Postoperative myocardial ischemia: etiology of cardiac morbidity or manifestation of underlying disease?

Perioperative outcomes following preoperative epidural analgesia in hip fracture patients undergoing surgical repair: A systematic review

OBJECTIVE

To examine the effectiveness and safety of epidural analgesia in the presurgical period on hip fracture patients undergoing surgical repair.

DESIGN

Systematic review.

METHODS

The study protocol was registered with the PROSPERO systematic reviews register: CRD42019140396. Electronic databases were searched for randomized controlled trials comparing preoperative epidural analgesia to other forms of pain management in hip fracture patients. The primary outcomes included perioperative cardiac events and mortality. Pain, non-cardiac complications, and adverse effects were also examined as secondary outcomes. Heterogeneity of the included studies was assessed using the I2 statistic and a random-effects meta-analysis was conducted once sufficient homogeneity was demonstrated.

RESULTS

Four studies met the inclusion criteria, which included a total of 221 patients. Preoperative epidural analgesia resulted in fewer cardiac events, which was a reported outcome in two included studies (RR 0.30; 95% CI 0.14-0.63; I2 = 0%). Preoperative epidural analgesia was also associated with decreased perioperative mortality in a meta-analysis of two studies (RR 0.13; 95% CI 0.02-0.98; I2 = 0%). Pain was not pooled due to variability in assessment methods, but preoperative epidural analgesia was associated with reduced pain in all four studies.

CONCLUSIONS

Preoperative epidural analgesia for hip fracture may reduce perioperative cardiac events and mortality, but the number of included studies in this systematic review was low. More research should be done to determine the benefit of early epidural analgesia for hip fractured patients.

Cardiac risk assessment for end-stage renal disease patients on the renal transplant waiting list

Cardiovascular disease is a leading cause of morbidity and mortality and is becoming more prevalent as the population ages and risk factors increase. This is most apparent in the end-stage renal disease (ESRD) patient population. In part, this is due to cofactors such as diabetes and hypertension commonly predisposing to progressive renal disease, as well as being a direct consequence of having renal failure. Of all major organ failures, kidney failure is the most likely to be managed chronically using renal replacement therapy and, ultimately, transplant. However, lack of transplant organs and a large renal failure cohort means waiting lists are often quite long and may extend to 5-10 years. Due to the cardiac risk factors inherent in patients awaiting transplant, many succumb to cardiac issues while waiting and present an increased per-procedural cardiac risk that extends into the post-transplant period. We aim to review the epidemiology of coronary artery disease in this population and the etiology as it relates to ESRD and its associated co-factors. We also will review the current approaches, recommendations and evidence for management of these patients as it relates to transplant waiting lists before and after the surgery. Recommendations on how to best manage patients in this cohort revolve around the available evidence and are best customized to the institution and the structure of the program. It is not clear whether the revascularization of patients without symptoms and with a good functional status yields any improvement in outcomes. Therefore, each individual case should be considered based on the risk factors, symptoms and functional status, and approached as part of a multi-disciplinary assessment program.

[Perioperative lumbar plexus block and cardiac ischemia in patients with hip fracture: randomized clinical trial]

BACKGROUND

Perioperative myocardial ischemia is common among patients undergoing hip fracture surgery. Our aim is to evaluate the efficacy of perioperative continuous lumbar plexus block in reducing the risk of cardiac ischemic events of elderly patients undergoing surgery for hip fractures, expressed as a reduction of ischemic events per subject.

METHODS

Patients older than 60 years, ASA II-III, with risk factors for or known coronary artery disease were enrolled in this randomized controlled study. Patients were randomized to conventional analgesia using opioid intravenous patient-controlled analgesia or continuous lumbar plexus block analgesia, both started preoperatively and maintained until postoperative day three. Continuous electrocardiogram monitoring with ST segment analysis was recorded. Serial cardiac enzymes and pain scores were registered during the entire period. We measured the incidence of ischemic events per subject registered by a continuous ST-segment Holter monitoring.

RESULTS

Thirty-one patients (intravenous patient-controlled analgesia 14, lumbar plexus 17) were enrolled. There were no major cardiac events during the observation period. The number of ischemic events recorded by subject during the observation period was 6 in the lumbar plexus group and 3 in the intravenous patient-controlled analgesia group. This difference was not statistically significant (p=0.618). There were no statistically significant differences in the number of cases with increased perioperative troponin values (3 cases in the lumbar plexus group and 1 case in the intravenous patient-controlled analgesia group) or in terms of pain scores.

CONCLUSIONS

Using continuous perineural analgesia, compared with conventional systemic analgesia, does not modify the incidence of perioperative cardiac ischemic events of elderly patients with hip fracture.

