Cardio 2

Chapter 17

Cardiovascular Emergencies

Part II

Dale A. LeCrone Sr NRPInstructor

Cardiac Monitoring and ECG Use

• ECG monitor can be used to: • Monitor during

transport.• Print strip for

dysrhythmia interpretation.• Print 12-lead ECG for

diagnosis.


• Three standard limb leads (Leads I, II, and II) for continuous monitoring• 12-lead ECG provides detailed information about the heart’s

conduction system • Records activity from 12 separate angles• Electrical “snapshot” of a part of the heart


• 12-lead ECG devices contain interpretation software. • Use as only one party of assessment• Some can transmit ECGs to receiving facility.

Electrode Placement

• Predetermined spots• Usually adhesive with

gel center

Electrode Placement

• Basic principles:• It may be necessary to shave body hair.• Rub the site with an alcohol swab before application. • Attach the electrodes to the ECG cable before placement and confirm correct

location.• Turn on the monitor, and print a sample strip.

Electrode Placement

• Artifacts can give false readings.• Straight line may indicate a loose or disconnected lead• Wavy baseline may be caused by movement or muscle tremor

The Leads

• Limb leads (I, II, III, and aVR, aVL, aVF)• For continuous monitoring:

• White—right upper chest near shoulder• Black—left upper chest near shoulder• Red—left lower abdomen• Green—right lower abdomen

The Leads

• Limb leads (cont’d)• For 12-lead ECG:

• White—right wrist• Black—left wrist• Red—left ankle• Green—right ankle

The Leads• Limb leads (cont’d)• Einthoven’s theory: Every

time the heart contracts, electrical energy is emitted.• Lead I—between right

and left arms• Lead II—between right

arm and left leg• Lead III—between left

arm and left leg

The Leads

• Limb leads (cont’d)• Augmented violated (aV) leads created using four limb electrodes

• Leads aVR, aVL, and aVF: combine two limb leads and use the other lead as the other pole.

The Leads• Precordial leads • Six additional

electrodes on the anterior chest

The Leads

• Right-sided ECGs• Used to evaluate the

electrical activity of the right ventricle• Precordial leads are

placed on the right anterior thorax

The Leads

• Posterior ECGs• Evaluates left ventricle

posterior wall electrical activity• Three precordial leads

placed on left posterior thorax

The Leads

• 15-lead ECG: standard 12-lead ECG plus leads V4R, V7, and V8.• Allows view of right ventricle and posterior wall of left ventricle

• 18-lead ECG: standard tracing plus leads V4R through V6R and V7 through V9

The Leads

• Unipolar versus bipolar leads• Leads I, II, III: bipolar leads containing positive and negative poles• Leads aVR, aVL, and aVF: unipolar leads

• One true pole • Other end referenced against a combination of other leads

The Leads

The Leads

• Lead polarity• Bipolar leads have a

negative and positive end.• Lead I: left arm is the

positive terminal• Lead II: left leg is the

positive terminal• Lead III: left leg is the

positive terminal

ECG Concepts

• Wave moves toward a positive electrode: deflection above baseline• Wave moves toward a negative electrode: deflection below baseline

ECG Concepts

• Baseline represents electrically silent period in cardiac cycle• Perpendicular wave results in:• A perfectly flat line• A line with a positive and a negative component (biphasic waves)

ECG Paper

• Graph paper moves past stylus at 25 mm/s• One 1-mm box — 0.04 seconds• One large box — 0.20 seconds• Vertical axis represents amplitude

• Standard amplitude calibration — 10 mm/mV

ECG Paper

Components of ECG Rhythm

• The ECG rhythm components correspond to electrical events in the heart.


• P wave: represents atrial depolarization• Smooth, round, upright shape• Normal duration of less than 100 ms• Amplitude less than 2.5 mm tall


• PR interval (PRI): includes atrial depolarization and conduction of impulse through AV junction• Normal duration of 0.12

to 0.20 seconds


• QRS complex: Three waveforms representing depolarization of two contracting ventricles• From beginning of Q wave to end of S wave• Sharp pointed waves, less than 120 ms• Indicates that impulse has proceeded normally


• QRS complex (cont’d)• Q wave: First negative deflection • R wave: First upward deflection • S wave: Downward deflection after the R wave

Components of ECG System

• J point: where QRS complex ends and ST segment begins• End of depolarization and

beginning of repolarization

• ST segment: begins at J point and ends at T wave


• T wave: represents ventricular repolarization• First half represents

absolute refractory period (ARP)• Second half represents

the relative refractory period (RRP)


• QT interval: represents all electrical activity of one completed ventricular cycle• Begins at onset of Q wave• Ends at the T wave• Normally lasts 360 to 440 ms

Approach to Dysrhythmia Interpretation• Method to interpret dysrhythmias• Identify the waves (P-QRS-T).• Measure the PRI.• Measure the QRS duration.• Determine rhythm regularity.• Measure the heart wave.

Rhythm Regularity

• Measure distance between R waves• Regular: distance between R waves is the same

Rhythm Regularity

• Measure distance between R waves (cont’d)• Irregularly irregular: no two R waves equal• Regularly irregular: R waves are irregular but follow a pattern

Determining Heart Rate

• 6-second method • Count the number of QRS complexes in a

6-second strip and multiply by 10.


