Week 7

• What are the main types of cardiac arrhythmias based on their site of origin?

  Sinus rhythms, atrial rhythms, and ventricular rhythms
• What are the characteristics of sinus bradycardia and sinus tachycardia?

  • Sinus Bradycardia: Slower-than-normal heart rate from the SA node; can be normal or clinical.
  • Sinus Tachycardia: Faster-than-normal heart rate from the SA node; can also be normal or clinical.

  
• What are the characteristics of atrial flutter?

  • Cause: Re-entrant circuit in the right atrium.
  • Ventricular Rate: Slower due to AV node blocking some impulses.
  • ECG: Absence of normal P waves; saw-tooth pattern (F-waves).

  
• What are the characteristics of atrial fibrillation?

  • Cause: Multiple random electrical impulses from ectopic sites in the atria.
  • Ventricular Rate: Irregular and varies in speed.
  • ECG: Absence of P waves; irregular narrow QRS complexes; undulating or flat baseline.

  
• What are the characteristics of AV nodal re-entrant tachycardia (AVNRT)?

  • Cause: Re-entrant circuit involving the AV node.
  • Atrial and Ventricular Rate: Identical, fast, and regular (150-250 bpm).
  • ECG: Regular rapid rhythm with no discernible P waves.

  
• What are the characteristics of ventricular tachycardia (V-tach)?

  • Cause: Single ectopic focus or circuit in the ventricles.
  • Heart Rate: Regular and fast (100-250 bpm).
  • ECG: Wide, bizarre QRS complexes; absence of P waves.
  • Clinical Significance: Can be brief or sustained, requiring intervention to prevent cardiac arrest.

  
• What are the characteristics of ventricular fibrillation (V-fib)?

  • Cause: Multiple weak ectopic foci in the ventricles.
  • Heart Function: Little to no blood pumped; leads to cardiac arrest if untreated.
  • ECG: Irregular, random waveforms; progresses to flatline without intervention.

  
• What defines bradyarrhythmias and their treatment options?

  • Definition: Heart rate below 45 bpm with symptoms like faintness.
  • Treatment: Atropine injection, isoprenaline infusion, permanent pacemaker.

  
• What defines tachyarrhythmias and their management options?

  • Types: Atrial tachyarrhythmias, supraventricular tachycardias, ventricular arrhythmias.
  • Management: Drugs for atrial/supraventricular; defibrillation and implantable defibrillator for ventricular.

  
• What is Torsades de Pointes and its cause?

  • Definition: A specific type of ventricular arrhythmia associated with delayed repolarization.
  • Cause: Certain drugs prolonging the QT interval.

  
• What are the treatment strategies for bradyarrhythmias and tachyarrhythmias?

  • Bradyarrhythmias: Atropine or isoprenaline for immediate effect; pacemaker for long-term.
  • Tachyarrhythmias: Atrial/supraventricular more responsive to drugs; ventricular often require electrical intervention.

  
• What is the significance of knowing the arrhythmia's origin?

  • Crucial for choosing the correct management strategy.
• How do antiarrhythmic drugs function at the AV node?

  • Slow down conduction within the node.
  • Reduce impulses reaching the ventricles if the source is in the atria.
  • Interrupt propagation if the source is in the AV node.

  
• What are the key issues with antiarrhythmic drugs?

  • Can cause new arrhythmias.
  • Prolong QT intervals on ECG.
  • Limited mortality benefits; some increase mortality in post-MI patients.
• What does the QT interval represent on an ECG?

  • Time for ventricles to depolarize and repolarize.
  • Begins at the start of the QRS complex and ends at the end of the T wave.
• What are the causes of prolonged QT interval?

  • Congenital long QT syndrome.
  • Acquired conditions: electrolyte disturbances, cardiac injury, certain medications.
• What is the clinical significance of QT prolongation?

  • Increases risk of Torsades de Pointes and sudden cardiac death.
  • Strict monitoring recommended for patients on QT-prolonging medications.

  
• How is the QT interval measured accurately?

  • Manual measurement using calipers or counting squares is more accurate than machine-generated measurements.
  • Corrected QT interval (QTc) accounts for heart rate.

  
• What are the limitations of automated QT measurements and Bazett’s formula?

