.1%). Number of grafts and use and cardiopulmonary bypass time were associated with this diagnosis and the mean age was significantly higher in this group. The diagnostic criteria elevated troponin I, which was positive in 99.1% of cases regardless of diagnosis of perioperative myocardial infarction. No significant difference was found between length of hospital stay and intensive care unit in patients with and without this complication, however patients with perioperative myocardial infarction progressed with worse left ventricular function and more death cases.

CONCLUSION

The frequency of perioperative myocardial infarction found in this study was considered high and as a consequence the same observed average higher troponin I, more cases of worsening left ventricular function and death.

Remote ischemic preconditioning: the surgeon's perspective

Since cardiac surgery began, surgeons have aimed to find methods of minimizing myocardial injury resulting from ischemia and reperfusion. The concept of somehow conditioning the heart in order to attenuate ischemia and reperfusion-related injury has evolved in cardiovascular research over decades, from ischemic preconditioning and postconditioning to, more recently, remote ischemic preconditioning (and postconditioning). Although many strategies have proven to be beneficial in the experimental arena, a few have been successfully translated into clinical practice. Remote ischemic preconditioning, with the use of brief episodes of ischemia and reperfusion of vascular territories remote from the heart, has been shown convincingly to decrease myocardial injury. To date, the translation of this powerful innate mechanism of myocardial and/or multiorgan protection from the animal lab to the operating theatre, using transient occlusion of blood flow to the upper limb with a blood-pressure cuff before cardiac surgery, has shown promising results, with several proof-of-principle and first randomized controlled clinical trials reporting benefits for patients undergoing cardiac surgery. If the efficacy of remote ischemic preconditioning can be conclusively proven, the clinical applications in cardiac surgery could be almost infinite, providing multiorgan protection in various surgical scenarios.

Fibrinogen beta-chain -C148T polymorphism is associated with increased fibrinogen, C-reactive protein, and interleukin-6 in patients undergoing coronary artery bypass grafting

The fibrinogen beta-chain (FGB) -C148T polymorphism is linked with plasma fibrinogen concentration in the general population. We examined whether the -C148T polymorphism is associated with pre- and early postoperative levels of fibrinogen, C-reactive protein (CRP), and interleukin-6 (IL-6) in 243 consecutive patients undergoing coronary artery bypass grafting (CABG) surgery. Plasma inflammatory markers were measured prior to and 5-7 days after surgery. The -C148T polymorphism was analyzed with the restriction fragment-length polymorphism method. The genotype distribution was as follows: CC-142 (58%), CT-85 (35%), and TT-16 (7%). Carriers of the -148T allele had higher preoperative plasma fibrinogen (4.42 ± 0.14 vs. 4.07 ± 0.11 mg/L, p = 0.04) and CRP levels (7.49 ± 1.2 vs. 4.26 ± 1.0 mg/L, p = 0.04) compared with non-carriers; 5 to 7 days after CABG, patients carrying -148T allele had increased CRP (70.4 ± 5.0 vs. 51.6 ± 4.25 mg/L, p = 0.005) and IL-6 levels (22.34 ± 2.64 vs. 15.53 ± 2.28 pg/L, p = 0.05), but not fibrinogen, compared with the remaining subjects. In-hospital nonfatal stroke occurred more frequently in -148T allele carriers (4% vs. 0%, p = 0.02). No genotype-associated differences were found in the occurrence of postoperative myocardial infarction and death. Presence of the -148T allele has also been associated with longer intensive care stay and intubation time (p = 0.01). Multivariate analysis identified the CT+TT genotype as an independent predictor of pre- and postoperative CRP levels. The results indicate that the presence of the -148T FGB allele determines higher pre- and postoperative levels of inflammatory markers, which might be associated with in-hospital clinical outcomes.

Detection of perioperative myocardial infarction with ischemia-modified albumin

We assessed the perioperative pattern of serum ischemia-modified albumin and its role as a myocardial ischemia indicator for early detection of perioperative myocardial infarction in patients undergoing off-pump coronary artery bypass grafting. Venous blood samples were collected from 63 consecutive patients before the operation, immediately after the operation, and at 3, 6, 12, and 24 h postoperatively. Serum ischemia-modified albumin levels were analyzed using an albumin cobalt binding test. The patients were divided into 2 groups retrospectively, according to the occurrence of perioperative myocardial infarction. The serum ischemia-modified albumin levels were compared between groups. The levels peaked immediately after the operation, followed by a gradual regression, but remained elevated during the first 24 h in all patients. The occurrence of perioperative myocardial infarction was identified in 10 patients who had significantly higher ischemia-modified albumin levels at 3 h postoperatively and slower regression rates. Perioperative serum ischemia-modified albumin levels might be helpful in predicting perioperative myocardial infarction.