Mortality Rates and Length of Stay in Patients With Acute Non-ST Segment Elevation Myocardial Infarction Hospitalized for Noncardiac Conditions on Surgical Versus Nonsurgical Services

Patients hospitalized for noncardiac conditions often experience increased levels of stress and hemodynamic challenges, making them susceptible to acute coronary events. The clinical features, management strategy, and outcomes of inpatient non-ST segment elevation myocardial infarction (NSTEMI) have not been described. This single-center retrospective study identified patients with inpatient NSTEMI from the University of North Carolina Hospitals discharge database in February 2008 to April 2014 using International Classification of Diseases, Ninth Revision (ICD-9) codes. This process generated an initial list of 485 cases that were subsequently manually reviewed. The associations of cardiac catheterization with in-hospital mortality and length of stay were analyzed using multivariable logistic regression and multiple linear regression. A total of 302 patients were confirmed to have inpatient NSTEMI, with 154 patients admitted to surgical and 148 admitted to nonsurgical services. The in-hospital mortality rate of patients with inpatient NSTEMI was high (19%). Patients with inpatient NSTEMI who underwent cardiac catheterization had lower in-hospital mortality rates than those who did not undergo cardiac catheterization (6% vs 25%; adjusted odds ratio 0.19, 95% confidence interval 0.07 to 0.50) and were discharged 6.8 days earlier (95% confidence interval 2.3 to 11.2 days). Inpatient NSTEMIs on surgical services compared with nonsurgical services were more likely to generate cardiology consultation (96% vs 62%, p <0.0001) and left heart catheterization (41% vs 24%, p = 0.002), with similar rates of revascularization (56% vs 56%, p = 1.0). In conclusion, both nonsurgical and surgical patients with inpatient NSTEMI who underwent invasive management had lower in-hospital mortality rates and shorter lengths of stay.

Type 2 myocardial infarction due to supply-demand mismatch

The best-accepted definition of myocardial infarction (MI) is provided by statements from the Universal Definition of MI Global Task force. This article, now in its third iteration, defines MI as myocardial cell death due to prolonged myocardial ischemia. It further delineates an increasingly incident subclassification of MI known as type 2 MI (T2MI). T2MI identifies instances of myocardial necrosis in which an imbalance between myocardial oxygen supply and/or demand occurs for reasons other than atherosclerotic plaque disruption. While associated with considerable risk (comparable to that of type 1 MI, which has well-defined management strategies), the spectrum of potential etiologies for T2MI makes development of precise diagnostic criteria and therapeutic implications of the diagnosis challenging.

Diagnosing Perioperative Myocardial Infarction in Cardioth oracic and Vascular Surgery

Patients undergoing cardiac and high-risk noncardiac surgery have a high incidence of perioperative myocardial infarction. The early diagnosis of perioperative myocardial injury in these patients is complicated. In the perioperative period, there is a high incidence of nonspecific electrocardiographic changes and cardiac biomarker release. It is becoming increasingly imortant to differentiate myocardial necrosis from nonspecific changes because of the need for early intervention and the poential long term implications of a perioperative myocardial event. Although sensitive and specific assays to assess myoardial damage have been developed, specific thresholds to establish the occurrence a significant perioperative event have not been firmly defined. This review will attempt to outline the current evidence supporting the use of clinical symptoms, electrocardiographic changes, and cardiac biomarkers in the diagnosis of perioperative myocardial infarction and the longerm implication of these findings.

A review of the peri-operative risk stratification assessment tools used for the prediction of cardiovascular complications in non-cardiac surgery

The development of atherosclerosis is a complex process that involves several inflammatory mechanisms. The evolution of a fatty streak to a mature occlusive atheromatous plaque occurs over several decades. However, during acute plaque rupture, to a varying degree, these same inflammatory systems are involved.Evidence exists that suggests a relationship between the activated inflammatory pathways; in the setting of lower respiratory tract or urinary tract infections and cardiac events such as unstable angina or myocardial infarctions.Peripheral vascular disease patients demonstrate atheromatous disease throughout their arterial tree, with coronary artery involvement in a significant proportion of individuals. The stress that a surgical intervention creates may be the catalyst for an acute coronary syndrome through the activation of these inflammatory pathways. Individual responses to the surgical insult are unpredictable and the extent to which the inflammatory mechanisms are stimulated is variable. The measurements of inflammatory biomarkers, such as C-reactive protein, have been associated with adverse short- and long-term mortality in patients who experience an acute coronary syndrome.This review article looks at the previous assessment tools that have been developed over time to try and predict the peri-operative risk of patients undergoing non-cardiac surgery, based on traditional patient parameters. We also explore the use of bio-markers in addition to these characteristics and how future work is being developed to look at the potential use of these to improve individual risk profiles.

