Introduction to 12-Lead ECG Ischemia, Injury & Infarction

Overview

Click To Begin 12-Lead ECG Ischemia, Injury & Infarction Training

Overview

Ischemia, Injury & Infarction

Tech Series
ECG Interpretation

Thomas E. O'Brien
AS CCT CRAT RMA

Learning Objectives

Upon completion of the accompanying narrative and practice the student will be able to:

  • Associate the views of a 12-Lead ECG with specific surfaces and the primary artery to that region of the heart
  • Know the difference between indicative and reciprocal views
  • Measure and recognize electrocardiographic changes caused by STEMI
    • ischemia
    • injury
    • infarction

12-Lead ECG

  • People may choose to analyze ECG’s in a number of different ways. The sequence doesn’t necessarily matter as long as you gather and report the proper information each time. I read from left to right as much as possible (in anatomic groupings).
  • If your protocols are different, always follow them.
  • The following slides will review the leads, surfaces, and associated coronary arteries which commonly supply that portion of the heart.

Views

Illustration

12lead ecg image coronary artery

This file is licensed under the Creative Commons Attribution-Share Alike 3.0
Author: Patrick J. Lynch, medical illustrator

II, III & aVF

  • Inferior wall of left ventricle
  • Right Coronary Artery
  • Marginal branch

V1 & V2

  • Septum
  • Left Coronary
  • Septal branch

V3 & V4

  • Anterior
  • Left Coronary
  • Anterior Descending and Diagonal arteries

I, aVL, V5 & V6

  • Lateral
  • Left Coronary
  • Circumflex & Obtuse marginal

Labeled Views

ischemia ecg image 1

Quick Check 1

Question 1

Name the inferior view leads.

Answer

II, III & aVF

Question 2

Name the main coronary artery that supplies this artery.

Answer

Right Main Coronary artery


Quick Check 2

Question 1

Name the septal view leads.

Answer

V1 & V2

Question 2

Name the artery that supplies the septal wall.

Answer

Left Main Coronary artery


Quick Check 3

Question 1

Name the anterior view leads.

Answer

V3 & V4

Question 2

Name the arteries that supply the anterior wall.

Answer

Anterior Descending and Diagonal artery

Question 3

Name the main coronary artery that supplies this artery.

Answer

Left Main Coronary artery


Quick Check 4

Question 1

Name the lateral view leads.

Answer

I, aVL, V5 & V6

Question 2

Name the arteries that supply the lateral wall.

Answer

Circumflex and Obtuse Marginal

Question 3

Name the main coronary artery that supplies this artery.

Answer

Left Main Coronary artery


Indicative vs. Reciprocal

Views of the heart

Views seen on a 12-Lead EKG that look directly at a surface of the heart are referred to as “indicative leads” i.e. the views provided on a standard (left side of the chest) ECG like II, III, aVF – inferior etc.

If additional views are required to view the right ventricle or posterior of the heart directly, the chest leads would actually have to be physically moved to either the right side or posterior wall of the chest.

This is not always practical or prudent in the emergency setting…so, many providers initially rely upon indirect (reciprocal) views.

Continued

Views of the heart that or indirect are often referred to as “mirror-image” or “reverse” or “reciprocal” views.

In this instance morphologic changes that we would typically expect to see would be the reverse or opposite change. Meaning, what we would expect to see elevated would be depressed and changes reflected in depression would be elevated.

What is up would be down and down would be up!


Ischemia, Injury Infarction

Part 1

Think of the process of ischemia, injury and infarction as a worsening continuum.

If immediate, aggressive and effective care is not provided, ischemia will worsen (or progress) to injury and ultimately infarction (tissue death)

Ischemia, injury and infarction each impact the cardiac complex in unique ways.

Part 2

12-Lead Analysis requires we follow these steps of analysis.

