12 Lead ECG Interpretation – Part 1

Category: Education

Presentation Description

This is designed for my students to review topics discussed in the classroom on 12 lead ecg interpretation. This is the first installment of several in this particular series.


Presentation Transcript

12 Lead ECG Interpretation – Part 1:

12 Lead ECG Interpretation – Part 1 Axis Deviation & Hemiblocks P. Johnson; BA, NREMT-P, WV-MCCP

Review notes from today’s in-class lecture:

authorstream.com pjohnson_ALSEDU Review notes from today’s in-class lecture Course Textbooks: Bob Page’s 12 Lead ECG Interpretation, & Barbara Aehlert’s Paramedic Practice Today


Understand the 12-Lead ECG printout Recognize axis deviation by utilizing the Rapid axis and Hemiblock Chart to determine the presence of anterior and posterior fascicular block. Describe the clinical significance of fascicular block in the acute-care setting. Objectives:

Understanding the 12-Lead ECG Printout:

Understanding the 12-Lead ECG Printout

ECG Machine Analysis:

ECG Accurately measures: Intervals PR, QRS, and QT intervals Voltage Measures height or vertical assessment of: P, QRS, and T waves Axis Angle P wave, QRS, and T wave ECG Machine Analysis

Units of Measure:

ECG Machine will measure in either: Milliseconds or seconds IE: 160 ms or 0.16 seconds Units of Measure

Units of Measure:

Units of Measure ECG Machine can also measure voltage in millimeters One small square = 1 mm Either mm or mv: 10mm = 1mv A positive number indicates height above the isoelectric line. A negative number indicates depth below the isoelectric line . IE: 3mm (above) or -10mm (below)

From Machine Analysis to Human Interpretation::

Machine algorithms are becoming increasingly more accurate, BUT ARE NOT WITHOUT ERRORS OR FLAWS. Areas of machine deficiency: Rhythm analysis- Heart Blocks Wide complex tachycardias From Machine Analysis to Human Interpretation:

Steps to Interpretation::

Find the isoelectric line Bottom of the calibration spike Confirm appropriate lead placement Review the V lead s R waves will progressively get taller Steps to Interpretation:

Locating the isoelectric line::

Locating the isoelectric line:

R wave progression in the V leads::

R wave progression in the V leads:

Determine Axis and Hemiblocks:

Determine Axis and Hemiblocks

- Axis -:

- Axis -


Axis is defined as the general direction of electrical impulses as they travel through the heart. 90% cancel one another out. 10% travel in one primary direction Assessing the axis deviation can provide clues to the severity of a patient’s condition. Axis:

Where Do I Look to Find Axis Deviations?:

Where Do I Look to Find Axis Deviations? Lead I, II, and III

Bob Page’s Axis and Hemiblock Chart::

Bob Page’s Axis and Hemiblock Chart:

Normal Axis:

Normal Axis

Left Axis Deviation:

Left Axis Deviation Two Types Physiological Left Axis Pathological Left Axis

Physiological Left-Axis Deviation:

Physiological Left-Axis Deviation A normal variant and is no cause for alarm. Lead I: up, Lead II: up or equal, Lead III: down Obesity Can cause the axis to be slightly rotated causing a negative deflection

Pathological Left Axis Deviation:

Pathological Left Axis Deviation Axis deviation – greater than a 40 degree deviation and indicates there is something wrong. – Anterior hemiblock Lead I: up, Lead II: down, Lead III: down

Right Axis Deviation:

Considered normal in children NOT NORMAL IN ADULTS! Can Indicate: Posterior hemiblock Right Ventricular hypertrophy Cor pulmonale / right sided heart failure Pulmonary embolism Arrhythmias Lead I : down, Lead II: up, down, or equal, Lead III: up Right Axis Deviation

Extreme Right Axis Deviation (ERAD):

Extreme Right Axis Deviation (ERAD) Axis deviation is toward the right shoulder and is predominantly negative in all three leads The impulse is originating in the ventricles and is wide, and fast…. Ventricular Tachycardia Negative deflection in Leads: I, II, and III.

- Hemiblocks -:

- Hemiblocks -


Hemiblocks Hemiblock – a blockage of one of the two fascicles of the left bundle branch system. Right bundle branch = one fascicle Left bundle branch = two fascicles ( hemifascicles ) Anterior Posterior

Hemiblocks….Why do I care?!?:

Four times higher mortality rate for patients with AMI Risk factor for complete heart block In the setting of an AMI, it can indicate proximal artery occlusion Hemiblocks ….Why do I care?!?

Left Anterior Hemiblock:

Left Anterior Hemiblock “Pathological left Axis” LAD feeds this hemifascicle This is the more common hemiblock Is well tolerated by an asymptomatic patient and requires no treatment generally In an AMI, it is more serious…. only two of the three fascicles are receiving blood !

Left Posterior Hemiblock:

Left Posterior Hemiblock “Right axis deviation” Is worse than an anterior hemiblock . Requires blood supply from the RCA and the Circumflex Assess your patient for right ventricular hypertrophy: JVD, pedal edema, and their patient history Treating for both conduction problems, as well as possibly hypotension/cardiogenic shock


authorstream.com pjohnson_ALSEDU For review of this and other powerpoint presentations after completion of your course, please visit me at: authorstream.com pjohnson_ALSEDU

Thank you!:

Thank you! Pictures from: Course Text-Bob Page: 12 Lead ECG Interpretation textbook, Barbara Aehlert : ECG Made Easy & Paramedic Practice Today, Microsoft clip art, and Personal ECG stock

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