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ered at high risk for DVT and are not otherwise anti- coagulated should receive low-dose heparin prophy-

laxis, preferably with LMWH. (Level of Evidence: A)

Prevention. Deep venous thrombosis and pulmonary embolism historically were relatively frequent complications of STEMI, but in the current era in which patients with STEMI almost universally receive anticoagulants, specific prophylaxis is seldom needed (1039). For patients with CHF after STEMI who are hospitalized for prolonged periods or unable to ambulate and who are not otherwise anticoagulat- ed, the best evidence of safety and efficacy supports the use of low-dose LMWH (1040). Dosing depends on the specific LMWH chosen, and product-specific information should be consulted at the time of treatment.

Treatment. A high index of suspicion for DVT and pul- monary embolism is necessary, and patients suspected of having either condition should be evaluated immediately with an appropriate evidence-based diagnostic strategy (1041). Most patients with DVT or pulmonary embolism should be anticoagulated with LMWH. It is at least as effec- tive as UFH in clinical trials, and a meta-analysis suggests it offers a lower total mortality (1042). Outside of carefully be evaluated with noninvasive techniques, such as carotid

duplex sonography, transcranial Doppler, magnetic reso- nance angiography, CT angiography, or transesophageal echocardiography. For carotid territory symptoms and signs, evidence for a surgically important stenosis (greater than 50% linear diameter reduction on a catheter-based cerebral angiogram using the North American Symptomatic Carotid Endarterectomy Trial [NASCET] method) (1029) should clearly be sought.

The subacute to chronic pathophysiology of STEMI pro- vides a rationale for clinicians to consider when choosing antithrombotic therapies for stroke prevention and treatment in this setting. A hypercoagulable state may exist for up to 6 months after STEMI (1030). This state may be accentuated by withdrawal of heparin and warfarin therapy (555).

In ISIS-2 (1031), use of aspirin was shown to reduce the occurrence of ischemic stroke. Thus, aspirin administration after STEMI, with or without ischemic cerebral infarction, is appropriate. However, for patients with ischemic cerebral infarction who undergo PCI and have no cardioembolic risk factors, the use of clopidogrel 75 mg/d (for at least 12 months) plus aspirin 75 to 162 mg/d (indefinitely) after STEMI is reasonable (578,728,1032). Patients with STEMI who have ischemic stroke but do not undergo PCI and do not have a cardiac source of embolism or surgically important carotid stenosis may be treated with aspirin/extended-release dipyridamole 25/200 mg plus aspirin 81 mg/d (1033).

A subgroup analysis from the CAPRIE trial (1032) in patients with a prior history of ischemic events suggested a benefit of clopidogrel (mean duration of treatment 1.6 years) over aspirin for the composite end point of ischemic stroke, MI, or vascular death (3.4% ARD, 95% CI 0.2 to 7.0; 14.9% RRR; p equals 0.045). Thus, for the STEMI patient who has an ischemic stroke without a documented cardiac source of embolism while on aspirin therapy, clopidogrel may be added for a period of 18 months.

Patients with cardiogenic sources of embolism, such as AF, LV mural thrombi, or akinetic segment of the LV myocardi- um, should receive moderate-intensity (INR 2 to 3) warfarin anticoagulation in combination with aspirin. The duration of moderate-intensity warfarin anticoagulation will vary according to the underlying strong source of cardiogenic embolism. Ischemic stroke patients with pre-existing or per- sistent AF require lifelong warfarin therapy (958), irrespec- tive of 2-dimensional echocardiography findings. In general, patients with STEMI with LV mural thrombus should receive 3 months of warfarin therapy, a time believed to be suffi- ciently long for clot adherence and re-endothelialization to occur, leading to reduced embolic risk. However, if follow- up 2-dimensional echocardiography at 3 months in the STEMI patient with acute ischemic stroke shows findings that suggest an ongoing risk of cardiogenic embolism (e.g., new or enlarging mural thrombi or thrombi that are pedun- culated or mobile), then long-term moderate-intensity war- farin anticoagulation is recommended.

If a surgically important internal carotid artery stenosis that explains the clinical findings is found, either carotid

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ria. Moreover, many patients undergoing emergency surgery tend to have comorbidities and risk factors, including decreased LV function, which are normally associated with an increase in operative mortality.

