emt ecg shorter

ECG paper speed 25 mm/sec (1 small box = 0.04 sec

1 big box = 0.20 sec)

Small box (1 mm) 0.04 sec (horizontal)

0.1 mV (vertical)

Large box (5 mm) 0.20 sec (horizontal)

0.5 mV (vertical)

P wave duration <0.12 sec (atrial depolarization)

PR interval 0.12–0.20 sec (atrial → ventricular depolarization)

QRS duration <0.12 sec (ventricular depolarization)

QT interval <½ RR interval (ventricular depolarization + repolarization)

ST segment Isoelectric (flat) between QRS and T wave

T wave Ventricular repolarization (should follow QRS direction)

U wave After T wave (hypokalemia

bradycardia)

Isoelectric line Flat baseline (no electrical activity)

Positive deflection Waveforms above baseline (e.g.

R wave)

Negative deflection Waveforms below baseline (e.g.

Q wave

Lead II Best for viewing P waves (upright)

Lead aVR All waves normally negative (checks for lead reversal)

Precordial leads V1-V6 (view anterior/lateral heart)

Limb leads I

II

Heart rate calculation (regular rhythm) 300 ÷ big boxes between R waves

Heart rate calculation (irregular) Count QRS in 6 sec × 10

Normal HR range 60–100 bpm

Bradycardia <60 bpm

Tachycardia >100 bpm

PR prolongation (>0.20 sec) 1st-degree AV block

PR shortening (<0.12 sec) WPW syndrome (delta wave)

Wide QRS (>0.12 sec) VTach

BBB

Prolonged QT Risk of Torsades (low K+/Mg2+

meds)

ST elevation STEMI

pericarditis

ST depression Ischemia

digoxin effect

Artifact causes Movement

loose electrodes

60-cycle interference Thick

fuzzy baseline (unplug devices)

Wandering baseline Patient movement (reposition electrodes)

Limb lead reversal P inverted in lead I (RA/LA swap)

Shockable rhythms VF

pulseless VTach

Non-shockable rhythms PEA

asystole

VF treatment Immediate defibrillation

Pulseless VTach treatment Defibrillation

PEA treatment CPR + find cause (H’s and T’s)

Asystole treatment CPR + epinephrine

Hyperkalemia ECG Peaked T → wide QRS → sine wave → asystole

Hypokalemia ECG Flat T

U waves

Hypercalcemia ECG Short QT

Hypocalcemia ECG Prolonged QT

Normal axis -30° to +90°

Left axis deviation -30° to -90° (LAFB

inferior MI)

Right axis deviation >+90° (RVH

LPFB)

LVH criteria (Sokolov) S in V1 + R in V5/V6 >35 mm

RVH criteria R in V1 >7 mm

right axis deviation

STEMI definition ST elevation >1mm in 2+ contiguous leads

Inferior STEMI ST elevation II/III/aVF

Anterior STEMI ST elevation V1-V4

Lateral STEMI ST elevation I/aVL/V5-V6

Posterior STEMI ST depression V1-V3 + tall R in V1

Pericarditis ECG Diffuse ST elevation

PR depression

Early repolarization Normal variant (ST elevation + J-point notch)

Pacemaker spike Vertical line before P or QRS

Failure to capture Spike but no QRS

Failure to pace No spike when needed

Lead aVR ST elevation Left main or triple-vessel disease

De Winter T waves ST depression + tall T (LAD occlusion)

Wellens syndrome Biphasic T in V2-V3 (LAD stenosis)

Brugada pattern RBBB + ST elevation V1-V2 (sudden death risk)

Torsades de Pointes Polymorphic VTach + prolonged QT → MgSO4

PVC features Wide QRS

no P wave

Bigeminy Every other beat is PVC

Trigeminy Every third beat is PVC

Atrial fibrillation Irregularly irregular

no P waves

Atrial flutter Sawtooth flutter waves (often 300 bpm atrial rate)

1st-degree AV block PR >0.20 sec

2nd-degree Type I (Wenckebach) PR lengthens until QRS drops

2nd-degree Type II PR fixed

random QRS drops

3rd-degree AV block P and QRS dissociated

Bundle branch block QRS >0.12 sec

RBBB "Rabbit ears" in V1

LBBB Notched QRS in V6

Pulseless electrical activity (PEA) ECG rhythm but no pulse → CPR

Agonal rhythm Slow

wide QRS (near-arrest)

Junctional rhythm 40–60 bpm

no P or inverted P after QRS

Accelerated junctional 60–100 bpm (digoxin toxicity)

Sinus tachycardia >100 bpm

normal P-QRS-T

Sinus bradycardia <60 bpm

normal P-QRS-T