【Anesthesia Hotspot】Perioperative myocardial infarction

Perioperative myocardial infarction case form: stage case analysis The patient, a 74-year-old female, was to undergo femoral artery-popliteal artery shunt
.

His medical history included severe hypertension, peripheral vascular disease, smoking history of 80 packs of cigarettes per year, and recently diagnosed diabetes
.

The patient successfully underwent cholecystectomy under general anesthesia 20 years ago
.

Medications currently used include lisinopril, glyburide, oxycodone, acetaminophen, and daily oral aspirin
.

The preoperative electrocardiogram showed sinus rhythm, 72 beats/min, standard voltage and left ventricular hypertrophy
.

His preoperative hemoglobin was 125 g/L and his creatinine was 1.
3 mg/dl
.

General anesthesia with tracheal intubation was planned, induced by propofol, maintained with fentanyl, N2O and isoflurane, and maintained with vecuronium bromide
.

At the same time, invasive arterial blood pressure monitoring was established
.

Initially, the patient tolerated the procedure well, and there was no evidence of myocardial ischemia on ECG monitoring (lead II and V5 with ST-segment analysis)
.

However, 1.
5 hours after surgery and blood loss of approximately 800 ml, the patient's heart rate rose to 110 beats/min and ST-segment elevation changes in ECG lead II
.

Multi-lead analysis revealed ST-segment elevation in leads II, III, and aVF
.

The patient's blood pressure slowly dropped from 135/85mmHg to 90/60mmHg over the next few minutes
.

What measures should be taken to reduce myocardial ischemia at this time? The goal of treatment of myocardial ischemia is to improve the balance between oxygen supply and demand
.

N20 should be discontinued and 100% oxygen given
.

Use volume replacement therapy and raise blood pressure with appropriate vasoconstrictors (eg, phenylephrine)
.

Drugs with beta-adrenergic activity (eg, ephedrine, epinephrine, and norepinephrine) should be avoided to avoid more severe tachycardia and increased myocardial oxygen consumption
.

Short-acting beta-blockers (eg, esmolol) can be used to slow the patient's heart rate.
The target heart rate should be close to the patient's basal heart rate, or the lowest heart rate that can be tolerated to maintain hemodynamic stability
.

At the same time, the patient's arterial blood gas, hemoglobin and blood electrolytes should be measured
.

Given the patient's preoperative hemoglobin level and intraoperative blood loss, the patient may require transfusion of packed red blood cells
.

If the above treatments fail to elevate blood pressure, lower heart rate, and relieve ST-segment changes, the patient may be in a state of cardiogenic shock due to left ventricular dysfunction or myocardial ischemia
.

What is the most likely mechanism of myocardial ischemia in this patient? The etiology of perioperative myocardial infarction is often multifaceted
.

In this patient, tachycardia, blood loss, and decreased hemoglobin content suggest that the most likely mechanism of myocardial ischemia is an imbalance between myocardial oxygen supply and consumption
.

Reflex tachycardia due to hypovolemia increases myocardial oxygen consumption
.

At the same time, the reduced oxygen-carrying capacity of the blood caused by the decreased hemoglobin content will impair myocardial oxygen supply
.

This patient's hypotension may be due to reduced myocardial preload or reduced stroke volume due to myocardial ischemia
.

What other mechanisms exist for perioperative myocardial ischemia/infarction? A considerable proportion of myocardial ischemia/myocardial infarction occurs at normal blood pressure and heart rate levels
.

Later cases mostly occur when atherosclerotic plaque ruptures resulting in platelet activation, release of vasoactive substances, thrombosis, and reduced coronary blood flow due to partial or complete vascular occlusion
.

Atheroma rupture can occur in patients with only mild coronary stenosis confirmed by coronary angiography
.

Moreover, stable plaques can acutely transform into unstable plaques, which are fragile and prone to rupture due to stress caused by local inflammation or sympathetic activation
.

Patients with large coronary atherosclerotic plaques are more likely to develop acute coronary syndrome due to multiple stress responses during surgery
.

What is the definition of myocardial infarction? The World Health Organization uses the following criteria to define myocardial infarction
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Two of the following must be present: ① typical ischemic chest pain; ② elevated serum creatine kinase (CK-MB); and/or ③ typical ECG findings, including presence and presence of pathological Q waves
.