Management of early postoperative coronary artery bypass graft failure

Perioperative graft failure following coronary artery bypass grafting (CABG) may result in acute myocardial ischaemia. Whether acute percutaneous coronary intervention, emergency reoperation or conservative intensive care treatment should be used is currently unknown. Between 2003 and 2009, 39 of the 5598 patients who underwent isolated CABG surgery underwent early postoperative coronary angiography for suspected myocardial ischaemia. Following angiography, two groups were identified: patients who underwent immediately reintervention (group 1); and those treated conservatively (group 2). Primary study endpoints were mortality and postoperative myocardial infarct size. Postoperative coronary angiography revealed early perioperative bypass graft failure in 32 of 39 patients. Acute percutaneous coronary intervention was performed in 15 patients, redo-CABG in 4 patients and conservative treatment in 13 patients. The number of failing bypass grafts were significantly higher in group 1 compared with group 2 (P = 0.0251). A trend toward lower post-procedural peak cardiac troponin T and creatinine phosphokinase serum levels in group 1 was observed (163.0 vs. 206.0 and 4.35 vs. 5.53, respectively) (P = 0.0662 and 0.1648). Early reintervention may limit the extent of myocardial cellular damage compared with conservative medical strategy in patients with myocardial ischaemia due to early graft failure.

The clinical significance of cardiac troponins in medical practice

Troponins are regulatory proteins that form the cornerstone of muscle contraction. The amino acid sequences of cardiac troponins differentiate them from that of skeletal muscles, allowing for the development of monoclonal antibody-based assay of troponin I (TnI) and troponin T (TnT). Along with the patient history, physical examination and electrocardiography, the measurement of highly sensitive and specific cardiac troponin has supplanted the former gold standard biomarker (creatine kinase-MB) to detect myocardial damage and estimate the prognosis of patients with ischemic heart disease. The current guidelines for the diagnosis of non-ST segment elevation myocardial infarction are largely based on an elevated troponin level. The implementation of these new guidelines in clinical practice has led to a substantial increase in the frequency of myocardial infarction diagnosis. Automated assays using cardiac-specific monoclonal antibodies to cardiac TnI and TnT are commercially available. They play a major role in the evaluation of myocardial injury and prediction of cardiovascular outcome in cardiac and non-cardiac causes. In this review we discuss the clinical applications of cardiac troponins and the interpretation of elevated levels in the context of various clinical settings.

Correlation of akinesia with graft patency and cardiac enzyme after off-pump coronary artery bypass graft surgery

BACKGROUND

The aim of the present study was to identify the clinical implications of newly developed akinesia in echocardiography after off-pump coronary artery bypass graft (CABG) surgery and its relationship with graft patency.

METHODS AND RESULTS

A total of 512 patients underwent off-pump CABG from January 2007 to November 2008. Two hundred and thirty-nine patients, whose echocardiography and multi-slice computed tomography data were available, were included in the study. Wall motion was subdivided into 16 segments and analyzed. Patients were separated into group A with newly developed akinesia (n=20), and group B without newly developed akinesia (n=219). Morbidity and early mortality, cardiac enzyme level, and graft patency were compared. The incidence of newly developed akinesia according to the anatomical territory was as follows: anterior, 5; lateral, 3; posterior, 7; and multiple territories, 5. Significant differences in preoperative ejection fraction were observed between the 2 groups (group A, 45.0+/-7%; group B, 58.0+/-12.2%, P<0.001). There was no statistical difference in the mean number of bypassed grafts and the complete revascularization rate. Complication and early mortality rates were insignificant between the 2 groups. There was little association between graft patency, cardiac enzyme level, and newly developed akinesia (P>0.05). Multivariate analysis showed that the preoperative ejection fraction was a risk factor for newly developed akinesia.

CONCLUSIONS

The mechanism of development of akinesia after off-pump CABG might be attributable to intraoperative coronary malperfusion, which is probably due to cardiac manipulation rather than graft occlusion.

Remote ischemic preconditioning reduces myocardial injury after coronary artery bypass surgery with crystalloid cardioplegic arrest

