CVS Week 4

Question 1

Topic 1: An Introduction to the ECG
* TLO 4.1.1: Identify components of the normal ECG (P wave, QRS complex, T wave) and their intervals.

Answer 1

o P wave: Atrial depolarization.
o QRS complex: Ventricular depolarization.
o T wave: Ventricular repolarization.
o PR interval: Time from the start of atrial depolarization to the start of ventricular depolarization.
o QT interval: Time from the start of ventricular depolarization to the end of ventricular repolarization.

Question 2

• TLO 4.1.2: Explain what each component reflects.

Answer 2

o P wave: Electrical activity during atrial depolarization (atrial contraction).
o QRS complex: Reflects electrical activity during ventricular depolarization (ventricular contraction).
o T wave: Represents ventricular repolarization.

Question 3

• TLO 4.1.3: Describe how a standard 12-lead ECG is derived:

Answer 3

o Lead placement and represented cardiac structures:
 Limb leads (I, II, III): Bipolar; record differences in electrical potential between limbs.
 Augmented limb leads (aVR, aVL, aVF): Unipolar; record potential between one limb and the average of the other two.
 Chest leads (V1-V6): Unipolar; record potential between the chest electrode and a central reference point. Each lead views the heart from a different angle to provide comprehensive electrical information.

Question 4

o Cardiac axis:

Answer 4

 Represents the overall direction of ventricular depolarization in the frontal plane.
 Provides information about the heart’s orientation and can indicate conditions like hypertrophy or bundle branch blocks.

Question 5

o Electrical deflection:

Answer 5

 The direction of deflection (upward or downward) depends on the direction of the electrical vector relative to the lead axis.
 A wave moving towards a positive electrode produces an upward deflection, and vice versa.

Question 6

Topic 2: A System to Interpret ECGs
* TLO 4.2.1: Describe a system used to interpret ECGs: rate, rhythm, axis, hypertrophy, ischemia.

Answer 6

o Rate: Determine heart rate (e.g., by counting large squares between R waves and dividing 300 by that number).
o Rhythm: Assess regularity of R-R intervals (e.g., sinus rhythm vs. irregular rhythm).
o Axis: Evaluate the general direction of ventricular depolarization.
o Hypertrophy: Look for signs of atrial or ventricular enlargement (e.g., tall R waves, wide P waves).
o Ischemia: Identify changes indicating reduced blood flow to the heart muscle (e.g., ST-segment depression or elevation, T wave inversion).

Question 7

• TLO 4.2.2: Identify the following on ECG:

Answer 7

o Sinus rhythm: Normal P wave preceding each QRS complex, regular R-R intervals, rate 60-100 bpm.
o Sinus bradycardia: Sinus rhythm with a heart rate <60 bpm.
o Sinus tachycardia: Sinus rhythm with a heart rate >100 bpm.
o Left axis deviation: Axis between -30° and -90°.
o Right axis deviation: Axis between +90° and +180°.

Question 8

Topic 3: Tachyarrhythmias – Common Examples
* TLO 4.3.1: Define tachyarrhythmia and describe generalized clinical manifestations.

Answer 8

o Tachyarrhythmia: An arrhythmia with a heart rate greater than 100 bpm.
o Clinical manifestations: Palpitations, presyncope, syncope, chest pain, dyspnea.

Question 9

• TLO 4.3.2 - 4.3.4: Focus conditions
  o Ventricular tachycardia (VT):

Answer 9

 Risk factors/etiology: Ischemic heart disease, cardiomyopathy, electrolyte imbalances.
 ECG: Wide QRS complexes, rate >100 bpm, often regular rhythm.
 Pathophysiology: Rapid firing of one or more ventricular ectopic foci.

Question 10

o Ventricular fibrillation (VF):

Answer 10

 Risk factors/etiology: Severe cardiac disease, myocardial infarction.
 ECG: Chaotic, irregular deflections; no distinct waves or complexes.
 Pathophysiology: Uncoordinated ventricular electrical activity leading to ineffective contraction.

Question 11

o Atrial fibrillation (AF):

Answer 11

 Risk factors/etiology: Severe cardiac disease, myocardial infarction.
 ECG: Chaotic, irregular deflections; no distinct waves or complexes.
 Pathophysiology: Uncoordinated ventricular electrical activity leading to ineffective contraction.

