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
ST Segment (12-lead ECG)
Look for Elevation or Depression
ST Elevation: Myocardial injury
ST Depression: Reciprocal changes, digoxin, and ischemia
Normal Sinus Rhythm
Originates in the SA Node
Atrial / Ventricular rhythm regular
Rate=60-100 bpm
P-wave before every QRS
PR-Interval=0.12-0.20 seconds
Constant
QRS duration=0.06-0.10
ConstantSinus Bradycardia
HR <60 bpm
Causes: vagal, drugs, ischemia, ICP, athlets (normal)
Sinus Tachycardia
HR 100-150 bpm
Causes: Stimulates, exercise, fever, alteration in fluid status
Causes of Atrial Dysrhythmias
Stress Electrolyte Imbalances Hypoxemia Injury to the Atria MI Valve disease COPD Digitalis Toxicity Hypothermia Hyperthyroidism Alcohol Intoxication Pericarditis Cardiomyopathy CHF PE
Significance of Atrial Fibrillation
- Decreased CO due to loss of “atrial kick”
- Can lead to LVF and Myocardial ischemia
- CO also affected by sporadic ventricular contractions
- Increased risk of thrombi formation
- PE and Stroke
Atrial Flutter
Irritable focus in atria
Sawtooth or flutter waves
Atrial rate = 250-350 bpm
Ventricular rate slower
Impulse conduction varies, may be fixed, i.e. 2:1, 3:1, 4:1
May be self-limiting or may require treatment with meds or cardioversion
Treatment of Atrial Flutter
Cardioversion Anticoagulants Diltiazem Digoxin Esmolol Metoprolol Amiodarone Ibutilide Radiofrequency Ablation
Ventricular Dysrhythmias
Ectopic beats originating in the Right or Left ventricle (Purkinje Fibers) Common causes: - Myocardial Ischemia, Infarction - Hypokalemia - Hypomagnesemia - Acid-Base Imbalances - Hypoxemia
Ventricular Tachycardia
Originates in the ventricles 3 or more PVCs in a row Rate: >100 bpm Rhythm is usually regular Wide QRS complex >0.12 seconds Pulse may or may not be present
Ventricular Fibrillation
Chaotic, completely unorganized rhythm
No cardiac output
Coarse versus Fine
CPR –> Defibrillation
“Artifact can mimic V. Fib.”
Asystole
Absence of QRS complexes confirmed in 2 leads
Flatline
