11.2 Electrocardiograms

11.2 Electrocardiograms

By Stacy King

Ventricular diastole

​ventricle relax, atria contract

Ventricular systole

ventricles contract, atria relax​

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Mean Arterial Pressure (map)

overall pressure within cardiovascular system

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MAP = 2/3 (Diastole) + 1/3 systole

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​Cardiac Cycles

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Amount of blood pumped by heart in 1 minute measured in liters/minute

• stroke volume

amount of blood pumped in 1 beat

• heart rate

number of beats per minute

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SV (ml/beat) x HR (beats/min) = Q (Cardiac Volume)

Ex. 72 beats/min x 70 mL/beat = 5,040 L/min

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Cardiac Output

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Intrinsic (ANS)

• PNS and SNS​

Extrinsic

• ​Endocrine and Baroreceptors- stretch/pressure in the carotid artery

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Regulation of the Heart

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Sympathetic

Increases rate and forces contractions

Parasympathetic (branches of Vagus n.)

Slows the heart rate

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Autonomic Regulation

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Multiple Choice

Heart rate can increase due to stimulation by this division of the autonomic nervous system?

• SNS

• PNS

• SAS

• NSS

​Pacemaker

​The SA node or sinus node is able to spontaneous generate and propagate electrical impulses

generating the heart rate​

60-100 b​pm

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Sinoatrial node​

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Multiple Choice

What is the pacemaker of the heart?

• SA node

• AV node

• Brain

• Spinal cord

• ​SA node

  • atrium contraction​

• ​AV node

• bundle of HIS

• right and left branching purkinje fibers

  • ventricle contraction​

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​Electrical innervation of the Heart

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Multiple Choice

What part of the hearts conduction system is shown in the diagram?

• SA node

• AV Node

• AV bundle

• Purkinje Fibers

Multiple Choice

What part of the hearts conduction system is shown in the diagram?

• SA node

• AV Node

• AV bundle

• Purkinje Fibers

Measures the electrical impulses ​of the heart

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Depolarization is the contraction phase (systole)

​Repolarization is the relaxation phase (diastole)

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P= atrial systole

QRS= ventricle systole

​T= ventricle diastole

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Electrocardiogram

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Multiple Choice

What is the name of the circled area of the ECG in the diagram?

• P Wave

• QRS Complex

• T Wave

• Cardiac Cycle

​Abnormal timing or contraction of the heart

• Bradycardia

  • ​resting heart rates that fall below 60 bmp

• Tachycardia

  • resting heart rate that is above 100 bpm

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​​Arrhythmia

Multiple Choice

Bradyarrhythmia is defined as:

• any rhythm disorder with a heart rate less than 40 beats per minute

• any rhythm disorder with a heart rate less than 60 beats per minute

• any symptomatic rhythm disorder with a heart rate less than 50 beats per minute

• any rhythm disorder with a heart rate less than 50 beats per minute

​Abnormal timing or contraction of the heart

• Premature atrial contraction​ (PAC)

  • ​atria, rather than SA node, cause beat (ectopic beat)

• Premature ventricular contractions (PVCs)​

  • ventricles contract too soon ​

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​​Arrhythmia

Multiple Choice

A condition in which Purkinje fibers fire before the SA node, causing the ventricles to contract prematurely.

• premature atrial contractions

• arrhythmia

• premature ventricular contractions

• atrial fibrillation

​Abnormal timing or contraction of the heart

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• ​Ventricular tachycardia (vtach)

  • ventricles, rather than SA node, cause beat ​

​​Arrhythmia

Multiple Choice

A life threatening arrhythmia in which the ventricles, rather than the SA node initiate the beat. The heart rate is between 150 and 250 bmp, requiring immediate medical intervention

• bradycardia

• premature atrial contraction (PAC)

• ventricular tachycardia

• atrial fibrillation

​Abnormal timing or contraction of the heart

• ​Atrial fibrillization (afib)

  • atria contract faster than 350 bpm

• Ventricular fibrillation (vfib)

  • ventricles contract faster than 350 bpm

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​​Arrhythmia

Multiple Choice

A condition in which the atrial tissue is very irritated, causing the atria to beat at a rate greater than 350bpm. The atria don’t beat in a coordinated manner, they simply quiver. On the ECG it is represented as a wavy line and the rhythm is irregular.

• premature atrial contraction (PAC)

• arrhythmia

• premature ventricular contraction (PVC)

• atrial fibrillation

​Abnormal timing or contraction of the heart

• ​Heart Block

  • impulse from SA node to AV node

    • first–impulse delayed

    • second–intermittently blocked

    • third–completely blocked

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​​Arrhythmia

Multiple Choice

Choose the 3rd degree heart block:

Artificial Pacemakers

devices used to regulate the contraction of atriums or ventricles​

AED (automated external difibulator)

emergency ​device used to send an electrical impulse to help reestablish heart rhythm

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Medical Devices​

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Multiple Choice

Why is defibrillation important? 

• It prevents rearrest from occurring
• It is not important for cardiac arrest
• There is a 100% success rate in regaining a normal cardiac rhythm
• It can restore a regular cardiac rythm