Cardiac Physiology and ECG Interpretation Quiz

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Questions and Answers

What is the most common cause of ventricular tachycardia (VT)?

Ischemic heart disease (correct)

Valvular heart disease

Electrolyte abnormalities

Medications

What is the typical heart rate range for accelerated idioventricular rhythm?

< 50 bpm

50-100 bpm (correct)

100-150 bpm

> 150 bpm

Which symptom is NOT commonly associated with ventricular tachycardia?

Lightheadedness (correct)

Cardiac arrest

Chest pain

Palpitations

What ECG finding is characteristic of ventricular tachycardia?

Wide QRS complex Signup and view all the answers

What can potentially occur if ventricular tachycardia leads to inadequate cardiac output?

Ventricular fibrillation Signup and view all the answers

What is primarily measured by ECG leads in the heart?

The extracellular current between polarized and depolarized cells Signup and view all the answers

Why do ECG leads not register 'plateaus' in cardiac myocytes?

Because plateaus are not changes in membrane potential Signup and view all the answers

What does the amplitude of ECG waves signify?

The magnitude of the electrical potential difference across the heart Signup and view all the answers

How do bipolar leads function in ECG measurements?

They assess voltage changes between two specific leads Signup and view all the answers

What do the X and Y axes on an ECG represent?

Time and electrical potential changes Signup and view all the answers

What is the primary purpose of the AV delay in cardiac physiology?

To synchronize atrial and ventricular activity Signup and view all the answers

What does the length of the vector indicate during depolarization?

The size of the electrical potential difference between points Signup and view all the answers

How do unipolar precordial leads differ from bipolar leads?

They compare voltage changes between the heart center and a chest wall location Signup and view all the answers

What does the Q-T interval of an ECG primarily represent?

The plateau phase of the ventricular myocyte action potential Signup and view all the answers

Which of the following dysrhythmias is characterized by rapid, irregular heart rates and no identifiable P waves?

Atrial fibrillation Signup and view all the answers

What is the typical ECG finding associated with ventricular tachycardia?

Wide QRS complexes Signup and view all the answers

Which type of heart block is characterized by a consistently prolonged P-R interval without dropped beats?

1st degree heart block Signup and view all the answers

What factor contributes to the pathophysiology of common dysrhythmias related to inflammation?

Chronic inflammation and myocardial fibrosis Signup and view all the answers

Which ECG finding is commonly associated with cardiac ischemia?

Elevated ST segment Signup and view all the answers

What is the primary pharmacologic action of anti-arrhythmic medications?

Alter electrical conduction and rhythm Signup and view all the answers

Which of the following is a characteristic of paroxysmal supraventricular tachycardia?

Abrupt onset and cessation Signup and view all the answers

What is the primary factor that can lead to ventricular fibrillation?

Widespread myocardial infarction Signup and view all the answers

Which symptom is commonly associated with Torsades de pointes?

Dizziness and syncope Signup and view all the answers

Which characteristic is true for the ECG of Torsades de pointes?

Polymorphic with varying amplitude QRS complexes Signup and view all the answers

What is a defining feature of First-Degree AV Block?

Consistent PR intervals with no drops Signup and view all the answers

Which condition can lead to Torsades de pointes due to prolonged repolarization?

Congenital QT abnormalities Signup and view all the answers

Which of the following is NOT associated with increased automaticity leading to cardiac dysrhythmias?

Stress and anxiety Signup and view all the answers

What typically characterizes Type I Second-Degree AV Block?

Prolonged PR intervals that gradually increase until a dropped beat Signup and view all the answers

Which electrical impulse feature is most affected in Second-Degree AV Block Type II?

Regular PR intervals with sudden loss of QRS complexes Signup and view all the answers

What is the gold standard for diagnosing obstructive sleep apnea (OSA)?

Polysomnogram Signup and view all the answers

Which finding in a physical examination increases the risk of OSA?

Higher Mallampati score Signup and view all the answers

Which of the following is a common characteristic of sleepwalking?

