Electrocardiogram Interpretation Quiz
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Questions and Answers

What characterizes ventricular tachycardia in terms of QRS complexes and rate?

  • Broad QRS complexes with a rate of 140-300 (correct)
  • Narrow QRS complexes with a rate of 60-100
  • Irregularly irregular rhythm with very high rates
  • Regular P waves at a rate of 120-180

    • Which of the following best describes the R-on-T phenomenon?

  • PVC occurring during the T wave of the preceding beat (correct)
  • PVC occurring during the P wave of the preceding beat
  • Normal rhythm occurring during the R wave of the previous beat
  • A series of PVCs following a normal sinus beat

    • Which treatment approach is correct for a patient experiencing pulseless ventricular tachycardia?

  • Administer antiarrhythmic medications immediately
  • Use oxygen therapy only without further action
  • Assess for possible need for invasive monitoring
  • Start CPR and prepare for defibrillation (correct)

    • Which condition is characterized by having electrical activity but no palpable pulse?

    <p>Pulseless electrical activity (PEA)</p> Signup and view all the answers

    What is the appropriate initial response to a patient in asystole?

    <p>Assess patient and check leads for rhythm confirmation</p> Signup and view all the answers

    What is the normal duration of the P-R interval in seconds?

    <p>0.12 - 0.20 sec</p> Signup and view all the answers

    What indicates ventricular repolarization on an ECG?

    <p>T wave</p> Signup and view all the answers

    How is the heart rate calculated using the R-R interval?

    <h1>of boxes divided into 300</h1> Signup and view all the answers

    Which segment is expected to be isoelectric during a normal ECG reading?

    <p>S-T segment</p> Signup and view all the answers

    What does a prolonged QT interval suggest?

    <p>Hypokalemia and hypocalcemia</p> Signup and view all the answers

    Which of the following best describes a standard small box on ECG paper?

    <p>1mm x 1mm, representing 0.04 sec</p> Signup and view all the answers

    What type of arrhythmia could a variable R-R interval indicate?

    <p>Arrhythmia</p> Signup and view all the answers

    What is the significance of a large ventricular mass on the QRS complex?

    <p>Leads to larger waves</p> Signup and view all the answers

    Which statement regarding the role of the AV node as a pacemaker is accurate?

    <p>The AV node functions as a backup pacemaker at a rate of 40-60 bpm.</p> Signup and view all the answers

    What is the function of the bundle of His in the conduction system?

    <p>It transmits impulses from the AV node to the bundle branches.</p> Signup and view all the answers

    Which condition is primarily caused by reduced oxygen to the myocardium?

    <p>Ischemia</p> Signup and view all the answers

    What occurs during the depolarization phase of a cardiac cell?

    <p>K+ moves out and Na+ moves into the cell.</p> Signup and view all the answers

    What type of ECG wave represents atrial depolarization?

    <p>P wave</p> Signup and view all the answers

    What could potentially cause dysrhythmias due to medication effects?

    <p>Improper drug levels or clearance</p> Signup and view all the answers

    Which of the following elements is commonly associated with dysrhythmias when imbalanced?

    <p>Potassium</p> Signup and view all the answers

    What is the heart rate when there are 4 large boxes between QRS complexes?

    <p>75 beats per minute</p> Signup and view all the answers

    What is the primary effect of sympathetic stimulation on the heart?

    <p>It increases cardiac workload.</p> Signup and view all the answers

    What is indicative of decremental conduction in the AV node?

    <p>Decreased conduction speed with increased stimulation.</p> Signup and view all the answers

    Which of the following is a characteristic of sinus bradycardia?

    <p>Heart rate less than 60 bpm</p> Signup and view all the answers

    Which ECG lead is specifically intended to view the interventricular septum?

    <p>V1</p> Signup and view all the answers

    How does atrial fibrillation affect AV node stimulation?

    <p>It results in less AV stimulation and less effect on ventricles.</p> Signup and view all the answers

    How is heart rate calculated based on the number of QRS complexes in a 6-second ECG strip?

    <p>Count the number of QRS complexes and multiply by 10</p> Signup and view all the answers

    What does an irregular spacing between QRS complexes indicate?

