Cardiac Dysrhythmias Flashcards
Conduction pathway
SA node –> Internodal pathways through the atria –> AV node –> Bundle of His –> Left and Right Blundle Branches –> Purkinje Fibers
Inherent rates
- SA Node:
- Faster pacemaker of the heart
- Reaches threshold at 60-100 bpm
- Dominant pacemaker of the heart
- Natural pacemaker of the heart
- AV Node:
- Latent pacemaker
- Reaches threshold at slower rate 40-60 bpm
- Purkinje Fibers (ventricles):
- Latent pacemaker
- Reaches threshold at slower rate 20-40 bpm
Medical management of dysrhythmias
- Treat underlying cause
- Vagal maneuvers
- Pharmacological therapy
- Termporary pacing
- Cardioversion
- CPR
- Asystole
- Ventricular fibrillation - CPR => defib
- Defibrillation
Surgical management of dysrhythmias
- Permanent pacing
- CABG
- ICD (AICD): Automated internal cardiac defib
- Open cardiac massage
Atrial Fibrillation
- Chaotic impulse formation in the atria producing impulses at rates of 400+/min
- No discernable P-wave, wavy baseline
- Irregular ventricular response.
- Abnormal ventricular conduction may occur.
- Results in loss of “atrial kick” => decrease CO
- High risk for pulmonary or systemic emboli
- Decreased CO also due to sporadic ventricular contractions
Pharmacologic interventions in atrial fibrillation
- Cardioconverting meds: Amiodarone, digoxin
- Control of ventricular rate: Diltiazem, metoprolol, esmolol, digoxin, verapamil.
- Anticoagulants: Heparin, coumadin, aspirin.
Amiodarone
- Decrease membrane excitability, prolonges action potential to terminate VT or VF
- Use: Treatment and prophylaxis of recurrent VF and hemodynamically unstable VT; rapid atrial dysrhythmias.
- Side effects: Bradycardia, hypotension.
Digoxin
- Improve symptoms, exercise tolerance, and quality of life
- No effect on mortality
Treatment for ventricular tachycardia
- Hemodynamically stable
- Amiodarone
- Lidocaine
- Hemodynamically unstable
- Cardioversion / Defibrillation
- Ventricular tachycardia, if not treated, can go to V-Fib
Treatment of asystole
- CPR
- Intubation
- Transcutaneous pacing
- IV: Epinephrine
Atropine - V-Fib deteriorates into asystole if not treated
- The only effective treatment for VF and pulseless VT is defibrillation
12-Lead ECG
- Leads
- 3 standard limb leads
- 3 augmented limb leads
- 6 precordial leads
- Impulses toward electrode
- Positive QRS complex
- Impulses away from electrode
- Negative QRS complex
Position of precordial leads
V1 – 4th ICS right of sternum V2 – 4th ICS left of sternum V3 – between V2 and V4 V4 – 5th ICS midclavicular line V5 – 5th ICS anterior axillary line V6 – 5th ICS midaxillary line
Squares (12-lead ECG)
Small = 0.04 seconds or 0.1 mv.
Large = 0.20 seconds or 0.5 mv.
- 5 large boxes = 1 second
- 10 large boxes = 2 seconds
- 15 large boxes = 3 seconds
- 30 large boxes = 6 seconds
Hashmarks at top of paper designate seconds
- Varies from 1-3 second intervals
- Check to see what system is being usedSteps in Rhythm Interpretation: Rate
Rule of 6s
- Count the number of complete QRS
complexes in a 6 second strip and
multiply by 10 (Quick Look)
Small Boxes
- 1500 small boxes in a minute
- Count the number of small boxes
between 2 R to R complexes and divide into 1500 (Accurate)
- Give range if rhythm is irregular
Rate Ruler
EKG Intervals
PR Interval – 0.12-0.20 Seconds
- Beginning of the P-wave
to beginning of QRS complex
QRS Interval – 0.06-0.10 Seconds
- Beginning to end of QRS complex
QT Interval – 0.34-0.44 Seconds
- Beginning of QRS complex to end of
T-wave
- Varies with rate