However, in 2000, the European Federation of Cardiology and the American College of Cardiology modified the current diagnostic criteria for myocardial infarction using an increase in sensitive biochemical markers such as troponin I and T to diagnose myocardial infarction
.

Are common perioperative myocardial infarction manifestations consistent with the World Health Organization's diagnostic criteria for myocardial infarction? Typically, perioperative myocardial infarction does not have the typical chest pain presentation due to anesthetic, analgesic, or sedative use, especially in patients with postoperative tracheal intubation
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In addition, perioperative myocardial infarction rarely presents typical ECG changes, such as ST-segment elevation or Q-wave formation
.

Therefore, the detection of biochemical indicators of myocardial injury can often provide the most definite diagnosis of perioperative myocardial infarction
.

According to one study, 12% of patients had elevated cardiac troponin T (cTnT), yet only 3% met the World Health Organization criteria for myocardial infarction
.

Which biochemical markers are commonly used to diagnose perioperative myocardial infarction? Biochemical markers of myocardial injury include serum creatine kinase (CK-MB), cTnT and cTnl
.

Compared with CK-MB, cTnT and cTnI have higher sensitivity and specificity for the diagnosis of myocardial infarction
.

What are the cutoff values ​​for CK-MB and cardiac troponin in the diagnosis of myocardial infarction? CK-MB is not specific to the myocardium, and other tissues such as muscle damage can also lead to increased CK-MB, so interpretation of the clinical significance of increased CK-MB is complicated
.

Cardiac troponin is a myocardial-specific protein, but it is also released during myocardial ischemia, which does not necessarily lead to myocardial necrosis
.

Therefore, there is a lot of controversy on how to set the troponin cut-off point for the diagnosis of myocardial infarction
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Several studies suggest that even small elevations in cardiac troponin in the perioperative period can indicate myocardial injury
.

The elevation of troponin and its accompanying myocardial injury can reflect short-term or long-term mortality
.

The critical value also decreased with time, suggesting a link between mild elevation of troponin and cardiac prognosis
.

The cut-off values ​​for troponin, etc.
, vary from institution to institution
.

In patients with vascular surgery, a CK-MB increase >10% (upper limit of normal = 170 IU), cTnI >1.
5 ng/ml or cTnT >0.
1 ng/ml can be used as independent predictors of 1- and 5-year mortality after a cardiovascular event predictor
.

What are the medical treatment options for patients with perioperative myocardial infarction? Treatment of perioperative myocardial infarction is based on direct correction of the imbalance between myocardial oxygen supply and oxygen consumption
.

In the case of ensuring myocardial perfusion pressure, careful use of beta-blockers can reduce myocardial oxygen consumption
.

For perioperative myocardial infarction and myocardial ischemia, the most studied and used drugs are beta-blockers
.

Many studies have demonstrated that perioperative management can reduce adverse cardiovascular events, especially in patients with high risk factors for coronary heart disease
.

High-risk patients include those with diabetes mellitus, hypertension, and those with myocardial ischemia induced by exercise or drug testing (Table 11.
1)
.

Furthermore, beta-blockers may be of greater benefit if given several days or weeks before surgery (recommended target heart rate <65 beats/min)
.

Table 11.
1 ACC/AHA recommendations for perioperative beta-blocker use based on reported randomized clinical trials Surgery without clinical risk factors 1 or more clinical risk factors for coronary heart disease or high cardiac risk Recent beta-blocker use Vascular Stabilizer IIb, Level of Evidence BIIa, Level of Evidence B: Myocardial ischemia in patients with preoperative examination: Level I, Level of Evidence B; patients without myocardial ischemia or without preoperative examination: Level IIa, Level of Evidence Level BI, Level of Evidence B Intermediate Risk Insufficient Information Level IIb, Level of Evidence CIIa Level of Evidence Level BI, Level of Evidence C Low Risk Insufficient Information Level of Evidence Insufficient Information Level I, Level of Evidence C Aspirin in the Treatment of Acute Myocardial Infarction is of great benefit
.

Its anti-inflammatory and antiplatelet properties reduce thrombotic activity, one of the main mechanisms of plaque rupture in myocardial infarction
.

The benefit of using aspirin in the perioperative period may be enhanced given the inflammatory response that accompanies the surgery
.

A meta-analysis indicated that perioperative use of aspirin at a dose of 325 mg or less was associated with a 50% reduction in postoperative myocardial infarction
.