    <p>There may be an irregular rhythm</p> Signup and view all the answers

    What does a peaked T wave typically indicate?

    <p>Potassium levels greater than 5.5 mEq/L</p> Signup and view all the answers

    Which lead placement is associated with a positive view of the left leg?

    <p>II</p> Signup and view all the answers

    Which of the following statements about P waves is correct?

    <p>Only one P wave should proceed each QRS complex</p> Signup and view all the answers

    How many limb leads provide a view of the heart in the frontal plane?

    <p>6</p> Signup and view all the answers

    What does a small variation in QRS spacing during breathing suggest?

    <p>Normal physiological response</p> Signup and view all the answers

    What is the primary function of pacemaker cells in the heart?

    <p>Provide electrical power source for the heart</p> Signup and view all the answers

    Which lead is considered the best for assessing heart rhythm in a standard ECG?

    <p>Lead II</p> Signup and view all the answers

    Which statement accurately represents the consequences of stimulation via the parasympathetic nervous system on the SA node?

    <p>Decreases heart rate and contraction force</p> Signup and view all the answers

    What aspect of ECG does not directly assess cardiac function?

    <p>Measurement of pumping ability</p> Signup and view all the answers

    How many views of the heart's electrical activity can a 12-lead ECG provide?

    <p>12</p> Signup and view all the answers

    Study Notes

    Interpretation of the Electrocardiogram

    • An electrocardiogram (ECG) records the electrical activity of 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 can detect changes in heart rhythm using 3 or 5 leads.
    • The EKG breaks down each heartbeat into a series of electrical waves (P wave, QRS complex, and T wave).
    • These waves are associated with the heart's contraction.
    • The P wave reflects activity in the heart's upper chambers.
    • The QRS complex and T wave reflect activity in the heart's lower chambers.

    What is an ECG?

    • The ECG measures the electrical activity in the heart.
    • Electrodes are placed on the surface of the patient's body for recording.
    • A 12-lead ECG displays different angles of the heart's electrical activity.
    • ECG monitoring detects changes in heart rhythm and includes using 3 or 5 leads.

    EKG Lead Placement-Standard Leads

    • Einthoven's Triangle: Leads I, II, and III are limb leads.
    • Lead II is generally best for evaluating heart rhythm.
    • Each heartbeat is characterized by a series of electrical waves (P wave, QRS complex, and T wave).
    • The P wave reflects activity in the atria (upper chambers of the heart).
    • The QRS complex and T wave reflect activity in the ventricles (lower chambers of the heart).

    Limb Leads or Wires

    • Leads I, II, and III are positioned to create Einthoven's triangle.

    Value of an ECG

    • An ECG helps to identify causes of symptoms.
    • It aids in determining the severity of heart problems.
    • It's used to evaluate the effectiveness of treatments.
    • An ECG doesn't directly measure the heart's pumping ability or cardiac output.
    • Resting ECGs may not rule out acute problems like a heart attack.

    Indications for ECG

    • Indications for an ECG include chest pain, shortness of breath, palpitations, and a history of heart disease or surgery.
    • It can also be used for pre-surgical screening.

    Cardiac Anatomy and Physiology

    • The heart consists of four chambers: two atria and two ventricles.
    • The heart has specialized cells for electrical conduction, including the sinoatrial (SA) node, atrioventricular (AV) node, and Purkinje fibers.
    • The heart consists of layers of tissue, including the endocardium, myocardium, and epicardium.
    • Atria are upper chambers, ventricles lower chambers.
    • Internal partitions are called septa.

    Types of Heart Cells

    • Pacemaker cells initiate the heart's electrical impulses.
    • Conducting cells transmit the electrical impulses throughout the heart.
    • Myocardial cells contract in response to impulses to pump blood.

    Cardiac Anatomy and Physiology (Specialized Conduction System)

    • Specialized cells conduct signals through the heart.
    • The sinoatrial (SA) node, the primary pacemaker, initiates the heartbeat.
    • Conduction system ensures coordinated atrial and ventricular contractions.

    Sinus Node (SA)

    • The SA node (sinoatrial node) is the natural pacemaker of the heart.
    • The SA node generates electrical impulses to regulate the heart rate (60-100 bpm).
    • Pacemaker cells produce impulses.
    • Impulses from areas outside the SA node (ectopic) affect the rate.