Coronary artery bypass grafting early after STEMI may carry substantial risk, particularly in unstable patients with Q-wave infarction and decreased LV function. Prior CABG, female gender, and advanced age compound this risk consid- erably (1045). Lee et al. (1048) reviewed 44 365 patients from New York State undergoing CABG. Mortality for those with or without a history of MI was 3.1% and 1.6%, respec- tively. Mortality was higher for patients with transmural infarction who underwent surgery within the first 24 hours (12.1% at less than 6 hours, 13.6% at 6 to 23 hours). At 2 weeks, mortality was 2.6%. Mortality for patients with non- transmural MIs was also elevated (11.5% at less than 6 hours, 6.2% at 6 to 23 hours) (Table 31) (1048). In another large series of 2296 patients undergoing CABG after MI, Creswell et al. reported mortality from surgery to be 9.1% at less than 6 hours after MI, 8.3% at 6 to 48 hours, 5.2% at 2 to 14 days, 6.5% at 2 to 6 weeks, and 2.9% at greater than 6 weeks. Urgency of surgery was the most important predictor of operative mortality (1049). When adjustments were made for the independent risk factors of urgency of operation, increased patient age, renal insufficiency, number of previ- ous MIs, and hypertension, the timing between MI and CABG was not a significant predictor for death.

In reviewing 11 retrospective and prospective observation- al studies regarding CABG and MI, Crossman et al. (1046) concluded that timing of surgery after infarction was not necessarily an independent predictor of outcome. However, these studies did “appear to support an approach of medical stabilization for unstable patients post MI wherever possible to convert high risk emergency operations to lower risk more elective procedures” (1046). The Writing Committee believes that if stable patients with STEMI with preserved LV function require surgical revascularization, then CABG can be undertaken within several days of the infarction with- out an increased risk. In addition, surgery for patients who have mechanical complications of MI, such as VSR or pap- illary muscle rupture, or who have ongoing ischemia that has supervised clinical trials, LMWH is generally superior,

because overshooting and undershooting the therapeutic range is commonplace with UFH in routine clinical practice. Low-molecular-weight heparin is less costly overall because it avoids intravenous administration and frequent laboratory testing. Dosing of LMWH depends on the specific product, and product-specific information should be consulted at the time of treatment. Warfarin should be initiated concurrently with LMWH, and LMWH should be continued until the INR reaches the therapeutic range of 2 to 3 (1041,1043). Warfarin should be continued for a duration specific to the individual patient’s risk profile (1044). Patients with contraindications to anticoagulation with heparins will require alternative ther- apies, and some will require placement of an inferior vena cava filter. Detailed discussion of warfarin therapy duration, alternative anticoagulants, and vena cava filter placement criteria are beyond the scope of this guideline, and the read- er should consult an evidence-based guideline on venous thromboembolic disease (1041,1043).

7.10. Coronary Artery Bypass Graft Surgery

After STEMI

7.10.1. Timing of Surgery

In patients who have had a STEMI, CABG mortality is elevated for the first 3 to 7 days after infarction, and the benefit of revascularization must be balanced against this increased risk. Patients who have been stabilized (no ongoing ischemia, hemodynamic com- promise, or life-threatening arrhythmia) after STEMI and who have incurred a significant fall in LV func- tion should have their surgery delayed to allow myocardial recovery to occur. If critical anatomy exists, revascularization should be undertaken during

the index hospitalization. (Level of Evidence: B)

There are no clear data regarding optimal timing of bypass surgery after STEMI (518,1045-1047). Most published stud- ies are retrospective and observational in nature, with het- erogenous patient cohorts and differences in inclusion crite-

Table 31. Comparison of Hospital Mortality for CABG With Respect to Time of Operation: Transmural Versus Nontransmural MI

Transmural MI Nontransmural MI Time Since Operation n* Mortality, % Mortality, %

Less than 6 hours 885 12.1 11.5

6-23 hours 556 13.6 6.2

1-7 days 7554 4.3 3.5

8-14 days 6712 2.4 2.7

Greater than or equal 28 658 2.6 2.7

to 15 days

CABG = coronary artery bypass graft surgery; MI = myocardial infarction.

*Number of the 44 365 patients in the NY State Cardiac Surgery Registry who underwent CABG as the sole procedure from 1993-1996 and whose data were used in the analysis.

Modified from Lee et al. Ann Thorac Surg 2001;71:1197-202, Copyright © 2001, with permission from the Society of Thoracic

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shortly after fibrinolytic therapy, primarily for continuing myocardial ischemia, have a higher operative mortality rate (13% to 17%) and increased use of blood products (1053,1055,1056) than hemodynamically stable patients operated on within 8 hours of fibrinolytic therapy, who have a relatively low (2.8%) mortality rate (1057). The only inde- pendent predictor of perioperative mortality in TIMI-II was performance of CABG within 24 hours of entry or PCI. The low 1-year mortality rate (2.2%) noted for operative sur- vivors in this group may support the use of emergency oper- ation for selected patients, however (1053). In the SHOCK trial (301), CABG was as successful as PCI in reducing mor- tality in patients with cardiogenic shock, although they had more complex coronary artery anatomy. The intraoperative use of aprotinin may reduce hemorrhage related to use of thrombolytic agents (1058).

