ACUTE CORONARY SYNDROME AND MYOCARDIAL INFARCTION

INTRODUCTION: Acute coronary syndrome (ACS) is an emergent situation characterized by an acute onset of myocardial ischemia that results in myocardial death, also known as myocardial infarction [MI]) if definitive interventions do not occur promptly. Although the terms coronary occlusion, heart attack, and MI are used synonymously, the preferred term is MI.  In unstable angina, there is reduced blood flow in a coronary artery, often due to rupture of an atherosclerotic plaque, but the artery is not completely occluded. This is an acute situation that is sometimes referred to as pre-infarction angina because the patient will likely have an MI if prompt interventions do not occur.

MYOCARDIAL INFARCTION: In an MI, an area of the myocardium is permanently destroyed, typically because plaque rupture and subsequent thrombus formation result in complete occlusion of the artery.

Vasospasm (sudden constriction or narrowing) of a coronary artery, decreased oxygen supply such as, from acute blood loss, anemia, or low blood pressure, and increased demand for oxygen for example, from a rapid heart rate, thyrotoxicosis, or ingestion of cocaine are other causes of MI.

In each case, a profound imbalance exists between myocardial oxygen supply and demand. An MI may be defined by the type, the location of the injury to the ventricular wall, or by the point in time in the process of infarction (acute, evolving, old).

CLINICAL MANIFESTATIONS: In many cases, the signs and symptoms of MI cannot be distinguished from those of unstable angina, hence, the evolution of the term ACS.

1) Chest pain that occurs suddenly and continues despite rest and medication is the primary presenting symptom.

2) Some patients have prodromal symptoms or a previous diagnosis of coronary artery disease (CAD), but about half report no previous symptoms.

3) Patient may present with a combination of symptoms, including chest pain, shortness of breath, indigestion, nausea, and anxiety.

4) Patient may have cool, pale, and moist skin; heart rate and respiratory rate may be faster than normal. These signs and symptoms, which are caused by stimulation of the sympathetic nervous system, may be present for only a short time or may persist.

ASSESSMENT AND DIAGNOSTIC METHODS: Patient history (description of presenting symptom; history of previous illnesses and family health history, particularly of heart disease). Previous history should also include information about patient’s risk factors for heart disease. Electrocardiography (ECG) within 10 minutes of pain onset or arrival at the emergency department; echocardiography to evaluate ventricular function. Cardiac enzymes and biomarkers (creatine kinase isoenzymes, myoglobin, and troponin).

MEDICAL MANAGEMENT: The goals of medical management are to minimize myocardial damage, preserve myocardial function, and prevent complications such as lethal dysrhythmias and cardiogenic shock. Reperfusion via emergency use of thrombolytic medications or percutaneous coronary intervention (PCI). Reduce myocardial oxygen demand and increase oxygen supply with medications, oxygen administration, and bed rest. Coronary artery bypass or minimally invasive direct coronary artery bypass (MIDCAB).

PHARMACOLOGIC THERAPY: Nitrates (nitroglycerin) to increase oxygen supply. Anticoagulants (aspirin, heparin). Analgesics (morphine sulfate). Angiotensin-converting enzyme (ACE) inhibitors. Beta-blocker initially, and a prescription to continue its use after hospital discharge.

RELATED;

1.  ANGINA PECTORIS  

2.  CONGESTIVE HEART FAILURE

3.  HYPERTENSION

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