Use of ivabradine and atorvastatin in emergent orthopedic lower limb surgery and computed tomography coronary plaque imaging and novel biomarkers of cardiovascular stress and lipid metabolism for the study and prevention of perioperative myocardial infarction: study protocol for a randomized controlled trial

Background

The incidence of perioperative myocardial infarction (PMI) globally is known to be around 2 to 3% and can prolong hospitalization, increased morbidity and mortality. Little is known about the pathophysiology and risk factors for PMI. We investigate the presence of elevated novel cardiac markers and preoperative coronary artery plaque through contemporary laboratory techniques to determine the correlation with PMI, as well as studying ivabradine and atorvastatin as protective pharmacotherapies against PMI in the context of orthopedic surgery.

Methods/Design

We aim to enroll 200 patients aged above 60 years who suffer from neck of femur fracture requiring surgery. Patients will be randomized to four arms (no study drugs, atorvastatin only, ivabradine only and ivabradine and atorvastatin). Our primary outcome is incidence of PMI. All patients will receive an electrocardiogram, cardiac echocardiography, measurement of novel cardiac biomarkers and computed tomography (CT) coronary angiography. A telephone interview post discharge will be conducted at 30 days, 60 days and 1 year.

Discussion

We postulate that ivabradine and atorvastatin will reduce the rate and magnitude of PMI following surgery by reducing heart rate and attenuating catecholamine-induced tachycardia postoperatively. Secondly, we postulate that postoperative reduction in heart rate and catecholamine-induced tachycardia with ivabradine will correlate with a reduction in cardiovascular novel biomarkers which will reduce atrial stretch and postoperative incidence of arrhythmia. We aim to demonstrate that treatment with ivabradine and atorvastatin will cause a reduction in the incidence and magnitude of PMI, the benefit of which is derived primarily in patients with greater atherosclerotic burden as measured by higher CT coronary calcium scores.

Trial registration

This study protocol has been listed in the Australia New Zealand Clinical Trial Registry (registration number: ACTRN12612000340831) on 23 March 2012.

Mortality rate in type 2 myocardial infarction: observations from an unselected hospital cohort

BACKGROUND

The classification of myocardial infarction into 5 types was introduced in 2007. The prognostic impact of this universal definition, with particular focus on type 2 myocardial infarction, has not been studied prospectively in unselected hospital patients.

METHODS

During a 1-year period, all hospitalized patients having cardiac troponin I measured were considered. The diagnosis of a myocardial infarction was according to the universal definition, and specified criteria were used in the classification of type 2 myocardial infarction. Follow-up was at least 1 year, with mortality as the end point.

RESULTS

A total of 3762 consecutive patients were studied, of whom 488 (13%) had a myocardial infarction. In 119 patients a type 2 myocardial infarction was diagnosed. After a median of 2.1 years (interquartile range, 1.6-2.5 years), 150 patients had died, with a mortality rate of 49% (58/119) in those with type 2 myocardial infarction and 26% (92/360) in those with type 1 myocardial infarction (P < .0001). In a multivariable Cox regression analysis the following variables were independently associated with mortality: current or prior smoker, high age, prior myocardial infarction, type 2 myocardial infarction, hypercholesterolemia, high p-creatinine, and diabetes mellitus. The multivariable-adjusted hazard ratio for type 2 myocardial infarction was 2.0 (95% confidence interval, 1.3-3.0). With shock as the only exception, mortality was independent of the triggering conditions leading to type 2 myocardial infarction.

CONCLUSIONS

Mortality in patients with type 2 myocardial infarction is high, reaching approximately 50% after 2 years. Further descriptive and survival studies are needed to improve the scientific evidence on which treatment of type 2 myocardial infarction is based.

Preoperative cardiac evaluation of the vascular surgery patient--an anesthesia perspective

The morbidity and mortality associated with vascular surgery procedures are largely the results of cardiac events. National guidelines have been regularly proposed and updated by the American College of Cardiology (ACC)/American Heart Association (AHA) to ensure optimal perioperative management and risk stratification. Controversy remains between experts and other cardiology societies regarding several patient care issues including revascularization before surgery, timing of β-blocker therapy, and the administration of antiplatelet therapy. Several landmark articles recently published have helped to modify the guidelines in the hope of improving vascular patient outcomes. In this review, we searched all recent available literature pertaining to perioperative cardiac evaluation before major vascular surgery. We propose an algorithm for preoperative cardiac evaluation, which is a modification to the AHA recommendations. Incorporated in this algorithm are recent published pivotal articles that can help in guiding physicians caring for the vascular patient requiring major operative or endovascular interventions.

