Acute coronary syndrome (ACS) refers to a group of conditions that include ST-elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), and unstable angina. It is a type of coronary heart disease (CHD), which is responsible for one-third of total deaths in people older than 35. Some forms of CHD can be asymptomatic, but ACS is always symptomatic.
ACS is a manifestation of CHD (coronary heart disease) and usually a result of plaque disruption in coronary arteries (atherosclerosis). The common risk factors for the disease are smoking, hypertension, diabetes, hyperlipidemia, male sex, physical inactivity, family obesity, and poor nutritional practices. Cocaine abuse can also lead to vasospasm. A family history of early myocardial infarction (55 years of age) is also a high-risk factor.
CHD affects about 15.5 million in the United States. The American Heart Association estimates a person has a heart attack every 41 seconds. Heart disease is the leading cause of death in the United States. Chest pain is among the top reasons for emergency department visits.
The underlying pathophysiology in ACS is decreased blood flow to part of heart musculature which is usually secondary to plaque rupture and formation of thrombus. Sometimes ACS can be secondary to vasospasm with or without underlying atherosclerosis. The result is decreased blood flow to a part of heart musculature resulting first in ischemia and then infarction of that part of the heart.
The classic symptom of ACS is substernal chest pain, often described as crushing or pressure-like feeling, radiating to the jaw and/or left arm. This classic presentation is not seen always, and the presenting complaint can be very vague and subtle with chief complaints often being difficulty breathing, lightheadedness, isolated jaw or left arm pain, nausea, epigastric pain, diaphoresis, and weakness. Female gender, patients with diabetes, and older age are all associated with ACS presenting with vague symptoms. A high degree of suspicion is warranted in such cases.
In the physical exam, general distress and diaphoresis are often seen. Heart sounds are frequently normal. At times, gallop and murmur can be heard. Lung exam is normal, although at times crackles may be heard pointing toward associated congestive heart failure (CHF). Bilateral leg edema may be present indicating CHF. The rest of the systems are typically within normal limits unless co-pathologies are present. The presence of abdominal tenderness to palpation should make the provider consider other pathologies like pancreatitis and gastritis. The presence of unequal pulses warrants consideration of aortic dissection. The presence of unilateral leg swelling should warrant work-up for pulmonary emboli. Hence a thorough physical exam is very important to rule out other life-threatening differentials.
The first step of evaluation is an ECG, which helps differentiate between STEMI and NSTEMI unstable angina. American Heart Association guidelines maintain that any patient with complaints suspicious of ACS should get an ECG within 10 minutes of arrival. Cath lab should be activated as soon as STEMI is confirmed in a percutaneous coronary intervention (PCI) center. Cardiac enzymes especially troponin, CK-MB/CK ratio is important in assessing the NSTEMI versus myocardial ischemia without tissue destruction. A chest x-ray is useful in diagnosing causes other than MI presenting with chest pain like pneumonia and pneumothorax. The same applies for blood work like complete blood count (CBC), chemistry, liver function test, and lipase which can help differentiate intraabdominal pathology presenting with chest pain. Aortic dissection and pulmonary emboli should be kept in differential and investigated when the situation warrants. 
The initial treatment for all ACS includes aspirin (300 mg) and heparin bolus and intravenous (IV) heparin infusion if there are no contraindications to the same. Antiplatelet therapy with ticagrelor or clopidogrel is also recommended. The choice depends on local cardiologist preference. Ticagrelor is not given to the patients receiving thrombolysis.  Supportive measures like pain control with morphine/ fentanyl and oxygen in case of hypoxia are provided as required. Nitroglycerin sublingual or infusion can be used for pain relief as well. In cases of inferior wall ischemia, nitroglycerine can cause severe hypotension and should be used with extreme caution, if at all. Continuous cardiac monitoring for arrhythmia is warranted. Further Treatment of ACS depends on whether it is a STEMI /NSTEMI or unstable angina. The American Heart Association (AHA) recommends an emergent catheterization and percutaneous intervention (PCI) for STEMI with door to procedure start time of fewer than 90 minutes. A thrombolytic (tenecteplase or other thrombolytic) is recommended if there is no PCI available and the patient cannot be transferred to the catheterization lab in less than 120 minutes. AHA guideline dictates the door to needle (TNK/other thrombolytics) time to be less than 30 minutes.
NSTEMI/Unstable Angina-Symptom control is tried along with the initial treatment with aspirin, and heparin. If the patient continues to have pain, then urgent catheterization is recommended. If symptoms are controlled effectively, then a decision can be made for the timing of catheterization and other evaluation techniques including myocardial perfusion study from case to case basis depending on comorbidities. ACS always warrants admission and emergent cardiology evaluation. Computerized tomography angiography might also be utilized for further workup depending on availability and cardiologist preference.
Beta-blockers, statin, and ACE inhibitors should be initiated in all ACS cases as quickly as possible unless contraindications exist. Cases not amenable to PCI are taken for CABG (coronary artery bypass graft) or managed medically depending upon comorbidities and patient choice.
Coronary heart disease and acute coronary syndrome remain widely prevalent and still is the top cause of death in people over 35 years of age. It is essential that providers all over the world maintain a high degree of suspicion and vigilance while assessing patients with possible ACS. Along with this, public education and recognition of symptoms are crucial. Another important aspect of controlling this disease is public education about lifestyle modification and making people aware of healthier life choices. A critical aspect of STEMI and ACS timely treatment depends on adequate emergency medical services availability and training. Another crucial step of ACS control and prevention is education about lifestyle modification including smoking cessation, regular physical activity, and dietary modifications. Only through this multi-prong approach can practitioners control this high mortality disease.
ACS is associated with very high morbidity and mortality and is best managed by a multidisciplinary team that includes the emergency department physician, cardiologist, internist, pharmacist, and primary caregivers. The condition is primarily managed by the cadiologist but the prevention is managed by the primary care provider and nurse practitioner. The patient should be urged to stop smoking, maintain a healthy body weight, exercise regularly and remain compliant with the medications. The outlook for patients who are treated promptly is good but those with severe disease and non-compliance have high morbidity including premature death. (Level V)
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