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Acute Coronary Syndrome

Updated : May 17, 2024





Background

Acute coronary syndrome is a term used to describe a spectrum of conditions related to the sudden reduction or blockage of blood flow to the heart muscle. ACS is a medical emergency and typically results from the rupture of a plaque in one of the coronary arteries, which supply oxygen and nutrients to the heart. The three main types of ACS are unstable angina, non-ST segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI).

Unstable angina is the least severe form of ACS. It occurs when there is a partial blockage of a coronary artery, reducing blood flow to the heart muscle. The key feature is chest pain or discomfort that is new, more severe, occurs at rest, or lasts longer than typical angina. It does not typically result in permanent damage to the heart muscle but is a warning sign of an impending heart attack.  Non-ST Segment Elevation Myocardial Infarction is a more severe condition than unstable angina. It occurs when there is a partial or temporary blockage of a coronary artery, leading to a lack of oxygen to a portion of the heart muscle.

While it does not result in full-thickness heart muscle damage (as seen in STEMI), it can still cause damage to the heart. ST-Segment Elevation Myocardial Infarction is the most severe form of acute coronary syndrome. It is a major heart attack and occurs when a coronary artery is completely blocked by a blood clot, resulting in a significant and sustained lack of blood supply to a portion of the heart muscle. This leads to rapid heart muscle damage, and it requires immediate medical attention.

Epidemiology

Acute coronary syndrome is a leading cause of morbidity and mortality worldwide, affecting millions of people each year. The incidence can vary by region, age, and other factors, but it is a common cardiovascular emergency. The prevalence is influenced by the prevalence of risk factors such as hypertension, diabetes, smoking, and obesity.

Historically, ACS has been more common in men than in women. However, the gender gap has been narrowing, and ACS is a significant cause of death and morbidity in both genders. Some studies have suggested a seasonal pattern in ACS, with an increased incidence during winter. Cold weather and other factors may contribute to this seasonal variation.

Anatomy

Pathophysiology

In the case of acute coronary syndrome, the fundamental pathophysiological mechanism involves a reduction in blood flow to a segment of the heart muscle. This reduction in blood flow is typically a consequence of the rupture of a plaque within a coronary artery, which leads to the formation of a thrombus.

However, ACS can also, in some instances, be attributed to vasospasm, with or without underlying atherosclerotic conditions. This reduced blood flow initially results in ischemia, a condition of insufficient blood supply, and subsequently, the infarction of that specific region of the heart occurs.

Etiology

Acute Coronary Syndrome is a manifestation of coronary heart disease. It is typically an outcome of the disruption of plaques within the coronary arteries. The prevalent risk factors associated with this ailment include smoking, diabetes, high blood pressure, elevated lipid levels, sedentary lifestyle, familial obesity, and poor dietary habits.

Furthermore, the abuse of cocaine can induce vasospasms, exacerbating the risk. Additionally, a family history of early myocardial infarction (occurring before age 55) also represents a significant risk factor.

Genetics

Prognostic Factors

Clinical History

ACS typically occurs in individuals with risk factors such as a history of coronary artery disease (CHD), smoking, hypertension, diabetes, hyperlipidemia, and a family history of heart disease. Previous episodes of angina or heart attacks may be present. Patients may have new or worsening chest pain or discomfort, often described as a crushing, squeezing, or pressure-like sensation, shortness of breath, nausea or vomiting, and diaphoresis.

Acute coronary syndrome typically has a sudden and acute onset. Symptoms may be persistent or intermittent, with episodes of rest angina, exertional angina, or both. The exact presentation of ACS can differ among individuals, and not everyone will have the same set of symptoms.

Physical Examination

Patients with ACS often exhibit general distress and diaphoresis. Heart sounds are usually normal, but in some cases, healthcare providers may detect additional sounds like gallops or murmurs. Lung examination typically reveals no abnormalities, though crackles may be heard in some cases, suggesting associated congestive heart failure. Bilateral leg swelling or edema may be present, which can be indicative of CHF.

Evaluations of other body systems typically yield results within normal limits unless there are concurrent medical conditions. When abdominal tenderness is noted upon palpation, healthcare providers should consider the possibility of other conditions, such as pancreatitis or gastritis. The presence of unequal pulses should raise suspicion of aortic dissection, warranting further evaluation. If unilateral leg swelling is detected, a thorough work-up for pulmonary emboli is advisable.

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Acute pericarditis

Aortic stenosis

Anxiety disorders

Asthma

Dilated cardiomyopathy

Esophagitis

Myocardial infarction

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

The management of Acute Coronary Syndrome (ACS) revolves around swift and precise interventions to alleviate symptoms, restore blood flow to the heart, and reduce cardiac damage. Key steps include immediate medical assessment and diagnosis through ECG and cardiac biomarker tests, followed by oxygen therapy, pain relief with nitroglycerin and opioids, and administration of antiplatelet and anticoagulant medications.