Perioperative myocardial ischemia and isolated systolic hypertension in non-cardiac surgery

PURPOSE

To determine whether patients with isolated systolic hypertension (ISH) undergoing non-cardiac surgery have a higher incidence of perioperative myocardial ischemia than normotensive patients and hence a greater risk for perioperative adverse events.

METHODS

After obtaining Research Ethics Board approval, patients were recruited to either an ISH group (systolic blood pressure [SBP] > 140 mmHg with diastolic blood pressure [DBP] < 90 mmHg) or a normotensive group (SBP < 140 mmHg and DBP < 90 mmHg), according to their resting preoperative blood pressure. The primary outcome was the overall incidence of perioperative myocardial ischemia (PMI) as determined by 48-hr ambulatory Holter monitoring. P values ≤ 0.05 were considered to be statistically significant.

RESULTS

A total of 312 (150 ISH and 162 normotensive) patients completed the study. Orthopedic surgery was the most frequent surgical procedure in both groups. The overall incidence of PMI was 19.7% in the ISH group compared with 18.8% in the normotensive group (difference 0.9%; 95% confidence interval [CI], -7.9% to 9.8%). The overall incidence of adverse events was 4.0% in the ISH group compared with 1.9% in the normotensive group (difference 2.2%; 95% CI, -1.6% to 5.9%).

CONCLUSION

In this study, we chose to examine ISH as potential cardiac risk factor for patients undergoing non-cardiac surgery. The incidence of myocardial ischemia, a surrogate outcome, was similar in the two groups. The relatively high incidence of myocardial ischemia (19.2%) was of particular interest in this relatively low cardiac risk surgical population. (ClinicalTrials.gov number, NCT01237652).

The pathophysiology of peri-operative myocardial infarction

SUMMARY

It is generally believed that plaque rupture and myocardial oxygen supply-demand imbalance contribute approximately equally to the burden of peri-operative myocardial infarction. This review critically analyses data of post-mortem, pre-operative coronary angiography, troponin surveillance, other pre-operative non-invasive investigations, and peri-operative haemodynamic predictors of myocardial ischaemia and/or myocardial infarction. The current evidence suggests that myocardial oxygen supply-demand imbalance predominates in the early postoperative period. It is likely that flow stagnation and thrombus formation is an important pathway in the development of a peri-operative myocardial infarction, in addition to the more commonly recognised role of peri-operative tachycardia. Research and therapeutic interventions should be focused on the prediction and therapy of flow stagnation and thrombus formation. Plaque rupture appears to be a more random event, distributed over the entire peri-operative admission.

Perioperative cardiac damage in vascular surgery patients

BACKGROUND

Patients undergoing vascular surgery are at increased risk for developing cardiac complications. Majority of patients with perioperative myocardial damage are asymptomatic. Our objective is to review the available literature addressing the prevalence and prognostic implications of perioperative myocardial damage in vascular surgery patients.

METHODS

An Internet-based literature search was performed using MEDLINE to identify all published reports on perioperative myocardial damage in vascular surgery patients. Only those studies published from 2000 to 2010 evaluating myocardial damage using troponin I or T, with or without symptoms of angina pectoris were included.

RESULTS

Thirteen studies evaluating the prevalence of perioperative myocardial ischaemia or infarction were included in the study. The incidence of perioperative myocardial ischaemia ranged from 14% to 47% and the incidence of perioperative myocardial infarction ranged from 1% to 26%. In addition, 10 studies evaluating the prognostic value of perioperative myocardial ischaemia towards postoperative mortality or the occurrence of major adverse cardiac events were included. In the retrieved studies, hazard ratios varied from 1.9 to 9.0.

CONCLUSION

The high prevalence and asymptomatic nature of perioperative myocardial damage, combined with a substantial influence on postoperative mortality of vascular surgery patients, underline the importance of early detection and adequate management of perioperative myocardial damage. This article provides an extended overview regarding the prevalence and prognostic value of perioperative myocardial ischaemia and infarction in vascular surgery patients. In addition, treatment options to reduce the risk of perioperative myocardial damage are provided based on the current available literature.

Morbidity and mortality caused by cardiac adverse events after revascularization for critical limb ischemia

BACKGROUND

We assessed cardiac adverse events (AEs) after primary lower extremity arterial revascularization (LEAR) for critical lower limb ischemia (CLI) in order to evaluate the impact of cardiac AEs on the clinical outcome. We created an optimized care protocol concerning CLI patients' preoperative work-up as well as intra- and postoperative surveillance according to recent important literature and guidelines.

