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Questions and Answers
What does an oddly shaped P wave potentially indicate?
What does an oddly shaped P wave potentially indicate?
Which of the following heart rates would classify as bradycardia?
Which of the following heart rates would classify as bradycardia?
In lead II, which electrode is positive?
In lead II, which electrode is positive?
Which of the following conditions might cause a T wave inversion?
Which of the following conditions might cause a T wave inversion?
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Which evaluation technique determines if the spacing between QRS complexes is equal?
Which evaluation technique determines if the spacing between QRS complexes is equal?
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What is the interpretation of a heart rate calculated by counting QRS complexes in a 6-second strip and multiplying by 10?
What is the interpretation of a heart rate calculated by counting QRS complexes in a 6-second strip and multiplying by 10?
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In which chest lead do you expect to view the interventricular septum?
In which chest lead do you expect to view the interventricular septum?
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What does an abnormal P wave indicate in an ECG tracing?
What does an abnormal P wave indicate in an ECG tracing?
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Which lead is considered best for monitoring heart rhythm on a 12-lead ECG?
Which lead is considered best for monitoring heart rhythm on a 12-lead ECG?
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What is the primary function of pacemaker cells in the heart?
What is the primary function of pacemaker cells in the heart?
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Which of the following is NOT a common indication for an ECG?
Which of the following is NOT a common indication for an ECG?
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What role do conducting cells play in the cardiac conduction system?
What role do conducting cells play in the cardiac conduction system?
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Which statement regarding autonomic nervous system influence on the SA node is correct?
Which statement regarding autonomic nervous system influence on the SA node is correct?
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Which characteristic is typically observed in a normal ECG tracing?
Which characteristic is typically observed in a normal ECG tracing?
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What does an increase in heart rate indicate when evaluating an ECG?
What does an increase in heart rate indicate when evaluating an ECG?
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Which of the following can indicate the presence of dysrhythmias on an ECG?
Which of the following can indicate the presence of dysrhythmias on an ECG?
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What does the T wave on an ECG represent?
What does the T wave on an ECG represent?
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Which of the following intervals is observed when measuring the time it takes for an impulse to travel from the SA node to the AV junction?
Which of the following intervals is observed when measuring the time it takes for an impulse to travel from the SA node to the AV junction?
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How is the heart rate calculated if there is no 6-second strip available?
How is the heart rate calculated if there is no 6-second strip available?
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What is the normal duration for the QRS interval?
What is the normal duration for the QRS interval?
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During which phase of the cardiac cycle is the U wave observed?
During which phase of the cardiac cycle is the U wave observed?
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What characteristic defines the S-T segment in a normal ECG?
What characteristic defines the S-T segment in a normal ECG?
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What effect does an increased heart rate have on the Q-T interval?
What effect does an increased heart rate have on the Q-T interval?
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What is the purpose of identifying the isoelectric baseline before measuring amplitude on an ECG?
What is the purpose of identifying the isoelectric baseline before measuring amplitude on an ECG?
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In a normal ECG tracing, which component precedes the QRS complex?
In a normal ECG tracing, which component precedes the QRS complex?
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The Sinoatrial node has the lowest degree of automaticity compared to other cardiac cells.
The Sinoatrial node has the lowest degree of automaticity compared to other cardiac cells.
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An EKG lead placement of Lead II is primarily used for visualizing gross changes in heart rhythm.
An EKG lead placement of Lead II is primarily used for visualizing gross changes in heart rhythm.
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Resting ECG tracing can definitively rule out acute problems such as myocardial infarction (MI).
Resting ECG tracing can definitively rule out acute problems such as myocardial infarction (MI).
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Sympathetic nervous system stimulation increases the rate of the SA node, resulting in a higher heart rate.
Sympathetic nervous system stimulation increases the rate of the SA node, resulting in a higher heart rate.
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Conducting cells in the heart are responsible for contracting in response to electrical stimuli.
Conducting cells in the heart are responsible for contracting in response to electrical stimuli.
