STEMI's, NSTEMI's and ischaemia

Question 1

Define STEMI.

Answer 1

A diagnosis made made through the observation of ST segment elevation and other signs/symptoms relevant to the condition. It should be fully confirmed through blood tests and angiography.

Question 2

What is the pathophysiology of a STEMI?

Answer 2

A STEMI occurs when a blood vessel which leads to your cardiac muscle is blocked by plaque, leading to your heart being unable to supply enough blood to the rest of your body.

Question 3

Where is the ST segment located?

Answer 3

Between the J-point and the T-wave.

Question 3

How much elevation in the ST segment is required for a STEMI to be identified?

Answer 3

2mm or more in chest leads, 1mm or more in limb leads.

Question 4

What are the sign and symptoms of an Acute Myocardial Infarction?

Answer 4

Pallor, chest pain raising into the right/both arms, nausea and vomiting. Patients can also present with epigastric pain, unexplained shortness of breath, fatigue and syncope.

Question 5

What leads show ST elevation in an inferior STEMI?

Answer 5

Leads 2, 3 and aVF.

Question 6

What leads show ST elevation in a lateral STEMI?

Answer 6

Leads 1, aVL, V5 and V6.

Question 7

What leads show ST elevation in an anterior STEMI?

Answer 7

Leads V1, V2, V3 and V4.

Question 8

How do you identify a posterior STEMI?

Answer 8

ST depression can be identified in V1-V4, so leads V7-V9 must be attached to identify ST elevation.

Question 9

What are the reciprocal changes for an inferior and a lateral STEMI?

Answer 9

Inferior: Leads 1 and aVL.
Lateral: Leads 2, 3 and aVF

Question 10

For patients with an inferior STEMI, how can Right Ventricular Infarction be suggested?

Answer 10

ST elevation in lead 1, ST depression in lead 2 or ST elevation higher in lead 3 than lead 2. Confirmation through ST elevation in lead V4R.

Question 11

Where should lead V4R be placed?

Answer 11

The 5th right intercostal space in the mid-clavicular line.

Question 12

How is a Left Coronary Mainstem identified?

Answer 12

ST elevation in lead aVR, ST depression in leads 1, 2, V4, V5, V6.

Question 13

What is the clinical difference between a STEMI and an NSTEMI?

Answer 13

A STEMI is characterized as a complete occlusion of the blood vessel, while an NSTEMI is a partial occlusion.

Question 14

What changes to an ECG do unstable angina and an NSTEMI cause?

Answer 14

Either no changes, inverted T-waves or ST depression.

Question 15

Name 2 factors influencing ischaemia and the presenting ECG.

Answer 15

Amount of myocardium suppled with blood, severity and duration of the ischaemia, electrical instability of the myocardium, the rate of development, degree and duration, and the presence or absence of collateral coronary circulation.

Question 16

What do Q-waves indicate?

Answer 16

Either a previous or current MI, due to a sign of scar tissue which has no electrical activity.

Question 17

Describe Wellen’s syndrome.

Answer 17

A clinical syndrome, indicated by biphasic or inverted T-waves in V2 and V3, as well as a history of recent chest pain.

Question 18

What can biphasic T-waves signify?

Answer 18

Ischaemia or hypokalaemia.

Question 19

How would you differentiate between an NSTEMI and unstable angina?

Answer 19

Through the identification of pathological T-waves.

Question 19

When are Q-waves considered pathological?

Answer 19

Being 1mm wide, being 2mm deep, or being 25% the depth of the QRS.