METHODS

We conducted a prospective analysis of clinical outcome after LEAR using patient-related risk factors, comorbidity, surgical therapy, and AEs. This cohort was divided into patients with and without AEs. AEs were categorized according to predefined standards: minor, surgical, failed revascularization, and systemic. The consequences of AEs were reoperation, additional medication, irreversible physical damage, and early death.

RESULTS

There were 106 patients (Fontaine III n=49, 46%, and Fontaine IV n=57, 56%) who underwent primary revascularization by bypass graft procedure (n=67, 63%) or balloon angioplasty (n=39, 37%). No difference in comorbidity was registered between the two groups. Eighty-four AEs were registered in 34 patients (32%). Patients experiencing AEs had significantly less antiplatelet agents (without AEs n=63, 88%, vs. with AEs n=18, 53%; p=0.000) and/or beta-blockers (without AEs n=66, 92%, vs. with AEs n=16, 47%; p=0.000) compared to patients without AEs. The two most harmful consequences of AEs were irreversible physical damage (n=3) and early death (n=8). Sixty percent (n=9) of systemic AEs were heart-related. The postprocedural mortality rate was 7.5%, with a 75% (n=6) heart-related cause of death.

CONCLUSION

AEs occur in >30% of CLI patients after LEAR. The most harmful AEs on the clinical outcome of CLI patients were heart-related, causing increased morbidity and death. Significant correlations between prescription of beta-blockers and antiplatelet agents and prevention of AEs were observed. A persistent focus on the prevention of systemic AEs in order to ameliorate the outcome after LEAR for limb salvage remains of utmost importance. Therefore, we advise the implementation of an optimized care protocol by discussing patients in a strict manner according to a predetermined protocol, to optimize and standardize the preoperative work-up as well as intra- and postoperative patient surveillance.

Heart Rate and Outcome in Patients with Cardiovascular Disease Undergoing Major Noncardiac Surgery

There is an increasing awareness that an elevated resting heart rate is associated with increased all-cause mortality in the general population and that this may be an independent coronary risk factor. This review was undertaken to determine whether heart rate is predictive of increased mortality and major morbidity in noncardiac surgical patients and whether heart rate manipulation improves perioperative outcome. A search of Medline from 1966 until October 2007 was conducted using the terms “heart rate “, “surgery”, “cardiac “, “morbidity”, “mortality” and “perioperative”. The main findings were that an elevated perioperative heart rate, an absolute increase in heart rate and heart rate lability are independent predictors of both short- and long-term adverse outcomes in patients at cardiovascular risk undergoing major noncardiac surgery. Although prospective nonrandomised and retrospective data suggest heart rate control improves perioperative outcome, there is conflicting evidence from randomised trials that perioperative heart rate control improves outcome. This may be because drug-associated bradycardia influences mortality in the perioperative period. Further studies reporting the absolute heart rate, the absolute change of heart rate and the time period of the observations are needed to identify ‘early warning systems’, which may allow earlier triage and improved outcome. Enthusiasm for this approach must be tempered by the appreciation that a J-shaped relationship probably exists between heart rate and morbidity, particularly following bradycardic therapy. Therefore, any bradycardic manipulation of heart rate in the perioperative period must be accompanied by simultaneous attention to other physiological variables associated with increased morbidity and mortality.

Platelet activation, myocardial ischemic events and postoperative non-response to aspirin in patients undergoing major vascular surgery

OBJECTIVES

Myocardial ischemia is the leading cause of postoperative mortality and morbidity in patients undergoing major vascular surgery. Platelets have been implicated in the pathogenesis of acute thrombotic events. We hypothesized that platelet activity is increased following major vascular surgery and that this may predispose patients to myocardial ischemia.

METHODS

Platelet function in 136 patients undergoing elective surgery for subcritical limb ischemia or infrarenal abdominal aortic aneurysm repair was assessed by P-selectin expression and fibrinogen binding with and without adenosine diphosphate (ADP) stimulation, and aggregation mediated by thrombin receptor-activating peptide and arachidonic acid (AA). Cardiac troponin-I (cTnI) was performed.

RESULTS

P-selectin expression increased from days 1 to 3 after surgery [median increase from baseline on day 3: 53% (range: -28% to 212%, P < 0.01) for unstimulated and 12% (range: -9% to 45%, P < 0.01) for stimulated]. Fibrinogen binding increased in the immediate postoperative period [median increase from baseline: 34% (range: -46% to 155%, P < 0.05)] and decreased on postoperative day 3 (P < 0.05). ADP-stimulated fibrinogen binding increased on day1 (P < 0.05) and thereafter decreased. Platelet aggregation increased on days 1-5 (P < 0.05). Twenty-eight (21%) patients had a postoperative elevation (> 0.1 ng mL(-1)) of cTnI. They had significantly increased AA-stimulated platelet aggregation in the immediate postoperative period and on day 2 (P < 0.05), and non-response to aspirin (48% vs. 26%, P = 0.036).