• Sequence method• Find R wave; count off

above sequence until next R wave.• If interval spans fewer

than three boxes, rate is greater than 100

• If more than five boxes, rate is less than 60


• 1500 method• Count the number of

small boxes between any two QRS complexes.• Divide by 1500.

Specific Cardiac Dysrhythmias

• Induced by many events• Flow of electricity through damaged or oxygen-deprived tissue may appear as

irregularities• Many can be traced to ischemia

• Most common cause of cardiac arrest

Specific Cardiac Dysrhythmias

• Dysrhythmia classifications• Disturbances of automaticity or conduction• Tachydysrhythmias or bradydysrhythmias• Life threatening or non-life threatening• By site from which they arise

Rhythms Originating in SA Node

• Normal sinus rhythm • Intrinsic rate of 60 to 100 beats/min• Upright P wave preceding each QRS complex


• Sinus bradycardia• Rate of less than 60 beats/min• Upright P wave preceding every QRS complex


• Sinus bradycardia (cont’d)• Serious causes include:

• SA node disease• AMI, which may stimulate vagal tone• Increased intracranial pressure• Use of beta blockers, calcium channel blockers, morphine, quinidine, or digitalis

• Treatment focuses on tolerance and cause.


• Sinus tachycardia• Rate is more than 100 beats/min.• Upright P waves precede QRS complexes.


• Sinus tachycardia (cont’d)• Hypoxia, metabolic alkalosis, hypokalemia, and hypocalcemia can lead to

electrical instability.• Circus reentry may occur.


• Sinus dysrhythmia• Slight variation in sinus rhythm cycling• Upright P waves precede QRS complexes


• Sinus dysrhythmia (cont’d)• More prominent with respiratory cycle fluctuation• Increased filling pressures during inspiration stimulate Bainridge reflex

• Increase in BP stimulates baroreceptor reflex


• Sinus arrest• SA node fails to initiate an impulse• Upright P waves precede QRS complexes.


• Sinus arrest (cont’d)• Common causes:

• Ischemia of the SA node• Increased vagal tone• Carotid sinus massage• Use of certain drugs

• Treatment may include a pacemaker.


• Sick sinus syndrome (SSS)• Variety of rhythms, poorly functioning SA• It shows on an ECG as:

• Sinus bradycardia• Sinus arrest• SA block• Alternating patterns of bradycardia and tachycardia

Rhythms Originating in the Atria

• Any atrial area may originate an impulse.• Rhythms have upright P waves preceding each QRS complex.• Not as well-rounded

• Heart rates usually from 60 to 100 beats/min


• Atrial flutter• Atria contract too fast for ventricles to match• Resemble a saw tooth or picket fence• F waves get blocked by AV node, creating several F waves before each QRS

complex


• Atrial flutter (cont’d)• Usually a sign of a serious heart problem • Treatment is usually medication or electrical cardioversion

• Only done in field if condition is critical


• Atrial fibrillation• Atria fibrillate or quiver• Random depolarization from atria cells depolarizing independently


• Atrial fibrillation (cont’d)• Irregularly irregular appearance• Usually signs of serious heart problem• Tendency to cause clots• Prehospital treatment is rare.


• Supraventricular tachycardia (SVT)• Tachycardic rhythm from pacemaker• Regular rhythm, rate exceeding 150 beats/min • QRS complexes: 40 to 120 ms.• May have cannon “A” waves


• Supraventricular tachycardia (cont’d)• Called paroxysmal SVT (PSVT) because of tendency to begin and end abruptly• May greatly reduce CO


• Premature atrial complex• A particular complex within another rhythm• Upright P wave precedes each QRS complex


• Premature atrial complex (cont’d)• Non-conducted PAC: P wave occurs early on the ECG and is not followed by a

QRS complex.• Can result from drugs or organic heart disease• Not treated in prehospital setting


• Wandering atrial pacemaker• Pacemaker moves from SA node to other areas• Upright P wave precedes each QRS (at least

3 shapes of P waves within a strip)


• Wandering atrial pacemaker (cont’d)• Most common with significant lung disease• Treatment in the prehospital setting is not usually indicated.


• Multifocal atrial tachycardia (MAT)• Pacemaker moves within various atrial areas• Rate of more than 100 beats/min• Upright P wave preceding each QRS complex

• P waves vary.


• Multifocal atrial tachycardia (cont’d)• PR interval: 120 to 200 ms• Most common with significant lung disease• Therapies for SVT generally ineffective

Rhythms Originating in the AV Node or AV Junction• The AV node will take over if the SA node fails.• Rhythms of AV node origin are known as “junctional” rhythms

• Have inverted or missing P waves

• An impulse generated in the AV node travels down into the ventricles and up toward the SA node.

