Arrhythmias and Therapy Flashcards
What is FIRST-DEGREE AV Block?
Disease of Electrical Conduction System:
Delay in the Impulse being Conducted through the AV Node
*PR Interval Prolongation (>0.2secs)
What is SECOND-DEGREE AV Block: MOBITZ I/WENCKEBACH?
Almost Always a Disease of AV Node
ECG Features:
1) Progressive Prolongation of PR Interval (>0.2secs) on Consecutive Beats
2) Followed by a Non-Conducted P Wave or ‘Dropped’ QRS Complex
What is SECOND-DEGREE AV Block: MOBITZ II?
Almost Always a Disease of the His-Purkinje System
ECG Features:
1) Intermittent Non-Conducted P Waves/Dropped QRS Complexes
2) PR Interval Remains Constant
What is THIRD-DEGREE or COMPLETE Heart Block?
Complete Absence of AV Conduction
ECG Features:
1) Atrial and Ventricular Conduction Rates are Independent From One Another
2) P Waves Bear No Relation to QRS Complexes
Describe ATRIAL FIBRILLATION (AF):
Type of Supraventricular Tachycardia
Disorganised Atrial Activity and Contraction
ECG Features:
1) Irregularly Irregular Rhythm
2) Atrial Rate >350bpm
3) No P Waves - Fibrillatory Waves Mimic P Waves
4) Variable Ventricular Rate
Describe ATRIAL FLUTTER:
Type of Supraventricular Tachycardia
Caused by Re-Entry Circuit within the Right Atrium
ECG Features:
1) Narrow QRS Complex Tachycardia
2) Atrial Rate = 250-350bpm
3) “Saw-Tooth” Pattern of Flutter Waves
4) Regular Ventricular Rate
How would a patient with AF PRESENT?
May be Asymptomatic
Possible Symptoms:
1) Palpitations
2) Dyspnoea
3) Chest Pain
4) Fatigue
What INVESTIGATIONS would be used to diagnose AF?
1) ECG
2) FBC - specifically Thyroid Function
3) Echocardiography
What is the purpose of CLASS I ANTI-ARRHYTHMIC (AA) drugs?
*Na+ Channel Blockers, i.e. Disopyramide
1) Manipulate Phase 0 of Non-Pacemaker Action Potentials (AP)
2) Can Delay the Onset of Depolarisation and Repolarisation of the Ventricles
3) Can Prolong Effective Refractory Period (ERP) between Heart Beats (Class Ia)
What is the purpose of CLASS II AA drugs?
- Beta-Blockers, i.e. Atenolol and Bisoprolol
- < HR
1) < Sympathetic Stimulation
2) Block Beta-1 Receptors at the SA and AV Nodes
3) Delay Phase 4 Depolarisation of Pacemaker APs
4) < SA Node Firing
5) Slow AV Node Conduction
What is the purpose of CLASS III AA drugs?
- K+ Channel Blockers, i.e. Amiodarone
1) Manipulate Phase 3 of Non-Pacemaker APs
2) Prolong Repolarisation of the Ventricles
3) Prolong ERPs between Heart Beats
What is the purpose of CLASS IV AA drugs?
- Calcium Channel Blockers, i.e. Verapamil and Diltiazem (Rate-Limiting)
- < HR
1) Depress Phase 4 Depolarisation of Pacemaker APs
What is the purpose of DIGOXIN?
*Cardiac Glycoside
1) Inhibits Na+/K+ ATPase Pump
2) +ve Inotrope - Improves Strength of Contraction
3) Allows More Ca2+ to be Available
What COHORT is Digoxin commonly prescribed to?
Elderly for Rate Control
What are the ISSUES surrounding Digoxin use?
Used by Elderly, often with Renal Impairment
Causes Toxicity due to Prolonged Half-Life
Has many Side-Effects, i.e. Nausea; Bradycardia; Arrhythmias
What is the TREATMENT for Digoxin TOXICITY?
Digiband
What are the ISSUES surrounding AMIODARONE use?
Interacts with Other Drugs, i.e. Digoxin
Many Side Effects Causing Tissue Abnormalities, i.e. Thyroid; Pulmonary Fibrosis
Why is it IMPORTANT to ANTICOAGULATE patients with AF?
> Risk of Clotting in RA due to Impaired RA Contractility
> Risk of Stroke and/or Peripheral Emboli
Other than AF, under what CIRCUMSTANCES would ANTICOAGULATION be INDICATED?
DVT/PE
After Surgery
Prolonged Immobilisation
Name a SIGNIFICANT ORAL ANTICOAGULANT:
Warfarin
What are Warfarin’s MECHANISMS of ACTION?
Inhibits Clotting Factors II, VII, IX and X
Vit K Antagonist
What are the ISSUES surrounding Warfarin use?
Drug Interactions
Can > Warfarin Activity - Promote Bleeding
Can < Warfarin Activity - Promoting Clotting
How can Warfarin effects be MONITORED?
1) Regular International Normalised Ratio (INR)
2) CHADS2 Score
How can Warfarin SIDE EFFECTS be ATTENUATED?
1) Be Aware of Alterations in Therapy
2) Patient Education
3) < Alcohol Intake
What might be a SAFER ALTERNATIVE to Warfarin in ANTICOAGULATIVE THERAPY?
Dabigatran or Rivaroxaban
Describe WOLFF-PARKINSON-WHITE (WPW) Syndrome:
Accessory Pathway (Bundle of Kent) Used Instead of AV Node to Conduct Impulses Between Atria and Ventricles
Can Facilitate Atrial and Ventricular Arrhythmias
Also, a Type of Re-Entrant Tachycardia via Accessory Pathway
Explain SUPRAVENTRICULAR TACHYCARDIAS (SVTs):
Abnormally Fast Heart Rhythm
Arising from Improper Electrical Activity Above the Ventricles
Ex) AF; Atrial Flutter; WPW
Describe VENTRICULAR TACHYCARDIA (V Tach):
Abnormally Fast and Regular Heart Rhythm
Arising from Improper Electrical Activity Provided to the Ventricles
What are the SYMPTOMS of V Tach?
1) Palpitations
2) Chest Pain
3) Dyspnoea
4) Dizziness
5) Syncope
What INVESTIGATIONS would be used to diagnose V Tach?
1) ECG
2) FBC
3) Angiography
What MANAGEMENT can help to PREVENT V Tach?
1) Diagnose and Treat the Underlying Cause
2) Implantable Cardiac Defibrillator and/or AA Drugs
How can ACUTE V Tach be TERMINATED?
1) Cardiac Arrest Protocol
2) DC Cardioversion or AA Drugs
What are the TREATMENTS for AF?
1) AA Drugs - Rate Control (1st Line = Beta-Blocker)
2) Radiofrequency Ablation
3) Anticoagulation
What is the TREATMENT for VENTRICULAR FIBRILLATION (V Fib)?
Cardiac Arrest Protocol
Describe the PREVALENCE of AF within the POPULATION:
1) > Risk 60 and Above
2) Highest Amongst the > 75 Cohort
Explain SINUS ARREST:
Transient Suppression of the SA Node; Electrical Impulses Cannot be Conducted to Myocardial Tissues