Remote ischemic preconditioning (RIPC) with transient upper limb ischemia reduces myocardial injury in patients undergoing on-pump coronary artery bypass grafting (CABG) with cross-clamp fibrillation or blood cardioplegia for myocardial protection. Whether or not such protection is still operative when standard crystalloid cardioplegic arrest is used is uncertain. Fifty-three consecutive, non-diabetic patients with triple-vessel disease and 64 +/- 12 years of age (mean +/- SD), who underwent elective CABG surgery with crystalloid (Bretschneider) cardioplegic arrest, were allocated in a prospective, randomized, single-blinded protocol to receive either a RIPC protocol (3 cycles of 5 min transient left upper arm ischemia induced by inflating a blood pressure cuff to 200 mmHg with 5 min of reperfusion) or control, respectively, after induction of anesthesia. Cardiac troponin I (cTnI) concentration was measured preoperatively and over 72 h postoperatively, and the area under the curve (AUC) was calculated. Peak postoperative cTnI concentration was significantly reduced from 13.7 +/- 7.7 ng/mL in controls to 8.9 +/- 4.4 ng/mL in RIPC (P = 0.008). Mean cTnI concentration was significantly lower at 6, 12, 24, and 48 h after surgery (ANOVA; P < 0.0001) in the RIPC patients (N = 27) than in controls (N = 26), resulting in a 44.5% reduction of cTnI (AUC at 72 h). RIPC by repetitive inflation of a cuff around the left upper arm before surgery enhances myocardial protection in patients undergoing CABG surgery with antegrade cold crystalloid cardioplegia.

Alpha-2 adrenergic agonists for the prevention of cardiac complications among patients undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may thereby prevent cardiac complications.

OBJECTIVES

This review assessed the efficacy and safety of preoperative (within 24 hours), intraoperative, and postoperative (first 48 hours) alpha-2 adrenergic agonists for preventing mortality and cardiac complications after surgery performed under either general or neuraxial anaesthesia, or both.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to August week 4 2008), EMBASE (1980 to week 36 2008), the Science Citation Index, and reference lists of articles.

SELECTION CRITERIA

We included randomized controlled trials that compared alpha-2 adrenergic agonists (clonidine, dexmedetomidine, or mivazerol) against placebo or non-alpha-2 adrenergic agonists. Included studies had to report on mortality, myocardial infarction, myocardial ischaemia, or supraventricular tachyarrhythmia.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed trial quality and extracted data. Two authors independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials.

MAIN RESULTS

We included 31 studies (4578 participants). Study quality was generally inadequate, with only six studies clearly reporting methods for blinding and allocation concealment. Overall, alpha-2 adrenergic agonists reduced mortality (relative risk (RR) 0.66; 95% CI 0.44 to 0.98; P = 0.04) and myocardial ischaemia (RR 0.68; 95% CI 0.57 to 0.81; P < 0.0001). However, their effects appeared to vary with the surgical procedure. The most encouraging data pertained to vascular surgery, where they reduced mortality (RR 0.47; 95% CI 0.25 to 0.90; P = 0.02), cardiac mortality (RR 0.36; 95% CI 0.16 to 0.79; P = 0.01), and myocardial infarction (RR 0.66; 95% CI 0.46 to 0.94; P = 0.02). With regard to adverse effects, alpha-2 adrenergic agonists significantly increased perioperative hypotension (RR 1.32; 95% CI 1.07 to 1.62; P = 0.009) and bradycardia (RR 1.66; 95% CI 1.14 to 2.41; P = 0.008).

AUTHORS' CONCLUSIONS

Our study provides encouraging evidence that alpha-2 adrenergic agonists may reduce cardiac risk, especially during vascular surgery. Nonetheless, these data remain insufficient to make firm conclusions about their efficacy and safety. A large randomized trial of alpha-2 adrenergic agonists is therefore warranted. Additionally, future research must determine which specific alpha-2 adrenergic agonist should be used, and whether it is safe to combine them with other perioperative interventions (for example beta-adrenergic blockade).

Troponin is superior to electrocardiogram and creatinine kinase MB for predicting clinically significant myocardial injury after coronary artery bypass grafting

AIMS

Cardiac biomarkers are routinely elevated after uncomplicated cardiac surgery to levels considered diagnostic of myocardial infarction in ambulatory populations. We investigated the diagnostic power of electrocardiogram (ECG) and cardiac biomarker criteria to predict clinically relevant myocardial injury using benchmarks of mortality and increased hospital length of stay (HLOS) in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS AND RESULTS

Perioperative ECGs, creatinine kinase MB fraction, and cardiac troponin I (cTnI) were assessed in 545 primary CABG patients. None of the ECG criteria for myocardial injury predicted mortality or HLOS. However, post-operative day (POD) 1 cTnI levels independently predicted 5-year mortality (hazard ratio = 1.42; 95% CI 1.14-1.76 for each 10 microg/L increase; P = 0.009), while adjusting for baseline demographic characteristics and perioperative risk factors. Moreover, cTnI was the only biomarker that significantly improved the prediction of 5-year mortality estimated by the logistic Euroscore (P = 0.02). Furthermore, the predictive value of cTnI for 5-year mortality was replicated in a separately collected cohort of 1031 CABG patients using cardiac troponin T.

CONCLUSION

Electrocardiogram diagnosis of post-operative myocardial injury after CABG does not independently predict an increased risk of 5-year mortality or HLOS. Conversely, cTnI is independently associated with an increased risk of mortality and prolonged HLOS.