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Study Notes
Interpretation of the Electrocardiogram
- An electrocardiogram (ECG) records electrical activity in the heart.
- Electrodes are placed on the patient's body to obtain the ECG.
- A 12-lead ECG provides 12 different views of the heart's electrical activity.
- ECG monitoring identifies changes in heart rhythm using 3 or 5 leads.
What is an ECG?
- Measures electrical activity in the heart.
- Achieved by placing electrodes on the patient's surface.
- 12-lead ECG gives 12 different perspectives of heart's electrical function.
- ECG monitoring uses 3 or 5 leads to detect major changes in heart rhythm.
- Shows electrical pathways in the heart.
- Plastic cups, adhesives, wires, and contact buttons are used.
EKG Lead Placement-Standard Leads
- Einthoven's Triangle uses leads I, II, and III for limb leads.
- Lead II is often best for examining heart rhythm.
- EKG breaks down each heartbeat into electrical waves.
- P wave signifies activity in the heart's upper chambers.
- QRS complex and T wave reflect activity in the lower chambers.
Limb Leads or Wires
- Electrodes/leads for recording heart's electrical activity from limbs.
- Diagram shows placement of limb leads on the patient's chest.
Value of an ECG
- Identifies primary cause of symptoms.
- Determines severity of a problem.
- Evaluates treatment effectiveness.
- Does not measure pumping ability or cardiac output.
- Resting ECG does not rule out acute problems like a heart attack (MI).
Indications for ECG
- Chief Complaint/Physical Exam
- Chest pain
- Orthopnea
- Paroxysmal nocturnal dyspnea
- Night sweats
- Syncope
- Palpitations
- Pedal edema
- Hypotension
- Past Medical History of heart disease or heart surgery.
- Screening prior to surgery.
Cardiac Anatomy and Physiology
- Diagram of the heart showing different parts: right atrium, right ventricle, left atrium, left ventricle, interatrial septum, interventricular septum.
- Structure and parts of the heart including the endocardium, myocardium, and epicardium.
- Heart's location relative to the body (base and apex).
Types of Heart Cells
- Pacemaker cells have high automaticity initiating heart's electrical activity.
- Conducting cells transmit electrical impulses throughout the heart.
- Myocardial cells contract in response to electrical signals, pumping blood.
Cardiac Anatomy and Physiology
- Diagram showing different parts of the heart's electrical conduction system, such as sinoatrial node, interatrial conduction tract, internodal atrial conduction tracts, atrioventricular node, bundle of His, left bundle branch, right bundle branch, and Purkinje network.
Sinoatrial Node (SA)
- Electrical activity in the heart begins at the SA node.
- The SA node acts as the heart's pacemaker, setting the heart rate to 60-100 beats per minute.
- Any signal originating outside of the SA node is called an ectopic impulse.
- The impulse travels through internodal pathways causing depolarization and leading to heart contraction.
Autonomic NS
- The SA node is innervated by both parasympathetic (vagus nerve) and sympathetic fibers (T1-4 spinal nerves).
- Vagus nerve stimulation slows the SA node rate, lowering heart rate and contraction force.
- Sympathetic fiber stimulation increases the SA node rate, accelerating heart rate and contraction force.
Atrioventricular Junction (AV)
- Electrical impulse moves through the AV Junction.
- An electrical bridge forms between the atria and ventricles.
- The AV junction includes the AV node and bundle of His.
- A 0.1-second delay is necessary to fill the ventricles prior to contraction.
- The AV node acts as a backup pacemaker if the SA node fails at 40-60 bpm.
- Decremental conduction signifies that increased stimulation of the AV node decreases its conduction speed.
- Atrial fibrillation and flutter reduce AV stimulation, thus ventricles are not as affected.
Bundle of His - Purkinje Fibers
- Electrical impulse moves through the AV node into the bundle of His and subsequently into the left and right bundle branches.
- Purkinje fibers carry the signal from the bundle branches to the myocardium to coordinate contraction.