It involves automatic motor activities Signup and view all the answers

Sleep terrors most commonly affect which group?

Young children Signup and view all the answers

Which of the following is NOT typically associated with REM sleep behavior disorder?

Generally pleasant sleep experience Signup and view all the answers

Which test is considered to have a high rate of false negatives in OSA diagnosis?

Home sleep test Signup and view all the answers

Which of the following parameters is measured in a home sleep test?

Oxygen saturation Signup and view all the answers

What is a common preventive measure for parasomnias like sleepwalking and sleep terrors?

Ensuring adequate sleep Signup and view all the answers

Which nucleus is primarily associated with promoting sleep through the release of inhibitory neurotransmitters?

Ventrolateral pre-optic nucleus Signup and view all the answers

What neurotransmitter is primarily associated with the arousal system in the brainstem that helps keep individuals awake?

Norepinephrine Signup and view all the answers

Which area is involved in regulating REM sleep specifically?

Locus ceruleus Signup and view all the answers

What role does the suprachiasmatic nucleus (SCN) play in sleep-wake regulation?

It regulates circadian rhythms based on light and dark information. Signup and view all the answers

Which neurotransmitters are secreted by the lateral hypothalamus to stabilize sleep states?

Orexin and Melanin-concentrating hormone (MCH) Signup and view all the answers

What happens to circadian rhythm in the absence of light/dark stimulation?

It lasts a little over 24 hours. Signup and view all the answers

Which of the following brain components is crucial for the arousal system?

Periaqueductal gray Signup and view all the answers

How do the arousal systems communicate with the sleep-inducing centers?

Indirectly through the suprachiasmatic nucleus Signup and view all the answers

Study Notes

Cardiology: Dysrhythmias and Basic ECG's

This is a BMS200 week 9 course content on cardiology concerning dysrhythmias and basic electrocardiograms (ECGs).
Learning outcomes include analysis of ECG characteristics, pathophysiology of dysrhythmias, description of supraventricular and ventricular dysrhythmias, conduction blocks, ECG findings related to cardiac ischemia, mechanisms of anti-arrhythmic medications, and the role of chronic inflammation and myocardial fibrosis in dysrhythmia development.
Students will learn to analyze a normal ECG, including heart rate and determination of rhythm, P-R, QRS, and Q-T intervals, and normal waveforms in P, QRS, and T waves.
The student will understand the etiology, pathophysiology, clinical features, ECG findings, and prognosis of atrial fibrillation, atrial flutter, sinus tachycardia, and paroxysmal supraventricular tachycardia, premature ventricular contraction, idioventricular rhythm, ventricular tachycardia, ventricular fibrillation, torsades de pointes, 1st-degree heart block, 2nd-degree heart block, and 3rd-degree heart block.
Basic ECG findings related to cardiac ischemia and correlation with vascular territories will be discussed.
The pharmacological mechanisms of action and adverse effects of common anti-arrhythmic medications.
The student will also understand the contribution of chronic inflammation and myocardial fibrosis to dysrhythmia development.

Learning Outcomes (Detailed)

Analyzing normal ECG characteristics (heart rate, rhythm, P-R, QRS, Q-T intervals, waveforms).
Describing how triggered activity, abnormal automaticity, and re-entry contribute to the pathophysiology of common dysrhythmias.
Outlining the epidemiology, pathogenesis, clinical features, ECG findings, and prognosis of various supraventricular and ventricular dysrhythmias (e.g., atrial fibrillation, atrial flutter, sinus tachycardia, PVCs, VT).
Describing the ECG findings in cardiac ischemia and correlating them to vascular territories.
Discussing the mechanism of action and adverse effects of common anti-arrhythmic medications.
Examining the role of chronic inflammation and myocardial fibrosis in dysrhythmia development.