Troponin I after cardiac surgery and its implications on myocardial protection, outcomes, and cost

BACKGROUND

Myocardial acidosis during cardiac surgery and postoperative troponin I are markers of myocardial damage that have been shown to predict adverse outcomes. We investigated the relationship between troponin I and myocardial tissue pH, patient outcomes, and cost.

METHODS

Data were prospectively collected on 205 cardiac surgery patients. Troponin I was sampled upon arrival to the intensive care unit (ICU) and every 6 hours thereafter for 24 hours. The lowest pH encountered during aortic cross clamp (LpH) was related to postoperative troponin I on the multivariate level. Multivariate models were constructed to predict adverse events (AE) and cost.

RESULTS

LpH was an independent inverse determinant of postoperative troponin I (P = .0067). Troponin I and its interaction with LpH were multivariate predictors of AE (P = .0012; .0001;odds ratio = 6.9, 10.2, respectively). Troponin I independently predicts surgical ICU (SICU) cost (P = .0256).

CONCLUSION

Postoperative troponin I elevation reflects intraoperative myocardial acidosis and damage. The strong relationship between troponin I, AE, and cost indicates the damage incurred is clinically and economically relevant. Strategies to ameliorate intraoperative myocardial tissue acidosis will decrease troponin I release, subsequent AE, and associated costs.

Impact of perioperative myocardial infarction on angiographic and clinical outcomes following coronary artery bypass grafting (from PRoject of Ex-vivo Vein graft ENgineering via Transfection [PREVENT] IV)

Myocardial infarction (MI) after coronary artery bypass grafting (CABG) is associated with significant morbidity and mortality. Frequency, management, mechanisms, and angiographic and clinical outcomes associated with perioperative MI remain poorly understood. PREVENT IV was a multicenter, randomized, placebo-controlled trial of edifoligide in 3,014 patients undergoing CABG. Angiographic and 2-year clinical follow-up were complete for 1,920 and 2,956 patients, respectively. Perioperative MI was defined as creatinine kinase-MB increase >or=10 times the upper limit of normal or >or=5 times the upper limit of normal with new 30-ms Q waves within 24 hours of surgery. Baseline characteristics, in-hospital management, and angiographic and clinical outcomes of patients with and without perioperative MI were compared. Perioperative MI occurred in 294 patients (9.8%). Patients with perioperative MI had longer surgery (250 vs 230 minutes; p <0.001), more on-pump surgery (83% vs 78%; p = 0.048), and worse target-artery quality (p <0.001). Patients with perioperative MI more frequently underwent angiography within 30 days of enrollment (1.7% vs 0.6%; p = 0.021). One-year angiographic vein graft failure occurred in 62.4% of patients with and 43.8% of patients without perioperative MI (p <0.001). Two-year composite clinical outcome (death, MI, or revascularization) was worse in patients with perioperative MI before (19.4% vs 15.2%; p = 0.039) and after (hazard ratio 1.33, 95% confidence interval 1.00 to 1.76, p = 0.046) adjusting for differences in significant predictors. In conclusion, perioperative MI was relatively common, was associated with worse outcomes, and mechanisms other than vein graft failure accounted for a substantial proportion of these MIs. Further research is needed into the prevention and treatment of perioperative MI in patients undergoing CABG.

Sodium-hydrogen exchange inhibition and beta-blockade additively decrease infarct size

BACKGROUND

Perioperative myocardial infarction adversely affects survival after cardiac operations. In animal studies Na+/H+ exchange inhibitors protect hearts against ischemia-reperfusion injury, but human trials have failed to consistently show beneficial effects. The aim of this study was to investigate whether the combination of the Na+/H+ exchange inhibitor cariporide and the beta-blocker metoprolol additively protects hearts from severe ischemia-reperfusion injury.

METHODS

Isolated Langendorff-perfused rat hearts were randomly assigned to a vehicle-treated control group, or groups with 10-minute preischemia infusions of cariporide (10 micromol/L), metoprolol (10 micromol/L), or both cariporide and metoprolol. The hearts were then subjected to 20 minutes of global ischemia followed by 60 minutes of reperfusion. At the end of reperfusion, the hearts were randomly assigned to undergo either infarct size measurements or left ventricular mitochondrial function analyses.

RESULTS

The combination of cariporide and metoprolol limited infarct size significantly compared with control group or cariporide alone (5% +/- 1% versus 58% +/- 9% or 38.4% +/- 4% of risk zone; p < 0.05). Cariporide alone did not reduce infarct size significantly as compared with the control group. As compared with the control group, cariporide and metoprolol decreased mitochondrial calcium content (6.4 +/- 1.2 versus 10.2 +/- 1.1 nmol/mg protein; p < 0.05), and increased respiratory control ratio (9.5 +/- 0.6 versus 5.3 +/- 0.7; p < 0.05). However, hearts treated with cariporide or metoprolol alone did not show significant improvement in mitochondrial calcium content (7.8 +/- 1.2 and 7.8 +/- 1.5 nmol/mg protein) or respiratory control ratio (5.0 +/- 0.7 and 7.3 +/- 0.7).

