Cardiac Conduction Disturbances

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Questions and Answers

What is the primary treatment for patients with asymptomatic first-degree AV block?

Amiodarone administration

No treatment as tolerated well (correct)

Pacemaker insertion

Digoxin therapy

Which medication is primarily used for rhythm control in patients with uncontrolled atrial fibrillation?

Amiodarone (correct)

BB (Beta Blockers)

Heparin

Coumadin

What characteristic distinguishes third-degree AV block from other types of AV block?

P waves are present but do not match with QRS (correct)

Regular P and QRS waves that match

Normal QRS complexes

Prolonged PR interval

What type of temporary treatment may be used for symptomatic third-degree AV block?

Temporary pacing Signup and view all the answers

What is the significance of a prolonged PR interval in first-degree AV block?

Indicates impaired electrical conduction Signup and view all the answers

What are the characteristics of a patient experiencing Ventricular Tachycardia?

Fast rate and regular rhythm with wide QRS Signup and view all the answers

Which treatment is recommended for Ventricular Fibrillation?

CPR and defibrillation Signup and view all the answers

In what scenario is CPR indicated in the treatment of Ventricular Tachycardia?

When the patient has no pulse Signup and view all the answers

Which of the following is a common cause of Ventricular Tachycardia?

Stimulants and caffeine Signup and view all the answers

What is the initial treatment for Pulseless Electrical Activity?

CPR and advanced cardiac life support (ACLS) protocol Signup and view all the answers

What is the normal heart rate for the SA node?

60-100 beats per minute Signup and view all the answers

What characterizes a prolonged PR interval?

Greater than 0.20 seconds Signup and view all the answers

Which of the following best describes ventricular dysrhythmias?

Originates from the ventricular region Signup and view all the answers

How is the QTc interval characterized when it is considered lengthened?

If the QT interval exceeds 0.47 seconds Signup and view all the answers

What is the normal duration of a QRS complex?

0.06-0.12 seconds Signup and view all the answers

What is the normal range for the QRS complex duration?

0.06 – 0.12 seconds Signup and view all the answers

Which condition is defined by a heart rate of less than 60 beats per minute?

Sinus Bradycardia Signup and view all the answers

What is a common treatment for Sinus Bradycardia?

Atropine Signup and view all the answers

What is a characteristic feature of Supraventricular Tachycardia (SVT)?

Rate exceeds 150 Signup and view all the answers

What indicates Atrial Flutter in an ECG reading?

Absent P waves and present F waves Signup and view all the answers

What is the typical treatment approach for uncontrolled Atrial Fibrillation?

Rate control with medications Signup and view all the answers

Which of the following is a cause of Sinus Tachycardia?

Hypovolemic shock Signup and view all the answers

What describes the rhythm of Atrial Fibrillation?

Irregularly irregular with varying ventricular rates Signup and view all the answers

Study Notes

Conduction Disturbances

Heart Anatomy: The heart contains the right coronary artery, the left coronary artery, and the anterior interventricular artery
Conduction System: The SA node initiates the heartbeat (60-100 bpm), followed by the AV node (40-60 bpm), then the bundle of His, left bundle branch, right bundle branch, and finally the Purkinje fibers (20-40 bpm).

Cardiac Conduction Intervals

PR Interval: 0.12-0.20 seconds. Measures time from atrial activation to ventricular activation
QRS Interval: 0.06-0.12 seconds. Measures time from ventricular activation to ventricular depolarization
QT Interval: Calculated interval, prolonged if >0.47 seconds. Measurement from the start of the QRS complex to the end of the T wave.

Analyzing Cardiac Rhythm

Rate: Normal range is 60-100 bpm. Bradycardia is <60 and Tachycardia is over 100 bpm.
Rhythm: Regular or irregular.
P Waves: One P wave for each QRS. Assess for more or less P waves than QRS waves. P absence indicates no atrial activation.
**PR Interval:**Normal is 0.12-0.20 seconds. Prolonged is >0.20 seconds. Represents the delay at the AV node.
QRS Complex: Normal is 0.06-0.12 seconds. Prolonged is greater than 0.12 seconds. Measures ventricular depolarization time.
QTc: Normal. Lengthened if over 0.47 seconds. Adjusted QT interval that takes into account heart rate.

Dysrhythmias

Classification by origin: Sinus node, atrial, AV node, and ventricular dysrhythmias are classified by their origin in the heart. AV node blocks are a specific type of AV nodal disturbance.
Atrial Dysrhythmias: Supraventricular tachycardia (SVT), atrial flutter, and atrial fibrillation (controlled vs uncontrolled).
Supraventricular Tachycardia (SVT): Characterized by a rapid heart rate (over 150 bpm), regular rhythm, shortened PR interval, and sometimes shortened QRS. Causes can include anxiety, stimulants, and hyperthyroidism. Valsalva maneuver and adenosine can often treat SVT.
Atrial Flutter: Characterized by a regular rhythm, absent P waves, and instead replaced by F waves, normal ventricular rate. Often related to heart and lung issues.
Atrial Fibrillation (AF): Characterized by an irregular rhythm, absent P waves, irregular ventricular rate, normal PR interval, and sometimes normal QRS interval. AF can be controlled or uncontrolled, impacting the ventricles varying degrees.
Ventricular Dysrhythmias: Ventricular tachycardia, Torsades de Pointes, and ventricular fibrillation.
Ventricular Tachycardia: Characterized by a wide, bizarre QRS complexes, a fast heart rate, and a regular rhythm. Causes include electrolyte imbalance, drug toxicity, and ischemia. Treatment approach depends on whether the patient has a pulse.
Torsades de Pointes: A type of polymorphic ventricular tachycardia. It's often associated with a prolonged QT interval. Treatment includes intravenous magnesium.
Ventricular Fibrillation: Characterized by an irregular rhythm and absent P waves and ventricular contraction. Treatment includes CPR, defibrillation, and medications such as epinephrine and amiodarone.

AV Blocks

First-degree AV block: Prolonged PR interval (> 0.20 seconds) with a regular rhythm. Causes include aging, CAD, and medications. No treatment is often needed.
Second-degree AV block Type I (Mobitz I/Wenckebach): PR interval gradually lengthens until a P wave is not followed by a QRS complex. Can be caused by medications and CAD.
Second-degree AV block Type II (Mobitz II): PR interval does not lengthen and there is a random absence of QRS complexes. This needs careful monitoring for complete block and possible permanent pacing.
Third-degree AV block (Complete Heart Block): P waves and QRS complexes are completely independent. Causes often include CAD, MI, and other conditions. Usually requires pacemaker.

Pacemakers

Temporary: Transcutaneous or transvenous. Deliver a pulse to the heart to help with bradycardia.
Permanent: Epicardial. Implanted devices that help trigger the heartbeat if conduction is failing.

Other Lethal Arrhythmias

Asystole: Absence of electrical activity and therefore a heartbeat.
Pulseless Electrical Activity (PEA): Electrical activity is present, but there is no heartbeat. Requires immediate intervention.

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Description

This quiz explores the anatomy and physiology of the heart's conduction system, including the roles of different cardiac intervals and rhythms. Test your understanding of heart rate, rhythm, and the conduction pathways crucial for effective heart function.