Depending on the type of ACS (STEMI or NSTEMI), revascularization procedures like primary percutaneous coronary intervention (PCI) or thrombolytic therapy may be employed. Beta-blockers, ACE inhibitors or ARBs, and statins are used for long-term management, with a focus on lifestyle modifications and cardiac rehabilitation. Psychological support complements these strategies to address the emotional impact of ACS, ensuring comprehensive care and better patient outcomes.

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

STEMI: Urgent revascularization is the goal. This can be achieved through primary percutaneous coronary intervention (PCI) or thrombolytic therapy. PCI is preferred if available within a timely window.

NSTEMI: An early invasive strategy, involving coronary angiography and PCI if indicated, is commonly employed.

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Lifestyle Modifications

Encourage patients to make lifestyle changes, such as quitting smoking, adopting a heart-healthy diet, losing weight if necessary, and managing underlying risk factors like hypertension and diabetes. 

Administration of pharmaceutical agent

Antiplatelet and Anticoagulant Therapy: 

Aspirin is administered promptly to inhibit platelet aggregation. Additional antiplatelet agents like P2Y12 inhibitors (e.g., clopidogrel, ticagrelor, or prasugrel) are initiated. Anticoagulants such as heparin or enoxaparin are given to prevent further clot formation. 

Beta-Blockers: 

Beta-blockers, like metoprolol, may be administered to reduce heart rate, blood pressure, and myocardial oxygen demand, especially if the patient is stable. 

Statin Therapy: 

Statins, such as atorvastatin or rosuvastatin, are initiated or continued to lower cholesterol levels and reduce the risk of future events. 

ACE Inhibitors or ARBs: 

Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) may be prescribed in the subacute phase to improve cardiac function and reduce the risk of complications. 

Medication

 

ticagrelor

Loading dose (following ACS event): 180 mg orally, single dose
The maintenance dose (for 1st 12 months after diagnosis): 90 mg orally two times
The maintenance dose (after 12 months from diagnosis): 60 mg orally two times
Also, continue with aspirin 75-100 mg



tirofiban 

25

mcg/kg

Solution

Intravenous (IV)

5

minutes



eptifibatide 

180

mcg/kg

Solution

Intravenous (IV)

1 - 2

minutes

Later, 2 mcg/kg/min intravenously for 72 hours



prasugrel 

Initial dose
:

60

mg

Tablet

Orally 

once a day


Maintenance dose: 10mg/day orally combined with 81-325mg/day aspirin



clopidogrel 

Non-ST-Elevation Myocardial Infarction (NSTEMI)
Loading dose:

300

mg

Tablet

Orally 

every day


Maintenance dose: 75 mg orally daily

ST-Elevation Myocardial Infarction (STEMI)
Loading dose: 300 mg orally daily
Maintenance dose: 75 mg orally daily with/without thrombolytics



heparin 

PCI
Without the GPIIb or IIIa inhibitor: 70 to 100 unit/kg Intravenous bolus initially
With GPIIb or IIIa inhibitor: 50 to 70 units/kg Intravenous bolus initially
STEMI
Patient who are on fibrinolytics: IV bolus of 60 units/kg (maximum: 4000 units), following 12 units/kg in hour as continuous IV infusion (max 1000 units/hr)
The dose must be adjusted to keep the aPTT between 50 to 70 seconds
NSTEMI/Unstable Angina
6 to 70 units/kg intravenous bolus initially (maximum: 5000 units), following 12-15 units/kg in hour intravenous infusion initially (maximum: 1000 units/hr)
The dose must be adjusted to keep the aPTT between 50 to 70 secs
Dosing considerations
There are several concentrations available; extreme caution is necessary to prevent a medication error



nadroparin 

Administer initial dose of 86 anti-Xa units/kg intravenously once bolus and the maximum dose not more than 9500 anti-Xa units
Fixed dosing:
<50 kg: dose of 3800 anti-Xa units once intravenous bolus
≥100 kg: dose of 9500 anti-Xa units once intravenous bolus
Administer maintenance dose of 86 anti-Xa units/kg subcutaneously each 12 hours and the maximum total daily dose not more than 19000 anti-Xa units
Fixed dosing:
<50 kg: dose of 3800 anti-Xa units subcutaneously each 12 hours
≥100 kg: dose of 9500 anti-Xa units subcutaneously each 12 hours



 
 

prasugrel 

Acute Coronary Syndrome
<75 years:
Loading dose: 60mg orally
Maintenance dose: 10mg/day orally combined with 81-325mg/day aspirin
>75 years:
Not recommended due to intracranial bleeding



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References

Acute Coronary Syndrome

Updated : May 17, 2024




Acute coronary syndrome is a term used to describe a spectrum of conditions related to the sudden reduction or blockage of blood flow to the heart muscle. ACS is a medical emergency and typically results from the rupture of a plaque in one of the coronary arteries, which supply oxygen and nutrients to the heart. The three main types of ACS are unstable angina, non-ST segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI).

