Lesson topic №24. ОКС (Acute Coronary Syndrome )
.pdfMedical Care and Coronary Interventions
Medical Care
Initial therapy for acute coronary syndrome should focus on stabilizing the patient's condition, relieving ischemic pain, and providing antithrombotic therapy to reduce myocardial damage and prevent further ischemia.
Morphine (or fentanyl) for pain control, oxygen, sublingual and/or intravenous nitroglycerin, soluble aspirin 162-325 mg, and clopidogrel with a 300to 600-mg loading dose are given as initial treatment.
Humidified oxygen may reduce the risk of nosebleeds in patients with acute coronary syndrome who are receiving antiplatelet and antithrombin therapy.
Do not administer nitrates if the patient is hypotensive (systolic BP <90 mm Hg); if right ventricular infarction, large pericardial effusion, or severe aortic stenosis is suspected; or if the patient recently received phosphodiesterase-5 inhibitors (eg, sildenafil).
Patients with known hypersensitivity to antiplatelet agents, active internal bleeding, and bleeding disorders should not receive antiplatelet or antithrombotic therapy.
High-risk patients with non–ST-segment elevation myocardial infarction (NSTEMI) acute coronary syndrome should receive aggressive care, including aspirin, clopidogrel, unfractionated or low molecular weight heparin (LMWH), intravenous platelet glycoprotein IIb/IIIa complex blockers (eg, tirofiban, eptifibatide), and a beta-blocker. The goal is early revascularization.
Intermediate–risk patients with NSTEMI acute coronary syndrome should rapidly undergo diagnostic evaluation and further assessment to determine their appropriate risk category.
Low-risk patients with NSTEMI acute coronary syndrome should undergo further follow-up with biomarkers and clinical assessment. Optimal medical therapies include use of standard medical therapies, including beta-blockers, aspirin, and unfractionated heparin or LMWH. The CURE study has shown that clopidogrel would be beneficial even in low-risk patients.10 If no further pain occurs, and follow-up studies are negative, a stress study should drive further management.
First-line therapy in patients with chest pain regardless of their risk strategy includes a combination of oxygen, aspirin, nitroglycerin, and morphine.
Mehta et al studied 3031 patients with acute coronary syndromes. Early intervention (coronary angiography 24 h after randomization; median time 14 h) in acute coronary syndromes did not differ greatly from delayed intervention (coronary angiography >24 h randomization; median time 50 h) in preventing the primary outcome (ie, composite of death, myocardial infarction, or stroke at 6 mo). Early intervention did reduce the rate of the secondary outcome (ie, death, myocardial infarction, or refractory ischemia at 6 mo) and improved the primary outcome in patients who were at highest risk (ie, Global Registry of Acute Coronary Events [GRACE] risk score >140).11
Anti-ischemic therapy
Nitrates do not improve mortality.
However, they provide symptomatic relief by means of several mechanisms, including
coronary vasodilation, improved collateral blood flow, decrease in preload
(venodilation and reduced venous return), and decrease in afterload (arterial
vasodilation).
Care should be taken to avoid hypotension because this can potentially reduce coronary perfusion pressure (diastolic BP - left ventricular diastolic pressure).
Beta-blockers are indicated in all patients unless they have the following contraindications:
Hypotension
Shock
Severe bradycardia
High-grade atrioventricular block Severe obstructive pulmonary disease
Beta-blockers reduce oxygen demand and ventricular wall tension.
They also decrease mortality and adverse cardiovascular events.
These drugs may prevent mechanical complications of myocardial infarction, including rupture of the papillary
muscle, left ventricular free wall, and ventricular septum.
Beta-blockers meliorate dynamic obstruction of the left ventricular outflow tract in patients with apical infarct
and hyperdynamic basal segments.
The most frequently used regimen is intravenous metoprolol 2-5 mg given every 5 minutes (up to 15 mg total) followed by 25-100 mg given orally twice a day.
Beta-blockers should not be used acutely in patients with cardiogenic shock or signs of heart failure on
presentation.
Antithrombotic therapy
Aspirin permanently impairs the cyclooxygenase pathway of thromboxane A2 production in platelets and, thus,
inhibits platelet function. Aspirin reduces morbidity and mortality and is continued indefinitely.
Clopidogrel (thienopyridine) inhibits adenosine 5'-diphosphate (ADP)–dependent activation of the glycoprotein
IIb/IIIa complex, a necessary step for platelet aggregation.
This process results in intense inhibition of platelet function, particularly in combination with aspirin.
In the Clopidogrel in Unstable Angina to Prevent Recurrent Events (CURE) trial, thienopyridine reduced the rate of
myocardial infarction by 20%.
Clopidogrel is a class I recommendation for patients when early noninterventional approach is planned in therapy for at least 1 month to as long as 9 months.
When percutaneous coronary intervention (PCI) is planned, clopidogrel is started and continued for at least 1 month
and up to 9 months, if the patient is not at high risk for bleeding.
The optimal dosage for clopidogrel is still being evaluated. Reports show that a loading dose of 600 mg might be more beneficial than 300 mg.
