ECG Interpretation

What is an ECG Electrocardiogram Traces the electrical activity of the heart 12 lead, 15 lead

Uses of ECG Tracing Ischemia/infarct Arrhythmias Ventricular and atrial enlargements Conduction defects Pericarditis Effects of some drugs and electrolytes

ECG

How to Conduct an ECG Patient lies flat on back Electrodes are placed on the body Sites may need to be shaved or cleaned to ensure the leads will stick properly. Patient will lie as still as possible, hold breath, or put hands under bottom to keep from moving. The results are then printed out on paper for MD to review.

ECG Strip

Lead Placements V1 - Junction of the 4th ICS, Right sternal border V2 - Junction of the 4th ICS, Left sternal border V3 - Midway between V2 and V4 V4 - Junction of 5th ICS, Mid clavicle V5 - Anterior aspect of axilla, same line as V4 V6 - Mid axilla, same line a V4 4 limb leads (for grounding etc)

Lead Placements Cont’

Normal Conduction Pattern

Understanding the Waves

Each wave P Q R S T

ECG Strip r/t heart

Understanding the Waves One small box = 0.04 seconds One large box = 0.2 seconds 5 large boxes = 1 second

http://en.wikipedia.org/wiki/File:ECG_principle_slow.gif

Understanding the Waves Baseline (what is it?) P wave Length of time it takes the impulse to pass from the SA node to the AV node Should precede every QRS wave PR interval Should be no longer than 0.12 – 0.2

Understanding the Waves QRS Should be no longer than 0.12 If energy is going towards a positive electrode (camera), the picture will show a positive QRS complex If energy is going away from positive electrode, the picture will show a negative QRS complex If energy is toward the positive electrode and then passes by it, the QRS will be biphasic Ventricle contracting

Understanding the Waves T wave Should always start from baseline Will indicate ischemia

Understanding an ECG Is as easy as… 1. 2. 3. = rate = intervals = rhythm

Step 1 = Rate Different ways to calculate a rate: a) ECG usually tells you b) Locate a QRS that is close to a big line and count to next big line: 300, 150, 100, 75, 60, 50 c) take a 6 second strip, count QRS and multiply by 10 (hint: the middle of V3 on the lead II strip is 6 seconds) One small box = 0.04 sec. One large box = 0.2 sec. 5 large boxes = 1 sec. 300, 150, 100, 75, 60, 50, 45, 37…

Step 1 = Rate (cont’) Checking the regularity: map out QRS’s

Step 2 = Intervals We assess intervals to see where the impulse is coming from (pacemaker beat) Remember: PR interval: normal is 0.12 - 0.2 QRS interval: normal is less than or equal to 0.12 One small box = 0.04 sec. One large box = 0.2 sec. 5 large boxes = 1 sec.

Step 3 = Rhythm The biggest question in relation to rhythm is…

Is this rhythm affecting my patient?

(Normal) Sinus Rhythm 60-80 bpm P preceding each QRS Normal intervals What do we want to do for this patient?

Normal ECG

Other Sinus Rhythms Sinus bradycardia a sinus rhythm with a rate <60 bpm What do we want to do for this patient?

Other Sinus Rhythms Sinus tachycardia a sinus rhythm with a rate >80 bpm What do we want to do for this patient?

Atrial Arrhythmias Atrial fibrillation (A-fib) irregular rate no discernable P waves increased risk of strokes due to clots that might form due to fibrillation (patients are usually on anticoagulation therapy) What do we want to do for this patient?

Atrial fibrillation

Atrial Arrhythmias Cont’ Atrial flutter saw tooth in appearance irregular rate

Atrial flutter What do we want to do for this patient?

Blocks 1st degree AV block a PR interval that exceeds 0.20 sec What do we want to do for this patient?

Blocks Cont’ 2nd degree AV block (Mobitz) a) type I (Wenckebach) longer and longer PR intervals until a QRS is dropped What do we want to do for this patient?

Blocks Cont’ b) type II P waves and then suddenly a QRS is dropped P’s are regular What do we want to do for this patient?

Blocks Cont’ 3rd degree AV block HR <40 bpm a complete block of electrical activity from atria to ventricle P’s are regular What do we want to do for this patient?

Ventricular Rhythms Ventricular fibrillation complete breakdown of all rhythm a) course b) fine What do we want to do for this patient?

V-fib What’s the first thing to do when coming up on a patient with this rhythm?

Ventricular Rhythms Cont’ Ventricular tachycardia (V-tach) impulse originates in the ventricle always has a wide QRS complex What do we want to do for this patient?

V-tach What’s the first thing to do when coming up on a patient with this rhythm?

Asystole Pulseless What do we want to do for this patient?

Coronary Arteries

MI’s

MI’s

MI’s How can you tell on an ECG that your patient is having a heart attack? T waves Different views of heart will show different injured areas of heart

MI’s T wave shouldering is classic

MI’s How else can you tell that your patient has had an MI? Cardiac Markers CK will show in 4-6 hours (starts to come back down after 1 day) Troponin will show in 4-6 hours (may stay elevated for weeks) Others are: LDH, CK-MB, myoglobin, AST

Locating an MI

I Lateral (circumflex) aVR V1 Anterior (Lt ant desc) V4 Anterior II Inferior (Rt coronary) aVL Lateral V2 Anterior V5 Lateral III Inferior aVF Inferior V3 Anterior V6 Lateral Your paper should look like this now…

ECG Tissue Damage Locations

Where is this MI?