BASIC ECG INTERPRETATION
ECG - is a series of waves and deflections recording the hearts electrical activity from a certain view.
Electrical Conduction Rate SA node
Rate: 60 100 bpm AV node
act as back-up
pacemaker Rate: 40 60 bpm Purkinje Fiber can act as back-up pacemaker Rate: 20 40 bpm
Breakdown of ECG strip
Components of the Cardiac CycleP wave: (SA node fires) Atrial depolarization Normal shape:
upright & round
P-R interval (PRI) impulse travels from
the SA node to the atria P wave followed by
isoelectric line From the beginning of
P wave to the beginning of Q wave
QRS Complex ventricular depolarization Impulse from the Bundle
of HIS throughout the ventricular muscles
T wave Ventricular
repolarization Resting phase of the
cardiac cycle upright & round
U wave Purkenji fiber
repolarization Etiology: hypokalemia
Electrode application White to right Red to ribs Black over the red.
Produces positive deflection Commonly used for routine
STEPS IN ANALYSING ECG
Step I: rhythm Regular
Normal: 60 100 bpm Bradycardia: < 60 bpm Tachycardia: > 100 bpm
HEART RATE CALCULATION
Method I For regular rhythm: Count the number of large boxes between
2 R waves and that number is divided into 300. Remember:
.20 sec/large box = 5 large boxes/sec. 60 sec/min x 5 = 300 large boxes/min.
What is the rate?
Rate: 300 / 4 = 75 bpm
Method II For fast heart rate: count the number of small boxes between two
R waves and that number is divided into 1500
Remember: 5 small boxes/large box 300 large boxes/min
300 x 5 = 1500
What is the rate?
Rate: 1500 / 10 = 150 bpm
Method III For irregular rhythm:
Count the R waves in 6 sec strip (between 3
hash marks) and multiply it by 10. Remember: 5 large boxes / sec
Find the R wave that fall on a large box line. Level the next large box line a rate of 300 150 100 75 60 50 43 37 33 & 30, until the next R wave.
Step 3 P wave configuration: round and upright
Location: precedes QRS complex Duration: .06 -.11 sec. (1.5 2.5 small boxes) Amplitude: up to 2.5mm
To ask: Are P wave present? Do they look the same? Is there P before every QRS?
Other P wave configurations
Step 4: PR interval From the start of Atrial depolarization to the beginning of
ventricular depolarization Location: beginning of P wave to beginning of Q wave Duration: .12 - .20 sec Amplitude: not measured Configuration: P wave followed by isoelectric line To ask? Are all P-R intervals consistent?
P-R interval (PRI)
Step 5: QRS complex Ventricular depolarization / atrial repolarization
Location: follows P-R interval Amplitude: varies with lead Duration: .04 -.12 (1-3 small boxes) Configuration: varies with lead
to ask? Are there QRS? Do they look the same? Do they come after the P wave? Are the R R intervals equal?
T wave Ventricular repolarization
Location: after S wave Amplitude: 5 mm or less Duration: not measured Configuration: Normal: rounded & upright Inverted Flat Peaked
ST segment End of ventricular depolarization to the beginning of
ventricular repolarization Location: end of S wave to beginning of T wave Amplitude: isoelectric Duration: not measured Configuration: nearly isoelectric
Elevated (> 1 2 mm) Sign of acute MI Depressed (> .5 mm) Sign of ischemia
QT interval Location: beginning of Q wave to end of T wave
Amplitude: not measured Duration: < the distance of the R-R interval Configuration: not measured
U wave Purkinje fiber repolarization
Location: follows T wave or may not be present Amplitude: not measured Duration: not measured Configuration: rounded & upright
First Rhythm Strip to Identify
ARTIFACTSFour Common Causes: Patient Movement Loose or defective electrodes Improper grounding Faulty ECG apparatus
Mechanism: Rhythm originates in the SA node
Rhythm: regular Rate: normal (60 100 bpm) P wave: normal / 1 per QRS complex PR interval: normal (.12 - .20 sec) QRS complex: normal (.04 - .12 sec) ST segment: not elevated or depressed T wave: normal
Normal sinus rhythm Etiology: Normal cardiac function Clinical Tip: A normal ECG does not exclude heart
depressed automaticity of the SA node with normal
ECG characteristics: all normal rate - < 60
Sinus BradycardiaEtiology: sleeping; young, athletic individuals Excessive vagal tone (straining, vomiting, intubation) Sick sinus syndrome, MI Digoxin toxicity, Sedative Hyperkalemia Trauma to conductive system
Clinical signs: low CO low perfusion lethargy, mental status change, anxiety, poor capillary refill, mottled skin, low UO syncope
BradycardiaNursing action: (if symptomatic) Document rhythm & notify MD Apply O2 & consider atropine Prepare for external pacing If with PVCs dont treat with lidocaine (this is the hearts
attempt to improve perfusion) Atropine SO4 0.5 mg IV (may repeat in 3-5 min)
Maximum dose: 3 mg Do not give < 0.5 mg may worsen the bradycardia Do not push slow
Mechanism: increased automaticity of the SA node with normal conduction3.
