CVS Cardiac Week 4 Flashcards
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.
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.
- TLO 4.1.2: Explain what each component reflects.
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.
- TLO 4.1.3: Describe how a standard 12-lead ECG is derived:
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.
o Cardiac axis:
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.
o Electrical deflection:
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.
Topic 2: A System to Interpret ECGs
* TLO 4.2.1: Describe a system used to interpret ECGs: rate, rhythm, axis, hypertrophy, ischemia.
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).
- TLO 4.2.2: Identify the following on ECG:
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°.
Topic 3: Tachyarrhythmias – Common Examples
* TLO 4.3.1: Define tachyarrhythmia and describe generalized clinical manifestations.
o Tachyarrhythmia: An arrhythmia with a heart rate greater than 100 bpm.
o Clinical manifestations: Palpitations, presyncope, syncope, chest pain, dyspnea.
- TLO 4.3.2 - 4.3.4: Focus conditions
o Ventricular tachycardia (VT):
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.
o Ventricular fibrillation (VF):
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.
o Atrial fibrillation (AF):
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.
o Atrial flutter:
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.
o Supraventricular tachycardia (SVT):
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.
Topic 4: Bradyarrhythmias - Heart Block
* TLO 4.4.1: Define bradyarrhythmia and describe generalized clinical manifestations.
o Bradyarrhythmia: An arrhythmia with a heart rate less than 60 bpm.
o Clinical manifestations: Lethargy, syncope, palpitations, heart failure
- TLO 4.4.2 - 4.4.4: Focus conditions
o 1st-degree heart block:
ECG: Prolonged PR interval (>200 ms).
Risk factors/etiology: Medications, increased vagal tone, conduction system disease.
Pathophysiology: Delay in AV node conduction.
o 2nd-degree heart block:
Mobitz type I (Wenckebach):
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.
o 2nd-degree heart block:
Mobitz type II:
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.
Topic 5: Diagnosis and Complications of Arrhythmias
* TLO 4.5.1: Identify modalities used to diagnose arrhythmias.
o ECG (12-lead).
o Holter monitor (24-hour ECG).
o Loop recorder (long-term ECG monitoring).
o Pacemaker interrogation.
- TLO 4.5.2: Describe complications of arrhythmias.
o Tachyarrhythmias:
Hemodynamic instability (e.g., hypotension, shock).
Thromboembolism (especially AF).
Heart failure.
Topic 6: Management of Arrhythmias and Lifestyle Modifications
* TLO 4.6.1: Identify pharmacological management options.
o Na+ channel blockers.
o β-blockers.
o K+ channel blockers.
o Ca2+ channel blockers.
- TLO 4.5.2: Describe complications of arrhythmias.
o Bradyarrhythmias:
Syncope.
Heart failure.
Asystole (cardiac arrest).
- TLO 4.6.2: Describe the mechanism of action.
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.
- TLO 4.6.3: Identify and describe interventional approaches.
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.
- TLO 4.6.4: Identify lifestyle modifications for secondary prevention.
o Address underlying conditions (e.g., hypertension, heart disease).
o Avoid triggers (e.g., caffeine, alcohol).
o Maintain a healthy lifestyle (diet, exercise). 1
Calcium channel blockers target the gating mechanism of voltage-gated Ca2+ ion channels. Which of the following drugs is not a calcium channel blocker?
a.
Amlodipine
b.
Amiodarone
c.
Verapamil
d.
Lercanidipine
e.
Diltiazem
Amiodarone
Amiodarone is not a calcium channel blocker. It is an antiarrhythmic which works by prolonging the action potential duration, prolonging there fractory period by acting at potassium channels, and affecting the flow of ions across the membrane.
The electrical activity of heart muscle can be recorded on the surface of the body as an electrocardiogram (ECG). What is the normal duration of the QRS interval?
a.
0.06–0.10secs
b.
0.12–0.20 secs
c.
0.30 secs
d.
0.11 secs
e.
Varies with the heart rate
a.
0.06–0.10secs
ventricular depolarization represented by QRS complex is normally 0.06-0.10 secs
A 67-year-old man was found collapsed at home. The paramedic’s acquired an ECG. What is the mostlikely diagnosis from the list below?
a.
Atrial flutter
b.
Ventricular fibrillation
c.
Complete heart block
d.
Left ventricular hypertrophy
e.
Atrial fibrillation
Certainty
: C=1 (Unsure:
b.
Ventricular fibrillation
In ventricular fibrillation, the electrocardiogram is bizarre and ordinarily shows no tendency toward a regular rhythm of any type
The electrical activity of heart muscle can be recorded on the surface of the body as an electrocardiogram (ECG). Which of the following does the S wave indicate on an ECG?
a.
Depolarization of the atria
b.
Depolarization of the interventricular septum from left to right
c.
Ventricular repolarization
d.
Depolarization of the area of the heart near the base
e.
Depolarization of the main mass of the ventricles
d.
Depolarization of the area of the heart near the base
The QRS complex shows the depolarization of the ventricles, which also masks the repolarization of the atria. The S wave represents the depolarization of the area of the heart near the base
Atrial fibrillation is a condition in which the pulse rate is irregularly irregular. Which of the followingstatements about atrial fibrillation is true?
a.
