Atrial Dysthymias
The Cardiac Conduction System
The conduction system initiates in the right atrium at the Sinoatrial (SA) node.
The SA node fires, generating impulses that stimulate the heart rhythm.
The impulses spread over the atria, causing them to contract.
The impulses travel through the Atrioventricular (AV) node, down the bundle branches into Purkinje fibers, resulting in ventricular contraction.
Normal conduction from top to bottom results in expected heart waveforms.
Monitoring and Basics
Focus will be on monitoring patients and understanding what is normal in cardiac activity.
Discussion on the autonomic nervous system, particularly:
Parasympathetic Nervous System (PNS) is associated with vagal maneuvers, slowing down heart functions.
Sympathetic Nervous System (SNS) increases heart functions, stimulating the SA node for higher heart rates and contractility.
Key Functions of Cardiac Cells
Cardiac cells can:
Excite - allow impulses to flow over the muscle electrically.
Conduct - transmit impulses orderly from one part of the heart to another.
Contract - respond to electrical signals mechanically.
Dysrhythmia Defined
Dysrhythmia indicates an abnormal heart rhythm due to:
Improper formation of impulses.
Faulty conduction of impulses.
Normal cycle includes:
Impulse from SA node → atrial contraction → AV node → bundle branches → ventricular contraction.
Presence of secondary pacemakers can alter normal rhythm.
Heart Rate Ranges
SA node typically functions at 60-100 beats per minute (bpm).
AV node operates at approximately 40-60 bpm.
Ventricular rate fires at 20-40 bpm.
Normal resting heart rate is often cited as 60-80 bpm.
Causes of Dysrhythmias
Various factors leading to dysrhythmias include:
Heart conditions and extra electrical pathways (accessory pathways).
Cardiomyopathy - Enlarged heart muscle increases dysrhythmia risk.
Heart failure and acute myocardial infarction elevate risk of lethal rhythms.
Other factors: electrolyte imbalances, alcohol, caffeine, nicotine, and electrical shocks.
Potassium Levels:
Normal potassium level: 3.5 - 5.0 mEq/L is critical for normal heart rhythm.
Levels below 3.5 can lead to irritability of the heart.
Emergency Response to Dysrhythmias
During a patient emergency, ensure basic circulatory assessment:
Check for pulse, airway, and breathing.
Connect to a heart monitor for rhythm monitoring.
Assess blood pressure and check lab values, including O2 saturation.
Quick identification and treatment of dysrhythmias can significantly affect patient outcomes.
Always verify lab values, especially potassium levels, before proceeding with further treatment.
Telemetry Monitoring Overview
Telemetry monitoring uses a single lead to assess heart rhythm and rate.
Twelve lead EKG allows for detailed assessment but is not the focus of current discussion.
A twelve lead EKG can offer insights within five minutes of patient's arrival in cases of chest pain.
Components of a twelve lead EKG:
Divided into 12 leads allowing assessment from multiple angles of the heart.
Importance in diagnosing electrolyte imbalances and heart attack history.
Systematic Approach to Rhythm Assessment
Best practice involves looking at rhythm strips systematically:
Presence of a P wave: Is it upright or inverted?
Evaluate atrial rhythm: Regular vs irregular.
Atrial rate calculation: Count P waves in a six second strip and multiply by 10.
Measure PR interval: Should be 0.12 - 0.20 seconds.
Evaluate ventricular rhythm: Regular or irregular?
Calculate ventricular rate: Count R waves in a six second strip and multiply by 10.
Measure QRS duration: Normal is less than 0.12 seconds.
Assess ST segment: Flat, elevated, or depressed.
Evaluate T wave: Is it upright or inverted?
Determine clinical significance: What are the patient’s symptoms and possible treatments?
Common Heart Rhythms
Normal Sinus Rhythm
Follows normal conduction pathway.
P waves present and consistent in appearance for each QRS complex.
QRS shape is normal and duration less than 0.12 seconds.
Sinus Bradycardia
Heart rate slow (less than 60 bpm).
Can be normal for athletes; may cause concern if symptomatic (i.e., low BP, weakness).
Treatment (if symptomatic): Administer atropine.
Sinus Tachycardia
Heart rate greater than 100 bpm.
Often indicates physiological stress or illness.
Can be treated by addressing underlying causes—pain, dehydration, anxiety, etc.
Premature Atrial Contractions (PACs)
Early beats originating from ectopic sites within the atria.
Patients may feel palpitations. Frequent PACs can signify more serious conditions such as supraventricular tachycardia (SVT).
Paroxysmal Supraventricular Tachycardia (PSVT)
No visible P wave, indicating rapid atrial beats.
Heart rate between 150-220 bpm leading to decreased cardiac output.
Treatments include vagal maneuvers, IV adenosine, or beta blockers.
Atrial Flutter
Rapid and organized atrial impulses, forming sawtooth-shaped waves (F-waves).
Associated with decreased cardiac output and higher risk for thrombus formation.
Treatments: control ventricular rate with beta blockers, convert rhythm via cardioversion or ablation if persistent.
Atrial Fibrillation
Chaotic atrial activity leading to disorganized ventricular response.
Irregular rhythm with no identifiable P waves; increased risk for strokes due to clots.
Long-term treatment often involves anticoagulants and rhythm control measures, including Maze procedure during cardiac surgery.
Conclusion of Cardiac Conduction and Monitoring
Proper assessment of heart rhythm and patient symptoms is crucial.
Understanding the various dysrhythmias and appropriate responses can significantly influence outcomes in clinical practice.