CONCLUSIONS

The combination of cariporide and metoprolol additively limits infarct size after severe ischemia-reperfusion injury in an isolated rat heart model. Infarct size reduction occurs in association with protection from increased mitochondrial calcium content after reperfusion.

Plasma Troponins as Markers of Myocardial Damage during Cardiac Surgery with Extracorporeal Circulation

All types of cardiac surgery involve considerable injury to the myocardium. However, it is difficult to differentiate, in the immediate post-operative state, between ischemic alterations associated with the cardiac surgery itself and the pathological alterations of a peri-operative myocardial infarction. The diagnosis of damaged myocardium, classically performed with the enzymatic markers creatine kinase (CK) and its muscle fraction (CK-MB), has become more precise with the option of measuring cardiac troponins T and I. We measured these markers in 58 patients undergoing elective cardiac surgery with extra-corporeal circulation (ECC). The patients included 37 cases undergoing valve surgery, 14 for coronary revascularization, 6 for mixed procedures, and 1 for closure of an inter-atrial communication. The markers were measured in plasma at baseline (at anesthesia initiation), 5 min post-ECC commencement, following aorta de-clamping, during the surgical closure, and 6, 18 and 42 hrs after surgery. All the markers were increased significantly relative to the baseline values. Troponin I, CK and CK-MB values peaked between 6 and 18 hrs after surgery, troponin T between 18 and 42 hrs, and myoglobin at the surgical closure. The values of all markers were higher in patients undergoing coronary surgery compared to those in patients undergoing valve surgery. In the evaluation of myocardial damage after surgery, the measurement of classical markers such as CK and myoglobin remain valid, but other markers such as troponins provide significant additional diagnostic benefit and, thus, need to be included in the routine biochemical measurements for monitoring myocardial damage associated with the surgical procedure.

Troponin T elevation after coronary bypass surgery: clinical relevance and correlation with perioperative variables

OBJECTIVE

Elevation in markers of myocardial necrosis is a common feature following coronary artery bypass surgery, but its relevance is unclear. The objective of this study was to evaluate the association between postoperative troponin T elevation, perioperative variables and clinical outcomes.

METHODS

We evaluated 100 low-risk patients undergoing first-time elective on-pump coronary artery bypass surgery. The mean age was 62 +/- 9.8 years and 83% were male; patients with diabetes mellitus, renal failure and impaired left ventricular function (ejection fraction < 40%) were excluded. Troponin levels were measured at baseline and 12 and 24 h following the onset of cardiopulmonary bypass. Predefined clinical endpoints included death, new Q waves on 12-lead electrocardiogram and inotropic requirement.

RESULTS

Postoperative troponin elevation occurred in 95%. Troponin T elevation was related to the duration of cardiopulmonary bypass (P = 0.0001) and aortic cross-clamp time (P = 0.0003). There was also an inverse relationship with perioperative core temperature (P = 0.0001). There was no association between postoperative troponin elevation and clinical outcomes.

CONCLUSIONS

Postoperative troponin T elevation occurs in the majority of patients undergoing elective on-pump coronary artery bypass surgery. In this low-risk cohort, troponin T elevation was associated with procedural duration but not with clinical outcome.

Inflammatory gene polymorphisms and risk of postoperative myocardial infarction after cardiac surgery

BACKGROUND

The inflammatory response triggered by cardiac surgery with cardiopulmonary bypass (CPB) is a primary mechanism in the pathogenesis of postoperative myocardial infarction (PMI), a multifactorial disorder with significant inter-patient variability poorly predicted by clinical and procedural factors. We tested the hypothesis that candidate gene polymorphisms in inflammatory pathways contribute to risk of PMI after cardiac surgery.

METHODS AND RESULTS

We genotyped 48 polymorphisms from 23 candidate genes in a prospective cohort of 434 patients undergoing elective cardiac surgery with CPB. PMI was defined as creatine kinase-MB isoenzyme level > or = 10x upper limit of normal at 24 hours postoperatively. A 2-step analysis strategy was used: marker selection, followed by model building. To minimize false-positive associations, we adjusted for multiple testing by permutation analysis, Bonferroni correction, and controlling the false discovery rate; 52 patients (12%) experienced PMI. After adjusting for multiple comparisons and clinical risk factors, 3 polymorphisms were found to be independent predictors of PMI (adjusted P<0.05; false discovery rate <10%). These gene variants encode the proinflammatory cytokine interleukin 6 (IL6 -572G>C; odds ratio [OR], 2.47), and 2 adhesion molecules: intercellular adhesion molecule-1 (ICAM1 Lys469Glu; OR, 1.88), and E-selectin (SELE 98G>T; OR, 0.16). The inclusion of genotypic information from these polymorphisms improved prediction models for PMI based on traditional risk factors alone (C-statistic 0.764 versus 0.703).