Dysrhythmias-Causes and Manifestations
- Hypoxia results in reduced oxygen to the myocardium causing ischemia, reduced PaO2, Hgb and blood flow.
- Ischemia causes heart attack (MI) and injury in the myocardium.
- Sympathetic overstimulation, like stress or anxiety, can induce dysrhythmias.
Dysrhythmias-Causes and Manifestations(Drugs)
- Certain drugs stimulate or irritate the heart due to improper levels or poor clearance of the drug.
- Sympathomimetic agents like Cocaine or Ritalin can induce infarction.
- Electrolyte imbalances in K+, magnesium, or calcium can cause irritation.
Depolarization and Repolarization
- Polarized cells have a negative charge inside and a positive charge outside.
- A sudden loss of the negative charge inside the cell is depolarization.
- The return of the electrical charge to the cell is repolarization.
Basic ECG Waves
- The graphic represents normal ECG waves(P, QRS, and T).
- Each wave reflects different stages of the heart's electrical activity.
Atrial Depolarization-P wave
- Depolarization of the atria is graphically represented.
- Small atria = small P wave.
- Size: <2.5 mm height and <3 mm length.
- Repolarization of atria is obscured by ventricular depolarization.
QRS complex
- Depolarization of the ventricles represented by waves.
- Large ventricular mass= larger QRS waves.
- Q= first negative deflection.
- R=first positive deflection.
- S= second negative deflection
T wave
- T wave indicates the final phase of ventricular repolarization.
- U wave: final phase of repolarization, preparing atria for next depolarization
U wave
- Final phase of repolarization for the atria and is marked on the ECG tracing.
ECG Paper and Measurements
- ECG paper has grid lines with boxes (light and dark lines).
- Small boxes for voltage (1 mm × 1 mm).
- Large boxes represent time (5 mm × 5 mm).
- Time on ECG paper moves at 25mm/sec.
- Small squares = 0.04sec
- Large squares = 0.2sec
- 5 large boxes = 1sec.
ECG Paper and Measurements (Voltage axis)
- Voltage or amplitude is measured vertically.
- Voltage is measured in millivolts (mV).
- 1 small box = 0.1 mV.
- 10 small boxes = 1 mV.
Intervals and Segments
- Segment = straight line between 2 waves.
- Interval = 1 wave(s) + connecting straight line(s).
- P-R interval = time for impulse to travel to AV junction.
- QRS interval = time for impulse to travel through ventricles.
- S-T segment = line between QRS and T waves.
- RR interval = time between consecutive ventricular contractions.
- QT interval = time for ventricular depolarization and repolarization.
PR Interval
- Time it takes for the heart's signal to travel to and across the AV junction (between the P wave and the QRS complex).
- Normal PR interval is 0.12-0.2 seconds.
QRS Interval
- Time needed for the signal to spread throughout the ventricles during the QRS complex.
- Normal QRS interval is less than 0.10 seconds; it's the time from the beginning of the QRS complex to the end.
S-T Segment
- Should be isoelectric (flat) or no more than 1 mm above or below the baseline.
- A depressed or elevated S-T segment may signal a heart attack or ischemia.
- Reference figures 10-9 or 11-9 should be consulted for specific information on elevation or depression.
RR Interval
- Time between two consecutive ventricular contractions.
- Precise RR intervals indicate a regular heart rate.
- Irregular intervals signal an irregular heart rhythm/arrhythmia.
QT Interval
- Time for ventricular depolarization and repolarization.
- Shortening of the QT interval occurs with an increased heart rate.
- Hypokalemia and hypocalcemia can result in a prolonged QT interval.
Measuring Heart Rate
- Calculated based on the time of QRS complexes in a 6-second strip.
- Measuring the number of large boxes seen between the QRS complexes in a 6-second period and multiplying the results by 10.
Heart Rate
- Observing the rhythmicity of the heart and quantifying its beat frequency over a 6-second period.
- The heart rate is calculated by counting the number of QRS complexes in 6 seconds and multiplying by 10 (for seconds).
