12-lead

V1 placement

4th intercostal space to the right of sternum

V2 placement

4th intercostal space to the left of sternum

V3 placement

Directly between V2 and V4

V4 placement

5th intercostal space at left mid-clavicular line

V5 placement

Level with V4 at left anterior axillary line

V6 placement

Level with V5 at left mid-axillary line

Lead I should normally be what?

Positively deflected

What may global negativity in Lead I indicate?

Limb leads may be reversed or right axis deviation

What is R-wave progression?

R-wave in V leads transitions from predominantly negative in V1 to predominantly positive in V6

Lateral leads

I, aVL, V5, V6

Lateral leads coronary supply

Left Circumflex Artery

Inferior leads

II, III, aVF

Inferior leads coronary supply

Posterior Descending Artery (Right Coronary Artery)

Septal leads

V1, V2

Septal leads coronary supply

Left Anterior Descending Artery

Anterior leads

V3, V4

Anterior leads coronary supply

Left Anterior Descending Artery

What are anatomically contiguous leads?

Anatomical lead groups

What should be evaluated on a 12-lead EKG for STEMI?

ST segment elevation

Where is the ST segment located?

At the J-point

What is the J-point?

Junction between S-wave end of QRS and ST segment

What should ST segment height be compared to?

TP segment height

STEMI criteria

ST segment 1 millimeter or higher than TP segment in two or more anatomically contiguous or numerically consecutive leads

If ST segment is not elevated, what diagnosis is not made?

STEMI

Can a Non-STEMI MI still occur without ST elevation?

Yes

How often do Non-STEMIs occur in myocardial infarctions?

50%

Numerically consecutive leads apply to what leads?

Precordial chest leads V1-V6

What does 1 mm or more elevation in two or more numerically consecutive leads indicate?

STEMI

Elevation in V2 and V3 indicates what?

Anteroseptal Wall MI

Elevation in V4 and V5 indicates what?

Anterolateral Wall MI

Hyperacute MI finding

T-wave tall and peaked

Hyperacute T-wave size

Up to 10 mm, 2/3 size of QRS

Acute ST segment elevation implies what?

Myocardial tissue injury is presently occurring

Acute ST segment elevation injury is probably due to what?

Occluded coronary artery

What happens if acute ST segment elevation is not corrected?

Tissue necrosis

Acute MI with pathological Q-wave indicates what?

Some myocardium can be saved while other portions are already necrotic

Old MI finding

Pathological Q-wave present with no active injury pattern

Old MI is associated with what?

Previous MI

ST segment depression indicates what?

Injury

Inverted T-waves are part of what?

MI evolution

Physiologic Q-wave

Normal finding

Physiologic Q-wave width

< 0.04 seconds, less than 1 small box

Pathological Q-wave is associated with what?

Previous MI

Pathological Q-wave width

0.04 seconds, more than 1 small box

When should a right-sided 12-lead EKG be performed?

When Inferior Wall MI is identified

Inferior Wall MI ST elevation leads

II, III, aVF

Right-sided 12-lead procedure

Move V4 to right side in same anatomical position, just on right side of sternum, and obtain another 12-lead

Right-sided 12-lead interpretation

Look specifically in new lead V4 for ST elevation > 1 mm

What does the Right Coronary Artery supply?

Posterior Descending Artery and Right Marginal Artery

What wall does the Posterior Descending Artery supply?

Inferior wall

What does the Right Marginal Artery supply?

Right ventricle

What does a right-sided 12-lead identify?

Whether occlusion is in posterior descending artery alone or proximal RCA causing inferior and right ventricular infarctions

When right ventricle is involved, be concerned with what?

Preload and nitroglycerin administration

When RVI is found, use caution with what?

Nitroglycerin

When RVI is found, consider what instead?

Fluid bolus to support preload, aspirin, and oxygen

Fluid bolus supports preload based on what law?

Starling’s Law

What are the two main bundle branches?

Right bundle branch and left bundle branch

Left bundle branch divides into what?

Left anterior fascicle and left posterior fascicle

Why are bundle branch blocks important to identify?

They can mimic or hide certain 12-lead findings

What method is used to identify bundle branch blocks?

Turn Signal Method

Turn Signal Method step 1

In Lead V1, see if QRS is wider than 0.12 seconds or 3 small boxes

If QRS in V1 is not wider than 0.12 seconds, what should you do?

Stop

Turn Signal Method step 2

With wide QRS in V1, determine if QRS is deflected up or down

Turn Signal Method step 3

Picture steering wheel making a turn

Right turn signal finding

QRS wide and deflected up

QRS wide and deflected up indicates what?

Right Bundle Branch Block

Left turn signal finding

QRS wide and deflected down

QRS wide and deflected down indicates what?

Left Bundle Branch Block

LBBB interpretation rule

12-lead interpretation is LBBB, treat patient’s clinical presentation

RBBB interpretation rule

12-lead interpretation is whatever found with RBBB, treat patient’s clinical presentation and 12-lead findings

Digitalis effect finding

ST segment depression with characteristic sag

Delta wave is associated with what?

Wolff-Parkinson-White

Osborn or J wave is associated with what?

Hypothermia