CONCLUSIONS

Functional genetic variants in cytokine and leukocyte-endothelial interaction pathways are independently associated with severity of myonecrosis after cardiac surgery. This may aid in preoperative identification of high-risk cardiac surgical patients and development of novel cardioprotective strategies.

Long-term outcome of patients with perioperative myocardial infarction as diagnosed by troponin I after routine surgical coronary artery revascularization

OBJECTIVE

Diagnosis of perioperative myocardial infarction (P-MI) after coronary artery bypass graft (CABG) surgery traditionally relied on a combination of electrocardiographic and enzyme assay changes. Patients with Q-wave P-MIs who survive to hospital discharge have a poorer long-term prognosis. Troponin assays are more sensitive and specific for detecting minor P-MI, with an increased incidence of P-MI being reported. This study investigated if P-MI after CABG surgery, as defined by troponin-I isozyme (cTn-I), correlated with long-term outcome.

DESIGN

A prospective, observational study.

SETTING

A single-institution, cardiothoracic specialty hospital.

PARTICIPANTS

Seventy patients undergoing elective CABG surgery.

INTERVENTIONS

Patients (n = 70) were stratified into low-risk and high-risk groups according to the absence (cTn-I <15 microg/L) or presence (cTn-I >or=15 microg/L) of P-MI after CABG surgery. Patients with (n = 24) and without (n = 46) P-MI were then followed for 3 years after CABG surgery to determine the impact of cTn-I-defined P-MI on long-term outcome.

MEASUREMENTS AND MAIN RESULTS

Most patients felt that their quality of life and activity index had improved and that their symptoms of angina had lessened at 12-month follow-up. However, cardiovascular event-free survival was significantly less in patients with P-MI (p = 0.01) 3 years postoperatively. The incidence for cardiovascular events was 0.24 versus 0.65 (p = 0.049) in those patients without and with P-MI, respectively. The hazard ratio (2.9; 95% confidence interval, 1.3-9.4) for cardiovascular incidents was also significantly greater in patients with P-MI. More specifically, the incidence of arrhythmia was 2.4% versus 26.1% (p < 0.01), and the incidence of vascular events was 4.9% versus 26.1% (p = 0.02) in patients without and with P-MI, respectively.

CONCLUSIONS

It was shown that P-MI as defined by cTn-I is associated with an increased long-term incidence of adverse cardiovascular events. An elevated peak cTn-I level (>or=15 microg/L) identified patients at increased risk but did not have a powerful positive predictive value for either cardiovascular (48%) or vascular (26%) complications. However, a peak cTn-I <15 microg/L was a negative predictor of adverse vascular outcome (95%). This may have implications for postoperative patient follow-up.

Effectiveness of triple-site triggered atrial pacing for prevention of atrial fibrillation after coronary artery bypass graft surgery

BACKGROUND

Recently, several temporary multisite pacing methods have been developed for prevention of postoperative atrial fibrillation (AF).

HYPOTHESIS

In this study, we evaluated the effect of triple-site temporary triggered pacing in the AAT mode on the development of AF in patients undergoing coronary artery bypass graft (CABG) at high risk for developing postoperative AF.

METHODS

A total of 70 patients undergoing CABG were randomly assigned either to pacing group (study group, n = 35 patients) or to no pacing group (control group, n = 35 patients). The external pacemaker was programmed to pace at the atrial triggered mode at a lower rate of 40 beats/min for 4 days.

RESULTS

Atrial fibrillation, defined as lasting > 30 s, occurred in 4 patients (11.4%) in the study group and in 16 patients (45.7%) in the control group (p = 0.003). Sustained AF, defined as AF lasting > 10 min, also was observed less frequently in the study group than in the control group (11.6 vs. 37.1%, p = 0.024). Triple-site triggered atrial pacing was observed to reduce the incidence of AF by 75% and the incidence of sustained AF by 69%.

CONCLUSIONS

We believe that multiple-site temporary pacing in the triggered mode is an effective way of preventing postoperative AF. This technique may be used especially in patients at high risk of developing AF.

The comparison and validity of troponin I assay systems in diagnosing myocardial ischemic injury after surgical coronary revascularization

OBJECTIVE

A prospective observational study was conducted to test the agreement between 2 commercially available automated cardiac troponin-I immunoassay systems (Opus Plus, Behring Diagnostics UK Ltd, Hounslow, UK; AxSYM, Abbott Laboratories, Abbott Park, IL) and to determine a normal reference range and threshold value indicative of perioperative myocardial infarction (PMI) after elective coronary artery bypass graft (CABG) surgery for the Opus Plus system.