    Autonomic Nervous System

    • The parasympathetic nervous system (e.g., vagus nerve) slows heart rate.
    • The sympathetic nervous system speeds heart rate.

    Atrioventricular Junction (AV Junction)

    • The AV junction is an electrical bridge between the atria and ventricles.
    • The AV node is a backup pacemaker to the SA node if the SA node fails.
    • The AV node delays impulses to allow ventricular filling.
    • The rate of impulse transmission through the node decreases as it is stimulated more often—this is called decremental conduction.
    • The AV node is less stimulated with atrial fibrillation or flutter reducing its impact on ventricle function.

    Bundle of His - Purkinje Fibers

    • The bundle of His carries impulses from the AV node to the ventricles.
    • Purkinje fibers distribute impulses throughout the ventricles, causing coordinated contraction.

    Dysrhythmias-Causes and Manifestations

    • Hypoxia reduces oxygen to the myocardium causing ischemia (reduced blood flow).
    • Ischemia can lead to a heart attack (MI) and myocardial injury from lack of oxygen.
    • Physical or emotional stress and cardiac ischemia can cause sympathetic stimulation.
    • Drugs and electrolyte imbalances (K+, magnesium, calcium) can also cause dysrhythmias.

    Depolarization and Repolarization

    • Polarization: Outside of the cell is positive, inside is negative.
    • Depolarization: Sudden loss of negative charge inside the cell.
    • Repolarization: Electrical charge returns to its baseline.
    • ECG electrodes detect these electrical waves.
    • The wave's size reflects the voltage from the heart.

    Basic ECG Waves

    • Waves on an ECG represent different phases of the heartbeat.
    • The P wave represents atrial depolarization.
    • The QRS complex represents ventricular depolarization.
    • The T wave represents ventricular repolarization.

    Atrial Depolarization-P Wave

    • The P wave represents atrial depolarization.
    • Small atria produce small P waves.
    • P wave size is typically less than 2.5 mm in height and 3 mm in length.
    • Repolarization of atria is masked by larger ventricular depolarization.

    QRS Complex

    • The QRS complex represents ventricular depolarization.
    • Larger ventricles produce larger waves.
    • A QRS complex contains a Q wave (negative), R wave (positive), and S wave (negative) deflection.

    T Wave

    • The T wave represents ventricular repolarization.
    • U wave: Final phase of ventricular repolarization, less prominent.

    U Wave

    • The U wave is the final phase of ventricular repolarization.
    • It often gets obscured or is small, but typically precedes a new cardiac cycle.

    ECG Paper and Measurements

    • ECG paper has a grid pattern of small and large boxes.
    • The time is measured horizontally, with a paper speed of 25 mm/second.
    • The voltage or amplitude is measured vertically, with 1 small box representing 0.1 mV and 10 small boxes equaling 1 mV.
    • Isoelectric baseline must be assessed before measuring wave amplitude.

    Intervals and Segments

    • Segments are straight lines between two waves.
    • Intervals include one or more waves.
    • Various intervals and segments are used, including PR, QRS, ST, RR, and QT.

    PR Interval

    • The PR interval is the time taken for the impulse to travel from the SA node to the AV node.
    • Normal PR intervals are between 0.12 and 0.20 seconds.

    QRS Interval

    • The QRS interval represents the time taken for the impulse to travel through the ventricles.
    • Normal QRS intervals typically last less than 0.10 seconds.

    S-T Segment

    • The ST segment is the time between the end of the QRS complex and the beginning of the T wave.
    • It should be isoelectric (flat line) or not more than 1 mm above or below the baseline.
    • Depressed or elevated segments are associated with myocardial ischemia or injury.

    RR Interval

    • The RR interval is the time between two successive R waves.
    • A regular RR interval signifies a regular heart rate.
    • Irregular intervals indicate an arrhythmia.

    QT Interval

    • The QT interval is the total time from the start of the QRS complex to the end of the T wave, reflecting ventricular depolarization and repolarization.
    • The length of the QT interval can be impacted by heart rate.
    • Abnormally prolonged QT intervals are associated with abnormalities like hypokalemia and hypocalcemia.