ECG characteristics: all normal Rate: 101 160 bpm P wave: normal or merge to T wave
Sinus tachycardiaEtiology: a natural response to environmental stimuli pain, fever, exercise, emotion, dehydration Drugs, caffeine, alcohol, Hyperthyroidism, shock, CHF, hypoxia Clinical signs: Increased workload of the heart decrease CO low perfusion angina, SOB, anxiety, hypotension, low UO Nursing action: if symptomatic Document rhythm & notify MD Apply O2 Treat underlying cause May consider vagal maneuver cough, bear down, blow through straw try blowing plunger off the syringe
Mechanism: reflux vagal tone inhibition associated with respiration. (rate increases with inspiration & drops with exhalation) 4.
ECG characteristics: Rhythm: irregular Others: All normal
Sinus ArrhythmiaEtiology: Normal phenomenon with inspiration (esp, in infant) Digitalis toxicity, MI, increased ICP Fever, anxiety, shock Nursing action: Document rhythm & notify MD if symptomatic No treatment
Mechanism: Signal to SA node is not generated or it fails to leave the SA node5.
Sinus pause / block - Basic rhythm resumes after a pause ECG Characteristics: Rhythm: irreg Rate: normal or < 60 Other waves: Normal except during pause or arrest
Sinus arrest basic rhythm does not resume after a pause6.
Sinus pause/arrest/block Etiology: High vagal tone or increased vagal stimulation Drug toxicity (esp. digoxin) MI, s/p cardiac surgery, SA node trauma lupus, metabolic disorders Clinical signs: If HR is 10 PACs = CHF Palpitations
Nursing Action: Document Treat underlying cause
AF Mechanism: Atrial quiver with ventricular response (> 100 = RVR (rapid) / 60 =100 CVR (controlled)) blood clots
ECG Characteristics: Rhythm: irreg Rate: Atria: 350-600 / Ventricle: varies P wave: none ( F wave) QRS comp: Normal Others: not measurable
Atrial Fibrillation Etiology: Atrial enlargement due to AV valve disorders Hpn, CAD, COPD, CHF, MI Hypoxia, drugs, digitoxicity, tobacco Clinical signs: Irregular pulse, palpitation, anxiety, SOB CHF
shock Nursing Action: Document rhythm & inform MD Apply O2 Possible Synchronize cardioversion Anticoagulant therapy
Mechanism: Extremely rapid atrial rate (saw-tooth configuration)9.
ECG characteristics: Rhythm: irreg / regular Rate: Atria: 250-350 / ventricle: varies QRS comp: Normal Others: not measurable
Atrial Flutter Etiology: Related to underlying heart disease Hyperthyroidism, alcoholism Clinical signs: decreased CO hypotension, mental status change,
fatigue, CHF, SOB Nursing Action if symptomatic: Document rhythm & notify MD Apply O2 Vagal maneuver If tachycardic consider synchronize cardioversion
PAT / SVT Mechanism: impulse originate above the ventricle, due to rapid
rate loss of atrial kick
ECG characteristics: Rhythm: regular Rate: 140 250 bpm P wave: hidden in T wave QRS comp: normal PRI: not measurable
Paroxysmal Atrial tachycardia (PAT) / Supraventricular tachycardia Etiology
Heart diseases, emotional stress Regular atrial rhythm Digitalis toxicity Clinical sign: loss of atrial kick decrease CO
decreased perfusion myocardia ischemia Nursing Action: Treat the cause Valsalva maneuver or carotid massage
Junctional rhythm / junctional escape rhythm Mechanism: Rhythm originate from AV junctional tissue (maybe an escape rhythm, enhanced automaticity of the AV node that override the SA node)
ECG characteristics: Rate: 40 60 bpm P wave: inverted or none or retrograde PRI: shortened QRS comp: normal Others normal unless distorted by the P wave
Accelerated junctional rhythm:12.
Rate: 61 100 bpm Nursing action: same as junctional rhytm
Rate: 101 180 bpm