CONCLUSIONS

This study has shown increased platelet activity and the existence of non-response to aspirin following major vascular surgery. Patients with elevated postoperative cTnI had significantly increased AA-mediated platelet aggregation and a higher incidence of non-response to aspirin compared with patients who did not.

Therapy insight: prophylaxis, monitoring and treatment of perioperative myocardial ischemia with emphasis on urological surgery

Unrecognized or silent perioperative myocardial ischemia is common in patients who undergo high-risk surgery, including cystectomy, and could predict cardiac morbidity and mortality in postoperative patients. This disorder is not merely a marker of extensive coronary disease but has a close association with perioperative myocardial infarction (PMI). In a review of published data, including meta-analyses, in the context of high-risk urological surgery, up to 50% of PMIs were found to go unrecognized if only clinical signs and symptoms are considered. Prevention and treatment of these previously unrecognized cardiac events might significantly reduce long-term morbidity and mortality. The emergence of reliable markers of PMI, such as increased levels of troponin I, could help in the detection of events that would have otherwise remained unnoticed. In this Review we examine the effect of these developments in the context of high-risk urological surgery. Changes to preoperative assessment, perioperative management, and prophylaxis of PMI are critically assessed. We performed a prospective audit using postoperative troponin I levels to assess the rate of silent perioperative myocardial ischemia and infarction. An increasingly proactive attitude towards perioperative monitoring for myocardial ischemia and infarction has evolved, and postoperative serial screening with troponin I might be beneficial in high-risk patients undergoing major urological surgery.

Perioperative cardiac events in patients undergoing noncardiac surgery: a review of the magnitude of the problem, the pathophysiology of the events and methods to estimate and communicate risk

This is the first of 2 articles evaluating cardiac events in patients undergoing noncardiac surgery. In this article, we review the magnitude of the problem, the pathophysiology of these events, approaches to risk assessment and communication of risk. The number of patients undergoing noncardiac surgery worldwide is growing, and annually 500,000 to 900,000 of these patients experience perioperative cardiac death, nonfatal myocardial infarction (MI) or nonfatal cardiac arrest. Although the evidence is limited, a substantial proportion of fatal perioperative MIs may not share the same pathophysiology as nonoperative MIs. A clearer understanding of the pathophysiology is needed to direct future research evaluating prophylactic, acute and long-term interventions. Researchers have developed tools to facilitate the estimation of perioperative cardiac risk. Studies suggest that the Lee index is the most accurate generic perioperative cardiac risk index. The limitations of the studies evaluating the ability of noninvasive cardiac tests to predict perioperative cardiac risk reveals considerable uncertainty as to the role of these popular tests. Similarly, there is uncertainty as to the predictive accuracy of the American College of Cardiology/American Heart Association algorithm for cardiac risk assessment. Patients are likely to benefit from improved estimation and communication of cardiac risk because the majority of noncardiac surgeries are elective and accurate risk estimation is important to allow informed patient and physician decision-making.

Intermittent Cardiac Troponin-I Screening is an Effective Means of Surveillance for a Perioperative Myocardial Infarction

OBJECTIVE

Several studies suggest that cardiac troponin-I (cTn-I) is a more sensitive indicator of cardiac injury compared with other biochemical markers of injury, but the strategy with the highest diagnostic yield (true positive and true negative) for perioperative surveillance is unknown. The authors undertook a prospective evaluation of the perioperative incidence of myocardial infarction (MI) and evaluated surveillance strategies for the diagnosis of MI.

DESIGN

Prospective, cohort study.

SETTING

Two university hospitals.

PARTICIPANTS

Four hundred sixty-seven high-risk patients requiring noncardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The diagnosis of myocardial injury was determined by cardiac protein markers combined with either postoperative changes on 12-lead electrocardiography or 1 of 3 clinical symptoms consistent with MI (chest pain, dyspnea, requirement for hemodynamic support). A receiver operating characteristic curve evaluating troponin in the diagnosis of MI revealed a value of 2.6 ng/mL as having the highest sensitivity and specificity. The sensitivity and specificity of cTn-I value > or =2.6 ng/mL, troponin > or =1.5 ng/mL, total creatine kinase (CK) > or =170 IU/L with MB > or =5%, and CK-MB > or =8 ng/mL were compared. Surveillance strategies were determined on a subset of patients (n = 257). The incidence of MI was 9.0% by cTn-I > or =2.6 ng/mL criteria, 19% by cTn-I > or =1.5 ng/mL, 13% by CK-MB mass, and 2.8% by CK-MB%. The specificity of cTn-I > or =2.6 ng/mL as an indicator of MI was 98%, and its positive predictive value (PPV) was 85%. Cardiac troponin-I > or =2.6 ng/mL had equal specificity but greater PPV than the cTn-I > or =1.5 ng/mL (specificity 98% and PPV 79%). If surveillance of cTn-I > or =2.6 ng/mL was used to detect MI, then the strategy with the highest diagnostic yield was surveillance on postoperative days 1, 2, and 3.