Rhythm
- Evaluating the heart's rhythm to see whether intervals between QRS complexes are consistent.
- Equal spacing implies a regular rhythm.
- Unequal spacing indicates an irregular rhythm.
P Wave
- Normal P wave is less than 2.5 mm height and less than 0.11 seconds.
- A positive P wave precedes the QRS complex.
- Abnormal P wave shape might imply atrial enlargement.
T Wave
- Normally positive in leads where the QRS is positive.
- Inversion in the T wave could indicate a heart attack (MI) or a myocardial infarction developing.
- Tall and Peaked T waves occur with electrolyte imbalances.
- Changes in T waves are observed with potassium levels above 5.5 mEq/L
Spiked T Wave
- Elevated T wave in a heart rate monitored at 6.8 mEq/L potassium (signifying potential electrolyte imbalance).
Common Dysrhythmias
- A list of common heart rhythm disorders that can appear on an EKG. (e.g., sinus bradycardia, sinus tachycardia, sinus dysrhythmia, atrial flutter, atrial fibrillation, PVCs, ventricular tachycardia, ventricular fibrillation, asystole, and pulseless electrical activity)
Sinus Bradycardia
- Heart rate below 60 beats per minute.
- Absolute bradycardia refers to heart rates under 60 bpm where that rate is normal for the person.
- Relative bradycardia is when a heart rate lower than 60 bpm is experienced with a body that can't tolerate that rate.
- Can cause hypotension, syncope, diminished cardiac output, heart failure (CHF) and shock.
- Stimulation from the vagus nerve could reduce heart rate.
- Damage to the SA node (MI) can cause long-term bradycardia.
- Drug therapies or pacemakers can help adjust heart rate.
Sinus Bradycardia
- Vagus nerve stimulation may induce transient bradycardia arising from carotid massage, tracheal suctioning, manipulation of tracheal tubes or catheters.
- MI and other SA node damage can lead to long-term bradycardia.
- Drug therapy or a pacemaker may help manage the heart rate.
Sinus Bradycardia
- Heart rate less than 60 beats per minute is indicative of sinus bradycardia.
- Rhythm is regular with a normal P wave occurring before each QRS complex.
- PR interval should not exceed 0.2 seconds.
- QRS complex duration is less than 0.10 seconds.
Sinus Tachycardia
- Normal sinus rhythm over 100 bpm.
- Triggered by sympathetic nervous system activation.
- Increased myocardial oxygen consumption and decreased diastolic time can lead to myocardial ischemia.
Sinus Tachycardia
- Could be caused by fever, pain, hypotension, hypovolemia, hypoxemia, heart failure, or beta agonist use.
- Treatment is aimed at addressing the underlying cause.
Sinus Tachycardia
- Heart rate over 100-150 beats per minute.
- Normal rhythm, with P waves preceding QRS complexes.
- PR interval should be less than or equal to 0.2 seconds.
- QRS complex duration should be less than 0.12 seconds.
Sinus Dysrhythmia
- A benign dysrhythmia where the sinus rhythm is irregular.
- Normal sinus rhythm but with irregular rhythm due to variation in heart rate with breathing cycles or respiratory patterns.
- Usually asymptomatic with little need for treatment.
Sinus Dysrhythmia
- Heart rate ranges from 60 to 100 beats per minute.
- The rhythm is irregular.
- P precedes each QRS complex.
- PR interval is less than or equal to 0.2 seconds.
Atrial Flutter
- "Sawtooth" pattern between normal QRS complexes in the EKG chart.
- Suggests minimal atrial function.
- Atrial contraction reduces atrial filling and ventricular filling.
- Thrombi formation in atria due to reduced blood flow is possible.
Atrial Flutter
- Usually a brief dysrhythmia.
- Possible progression to atrial fibrillation or reversion to a normal heartbeat.
- Commonly associated with pulmonary illnesses.
- MI or valve malfunction can trigger.
Atrial Flutter
- Atrial rate of 180-400 beats per minute.
- Ventricular rate is lower and varies but always slower than the atrial rate.