DESIGN

Prospective, observational study. Setting : Single institution, cardiothoracic specialty hospital.

PARTICIPANTS

Seventy patients undergoing elective CABG surgery.

INTERVENTIONS

After institutional review board approval, patients received standardized anesthetic, surgical, and myocardial preservation techniques. Serial electrocardiographs, creatine kinase-MB, troponin-I, and perioperative outcome data were collected. Correlation between the immunoassay systems was tested using 124 duplicate samples from the first 18 patients. The normal reference range and threshold value indicative of PMI were tested for the Opus Plus system using duplicate samples from all 70 patients.

MEASUREMENTS AND MAIN RESULTS

Peak troponin-I concentrations (median [interquartile range]) differed significantly when measured by the Opus Plus and AxSYM immunoassay systems (5.61 [3.20-22.35] microg/L v 46.50 [14.55-70.95] microg/L, respectively; p < 0.001). There was clear proportional bias that was corrected with log transformation of the raw data. By using confidence interval and receiver operating characteristic curve analysis, the authors showed that a value > or =15 mug/L was indicative of PMI (Opus Plus system) and accordingly report a 35.7% (2.9% Q-wave) overall incidence of PMI in this study population (n = 70).

CONCLUSIONS

These data highlight differences between commercially available troponin-I assay systems. The authors recommend that each institution establish a local reference range and threshold indicative of perioperative myocardial infarction for its specific patient population and assay system and provide sample methodology.

Diagnostic discrimination between graft-related and non-graft-related perioperative myocardial infarction with cardiac troponin I after coronary artery bypass surgery

AIMS

The rise of markers for myocardial injury indicates early graft-related or non-graft-related perioperative myocardial infarction (PMI) after coronary artery bypass grafting (CABG). A diagnostic discrimination between these two situations may enable adequate therapeutic measures, limiting myocardial damage, and improving outcome.

METHODS AND RESULTS

In a prospective study, 94 among 3308 consecutive CABG patients underwent acute reangiography because of evidence of PMI. Of these 94 patients, 56 had graft-related PMI (group 1), 38 patients had non-graft-related PMI (group 2), and 95 patients without evidence of PMI and angiographically patent grafts served as control (group 3). Cardiac troponin I (cTnI), creatine kinase (CK), and its MB fraction were determined. CTnI, but not CK/CK-MB levels were significantly higher in group 1 than in groups 2 and 3 at 12 and 24 h after aortic unclamping (P<0.0001). Receiver operating characteristic and multivariable logistic regression analyses indicated cTnI as the best discriminator between PMI 'in general' and 'inherent' release of cTnI after CABG with a cut-off value of 10.5 ng/mL and between graft-related and non-graft-related PMI with a cut-off value of 35.5 ng/mL.

CONCLUSION

Perioperative cTnI elevation after CABG separates among patients with graft-related, non-graft-related, and without PMI, however, not earlier than 12 h after surgery.

Increased risk of heart failure as a consequence of perioperative myocardial injury after coronary artery bypass grafting

OBJECTIVE

To analyse the relation between perioperative myocardial injury (PMI) and the risk of subsequent heart failure after coronary artery bypass grafting (CABG).

DESIGN AND SETTING

Clinical data were documented prospectively in all patients and stored in a computer. All hospital readmissions were identified and the registered primary diagnoses were analysed. Survival information on all patients was obtained by use of combined registers. The study was carried out at the cardiac surgical referral centre of University Hospital, Uppsala, Sweden.

PATIENTS

7493 patients discharged alive after primary CABG between 1987 and 1996 were followed up until the first hospital readmission for heart failure, death, or 31 December 1996 was reached.

MAIN OUTCOME MEASURES

Hospital readmission for heart failure or late mortality.

RESULTS

Of the patients studied 576 (7.7%) were readmitted for heart failure. Actuarial freedom from readmission for heart failure after four years was 93%, and after seven years, 89%. Of the 576 patients, 114 (20%) had had PMI, which increased the risk of heart failure independently (hazard ratio (HR) 2.3, 95% confidence interval (CI) 1.8 to 2.8). Increased age, female sex, diabetes, previous myocardial infarction, dyspnoea, preoperative atrial fibrillation, left ventricular dysfunction, and triple vessel disease were independent risk factors for heart failure. The use of an internal mammary artery decreased the risk. PMI implied increased mortality (HR 1.4, 95% CI 1.1 to 1.8). Late mortality was greatly increased in patients readmitted for heart failure.

CONCLUSION

PMI increased the risk of heart failure and late death after CABG, and heart failure had a notable adverse effect on late survival.

