Cardio pulm Heart Rhythms and ECG

What is the ECG?

measurement of cardiac depolarization

Why and when would a picture of the electrical activity of the heart be useful?

MI indicator

How do doctors use the ECG to diagnose MI?

ST segment elevated or depressed or the T wave is inverted

Limb leads

I, II, III

Augmented leads

AVR, AVF, AVL

Gives you a 180 degree view within the FRONTAL plane of the heart

Precordial leads

V1- V6

Gives 180 degree view TRANSVERSLY through the heart

Negative deflection

Depolarization move away from + electrode and towards - electrode

Positive Deflection

Depolarization moves towards + electrode and away from - electrode

Infarction area with 12 lead EKG

I, aVL, V5, V6= lateral

II, III, AVF= Inferior

V1, V2= septal

V3, V4= anterior

Normal EKG

PR interval duration: .12-.20 s

Q wave: duration- <.04 s amplitude- <25% of R wave

ST segment Amplitude: should be 0

Determining rate of EKG

300/ # of boxes from R to R

Atrial rhythms

if QRS complex looks normal in form- dysrhythmia is typically atrial in origin

Ventricular rhythms

if QRS complex looks abnormal and you lack a P wave- dysrhythmia is typically ventricular in origin

Premature Atrial contraction (PAC)

R to R wave not symmetrical

early beat that comes before P wave or looks odd

Atrial rate 60-100 bpm

Clinical implications: nothing HR usually normal

Little clinical significance

Supraventricular Tachycardia (SVT)

Single irritable atrial pacemaker in the atria begins to fire rapidly

Ventricles contract for each impulse from atria

Atrial rate 150-250 bpm

Clinical implications: ventricles moving so fast they can't fill

Atrial flutter

Saw tooth F waves with QRS complex

AV node becomes primary pacemaker

Atrial rate 250-350 bpm

Atrial Fibrillation

No p wave

Uneven R-R interval

Need anticoagulants

Atrial rate 350-450 bpm

Produces fibrillations of the atria

AV node primary pacemaker

Clinical implication: people don't realize they have it

Find when taking pulse

Premature Ventricular Contractions (PVCs)

A depolarization that arises in either on the ventricles prior to the subsequent beat

Shortening R-R interval

Wide QRS

>6 PVCs per min considered pathological

Coupling and tripling PVCs very dangerous

Clinical implications: delay therapy till PVCs stop or calm down

Ventricular Tachycardia

150-250 bpm

Resemble PVCs

very irritable ventricular focus paces rapidly

Clinical implications: if develops stop treatment and lay pt down

Ventricular flutter

250-300 bpm

Single ventricular automaticity focus

Ventricles don't have enough time to fill

Ventricular Fibrillation

Hypoxia of coronary arteries

Lethal rhythm

Unorganized unidentifiable wave forms

pulseless

First degree heart block

Prolonged PR interval- normal is less than 1 box

everything else normal, except prolonged PR interval

Second degree heart block type 1

1) Progressive increase of the PR interval

2) Progressive shortening of the R-R interval

3) Dropped QRS

Common with acute inferior wall MI

Second degree heart block type 2

No QRS complex

P waves followed by no QRS

no pattern

Third degree AV block

No communication between atria and ventricles

DANGEROUS

Pacemaker rhythms

sharp spike

Bundle branch block

depolarization of ventricles does not happen at the same time because of block in the bundle branches

Widened QRS

Double spike- the mountains in the grinch