Cardiopulmonary Anatomy & Physiology Chapter 19: Electrocardiogram and Cardiac Arrythmias in Adults

myocardial cells

working or mechanical cells responsible for contraction

pacemaker cells

specialized cell of the electrical conduction system that spontaneously generates and conducts impulses

Automaticity

the ability of pacemaker cells to initiate an electrical impulse without being stimulated by another source

Excitability (irritability)

ability of cardiac muscle cells to respond to an outside stimulus

Conductivity

ability of a cardiac cell to receive an electrical stimulus and conduct that impulse to an adjacent cardiac cell

Contractility

the ability of cardiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus

antiarrhythmic drugs

medications used to correct irregular heartbeats; either slows down or speeds up heart beat

arryhthmia/dysrhythmia

an irregular heartbeat or abnormal sinus rhythm

Electrocardiogram (ECG)

voltmeter that records electrical voltages (potentials) generated by depolarization of heart muscle

ECG leads

electrodes places on the skin and attached to a specialized voltmeter (ECG)

-Conduction disturbances

-The electrical effects of medications and electrolytes

-the presence of ischemic damage

name 3 important things the ECG can inform us about

FALSE: the ECG provides electrical information about the heart, NOT mechanical information

True or False: The ECG can provide information about the mechanical (contractile) condition of the myocardium.

Bipolar limb leads

(Leads I,II,III) leads composed of two opposite polarity electrodes

Precordial Chest Leads

(Leads v1-v6) Leads placed on a horizontal plane through the chest; consisting of six positive unipolar electrodes on the surface of the chest

P-wave

part of the ECG that represents depolarization of the atria (atrial systole)

QRS complex

part of the ECG that represents ventricular depolarization

T-wave

part of the ECG that represents ventricular repolarization

ECG graph paper

a grid permitting time management along the horizontal lines, and voltage measurement along the vertical lines

count each R-wave and multiply by 10

how does one calculate heart rate on ECG graph paper?

myocardial injury/infarction

what does an elevated ST segment indicate?

6 seconds

how many seconds long is an ECG graph paper strip?

absolute refractory period

from the beginning of the QRS complex to the middle of the T-wave; no outside stimulus can cause the cells to depolarize.

relative refractory period

from the middle of the T-wave to the end of the T-wave; A strong enough outside stimulus can initiate depolarization of the only partially recharged cells.

It is a dangerous period that can possibly cause a lethal arrhythmia.

what is the significance of the relative refractory period?

60-100 beats/minute

what is the rate of a Normal Sinus Rhythm?

Sinus Bradycardia

how would we define a sinus rhythm less than 60 beats/minute?

-oxygen administration

-atropine (parasympatholytic)

name 2 ways to treat sinus bradycardia

Sinus tachycardia; Beta blocker drugs (sympatholytic)

how would we define a sinus rhythm greater 100 beats/minute? how would we treat that condition?

Sinus Arrythmia

when the SA node fires irregularly, this is called...

1. P-P interval is consistent

2. R-R interval is consistent

name two determining factors of a Normal Sinus Rhythm

1:1; Each QRS Complex should be preceded by 1 P-wave

in a Normal Sinus Rhythm, how what should the P-Wave to QRS Complex ratio be?

Premature Atrial Contraction (PAC)

and ectopic focus that originates outside of the SA node in the atria will cause...

Supraventricular Arrhythmia

an ectopic focus located above the ventricles will cause...

Atrial Flutter

this is caused by a single ectopic focus above the AV node with electrical impulses at a rapid rate; Produces F-waves (saw-tooth pattern) that replace the P-Waves

Atrial Fibrillation (A-Fib)

This arrhythmia is caused by multiple randomly/chaotic firing ectopic atrial foci; Causes atrial "quivering" (no pumping)

Reduces ventricular filling by 20% due to loss of atrial kick

how does atrial fibrillation affect ventricular filling?

Stroke (due to pooling of blood in the left atrium)

Name the risk of left atrium fibrillation

pulmonary embolism (due to pooling of blood in the right atrium)

Name the risk of right atrium fibrillation

Junctional Arrythmia

Supraventricular arrythmia where the SA node is blocked or fails to fire so the AV node assumes the role of pacemaker

an inverted (upside-down) P-Wave

name a key identifier of a Junctional Arrhythmia on an ECG

40-60 beats/min

what is the AV nodes pacemaker rate?

True

True or False: Ventricular Arrythmias are considered more dangerous that Supraventricular Arrhythmias

20-40 beats/minute

what is the pacemaker rate of the Purkinje Fibers?

the ventricles

cells in which part of the heart are considered the least efficient pacemakers?

premature ventricular contraction (PVC)

this arrhythmia is caused by an ectopic focus arising from the ventricles below the Bundle of His, where the QRS (of the ectopic focus) is not preceded by a P-Wave

-QRS (of ectopic focus) not preceded by P-Wave

-Compensatory Pause

name two identifying factors of a Premature Ventricular Contraction

Unifocal PVC

a PVC in one area of the ventricle is called...

Multifocal PVCs

a PVC in different areas of the ventricle is called...

Ventricular Tachycardia (VT)

this arrhythmia is characterized by "successive runs of PVCs," and is lethal

Immediate defibrillation

how do we treat ventricular tachycardia?

high chance of progression to ventricular fibrillation

why is ventricular tachycardia considered lethal?

Ventricular Fibrillation (VF)

most lethal arrhythmia; nonfunctional ventricles that quiver with no pumping activity

there's no recognizable waves or complexes

how can you identify ventricular fibrillation on an ECG?

Asystole

"not a rhythm;" Absence of all cardiac electrical activity, represented by a flat line; indicative of clinical death.

myocardial infarction

what is the major cause of asystole

Pulseless Electrical Activity (PEA)

when there is electrical activity but the heart does not contract, this is called...

Second Degree Heart Block AKA Type I (Wenckebach) Heart Block

heart block where the PR segment gradually lengthens until the QRS fails to appear (non-conducted P-Wave)

Third Degree Heart Block

heart block where none of the SA nodal impulses (P-Waves) transmit to the ventricles; no relation between P and QRS waves