- Rhythm is regular.
- P waves have a sawtooth appearance with 3-4 flutter waves for each QRS.
Atrial Fibrillation
- Atrial electrical activity is completely irregular and chaotic.
- Atrial myocardium quivering results in lost pumping ability.
- Increased risk of atrial thrombi formation and embolization.
- Reduced time for atrial filling and reduced ventricular filling.
Atrial Fibrillation
- Does not substantially impair cardiac output (CO).
- Common in patients with pulmonary diseases.
- QRS have a normal appearance but irregular rhythm compared to other waves.
Atrial Fibrillation
- Atrial rate is exceeding 400/min.
- Ventricular rate is less than atrial rate.
- P waves have a variety of appearances.
- Unable to measure and determine interval.
- QRS complexes with narrow duration.
Ventricular Dysrhythmias
- A broad classification covering several types of heart rhythm disorders that originate in the ventricles. This section introduces this category of cardiac disturbances.
Premature Ventricular Contraction (PVC)
- Extra heartbeats that originate in one of the ventricles.
- Seen in both healthy and disordered hearts.
- Common causes: stress, excessive caffeine, hypoxia, and MI.
Premature Ventricular Contraction (PVC)
- Premature QRS complexes are wider than normal (>0.12 seconds).
- Absence of P wave preceding QRS complex.
- ST segment is opposite in direction.
- Usually followed by a compensatory pause.
PVC's
- Unifocal- originating from same site, with similar appearance between contractions.
- Fewer than 6 PVCs/minute: monitor, and give oxygenation.
- More than 6 PVCs/minute: consider administering lidocaine to reduce heart rate and give supplemental oxygen.
PVC's to Watch
- Multifocal PVCs (multiple origins).
- Couplets (two PVCs in a row).
- Salvos (three or more PVCs in a row).
- R-on-T phenomenon (a PVC occurring during ventricular repolarization).
Bigimeny PVC's
- A pattern of alternating regular beats and PVCs.
Trigeminy
- Pattern where PVCs occur every third beat.
Ventricular Tachycardia
- Rapid heartbeats originating in the ventricles (140-300 beats per minute).
- Lack of identifiable P waves.
- Reduced cardiac output is a consequence.
- Regular rhythm and uniform appearance on ECG.
- This rhythm is usually from severe ischemia.
Ventricular Tachycardia
- Often originates from severe myocardial ischemia.
- Rapid deterioration requiring immediate emergency treatment.
- Untreated ventricular tachycardia can progress to ventricular fibrillation, potentially fatal without intervention.
- Lidocaine and oxygen administration are common treatments.
Ventricular Fibrillation
- Chaotic and disorganized ventricular electrical activity.
- Characterized by a wavy and irregular pattern on an ECG.
- Cardiac output drops to zero, leading to loss of consciousness.
- Requires immediate intervention, such as defibrillation, due to life-threatening nature.
V fib
- Rapid and chaotic electrical activity in the ventricles, showing on the ECG as a disorganized rhythm.
- Life-threatening condition, needing immediate treatment; often requiring defibrillation. This is less chaotic than other forms of ventricular fibrillation.
V Fib
- PVCs can transition into ventricular fibrillation.
- Successful defibrillation can restore normal heartbeats.
Asystole
- The heart's electrical activity stops completely resulting in a flat line on an ECG.
- A critical condition necessitating immediate treatment.
- Assessing the patient and checking the ECG leads are paramount.
Pulseless Electrical Activity (PEA)
- Clinically diagnosed condition where the ECG shows electrical activity but there is no pulse.
- The heart's electrical impulses do not result in mechanical pumping.
- A possible result of various problems involving the heart or body, such as tension pneumothorax, cardiac trauma, or extreme electrolyte or acid-base imbalances.
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Description
Test your knowledge on key concepts in ECG interpretation with this quiz. Questions cover various P wave shapes, heart rate classifications like bradycardia, and the significance of T wave inversions. Perfect for any medical professional or student looking to sharpen their cardiology skills.