Heart fatty acid binding protein in the rapid evaluation of myocardial damage following valve replacement surgery

BACKGROUND

Myocardial damage occurs following valve replacement surgery. We estimated the value of heart fatty acid binding protein (H-FABP) in these patients.

METHODS

Sixty elected patients were enrolled and distributed into single (group A) and double (group B) valve replacement groups. The clinical data were outlined and blood samples were collected perioperatively for determination of plasma levels of H-FABP, cardiac troponin-I (cTn-I), and CK-MB in both groups.

RESULTS

56 patients completed the study and no significant difference of clinical data was observed except CPB time and ACC time between groups. H-FABP level elevated quickly after reperfusion and peaked significantly earlier than cTn-I and CK-MB, it also declined rapidly but did not return to baseline at 24 h after reperfusion. Three markers' levels were all higher in group B than in group A after reperfusion with significant differences at their peaks and thereafter. Patients with postoperative complications had significantly higher H-FABP levels than usual. H-FABP peak level associated well with the length of CPB and ACC as well as with other 2 markers' peak levels in both groups.

CONCLUSION

Compared with cTn-I and CK-MB, H-FABP is an earlier and potentially useful marker in the rapid evaluation of myocardial damage following valve replacement surgery with CPB.

Determination of Troponin I Release After CABG Surgery

BACKGROUND

Troponin I is used to diagnose myocardial infarction (MI). Its use and pattern of elevation is not well defined in coronary artery bypass graft (CABG) surgery. This study assessed the timing of troponin I elevation in patients undergoing urgent CABG.

METHOD

Patients undergoing urgent isolated-CABG with cardiopulmonary bypass were studied prospectively. Blood samples were taken to measure CK, CK-MB, and troponin I: preoperatively, 7 hours postoperatively, 14 to 18 hours postoperatively, 30 to 48 hours postoperatively, and on postoperative day 4. Electrocardiograms and in-hospital course were recorded. Perioperative MI (PMI) was defined by either (i) ECG criteria of new Q-waves in the presence of CK-MB elevation >50 microg/L or (ii) CK-MB > 100 microg/L.

RESULTS

Of the 50 patients studied, 6 met the criteria for PMI (12%); 2 by criteria (i) and 4 by criteria (ii). In patients not meeting the criteria for MI the troponin I level peaked at 7 hour post-op with a mean of 20.97 microg/L (95% CI, 17.11 to 24.83). At this time, patients who met the criteria for MI had a mean troponin I level of 46.85 microg/L (95% CI, 36.40 to 57.30). Of variables investigated for the 44 patients who did not meet MI criteria, only preoperative troponin I level impacted peak postoperative troponin I.

CONCLUSIONS

CABG elevates troponin I far beyond current diagnostic benchmarks without the clinical occurrence of a MI and appears to peak during the second postoperative day. An elevated preoperative troponin I may predict an elevated peak postoperative troponin I in patients who do not have a PMI.

Increased creatine kinase MB level predicts postoperative mortality after cardiac surgery independent of new Q waves

BACKGROUND

Recent consensus statements recommend cardiac enzyme release as the essential criterion for diagnosing myocardial infarction. However, the outcome implications of cardiac enzyme release in patients undergoing coronary artery bypass grafting are controversial.

METHODS

Eight hundred patients were followed for 30 days after elective on-pump coronary artery bypass grafting in a multicenter, prospective, randomized trial of the anti-C5 complement antibody pexelizumab. Data from centralized electrocardiography and creatine kinase MB analyses were examined for any association with death or severe left ventricular dysfunction.

RESULTS

More than half of the 800 patients had peak creatine kinase MB levels of more than 5 times the upper limit of 5 ng/mL set by the core laboratory. The median peak value was 29 ng/mL. The incidence of the combined outcome (death or severe left ventricular dysfunction) was 1.7% if the peak creatine kinase MB level was less than 25 ng/mL and 18.0% if 100 ng/mL or greater (P < .01). Similarly, the incidence of new Q-wave myocardial infarction was 3.9% if the peak creatine kinase MB level was less than 25 ng/mL and 30.6% if 100 ng/mL or greater (P < .01). In a multivariate analysis that included preoperative and intraoperative factors, as well as peak enzyme release and Q-wave myocardial infarction, the strongest predictor of the combined outcome was a peak creatine kinase MB level of 100 ng/mL or greater. New Q-wave myocardial infarction did not significantly predict the combined outcome.

CONCLUSIONS

Increased postoperative peak creatine kinase MB level, especially when 20 times or more of the upper limit of normal, indicates increased risk of severe postoperative left ventricular dysfunction and mortality within 30 days of coronary artery bypass grafting. High peak enzyme level is a stronger predictor of adverse outcomes than is postoperative Q-wave myocardial infarction in this population.