    Measuring Heart Rate

    • Calculate heart rate by analyzing the time between R waves in a six-second strip.
    • Divide the total number of large boxes between the R waves by 300 to get the heart rate in beats per minute.
    • Count the number of QRS complexes in 6 seconds.
    • Multiply the count by 10 for the heart rate in beats per minute.

    Heart Rate

    • Measure the heart rate in beats per minute using a six-second strip.

    ECG Leads

    • Limb leads (I, II, III, AVR, AVL, AVF) are bipolar and measure voltage differences between electrodes.
    • Augmented unipolar limb leads (AVR, AVL, AVF) use one limb as positive, and other limbs negative.
    • Chest leads (V1–V6) are unipolar and measure voltage at different chest locations.

    Normal Tracings

    • Displays typical ECG patterns in various limb and chest leads.

    Rate

    • Heart rate is determined by analyzing the rhythm strip and determining how long it takes for a complete heartbeat cycle to occur.
    • Tachycardia exists if the heart rate is over 100 beats/minute.
    • Bradycardia exists if the heart rate is below 60 beats/minute.

    Rhythm

    • Analyze if the rhythm spacing between successive QRS complexes is regular.
    • Evaluate fluctuations in rhythm.

    P wave

    • Normal P waves are small, positive deflections less than 2.5 mm in height and 1 millisecond in duration (0.11 sec).
    • Enlarged atria can produce larger P waves.

    T Wave

    • Normal T waves are upright; inverted T waves may indicate myocardial infarction (MI).
    • T wave height varies depending on heart rate, electrolytes (e.g., potassium) and other factors like ischemia.

    Spiked T Wave

    • High potassium levels can cause a spiked, or elevated, T wave pattern.

    Common Dysrhythmias

    • Common conditions include sinus bradycardia, sinus tachycardia, sinus dysrhythmia, atrial flutter, atrial fibrillation, and ventricular dysrhythmias (premature ventricular contractions, ventricular tachycardia, ventricular fibrillation, and asystole).

    Sinus Bradycardia

    • A consistently slow heart rate (under 60 bpm even for those who are normally slower) that could indicate significant medical problems.
    • Can result from vagal stimulation, damage to the SA node, or certain medications.

    Sinus Tachycardia

    • A consistently rapid heart rate (over 100 bpm in adults) that can be triggered by stress, fever, pain, or other conditions.

    Sinus Dysrhythmia

    • Sinus rhythm that is irregular but remains within the normal range.

    Atrial Flutter

    • A rapid but regular firing pattern of the atria.

    Atrial Fibrillation

    • An irregular and rapid rhythm of the atria.

    Ventricular Dysrhythmias

    • Conditions involving abnormal electrical activity in the ventricles of the heart, often requiring immediate medical intervention.
    • Common examples include premature ventricular contractions (PVCs), ventricular tachycardia, and ventricular fibrillation.

    Premature Ventricular Contraction (PVC)

    • Early ventricular contractions that are typically not life-threatening when infrequent.
    • Can happen in normal or abnormal hearts caused by factors like stress.

    PVCs to Watch

    • Certain PVC patterns suggest more significant heart issues, needing further evaluation.
    • PVC patterns warrant immediate intervention in certain circumstances.

    Ventricular Tachycardia

    • Rapid irregular heartbeat originating in the ventricles, typically requiring immediate medical attention due to significant impact on cardiac output.

    Ventricular Fibrillation

    • A chaotic and very rapid ventricular rhythm characterized by disorganized electrical activity typically fatal without immediate intervention.

    Asystole

    • Total absence of electrical activity in the heart and represents complete cardiac standstill.

    Pulseless Electrical Activity (PEA)

    • Presence of electrical activity without a corresponding mechanical heart contraction. Requires immediate medical attention due to lack of effective cardiac output.

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    Interpretation of ECGs - Chapter 11 PDF

    Description

    Test your knowledge on the interpretation of electrocardiograms (ECGs). This quiz covers the basics of ECGs, their lead placements, and the significance of different heart activity waves. Perfect for medical and nursing students looking to enhance their understanding of cardiac monitoring.

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