  • Automated measurements often overestimate QT intervals.
  • Bazett’s formula may overcorrect at high heart rates and undercorrect at low heart rates.

  
• What are alternative methods for QT correction?

  • Framingham and Hodges formulas provide more accurate corrections.
  • QT nomogram plots QT interval and heart rate to assess Torsades de Pointes risk.

  
• What are the clinical applications and recommendations for QT prolongation assessment?

  • Manually measure QT interval and use QT nomogram.
  • Rule out reversible causes before altering medication regimens.
  • Continuous monitoring and optimization of electrolytes are critical.

  
• What should be avoided in patients with prolonged QT interval?

  • Avoid drugs that may prolong the QT interval to prevent Torsades de Pointes.
  • Be cautious combining drugs that may have additive effects.

  
• How does atrial fibrillation affect normal heart function?

  • Electrical impulses arise from areas other than the SA node, causing the atria to quiver.
  • Leads to inefficient blood filling of the ventricles and pooling in the atria.

  
• What are the four modifiable risk factors for atrial fibrillation?

  • Hypertension
  • Pre-diabetes
  • Smoking
  • Alcohol consumption
• How is atrial fibrillation classified?

  • First diagnosed AF
  • Paroxysmal AF: terminates spontaneously within 7 days.
  • Persistent AF: lasts > 7 days, does not self-terminate.
  • Long-standing persistent AF: lasts > 1 year.
  • Permanent AF: patient accepts they will remain in AF.

  
• What are the two main components of treating atrial fibrillation?

  • Preventing a stroke.
  • Controlling symptoms (rate control and rhythm control strategies).
• How is the risk of stroke calculated in atrial fibrillation?

  • Using the CHA2DS2-VA score.
  • Score of 2 or more: anticoagulant recommended.
  • Score of 1: consider anticoagulant.
  • Score of 0: no anticoagulant needed.
• What are the dosing guidelines for Dabigatran in atrial fibrillation?

  • Usually 150 mg BD; decrease to 110 mg BD for >75 years or CrCl 30-50 mL/min; avoid if CrCl <30 mL/min.
• What are the dosing guidelines for Rivaroxaban in atrial fibrillation?

  • Usually 20 mg once daily; decrease to 15 mg daily if CrCl 15-50 mL/min; do not use if CrCl <15 mL/min.
• What are the dosing guidelines for Apixaban in atrial fibrillation?

  • Usually 5 mg twice daily; decrease to 2.5 mg twice daily if weight <60 kg, age >80 years, or SCr >133 µmol/L.
• What are the key points regarding Warfarin as an anticoagulant?

  • Narrow therapeutic range; individualize doses.
  • Monitor INR frequently initially; stable doses can be monitored monthly or bi-monthly.
  • Optimal INR range is 2 to 3.
• What factors affect Warfarin's effectiveness?

  • Food and alcohol interactions.
  • Drug interactions: enzyme inducers decrease INR; enzyme inhibitors increase INR.
• What are the key points regarding the effectiveness of oral anticoagulants?

  • All are effective at reducing stroke incidence.
  • NOACs are more effective than Warfarin with lower bleeding risk.
  • Apixaban has the lowest risk for major bleeding among NOACs.

  
• What should patients with a CHA2DS2-VA score of two or more receive?

  • An oral anticoagulant to reduce the likelihood of experiencing a stroke.
• What are the two strategies for controlling symptoms in atrial fibrillation?

  • Rate control strategy: slows ventricular rate to <110 bpm.
  • Rhythm control strategy: converts heart back to sinus rhythm.
• What considerations are there before cardioverting a patient with atrial fibrillation?

  • Estimate stroke risk using CHA2DS2-VA score.
  • Anticoagulate if AF is present for >24 hours and score indicates high risk.

  
• What is the treatment focus for atrial fibrillation?

  Controlling symptoms
• What are the two strategies for controlling symptoms in atrial fibrillation?

  • Rate control strategy
  • Rhythm control strategy
• What is the goal of the rate control strategy in atrial fibrillation?

  To slow the ventricular rate to <110 bpm while the atria are still fibrillating
• What does the rhythm control strategy aim to achieve in atrial fibrillation?

  To convert the heart back into sinus rhythm and maintain it