7.10.4. Coronary Artery Bypass Graft Surgery

for Recurrent Ischemia After STEMI

Class I

Urgent CABG is indicated if the coronary angiogram

reveals anatomy that is unsuitable for PCI. (Level of

Evidence: B)

Coronary artery bypass graft surgery should be considered when recurrent ischemia occurs in patients with STEMI whose coronary artery anatomy is not suitable for PCI. Operative mortality in such patients is correlated closely with ejection fraction, and for patients with normal ejection fraction, it is nearly the same as that of elective CABG (1059-1061). The survival benefit for patients with reduced LV function supports the use of CABG in this situation.

7.10.5. Case Selection Concerns in CABG

After STEMI

As cardiac surgical programs and individual surgeons come under scrutiny with regard to operative mortality rates, con- cern has been raised about the possibility that salvageable but high-risk patients may not be offered surgery. Omoigui et al. (1062) suggested that the reduction in mortality noted in New York State was caused by an outmigration of high-risk patients due to the increased scrutiny provoked by public release of mortality data. In a survey of New York State car- diac surgeons, Burack et al. (1063) reported that many sur- geons refused to operate on at least 1 high-risk patient over the prior year, primarily because of public reporting. The Writing Committee believes strongly that patients should be offered surgical treatment if the treating team believes that the benefits outweigh the risks and that meaningful survival of the patient could result. Furthermore, appropriately vali- dated risk-adjusted outcome measures should be used when evaluating the performance of an individual surgeon or sur- gical program. The ACC/AHA Guideline Update on Coro- nary Artery Bypass Graft Surgery has addressed the issue of institutional and individual surgical caseloads (518). Studies suggest that survival after CABG has improved over the last been unresponsive to other medical therapy and have vessels

suitable for bypass, cannot usually be delayed. However, patients who have had a significant decrease in LV function as a result of STEMI and who are hemodynamically stable may benefit from a longer period of medical treatment to allow myocardial recovery to occur before surgical revascu- larization is undertaken. If a patient has critical coronary anatomy, such as greater than 75% left main coronary artery stenosis, then CABG should be undertaken during the same hospitalization. (See Section 3.2.2 of the ACC/AHA Guidelines for Coronary Artery Bypass Graft Surgery (518).)

7.10.2. Arterial Grafting

Class I

An internal mammary artery graft to a significantly stenosed LAD should be used whenever possible in

patients undergoing CABG after STEMI. (Level of

Evidence: B)

The routine use of the left internal mammary artery (IMA) for LAD grafting, with supplemental saphenous vein grafts to other coronary lesions, is generally accepted as the stan- dard grafting method. A large, long-term follow-up study comparing patients receiving the left IMA-to-LAD and sup- plemental vein grafts to patients receiving saphenous vein grafts only demonstrated a significantly lower rate of recur- rent angina and MI, a lower incidence of reoperation or PCI, and a higher actuarial 10-year survival among patients with IMA grafts (1050). Despite the clear advantage of the IMA graft, not all patients receive arterial grafts. In the PAMI-2 trial (522) of 120 patients undergoing surgery, only 31% received an IMA graft; no patients had cardiogenic shock at the time of surgery. On the other hand, Hirose et al. (1051) used arterial conduits in 96% of 47 patients undergoing emergency CABG within a mean of 27 hours from infarc- tion, and operative mortality was 6.4%. In a further study, Hirotani et al. (1052) performed CABG on 68 patients with- in 30 days of infarction, with a mortality rate of 7.4%. CABG without arterial grafts was the sole predictor of an adverse survival. Although surgeons may be reluctant to use the IMA in patients after STEMI because of limited flow through the arterial graft and the time necessary to harvest it, the data suggest that IMA grafts can be used safely soon after STEMI with no increase in mortality; their use is associated with bet- ter long-term survival.

7.10.3. Coronary Artery Bypass Graft Surgery

After Fibrinolytic Therapy

In the 3339 patients enrolled in the TIMI-II trial, CABG was performed as an emergency procedure (1.6%) or electively (10% during initial hospitalization), primarily for left main coronary stenosis or coronary anatomy not amenable to PCI and continuing, recurrent, or exercise-induced ischemia (1053). Of the 41 021 patients enrolled in the GUSTO-I trial, CABG was used in 8.6% at a mean of 8.5 days after fibri- nolytic therapy (1054). Unstable patients undergoing CABG

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timing of surgery has not been established. The risk is great- est within the first 48 hours of infarction and decreases over the next 2 weeks. Risk of operation is greatest for patients with decreased LV function, advanced age, female sex, renal failure, peripheral vascular disease, diabetes, chronic obstructive pulmonary disease, and previous CABG (1048,1061,1065).

7.10.7. Coronary Artery Bypass Surgery

After STEMI and Antiplatelet Agents