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Unstable Angina is a manifestation of Acute Coronary Syndrome (ACS). It is resulted from a significant impedance of the blood flow in one of the coronary arteries that nourished the myocardium. It is considered a medical emergency situation that requires transfer to the hospital for urgent management, as it may aggravate to a Heart Attack, and is associated with a high risk of death.
Elevated myocardial oxygen demand due to:
Can contribute to myocardial ischemia.
Atherosclerosis is considered the main underlying cause of unstable angina. As Atherosclerosis induces the formation of outgrowing plaque of the lipid core covered by the fibromuscular cap, that leads to narrowing in coronary arteries and subsequent myocardial ischemia. Intraplaque proteases and elastases, along with shearing forces from blood flow and endothelial wall stress, can cause moderate to large disturbances in atherosclerotic plaque that may lead to its rupture.
Exposure to collagen and other subendothelial components will activate platelet adhesion and aggregation. Platelets will release cytokines that induce vasoconstriction and lead to the activation of the coagulation cascade and the formation of a thrombus, which is further stabilized by fibrin activation. As a result, a significant coronary artery stenosis will occur, which will be sufficient to induce clinical symptoms.
Although the thrombus in unstable angina is considered to be a non-occlusive thrombus, that is not associated with myocardial infarction and cardiac biomarkers release from necrotic myocardial tissue into blood circulation, it is associated with a high risk of developing into an occlusive thrombus.
Studies have identified some genes that may be linked with unstable angina, as in chromosome 2q36-q37.3, chromosome 3q26-q27, and chromosome 20q11-13. In addition, a polymorphism in glycoprotein Ia may affect platelet aggregation timing, a polymorphism in the matrix metalloproteinase (MMP) gene is linked with poor prognosis, and some polymorphisms in interleukin-related genes are suspected to be linked with the development of unstable angina.
Patients with unstable angina are typically present with sudden retrosternal chest pain that can be radiate to the shoulders, arms, neck, or jaw. Other symptoms, such as palpitations, dyspnea, diaphoresis, dizziness, nausea and vomiting can also present. Unstable angina chest pain is known to be with persistent intensity that may get worse over time, and it is not only induced by excretion, nor completely alleviated with rest or Nitroglycerine. Lasts longer than 15 to 20 minutes.
Unstable angina may lead to hemodynamic instability and microembolism formation, which are accompanied by Stroke, Myocardial Infarction, Heart Failure, Arrhythmias, and Valvular Disease.
Thrombolysis in Myocardial Infarction (TIMI) Risk Score is used as a prognostic tool, based on a scale out of 7points.
Classification
Braunwald Classification of Unstable Angina:
Initial assessment and urgent testing must be done for the diagnosis of unstable angina and the selection of appropriate management.
References
https://www.heart.org/en/health-topics/heart-attack/angina-chest-pain/unstable-angina
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