The ventricular rate exceeds the atrial rate
b.
The ventricular rhythm is regular
c.
It is associated with tricuspid incompetence
d.
There are multiple P waves on the ECG
e.
It may be due to multiple re-entrant excitation waves in the atria
e.
It may be due to multiple re-entrant excitation waves in the atria
Atrial fibrillation is due to multiple circulating re-entrant excitation in theatria. This results in an irregular and fast atrial rate (up to 500 per minute).Hence the AV node also discharges at an irregular, but slower rate (about90–150 beats per minutes). P waves cannot usually be detected on theECG
Abnormal rhythms of the heart occur when the normal conduction is disrupted. What is first-degreeheart block?
a.
Conduction through theatrioventricular node takeslonger than normal,prolonging the PR interval
b.
Atria and ventricles are completely separated and beat independently
c.
Heart rate varies with occasional extra beats
d.
PR interval lengthens progressively until a ventricular beat is dropped
e.
Not all atrial impulses are conducted to the ventricles
a.
Conduction through theatrioventricular node takeslonger than normal,prolonging the PR interval
First-degree atrioventricular (AV) block occurs whenconduction through the AV node takes longer thannormal.
To gather information about impulse conduction from the atria to the ventricles, which ECG componentwill provide this information?
a.
ST segment
b.
PRinterval
c.
P wave
d.
T wave
b.
PRinterval
The PR interval is the time from the onset of the P wave to the start of the QRScomplex. It reflects conduction through the AV node
Cardiac output is determined by stroke volume and heart rate. Which of the following options increasesheart rate in sinus rhythm?
a.
Atropine
b.
Digoxin
c.
Atenolol
d.
Propranolol
e.
Verapamil
a.
Atropine
Atropine is a muscarinic receptor antagonist, producing an initial bradycardiabecause of central stimulation, followed by tachycardia (the vagus is blockedso that sympathetic effect is unopposed)
SAQ: A 54-year-old man with obesity, hypertension, obstructive sleep apnea, and excessive alcoholconsumption comes to the emergency room with a 3-day history of palpitations, fatigue, and shortnessof breath. He has had similar symptoms in the past, but these were always short-lived and he did notpreviously seek medical attention. On physical examination, his heart rate is 110 bpm irregularlyirregular, and blood pressure is 126/87 mmHg. Cardiopulmonary examination is normal apart from theirregular rhythm.
What is the most likely diagnosis?
What is the next diagnostic step?
What is the next step in therapy?
atrial fibrillation
ECG
Rate control
What is the most likely diagnosis?
Answer = Paroxysmal atrial fibrillation
What is the next diagnostic step?
Answer = Electrocardiogram
What is the next step in therapy?
Answer = Anticoagulation and rate control
Considerations:
This 54-year-old patient has several risk factors for the development of atrial fibrillation. Hypertension,obesity, sleep apnea, and heavy alcohol consumption–especially binge drinking–are all associated with agreater risk for atrial fibrillation. Thus, while other supraventricular tachycardias are possible, atrialfibrillation or atrial flutter is the most likely diagnosis. The irregularly irregular pulse is also verysuggestive. An ECG should confirm the diagnosis and differentiate between atrial fibrillation and atrialflutter.
The first priority should be prevention of thromboembolic stroke, which is perhaps the directconsequence of atrial fibrillation or flutter. For most patients and for patients in whom an early rhythmcontrol strategy is planned, stroke prevention requires systemic anticoagulation with warfarin or a noveloral anticoagulant (NOAC). Control of the ventricular rate is also important to limit symptoms and toavoid the deleterious effects of persistent tachycardia on left ventricular function. Rate control isgenerally achieved with negatively chronotropic drugs such as beta-blockers and nondihydropyridinecalcium channel blockers such as diltiazem.
Acute cardioversion of atrial fibrillation or atrial flutter episodes with a definite onset within the last 48hours can be considered, although in this case the onset of symptoms is outside this timeframe. Ifspontaneous conversion to sinus rhythm does not occur, cardioversion can be undertaken after either atleast 3 weeks of therapeutic anticoagulation or a transesophageal echocardiogram demonstrating theabsence of left atrial appendage thrombus.
Underlying potentially reversible causes of atrial fibrillation such as hyperthyroidism should beexcluded, and an echocardiogram to assess for structural heart disease– especially mitral valve diseaseand left ventricular dysfunction–should be ordered. Patients with symptoms or signs suggestive ofcoronary artery disease may require noninvasive testing to exclude active ischemia.
TLO 4.3.4: Describe the pathophysiological process - Focus conditions: atrial fibrillation
Topic 6: Management of Arrhythmias and Lifestyle Modifications
TLO 4.6.1: Identify appropriate pharmacological management options for the treatment of arrhythmias
* Na+ channel blockers
* β-blockers
* K+ blockers
* Ca2+ channel blockers
TLO 4.6.2: Describe the mechanism of action for each of the options identified in TLO 4.6.1
TLO 4.6.3: Identify and describe appropriate interventional approaches to arrhythmias:
* defibrillation
* pacemakers –transcutaneous and permanent pacing
* ablation
TLO 4.6.4: Identify the lifestyle modifications required for secondary