Unstable angina is the least severe form of ACS. It occurs when there is a partial blockage of a coronary artery, reducing blood flow to the heart muscle. The key feature is chest pain or discomfort that is new, more severe, occurs at rest, or lasts longer than typical angina. It does not typically result in permanent damage to the heart muscle but is a warning sign of an impending heart attack.  Non-ST Segment Elevation Myocardial Infarction is a more severe condition than unstable angina. It occurs when there is a partial or temporary blockage of a coronary artery, leading to a lack of oxygen to a portion of the heart muscle.

While it does not result in full-thickness heart muscle damage (as seen in STEMI), it can still cause damage to the heart. ST-Segment Elevation Myocardial Infarction is the most severe form of acute coronary syndrome. It is a major heart attack and occurs when a coronary artery is completely blocked by a blood clot, resulting in a significant and sustained lack of blood supply to a portion of the heart muscle. This leads to rapid heart muscle damage, and it requires immediate medical attention.

Acute coronary syndrome is a leading cause of morbidity and mortality worldwide, affecting millions of people each year. The incidence can vary by region, age, and other factors, but it is a common cardiovascular emergency. The prevalence is influenced by the prevalence of risk factors such as hypertension, diabetes, smoking, and obesity.

Historically, ACS has been more common in men than in women. However, the gender gap has been narrowing, and ACS is a significant cause of death and morbidity in both genders. Some studies have suggested a seasonal pattern in ACS, with an increased incidence during winter. Cold weather and other factors may contribute to this seasonal variation.

In the case of acute coronary syndrome, the fundamental pathophysiological mechanism involves a reduction in blood flow to a segment of the heart muscle. This reduction in blood flow is typically a consequence of the rupture of a plaque within a coronary artery, which leads to the formation of a thrombus.

However, ACS can also, in some instances, be attributed to vasospasm, with or without underlying atherosclerotic conditions. This reduced blood flow initially results in ischemia, a condition of insufficient blood supply, and subsequently, the infarction of that specific region of the heart occurs.

Acute Coronary Syndrome is a manifestation of coronary heart disease. It is typically an outcome of the disruption of plaques within the coronary arteries. The prevalent risk factors associated with this ailment include smoking, diabetes, high blood pressure, elevated lipid levels, sedentary lifestyle, familial obesity, and poor dietary habits.

Furthermore, the abuse of cocaine can induce vasospasms, exacerbating the risk. Additionally, a family history of early myocardial infarction (occurring before age 55) also represents a significant risk factor.

ACS typically occurs in individuals with risk factors such as a history of coronary artery disease (CHD), smoking, hypertension, diabetes, hyperlipidemia, and a family history of heart disease. Previous episodes of angina or heart attacks may be present. Patients may have new or worsening chest pain or discomfort, often described as a crushing, squeezing, or pressure-like sensation, shortness of breath, nausea or vomiting, and diaphoresis.

Acute coronary syndrome typically has a sudden and acute onset. Symptoms may be persistent or intermittent, with episodes of rest angina, exertional angina, or both. The exact presentation of ACS can differ among individuals, and not everyone will have the same set of symptoms.

Patients with ACS often exhibit general distress and diaphoresis. Heart sounds are usually normal, but in some cases, healthcare providers may detect additional sounds like gallops or murmurs. Lung examination typically reveals no abnormalities, though crackles may be heard in some cases, suggesting associated congestive heart failure. Bilateral leg swelling or edema may be present, which can be indicative of CHF.

Evaluations of other body systems typically yield results within normal limits unless there are concurrent medical conditions. When abdominal tenderness is noted upon palpation, healthcare providers should consider the possibility of other conditions, such as pancreatitis or gastritis. The presence of unequal pulses should raise suspicion of aortic dissection, warranting further evaluation. If unilateral leg swelling is detected, a thorough work-up for pulmonary emboli is advisable.

Acute pericarditis

Aortic stenosis

Anxiety disorders

Asthma

Dilated cardiomyopathy

Esophagitis

Myocardial infarction

The management of Acute Coronary Syndrome (ACS) revolves around swift and precise interventions to alleviate symptoms, restore blood flow to the heart, and reduce cardiac damage. Key steps include immediate medical assessment and diagnosis through ECG and cardiac biomarker tests, followed by oxygen therapy, pain relief with nitroglycerin and opioids, and administration of antiplatelet and anticoagulant medications.