The relative benefit of aspirin (given by gastric tube or rectum) for secondary prevention of myocardial injury far outweighs the increased risk of surgical bleeding
.

Heparin is an important treatment for acute myocardial infarction
.

However, postoperative use of unfractionated heparin, other anticoagulants (eg, low-molecular-weight heparin or direct thrombin inhibitors such as bivalirudin), and antiplatelet agents must assess the risk of surgical wound bleeding
.

Commonly used antiplatelet drugs include clopidogrel and glycoprotein IIb/IIIa antagonists
.

Cardiologists must be consulted before the use of anticoagulants and antiplatelet drugs, and anterior myocardial infarction or left ventricular function should also be considered when other necessary treatments such as angiotensin-converting enzyme inhibitors (ACEI) are used.
incomplete situation
.

In the prevention of myocardial infarction, statins (HMG-CoA reductase inhibitors) have received much attention
.

Although preliminary studies suggest that use in the acute phase may be beneficial, the use in acute myocardial infarction requires further study
.

Preoperative use of α2-adrenergic agonists such as clonidine and dexmedetomidine may be beneficial; however, the slow onset of α2-adrenergic agonists limits their use in well-diagnosed myocardial infarction use
.

When there is ECG evidence of progression of myocardial ischemia and hemodynamically stable, nitroglycerin dilation of the coronary arteries is beneficial
.

What are the necessary management of progressive myocardial ischemia or myocardial infarction? Intra-aortic balloon placement is an important treatment for refractory or refractory myocardial infarction
.

The fundamental measure for the treatment of acute myocardial infarction is coronary recanalization
.

Thrombolytic therapy is controversial due to recent surgical incisions, and is less effective than percutaneous coronary interventions (PCI)
.

Consultation with an interventional cardiologist is necessary when acute myocardial infarction is present
.

Timely transfer of the patient to the interventional cath lab for angiography and possible coronary angioplasty, with or without stent placement, can effectively save the damaged myocardium
.

According to the ACC/AHA guidelines for perioperative cardiac evaluation in non-cardiac surgery, what is the correct strategy for assessing cardiovascular risk in such patients? The ACC/American Heart Association (AHA) classifies preoperative cardiovascular risk based on the following 3 aspects and lists the corresponding cardiac assessment protocols
.

First, available evidence of cardiac disease and/or clinical risk factors helps determine cardiac assessment (Table 11.
2, Table 11.
3)
.

Patients with pre-existing cardiac disease (the main risk factor) require further evaluation before surgery, whereas those with only clinical risk factors may or may not require further testing
.

Previous guidelines classified clinical risk factors into mild, moderate, and high risk; however, the most recent ACC/AHA guidelines have changed this stratification to a list of clinical risk factors
.

Second, assessment of patient organ function will be considered
.

Third, each procedure is appropriately classified according to the type of procedure as high (eg, cardiovascular), intermediate, and low risk (Table 11.
4)
.

According to the latest protocol, the patient has a clinical risk factor (diabetes mellitus) and is scheduled to undergo a high-risk surgery (vascular surgery)
.

The case did not describe the patient's organ function
.

In addition, physicians considered further cardiac evaluation of the patient according to guidelines and initiated perioperative beta-blockers
.

Table 11.
2 Cardiac conditions requiring further evaluation before surgery 1 .
Unstable coronary syndrome - unstable or severe angina pectoris 2.
Decompensated congestive heart failure - NY grade V grade 3.
Malignant arrhythmias, including i) high-grade AV block a) Mohs type I AV block b) third-degree AV block ii) supraventricular tachycardia c) atrial fibrillation with fast ventricular rated ) Symptomatic bradycardia e) Symptomatic ventricular arrhythmia iii) Recent onset ventricular tachycardia 4.
Severe valve disease i) Severe aortic stenosis ii) Severe mitral stenosis Table 11.
3 Clinical risk factors for perioperative cardiac events 1 .
History of ischemic heart disease 2.
History of compensated or early heart failure 3 .
History of cerebrovascular disease 4.
Diabetes 5.
Renal Insufficiency Table 11.
4 Cardiac Risk Grading Based on Type of Procedure Risk Grading Risk Grading (Risk of Cardiac Event) Type of Surgery Vascular Surgery (>5%) Aortic and Other Major Vessel Surgery Peripheral Vascular Surgery Intermediate Risk 1% to 5% Intraperitoneal and intrathoracic surgery carotid endarterectomy head and neck surgery orthopedic surgery prostate surgery low risk <1% endoscopy superficial surgery cataract surgery breast surgery outpatient surgery preoperative coronary revascularization in reducing perioperative myocardium What is the role of infarction? PCIPCI includes coronary angioplasty with or without stenting
.