Pre-Assessment Questions

Question 1: What electrical event occurs during the Q-T interval of an ECG ?
- Repolarization of the ventricular myocyte
Question 2: Where in the heart are the cells responsible for the cardiac pacemaker located?
- The right atrium, close to the entrance of the superior vena cava

Review: Electrocardiogram (ECG)

ECG records electrical impulses produced by heart muscle depolarization and repolarization.
The amplitude of ECG waves reflects the amount of electrical activity. Larger waves correspond to larger areas of activated myocardial tissue.
Upward deflections indicate electrical impulse movement toward the electrode; downward deflections suggest movement away.
Conducting tissues (SA node, AV node, bundle branches) generate less electrical activity than myocardial tissue, making them less prominent on an ECG.
ECG primarily reflects activity of larger myocardial cells that contract and pump blood.
The duration of waves (P, QRS, T) provides information about timing of electrical events. Example: a prolonged QRS may indicate delayed ventricular conduction.
ECG leads measure the extracellular current that travels from depolarized cells to polarized (resting) cells.
ECG leads only "notice" changes in membrane potential.
"Plateaus" do not register as waves (phase 4, 2 of a myocyte).
ECG lead placement (coronal, cross-sectional) gives a 3-dimensional view of heart's electrical activity.
Bipolar leads compare voltage changes between two leads (e.g., lead I compares right and left arms). Unipolar/precordial leads compare voltage changes between a lead and center of the heart.
The x-axis of an ECG represents time in seconds; the y-axis depicts voltage in mV.

Approach to Interpreting ECG

Determine heart rate.
Methods: Divide 300 by the number of large boxes between R waves.
Determine the rhythm (regular or irregular).
Identify the origin of impulses (is there a P wave before the QRS?).
Regular, or regularly irregular, or irregularly irregular rhythms.

Step 3-Intervals (1)

Examine intervals for widening or shortening; this can indicate conduction system problems.
Major intervals of interest: P-R interval (prolongation = AV nodal dysfunction), QRS interval (delay in ventricular excitation), QT interval (repolarization abnormalities).

Step 3- Intervals (2)

Evaluate intervals to understand conduction pathway problems.

Step 4 - Waves

Examine the positioning and morphology of waves (upward or downward).
Compare wave sizes to normal.
Check for abnormal waves or variations in appearance

Step 4 - Q-Waves

Abnormal Q waves suggest possible prior myocardial infarction (MI). Significant Q waves typically are wide, large, and measurable, and present in leads V1–V3.

Step 4 - ST Segments

Evaluate ST segments to identify possible MI or other conditions.

Steps 4 - T-Waves

Examine T-wave morphology (shape & position).
Determine presence of abnormal T waves (e.g., increased or decreased amplitude, inverted, elevated or depressed segments). These abnormalities might indicate problems/ conditions like hypokalemia, hyperkalemia.

Steps 4 - P-Waves

Examine P-wave shape & position
Determine the presence of absent or multiple P-waves
Characterize the atrial axis.

General Pathophysiology of Dysrhythmias (1)

Re-entry occurs when a depolarization wave enters a damaged area where conduction is slower than normal.
- This damaged tissue results in the wave taking an alternative/slower pathway leading to re-excitation, resulting in tachycardia.

General Pathophysiology of Dysrhythmias (2)

Ectopic foci can be caused by local changes in electrolyte concentration in scar tissue, a phenomenon called abnormal automaticity.
Inhibition of Na+/K+ pump, leading to accumulation of Na+ and Ca2+ resulting in partial depolarization, leading to abnormal cell activity.

General Pathophysiology of Dysrhythmias (3)

Triggered activity is an abnormal depolarization of ventricular myocytes that occurs before the original action potential has completed its course, an example being PVCs.
Conditions like Bradycardia and reduced or prolonged phase 3 of the action potential duration favor triggering activity..

Chronic Inflammation and Myocardial Fibrosis and Dysrhythmias

Immune cells (macrophages, mast cells, T-cells) promote myocardial repair or fibrosis based on conditions.
Myocardial fibrosis promotes re-entry.