  • ST segment for presence of deviation
  • T wave morphology changes
  • Q wave morphology changes

Part 3

The changes I have been referring to must occur in anatomically contiguous leads. This refers to 2 or more leads “looking” at (viewing) the same part of the heart or numerically consecutive chest leads

Examples Include:

  • II, III, aVF (2 of the 3 leads must show changes. It does not have to be all three)
  • I, aVL can show changes and not effect V5 and V6 to still be clinically significant
  • Numerically consecutive chest leads

We always recall that V1 is next to V2, but do not forget that V2 is also contiguous with (next to) V3…if V2 & V3 are showing changes, this is clinically significant too. See the next slide for an illustration.


Numerically Consecutive Contiguous Leads

Illustration

12lead ecg image chest leads


Ischemia

Introduction

Ischemia causes a delay in repolarization and causes specific changes to either or both the ST segment and T wave.

Ischemia is evidenced when ST segment depression of 1 mm or more or T wave inversion is seen in two or more anatomically contiguous leads

ST Segment Depression

12lead ecg image st segment depression

T Wave Inversion

12lead ecg image T wave inversion

Injury

Introduction

Ischemia delayed for even a few minutes can progress (worsen) to myocardial injury.

Injury is evidenced when ST segment elevation of 1 mm or more is seen in two or more anatomically contiguous leads

EKG

Injury Examples.
Note: ST Elevation in both examples

12lead ecg image ischemia

Infarction

Introduction

A normal (physiologic) “Q” wave measures less than 0.04 second

Depth measures less than 1/3 height of R wave

12lead ecg image infarction

EKG

An abnormal (pathologic) “Q” wave measures 0.04 (small box) second or greater in duration and/or the depth measures greater than or equal to 1/3 height of R wave

Once an MI is completed, the ST segment will return to the baseline and the T wave will return to its normal orientation, but “Q” waves are often the one remaining change to a cardiac complex as evidence that tissue necrosis or tissue death (infarction) has occurred.

12lead ecg image infarction 2

Quick Check 5

Question

What is the term used that refers to direct changes seen on a 12-Lead ECG?

Answer

Indicative changes

Question

What is the term used that refers to reverse or indirect changes seen on a 12-Lead ECG because the ECG is looking at that surface of the heart indirectly?

Answer

Reciprocal


AMI Location Practice 1

ECG

Identify the location of the AMI on this 12-Lead ECG

ischemia ecg image 1

Location

ST elevation in Inferior Leads II, III and aVF

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg image 2

Location

Pathologic Q wave noted in Inferior Leads II, III, aVF


AMI Location Practice 2

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg image 3

Location

Pathologic Q wave noted in Leads III and aVF

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg image 4

Location

Note ST depression and T wave inversion in V1 - V6


AMI Location Practice 3

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg image 5

Location

ST depression is observed in leads V2, V3, V4, V5, V6 and Lead I

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg image 6

Location

ST elevation noted in leads V4, V5, V6, I and aVL. Lateral wall


AMI Location Practice 4

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 7

Location

ST elevation noted in Inferior leads II, III and aVF

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 8

Location

ST elevation noted in Inferior and Anterior leads II, III, aVF and V3, V4


AMI Location Practice 5

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 9

Location

ST elevation noted in Inferior leads II, III and aVF. Reciprocal (mirror image) ST depression noted in V1, V2, V3 and V4. Possible inferoposterior wall AMI

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 10

Location

Note ST elevation in Inferior leads II, III and aVF


AMI Location Practice 6

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 11

Location

ST elevation noted in Anterior, Lateral and Septal leads V2, V3, V4, V5 and Lead I

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 12

Location

Anterior Lateral and Septal ST elevation in Leads V1, V2, V3, V4, V5 and Lead I (aVL is questionable)


AMI Location Practice 7

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 13

Location

Note ST elevation in Leads V2, V3, V4, V5 and V6. Anterolateral AMI with Septal extension

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 14

Location

ST segment Elevation noted in Septal, Anterior and Lateral Leads V1, V2, V3, V4, V5 and I


AMI Location Practice 8

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 15

Location

Lateral ST elevation noted in leads V2, V3, V4, V5, V6, I and aVL

ECG

Identify the location of the AMI on this 12-Lead ECG

12lead ecg ischemia 16

Location

ST depression noted in Anterior and Lateral leads V3, V4, V5, V6, I. ST depression is also noted in leads II, III and aVF