Equipment 8-108-01 - ECG Interpretation Guide

CMH EMS & MIH Protocols

Check lead placement.

Lead I positive and aVR negative: Good placement.

Interpret underlying rhythm.

Evaluate regularity:

Regular, regularly irregular, or irregular?

Evaluate rate:

Bradycardia, normal, or Tachycardia?

Evaluate P-waves:

Look for heart block:
- PR greater than 200 ms: First-degree.
- PR widening: Second-degree, type I.
- Dropping P-waves: Second-degree, type II.
- P-waves not associated: Third-degree.
Greater than 2.5 mm high: Right atrial enlargment or PE.
"M" shape: Left atrial enlargment.

Evaluate QRS:

Adult	Pediatric
Greater than 120 ms with P-waves: Bundle branch block. Evaluate first deflection in QRS going right-to-left in V1:	Greater than 90 ms with P-waves: Bundle branch block. Evaluate first deflection in QRS going right-to-left in V1:

Upward: RBBB.
Downward: LBBB (LBBB or ventricular pacing, go to Sgarbossa).

QTc greater than 450: Prolonged QT.
Peaked T-waves: Hyperkalemia.
Q-wave greater than 1/3 of R-wave height or width: Pathological Q-wave (previous MI or late development of current MI).
Q-wave greater than 35 mm as measured by combining V1 and V5: Left ventricular hypertrophy.
Q-wave greater than 7 mm in V1: Right ventricular hypertrophy.
Delta-wave (sloped R-wave) with PR less than 120 ms: Wolff-Parkinson-White.

Evaluate axis:

Between -30° and 90° (I+ and aVF+): Normal axis.
Between 90° and 180° (I- and aVF+): Right axis deviation. Could be caused by left posterior hemiblock, RBBB, right ventricular hypertrophy, pulmonary disease, or slender build.
Between -30° and -90° (I+ and aVF-): Left axis deviation. Could be caused by inferior MI, left anterior hemiblock, LBBB, left ventricular hypertrophy, obesity, or pregnancy.
Between -90° and -180° (I- and aVF-): Extreme right axis deviation. Probably caused by a STEMI.

Determine if Cath Lab should be activated.

Cath Lab activations (Basic):

ST elevation in all or most of the leads: Pericarditis. Do not activate the Cath Lab.
ST elevation of 1 mm or greater in the following leads:
- V3 and V4: Anterior STEMI. Activate the Cath Lab.
- Two or more in II, III, and/or aVF: Inferior STEMI. Activate the Cath Lab.
- Two or more in I, aVL, V5, and/or V6: Left Lateral STEMI. Activate the Cath Lab.
- V1 and V2: Septal STEMI. Activate the Cath Lab.

Cath Lab activations (Intermediate):

ST elevation of 0.5 mm or greater in the following leads:

V4R: Right Lateral STEMI. Activate the Cath Lab.
V8 and V9: Posterior STEMI. Activate the Cath Lab.

LBBB or ventricular pacing:

ST ELEVATION of 1 mm or greater CONCORDANT with QRS in any lead: Sgarbossa A criteria STEMI. Activate the Cath Lab.
ST DEPRESSION of 1 mm or greater in any leads V1, V2, or V3: Sgarbossa B criteria STEMI. Activate the Cath Lab.
ST ELEVATION of 5 mm or greater DISCORDANT with QRS in any lead: Sgarbossa C criteria STEMI. Activate the Cath Lab.

Cath Lab activations (Advanced):

Any amount of ST ELEVATION in both aVR and V1 with any amount of ST DEPRESSION in most other leads:

If found after a hypoxic episode: Not cardiac-related. Do not activate the Cath Lab.
If NO recent hypoxic episode: Three Vessel Disease. Activate the Cath Lab.

T-waves 10 mm or taller with any amount of ST DEPRESSION in one or more leads V1 through V4: DeWinters Anterior STEMI. Activate the Cath Lab.
T-waves that are downward and symmetric in one or more leads V1 through V6.: Occurs between episodes of chest pain and goes away while pain is present. Wellens Syndrome. Activate the Cath Lab.

Citations:

Protocol 9-010 - References
American Heart Association, 2020
Cooper, 2015

Change Log:

Date	Link to previous version	Description of change
08/24/18	pdf	Fixed axis determination from I, II, III leads to I & AVF.
07/23/19	pdf	Added p-wave to LBBB definition. Improved graphics for 12-lead placement.
11/27/19	pdf	Added clarifying definitions for right-sidedposterior STEMI (0.5 mm). Serious re-write to include types of STEMIother cath lab activations. Made the page more badge-buddy friendly.
04/04/20		Added content from old Section 2-051 - EKG Interpretation Guide.
07/04/20	pdf	Renumbered the section to allow for future additions.
02/22/21	pdf	Added clarification for QRS width in adult vs pediatric.
06/11/21	pdf	Moved to emsprotocols.online
11/30/21		Updated link to Albuterol.

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