Depending on the type of ACS (STEMI or NSTEMI), revascularization procedures like primary percutaneous coronary intervention (PCI) or thrombolytic therapy may be employed. Beta-blockers, ACE inhibitors or ARBs, and statins are used for long-term management, with a focus on lifestyle modifications and cardiac rehabilitation. Psychological support complements these strategies to address the emotional impact of ACS, ensuring comprehensive care and better patient outcomes.

STEMI: Urgent revascularization is the goal. This can be achieved through primary percutaneous coronary intervention (PCI) or thrombolytic therapy. PCI is preferred if available within a timely window.

NSTEMI: An early invasive strategy, involving coronary angiography and PCI if indicated, is commonly employed.

Encourage patients to make lifestyle changes, such as quitting smoking, adopting a heart-healthy diet, losing weight if necessary, and managing underlying risk factors like hypertension and diabetes. 

Antiplatelet and Anticoagulant Therapy: 

Aspirin is administered promptly to inhibit platelet aggregation. Additional antiplatelet agents like P2Y12 inhibitors (e.g., clopidogrel, ticagrelor, or prasugrel) are initiated. Anticoagulants such as heparin or enoxaparin are given to prevent further clot formation. 

Beta-Blockers: 

Beta-blockers, like metoprolol, may be administered to reduce heart rate, blood pressure, and myocardial oxygen demand, especially if the patient is stable. 

Statin Therapy: 

Statins, such as atorvastatin or rosuvastatin, are initiated or continued to lower cholesterol levels and reduce the risk of future events. 

ACE Inhibitors or ARBs: 

Angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) may be prescribed in the subacute phase to improve cardiac function and reduce the risk of complications. 

ticagrelor

Loading dose (following ACS event): 180 mg orally, single dose
The maintenance dose (for 1st 12 months after diagnosis): 90 mg orally two times
The maintenance dose (after 12 months from diagnosis): 60 mg orally two times
Also, continue with aspirin 75-100 mg



tirofiban 

25

mcg/kg

Solution

Intravenous (IV)

5

minutes



eptifibatide 

180

mcg/kg

Solution

Intravenous (IV)

1 - 2

minutes

Later, 2 mcg/kg/min intravenously for 72 hours



prasugrel 

Initial dose
:

60

mg

Tablet

Orally 

once a day


Maintenance dose: 10mg/day orally combined with 81-325mg/day aspirin



clopidogrel 

Non-ST-Elevation Myocardial Infarction (NSTEMI)
Loading dose:

300

mg

Tablet

Orally 

every day


Maintenance dose: 75 mg orally daily

ST-Elevation Myocardial Infarction (STEMI)
Loading dose: 300 mg orally daily
Maintenance dose: 75 mg orally daily with/without thrombolytics



heparin 

PCI
Without the GPIIb or IIIa inhibitor: 70 to 100 unit/kg Intravenous bolus initially
With GPIIb or IIIa inhibitor: 50 to 70 units/kg Intravenous bolus initially
STEMI
Patient who are on fibrinolytics: IV bolus of 60 units/kg (maximum: 4000 units), following 12 units/kg in hour as continuous IV infusion (max 1000 units/hr)
The dose must be adjusted to keep the aPTT between 50 to 70 seconds
NSTEMI/Unstable Angina
6 to 70 units/kg intravenous bolus initially (maximum: 5000 units), following 12-15 units/kg in hour intravenous infusion initially (maximum: 1000 units/hr)
The dose must be adjusted to keep the aPTT between 50 to 70 secs
Dosing considerations
There are several concentrations available; extreme caution is necessary to prevent a medication error



nadroparin 

Administer initial dose of 86 anti-Xa units/kg intravenously once bolus and the maximum dose not more than 9500 anti-Xa units
Fixed dosing:
<50 kg: dose of 3800 anti-Xa units once intravenous bolus
≥100 kg: dose of 9500 anti-Xa units once intravenous bolus
Administer maintenance dose of 86 anti-Xa units/kg subcutaneously each 12 hours and the maximum total daily dose not more than 19000 anti-Xa units
Fixed dosing:
<50 kg: dose of 3800 anti-Xa units subcutaneously each 12 hours
≥100 kg: dose of 9500 anti-Xa units subcutaneously each 12 hours



prasugrel 

Acute Coronary Syndrome
<75 years:
Loading dose: 60mg orally
Maintenance dose: 10mg/day orally combined with 81-325mg/day aspirin
>75 years:
Not recommended due to intracranial bleeding