Withhold clopidogrel for at least 5 days before elective coronary artery bypass grafting (CABG).
Anticoagulation
Unfractionated heparin was associated with a 33% reduction in the risk of myocardial infarction or death in patients with unstable angina who were treated with aspirin plus heparin compared with aspirin alone.
LMWHs might be superior to heparin in reducing cardiovascular outcomes with a safety profile similar to that
of heparin in patients receiving medical care.
In summary, for patients in whom an invasive strategy is selected, regimens with established efficacy include
enoxaparin and unfractionated heparin (Class I, Level of Evidence:
A) and bivalirudin and fondaparinux (Level of Evidence:
B). For patients in whom a conservative strategy is selected, regimens using either enoxaparin or UFH (Class I,
Level of Evidence: A) or fondaparinux (Level of Evidence: B) have established efficacy.
In patients in whom a conservative strategy is selected and who have an increased risk of bleeding, fondaparinux is preferable (Level of Evidence: B).
For unstable angina/NSTEMI patients in whom an initial conservative strategy is selected, fondaparinux is
preferable to UFH as anticoagulant therapy unless CABG is planned within 24 hours (Class IIa, Level of Evidence:
B).
Thrombolysis
Thrombolysis has no role in NSTEMI acute coronary syndrome.
Consultations
Diet
Patients should receive nothing by mouth (NPO) until their condition is stabilized and treated.
Maintain the patient's NPO status from midnight before cardiac catheterization if it is being considered.
After initial therapy and admission, a dietitian should instruct the patient regarding an appropriate diet, as recommended by the AHA. A low-salt, low-fat, and low-cholesterol diet is generally recommended.
Activity
Limit patients to bed rest to minimize their oxygen consumption until reperfusion and initial therapy are complete. After that, the patient's activity may slowly be increased as tolerated and as the clinical situation allows.
Start cardiac rehabilitation before the patient is discharged.
Further inpatient care
Patients may receive additional care in a telemetry-monitored unit if their condition is stable. Carefully monitor patients for arrhythmia, recurrent ischemia, and other possible complications. If patients have not undergone
cardiac catheterization and if they have no complications, an ischemia-driven approach to PCI can be taken.
Patient Education
The mnemonic ABCDE might be helpful.
A = Aspirin and antianginals
B = Beta-blockers and BP
C = Cholesterol and cigarettes
oEducate all patients who have had a myocardial infarction about the critical role of smoking in the development of coronary artery disease.
oSmoking-cessation classes should be offered to help patients avoid smoking after a myocardial infarction.
oCigarette smoking is a major risk factor for coronary artery disease. The risk of recurrent coronary events decreases 50% at 1 year after smoking cessation.
oProvide all patients who smoke with guidance, education, and support to avoid smoking.
oBupropion increases the likelihood of successful smoking cessation.
D = Diet and diabetes
oDiet plays an important role in the development of coronary artery disease.
o
o
Educate patients who have had a myocardial infarction about the role of a low-cholesterol and lowEducate patients about AHA dietary guidelines regarding a low-fat, low-cholesterol diet.
oA dietitian should see and evaluate all patients who have had a myocardial infarction before they are discharged.
E = Exercise and education
oA cardiac rehabilitation program after discharge might reinforce education and enhance compliance.
oFailure to diagnose a myocardial infarction is the leading cause of litigation against emergency physicians and cardiologists.
oConsider the possibility of atypical presentations in women, elderly patients, and patients with diabetes.
o ECGs should be reviewed promptly.
oEarly imaging is useful to assess wall-motion abnormalities in difficult cases with nondiagnostic ECGs, such as those involving a left bundle-branch block.
o Involve a cardiologist when in doubt.
Elderly patients
o Elderly patients are at increased risk for adverse outcomes.
oDecisions about their care should reflect considerations of their general health, cognitive status, and life expectancy.
oAltered pharmacokinetics and sensitivity to drugs are other issues to be considered.
Women
oWomen with acute coronary syndrome should be cared for as men are.
oLike their male counterparts, women with unstable angina and/or NSTEMI should receive aspirin and clopidogrel.
oIndications for testing are similar in men and women.
Patients with diabetes mellitus
oOutcomes are worse in patients with diabetes than in those without diabetes.
o Tight glycemic control should be maintained.
Patients who have undergone CABG
o Medical treatment should follow the same guidelines as those established for patients who have not undergone CABG.
o Have a low threshold for catheterization in patients with acute coronary syndrome who underwent CABG.
Patients with cocaine use
o Give nitroglycerin and oral calcium antagonists for patients with STEMI or depression that accompanies chest discomfort.
oImmediately perform catheterization if ST elevation persists after the administration of nitroglycerin and calcium channel blockers.
Patients with Prinzmetal angina
oPerform angiography in patients with episodic chest pain and ST-segment elevation that resolves with nitroglycerin and/or calcium channel blockers.
oAdminister nitrates and calcium channel blockers in patients whose catheterization does not show obstructive coronary artery disease.
Patients with syndrome X
oOffer reassurance, and provide medical therapy with nitrates, beta-blockers, and calcium channel blockers alone or in combination.