Rhythms Originating in the AV Node or AV Junction• Three possibilities:• Upside-down P wave immediately followed by QRS complex• Smaller P wave hidden within QRS complex• Inverted P wave after the QRS complex

• Rates of 40 to 60 beats/min

Rhythms Originating in the AV Node or AV Junction• Junctional (escape) rhythm• Occur when SA node does not function

• AV node becomes the pacemaker• Most common with significant SA node problems• Treatment is usually an implanted pacemaker.

Rhythms Originating in the AV Node or AV Junction• Accelerated junction rhythm• Present with rate exceeding 60 beats/min but less than 100 beats/min• Regular rhythm, little variation between

R-R intervals• Seldom treated in the prehospital setting

Rhythms Originating in the AV Node or AV Junction• Junctional tachycardia• Junctional rhythm rate higher than 100 beats/min• Regular rhythm, little variation between

R-R intervals• Seldom requires prehospital treatment

Rhythms Originating in the AV Node or AV Junction• Premature junctional complex• Particular complex within another rhythm• P wave will be inverted and upside down

• PR interval: less than 120 ms• QRS complex: 40 to 120 ms

• Rarely treated in the prehospital setting

Heart Blocks

• SA node initiates impulses resulting in heart contractions• Delayed when they reach AV node so atria can contract and fill the ventricle

• Sometimes impulses are delayed longer than usual, causing heart blocks.

Heart Blocks

• First-degree heart block• Occurs when each impulse is delayed slightly longer than normal• Least serious type of block• Rarely treated in a prehospital setting

Heart Blocks

• Second-degree heart block: Mobitz type I (Wenckebach)• Occurs when each impulse is delayed a little longer, until an impulse cannot

continue• P wave followed by P wave, followed by QRS complex with normal PR interval• Not treated in the prehospital setting

Heart Blocks

• Second-degree heart block: Mobitz type II (classical)• Occurs when several impulses cannot continue• Upright P wave precedes some QRS complexes, with an always constant PR

interval• Only treated in the field if with bradycardia

Heart Blocks

• Third-degree heart block• Occurs when all impulses cannot continue, causing a QRS complex• Ventricles develop their own pacemaker.• Identified by nonconductor P waves• Treated in the field only if with bradycardia

Rhythms Originating in the Ventricles• Ventricles may become the pacemaker if AV node does not take over

after SA node fails• Wide QRS complexes and missing P waves• Impulses must travel cell by cell.

• The impulses will travel more slowly.• Normally 20 to 40 beats/min

Rhythms Originating in the Ventricles• Idioventricular rhythm • Occurs when SA and VA nodes fail• May or may not result in a palpable pulse• Treatment includes improving the CO.

Rhythms Originating in the Ventricles• Accelerated idioventricular rhythm• Occurs when idioventricular rhythm exceeds

40 beats/min but less than 100 beats/min• Rarely treated in the prehospital setting

Rhythms Originating in the Ventricles• Ventricular tachycardia • Occurs when SA and AV nodes fail, and rate exceeds 100 beats/min• QRS complexes usually have uniform tops and bottoms (monomorphic).

Rhythms Originating in the Ventricles• Ventricular tachycardia (cont’d)• Occasionally QRS complex will vary in height

• Torsades de pointes • Requires treatment to maintain adequate CO

Rhythms Originating in the Ventricles• Premature ventricular complex

(ectopic complex)• Particular complex within another rhythm• Occurs earlier than expected, causing a R-R interval between it and the

previous complex

Rhythms Originating in the Ventricles

• Premature ventricular complex (cont’d)• Unifocal: from same

spot within ventricle

• Multifocal: two premature complexes with different appearances

Rhythms Originating in the Ventricles• Premature ventricular complex (cont’d)• Couplet: Two complexes occurring together• Salvos: Three or more occurring in a row • Bigeminy: Salvos alternate with normal complex• Trigeminy: Third beat is a premature complex

Rhythms Originating in the Ventricles• Premature ventricular complex (cont’d)• Usually from ischemia in ventricular tissue• May occur when ventricles are not fully repolarized, resulting in ventricular

fibrillation• Rarely treated in the field

Rhythms Originating in the Ventricles• Ventricular fibrillation• Entire heart is fibrillating without organized contraction• Occurs when many different heart cells become depolarized independently

Rhythms Originating in the Ventricles• Ventricular fibrillation (cont’d)• Coarse (early stages): chaotic wave height high • Fine: great reduction in chaotic wave height

Rhythms Originating in the Ventricles• Asystole (flat line)• Entire heart no longer contracting• Heart cells no longer have energy• Complete absence of electrical activity

Rhythms Originating in the Ventricles• Asystole (cont’d)• Agonal rhythm: Flat baseline is interrupted by a small sinusoidal complex• Generally considered a confirmation of death

Artificial Pacemaker Rhythms

• Ventricular pacemaker: attached to ventricles• Spike followed by a wide QRS complex

• Another is attached to atria and ventricle• Spike followed by a P wave and another spike followed by a wide QRS

complex


• Newer pacemakers—sensors identify rate of spontaneous depolarization• Generate impulses when natural pacemakers have slowed


• If pacemaker is failing, spikes will be visible but not followed by a QRS complex.• “Loss of capture” • Patients need TCP as quickly as possible.• May fail because of a “runaway” pacemaker

Education

Cardio 2