CONCLUSIONS

Perioperative cardiac injury continues to occur frequently after noncardiac surgery, as detected by cTn-I. Serial monitoring of cardiac troponin-I on postoperative days 1, 2, and 3 provides the strategy with the highest diagnostic yield for surveillance of MI.

Perioperative myocardial infarction—aetiology and prevention

Perioperative myocardial infarction (PMI) is one of the most important predictors of short- and long-term morbidity and mortality associated with non-cardiac surgery. Prevention of a PMI is thus a prerequisite for an improvement in overall postoperative outcome. The aetiology of PMI is multifactorial. The perioperative period induces large, unpredictable and unphysiological alterations in coronary plaque morphology, function and progression, and may trigger a mismatch of myocardial oxygen supply and demand. With many diverse factors involved, it is unlikely that one single intervention will successfully improve cardiac outcome following non-cardiac surgery. A multifactorial, step-wise approach is indicated. Based on increasing knowledge of the nature of atherosclerotic coronary artery disease, and in view of the poor positive predictive value of non-invasive cardiac stress tests, and the considerable risk of coronary angiography and coronary revascularization in high-risk patients, the paradigm is shifting from an emphasis on extensive non-invasive preoperative risk stratification to a combination of selective non-invasive testing and aggressive pharmacological perioperative therapy. Perioperative plaque stabilization by pharmacological means may be as important in the prevention of PMI as an increase in myocardial oxygen supply or a reduction in myocardial oxygen demand.

Postoperative 12-lead ECG predicts peri-operative myocardial ischaemia associated with myocardial cell damage

Peri-operative myocardial ischaemia is the single most important risk factor for an adverse cardiac outcome after non-cardiac surgery. The present study examines whether intermittent 12-lead ECG recordings can be used as an early warning tool to identify patients suffering from peri-operative myocardial ischaemia and subsequent myocardial cell damage. Fifty-five vascular surgery patients at risk for or with a history of coronary artery disease were monitored for peri-operative myocardial ischaemia using intermittent 12-lead ECG recordings taken pre-operatively and at 15 min, 20 h, 48 h, 72 h and 84 h postoperatively. The effectiveness of the 12-lead ECG was gauged by examining concordance with continuous 3-channel Holter monitoring and capturing peri-operative myocardial ischaemia by serial analyses of creatine kinase myocardial band isoenzyme and cardiac troponin T and I. The incidence of peri-operative myocardial ischaemia detected by 12-lead ECG was 44% and was identifiable in most patients (88%) 15 min after surgery. The incidence of peri-operative myocardial ischaemia detected by continuous monitoring was 53%, with the most severe episodes occurring intra-operatively and during emergence from anaesthesia. The concordance of the 12-lead method with continuous monitoring was 72%. The concordance of creatine kinase myocardial band isoenzyme activity with the 12-lead method was 71% and with Holter monitoring 57%. The concordance of mass concentration of creatine kinase myocardial band with 12-lead ECG recordings was 75%, and the corresponding value for Holter monitoring was 68%. The concordance of cardiac troponin T and I levels with the 12-lead method was 85% and 87%, respectively, and concordance with Holter monitoring was 72% and 66%, respectively. The postoperative 12-lead ECG identified peri-operative myocardial ischaemia associated with subsequent myocardial cell damage in most patients undergoing vascular surgery.

Preoperative cardiac evaluation

Guidelines on perioperative cardiovascular evaluation for noncardiac surgery have been published. The integration of clinical risk factors, surgery-specific risk,and functional capacity should be used to determine the need for further diagnostic evaluation. The use of beta-adrenergic blockade in high-risk patients,particularly those with documented myocardium at risk undergoing vascular surgery, has been shown to reduce perioperative risk and may obviate the need for more invasive procedures. Coronary intervention should be reserved for those patients who warrant intervention independent of the noncardiac surgery.

Cost-effectiveness of differing perioperative beta-blockade strategies in vascular surgery patients

OBJECTIVES

To determine the incremental value of different strategies of both oral and intravenous beta-blockade during the perioperative period in high-risk vascular patients in reducing costs and improving outcomes.

