Acute Coronary Syndrome

Acute Coronary Syndrome (ACS) is defined as a broad category of acute myocardial events which broadly fall under three categories: STEMI, Non-STEMI and Unstable Angina. The term Acute Coronary Syndrome has recently replaced  other more specific terms which have been previously used to describe problems with the heart, such as acute myocardial infarction, heart attack, transmural and non-transmural myocardial infarction.

Acute Coronary Syndrome is almost always secondary to a rupture of an artherosclerotic plaque and subsequent coronary artery thrombosis, resulting in myocardial ischemia.

Acute Coronary Syndrome falls under the following three categories:

1. STEMI (ST -Elevation Myocardial Infarction)

2.Non-STEMIO (Non-ST Elevation Myocardial Infarction) and

3. Unstable Angina

STEMI Definition

A STEMI can be defined as a myocardial infarction, in which an ECG (EKG if you’re American) identifies a raise in the ST segment of the ECG in two or more continguous leads (views of the similar apsect of the heart from a different angle). Each ST elevation must be greater than or equal to 2mm in the vector leads (augmented leads) and greater than 1mm in the limb leads. A STEMI identifies current infarction to the myocardium as a result of ischemia (most likely due to a rupture of atherosclerotic plaque with subsequent coronary thrombosis).

Non-STEMI Definition

A non-STEMI can be defined as an acute myocardial infaction, in which the ECG does not show any changes, or significant changes to the ST segment of the ECG. The reason that a Non-STEMI may not show acute changes to the ST segment of the ECG includes: infarction in an un-seen/unusual part of the heart, or complications.

Unstable Angina

Angina is common in people who have coronary artery disease and is a disease process involving long-term atherosclerotic plaque build up resulting in a reduction of less than 25% of normal coronary artery blood flow. As a result, the heart is not able to compensate for any increased blood flow requirements, due to exercise, stress or any other level of exertion. In unstable angina, this reduction in coronary blood flow has become so significant that, without the disruption of a atherosclerotic plaque, it may still cause ischemia to the myocardium and a subsequent myocardial infarct.

Here is a link to a video about Acute Coronary Syndrome:

httpv://www.youtube.com/watch?v=ZSmuilMhwvk

Acute Coronary Syndrome Management

Acute coronary syndrome management includes the following steps:

1. Reasure the patient – no point having their heart work any harder than it already is. Fear has been identified as one of the greatest stresses placed on the heart during an Acute Coronary Syndrome.

2. Place the patient at rest – this allows the patient to rellax, and not utilise as much energy (this is why we try our best to avoid walking patients with chest pain).

3. Administer oxygen – this provides an increase in inspired oxygen partial pressures, which, in theory decreases the amount the heart has to work to get oxygen. There is currently some research that suggests that oxygen is actually counter-productive in suspected acute coronary syndrome patients, because oxygen is a potent vaso-constrictor, and may cause vaso-constriction to the coronary arteries. Currently, however, all Australian Ambulance services and medical guidelines indicate oxygenation for patients with chest pain.

4. Administer aspirin (acetylsalicylic acid) – 150mg-300mg per oral, which stops platelet aggregation (makes the blood less sticky).

5. Administer GTN (glycerin-tri-nitrate) – 600 mcg sub-lingually, which causes vaso-dilation and theoretically opens up the obstructed coronary arteries. It also reduces preload to the heart, which in turn reduces the stress placed on the heart during left ventricular contractions.

6. Morphine – 2.5 mg IV increments to titrate patients pain and comfort levels.

7. 12 Lead ECG – This should be done as early as is practical and repeated regularly so that serial ECGs can be reviewed for signs of ischemia progression.

8. Bloods should be taken early to assess for troponin I and T level changes, CK levels, and recent studies have show benefits assessing elevated B-type natriuretic peptides, which are associated with the presence of myocardial ischemia. However, the accuracy of B-type natriuretic peptides does not seem to be high enough for use in clinical use currently in Australia.

9. Other causes of chest pain should be considered and ruled out.