Whether this technique is routinely used before elective surgery remains controversial
.

To date, no randomized clinical trials have been reported evaluating percutaneous transluminal coronary angioplasty in reducing perioperative myocardial infarction
.

There are only a few retrospective cohort studies of percutaneous transluminal coronary angioplasty for the reduction of angina symptoms and/or risk of perioperative myocardial ischemia in patients
.

Collectively, these three reports indicated a reduction in the incidence of perioperative myocardial infarction and cardiac death
.

Unfortunately, the above studies did not include an analysis of the control group
.

The placement of coronary stents, whether ordinary metal stents or drug-eluting stents, suggest that antiplatelet therapy such as aspirin and clopidogrel should be used before surgery to reduce stent thrombosis
.

The duration of dual antiplatelet therapy after PCI and coronary stenting is currently under debate
.

However, widely used antithrombotic strategies should include clopidogrel for 6 weeks and aspirin for life
.

Stent manufacturers recommend clopidogrel for at least 3 months after sirolimus-eluting stents and at least 6 months after paclitaxel-eluting stents
.

In addition, more recent studies suggest that dual antiplatelet therapy is required for more than one year after implantation of drug-eluting stents
.

Elective surgery should be postponed if the patient does not receive dual antiplatelet therapy for an adequate duration
.

The optimal management of patients who require surgery within the time window of dual antiplatelet therapy is unclear
.

Consultation with a cardiologist is essential; when clopidogrel is discontinued, a glycoprotein IIb/IIIa antagonist may be considered
.

Because of this management dilemma, the prophylactic use of PCI stenting as a strategy to reduce perioperative cardiac risk has not been supported by the literature
.

If PCI and coronary stenting have been performed before surgery, there should be at least 6 weeks before surgery
.

In drug-eluting stents, the interval is at least 12 months (Fig.
11.
1)
.

Surgical Coronary Revascularization Currently, coronary artery bypass grafting has been performed for revascularization and to reduce cardiovascular risk in high-risk patients undergoing non-cardiac surgery
.

However, the preventive coronary revascularization trial showed that coronary revascularization prior to elective vascular surgery did not improve long-term outcomes
.

Therefore, the indications for coronary revascularization prior to elective surgery should be consistent with patients undergoing coronary artery bypass grafting not intended for noncardiac surgery
.

Key information 1 .
Perioperative myocardial infarction results in a significant increase in morbidity and mortality; and costs healthcare providers billions of dollars annually
.

2.
Perioperative myocardial infarction is caused by two overlapping underlying factors: (1) myocardial oxygen consumption/oxygen supply imbalance
.

②Plaque rupture and thrombosis lead to coronary obstruction
.

3.
Perioperative myocardial infarction is often diagnosed by elevated myocardial enzymes, because the symptoms of common myocardial infarction are masked by anesthetics and analgesics; meanwhile, perioperative myocardial infarction has little or no typical ECG changes
.

4.
Perioperative use of beta-blockers has been shown to be the most effective treatment for reducing perioperative myocardial infarction, especially in high-risk patients, including those undergoing vascular surgery
.

5.
Perioperative use of aspirin and statins may also reduce the risk of perioperative myocardial infarction
.

Question 1.
What are the commonly used biochemical indicators for the diagnosis of perioperative myocardial infarction? Answer: Biochemical markers for diagnosing perioperative myocardial infarction include CK-MB and cTnT or cTnI
.

Among them, cardiac troponin is a highly specific and sensitive indicator of myocardial injury and has been shown to be more effective than CK-MB
.

2.
What are the limitations in explaining the rise in markers of myocardial injury? Answer: CK-MB is not specific to myocardial tissue, and perioperative CK-MB elevation can also have other causes (eg, muscle damage)
.

Troponin is myocardial specific, but it can also be elevated during myocardial ischemia, which does not necessarily lead to acute myocardial necrosis
.

3.
Why is aspirin used in the management of acute myocardial infarction? Answer: Aspirin has anti-inflammatory and anti-platelet aggregation effects, which play an important role in reducing the mechanism of thrombosis caused by plaque rupture in acute myocardial infarction
.

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