DESIGN

Decision analytic model incorporating costs from provider's perspective

INTERVENTIONS

Five perioperative strategies in patients undergoing abdominal aortic aneurysm surgery: (1). no routine beta-blockade, (2). preoperative oral bisoprolol for 7 days followed by perioperative intravenous metoprolol and oral bisoprolol based on preoperative titration, (3). immediate preoperative atenolol with postoperative intravenous then oral atenolol, (4). intraoperative esmolol and postoperative intravenous then oral atenolol, and (5). intraoperative and 18 hours of postoperative esmolol then atenolol.

MEASUREMENTS AND MAIN RESULTS

Perioperative death was associated with a net increase of US dollars 21909 in charges to Medicare, whereas sustaining a perioperative myocardial infarction was associated with a net increase in charges of US dollars 15000. There is a net hospital saving of US dollars 500 using a strategy of titration of an oral beta-blocker medication for a minimum of 7 days, with a net increase in efficacy of 0.0304. All of the strategies involving acute perioperative blockade were associated with a net cost savings and increase in efficacy, although less than the strategy involving preoperative oral titration.

CONCLUSION

Perioperative beta-blockade is both cost effective as well as efficacious from a short-term provider perspective. The optimal strategy of treatment for patients who do not present to surgery already on beta-blockers requires further study, although all strategies save money even accounting for pharmaceutical costs.

Sensitivity of routine intensive care unit surveillance for detecting myocardial ischemia*

OBJECTIVE

To assess the effectiveness of routine intensive care unit surveillance compared with frequent 12-lead electrocardiogram monitoring for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia in vascular surgery patients.

DESIGN

Prospective cohort trial.

SETTING

Intensive care unit.

PARTICIPANTS

We studied 149 patients undergoing elective infrainguinal or aortic vascular surgery who were admitted to the intensive care unit postoperatively.

INTERVENTIONS

Patients were simultaneously monitored with a 10-electrode/12-lead electrocardiogram obtained every 2 mins (criterion standard) and routine intensive care unit surveillance that included standard monitoring (five-electrode/two-lead electrocardiogram with ST segment trends and routine 12-lead electrocardiogram) and clinical assessment for detecting myocardial ischemia. The results of the criterion standard were not available to the caregivers.

MEASUREMENTS AND MAIN RESULTS

We measured the ability of routine intensive care unit surveillance to detect the first 20 mins of electrocardiogram evidence suggestive of myocardial ischemia, defined as ST segment depression or elevation of >/=1 mm in two consecutive leads, during the first postoperative day. Seventeen patients (11%) had electrocardiogram evidence suggestive of prolonged myocardial ischemia, the majority of which occurred in leads V2-V4. The sensitivity of routine intensive care unit surveillance for detecting the first episode of electrocardiogram evidence suggestive of prolonged myocardial ischemia in a patient was 12% (95% confidence interval, 7-17%), and the specificity was 98% (95% confidence interval, 95-100%) with a positive predictive value of 40% (95% confidence interval, 32-48%), a negative predictive value of 90% (95% confidence interval, 85-94%), a positive likelihood ratio of 6, and a negative likelihood ratio of 1. The sensitivity of routine intensive care unit surveillance for detecting all episodes was 3% (95% confidence interval, 2-3%) and the specificity 99% (95% confidence interval, 99-100%) per 20-min monitoring interval, with a positive predictive value of 17% (95% confidence interval, 16-18%), negative predictive value of 95% (95% confidence interval, 95-96%), positive likelihood ratio of 3, and negative likelihood ratio of 1.

CONCLUSIONS

Routine intensive care unit surveillance has low sensitivity for detecting electrocardiogram evidence suggestive of prolonged myocardial ischemia compared with frequent 12-lead electrocardiograms. Because detecting electrocardiogram evidence suggestive of prolonged postoperative myocardial ischemia is important, physicians should consider alternative strategies to detect myocardial ischemia.

Perioperative beta-blockers in high-risk patients

One major risk to patients in the preoperative period is that of myocardial ischemia or infarction and cardiovascular death in high-risk patients. Historically, attempts to decrease the incidence of perioperative cardiac complications have focused on preoperative evaluation and identification of patients at risk for complications with referral for additional testing and/or revascularization. Evidence suggests that the use of perioperative beta-blockers in high-risk individuals can reduce the incidence of perioperative cardiac events. The Agency for Healthcare Research and Quality has identified that the use of perioperative beta-blockers can reduce perioperative morbidity and mortality. The focus of this article is to describe the evidence supporting perioperative beta-blocker use, to discuss potential barriers to their use, and to propose a strategy to improve their use.