Supraventricular Dysrhythmias

Atrial fibrillation is the most common type of arrhythmia, often linked to chronic lung or heart disease.
Risk factors for atrial fibrillation include age, hypertension, chronic lung and/ or heart disease.
Other supraventricular dysrhythmias include atrial flutter, sinus tachycardia (can be normal or a problem), and paroxysmal supraventricular tachycardia.

Atrial Fibrillation ECG - (1, 2)

Narrow complex, regularly irregular rhythm, no distinguishable P waves.

Supraventricular Dysrhythmias - Atrial Flutter

Very common and characterized by a regular atrial rhythm, usually with a fast atrial rate (300 bpm).
The ventricular rate can be regular or irregular.

Supraventricular Dysrhythmias - Sinus Tachycardia

Normal rhythm but a fast heart rate (150 - 250 bpm), resulting from increased cardiac output.
Can be normal or pathological, as often an indication of elevated catecholamines due to exercise, pain, or anxiety.

Supraventricular Dysrhythmias - Paroxysmal Supraventricular Tachycardia (SVT)

Intermittent/ sudden episodes of supraventricular tachycardia
Can originate in the atria or AV node resulting in regular or irregular rhythms.
Many causes, including hyperthyroidism, anxiety, cocaine, structural heart disease.

Ventricular Dysrhythmias - Premature Ventricular Contractions (PVCs)

Starts with a heartbeat arising from the ventricle before the next expected.
Can be in isolation (single PVC), doublets, or triplets (normal heart beat (QRS) followed by 2 (PVCs), or followed by 3 (PVCs) followed by a normal heart beat.
Etiology is often unknown, caffeine, anxiety, sleep deprivation.

Ventricular Dysrhythmias - Idioventricular Rhythm

Slow, regular ventricular rhythm with a rate below 50 bpm and no P waves.
Usually, the result of failing SA and AV nodes.

Ventricular Dysrhythmias - Ventricular Tachycardia (VT)

Characterized by three or more consecutive premature ventricular contractions, sometimes with a rate of 100-250 bpm.
Etiology often linked to ischemic heart disease, can result in sudden cardiac death from progression to ventricular Fibrillation.

Ventricular Dysrhythmias - Ventricular Fibrillation

Irregular electrical activity with ventricular rate exceeding 300 bpm.
Life threatening requiring immediate treatment (defibrillator and CPR)
Often related to cardiac ischemia, or other problems.

Ventricular Dysrhythmias - Torsades de Pointes

A specific form of polymorphic ventricular tachycardia
Often associated with QTc prolongation (lengthening of the QT interval), which can trigger arrhythmia.

Conduction Blocks - First-Degree AV Block

Prolonged PR interval (>0.20 seconds), with each impulse conducted to the ventricles, usually asymptomatic.

Conduction Blocks - Second-Degree AV Block Type 1 (Wenckebach)

Progressive lengthening of the PR interval until a QRS complex is dropped, usually asymptomatic.

Conduction Blocks - Second-Degree AV Block Type 2

Fixed PR intervals with occasional dropped QRS complexes. More serious than Type I (Wenckebach), sometimes progressing to third-degree heart block.

Conduction Blocks - Third-Degree AV Block (Complete Heart Block)

No impulse transmission from the atria to the ventricles which results in independent atrial and ventricular rates.
Likely needs immediate treatment or a pacemaker.

Cardiac Ischemia and ECG

Ischemia typically first shows as inverted T waves in any lead.
ST elevation in leads matching the location of the injury.
Q waves may be present with or without ST elevation in cases concerning old or previous myocardial infarction.

Anti-Arrhythmic Mechanism of Action

Class 1: Bind and inhibit Na+ channels.
Class 2: Beta-blockers.
Class 3: Block K+ channels prolonging repolarization.
Class 4: Block Ca2+ channels to reduce influx.

Additional Information:

Cases from the class, and potential ECG abnormalities can arise from placing the ECG incorrectly, which can distort the information provided.

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Test your knowledge on ventricular tachycardia, ECG waveforms, and cardiac physiology. This quiz covers common causes, symptoms, and ECG measurements related to heart rhythms. Ideal for students studying cardiology and electrophysiology.