Question 12

o Atrial flutter:

Answer 12

 Risk factors/etiology: Similar to AF; often associated with structural heart disease.
 ECG: Sawtooth pattern of flutter waves, usually regular ventricular response (but can be irregular).
 Pathophysiology: A re-entrant circuit in the atria.

Question 13

o Supraventricular tachycardia (SVT):

Answer 13

 Risk factors/etiology: Often occurs in young individuals; can be triggered by stress, caffeine.
 ECG: Narrow QRS complex tachycardia, often with absent or hidden P waves.
 Pathophysiology: Re-entrant circuit involving the AV node or an accessory pathway.

Question 13

Topic 4: Bradyarrhythmias - Heart Block
* TLO 4.4.1: Define bradyarrhythmia and describe generalized clinical manifestations.

Answer 13

o Bradyarrhythmia: An arrhythmia with a heart rate less than 60 bpm.
o Clinical manifestations: Lethargy, syncope, palpitations, heart failure

Question 14

• TLO 4.4.2 - 4.4.4: Focus conditions
  o 1st-degree heart block:

Answer 14

 ECG: Prolonged PR interval (>200 ms).
 Risk factors/etiology: Medications, increased vagal tone, conduction system disease.
 Pathophysiology: Delay in AV node conduction.

Question 15

o 2nd-degree heart block:
 Mobitz type I (Wenckebach):

Answer 15

 ECG: Progressive PR interval lengthening until a QRS complex is dropped.
 Risk factors/etiology: Medications, increased vagal tone, inferior wall MI.
 Pathophysiology: Progressive AV node conduction delay.

Question 16

o 2nd-degree heart block:
 Mobitz type II:

Answer 16

 ECG: Consistent PR intervals with intermittent dropped QRS complexes.
 Risk factors/etiology: Conduction system disease, anterior wall MI.
 Pathophysiology: Abrupt, intermittent block in the His-Purkinje system.

Question 17

Topic 5: Diagnosis and Complications of Arrhythmias
* TLO 4.5.1: Identify modalities used to diagnose arrhythmias.

Answer 17

o ECG (12-lead).
o Holter monitor (24-hour ECG).
o Loop recorder (long-term ECG monitoring).
o Pacemaker interrogation.

Question 18

• TLO 4.5.2: Describe complications of arrhythmias.
  o Tachyarrhythmias:

Answer 18

 Hemodynamic instability (e.g., hypotension, shock).
 Thromboembolism (especially AF).
 Heart failure.

Question 19

Topic 6: Management of Arrhythmias and Lifestyle Modifications
* TLO 4.6.1: Identify pharmacological management options.

Answer 19

o Na+ channel blockers.
o β-blockers.
o K+ channel blockers.
o Ca2+ channel blockers.

Question 19

• TLO 4.5.2: Describe complications of arrhythmias.
  o Bradyarrhythmias:

Answer 19

 Syncope.
 Heart failure.
 Asystole (cardiac arrest).

Question 20

• TLO 4.6.2: Describe the mechanism of action.

Answer 20

o Na+ channel blockers: Slow conduction velocity by blocking sodium channels.
o β-blockers: Decrease heart rate and contractility by blocking β-adrenergic receptors.
o K+ channel blockers: Prolong repolarization by blocking potassium channels.
o Ca2+ channel blockers: Reduce contractility and conduction by blocking calcium channels.

Question 21

• TLO 4.6.3: Identify and describe interventional approaches.

Answer 21

o Defibrillation: Electrical shock to terminate life-threatening arrhythmias (VF, VT).
o Pacemakers:
 Transcutaneous pacing: Temporary pacing via skin electrodes.
 Permanent pacing: Implanted device to regulate heart rhythm.
o Ablation: Procedure to destroy arrhythmogenic tissue.

Question 22

• TLO 4.6.4: Identify lifestyle modifications for secondary prevention.

Answer 22

o Address underlying conditions (e.g., hypertension, heart disease).
o Avoid triggers (e.g., caffeine, alcohol).
o Maintain a healthy lifestyle (diet, exercise). 1