Cardiac Conduction Flashcards
Properties of heart cells
1. Automaticity To spontaneously initiate an action potential SA node: 60-100/min AV node: 40-60/min Purkinjes: 20-40/min 2. Excitability To respond to an impulse and then generate it’s own action potential 3. Conductivity To conduct impulses
Depolarization and Repolarization
- Depolarization wave From the SA node to the AV node & over to the LA = P wave Thru the AV node, Bundle of His, L&R bundle branches, & perkinjes = PR interval Thru the ventricular wall = QRS - Repolarization Of the atrial = hidden Of the ventricles = T wave Of the perkinjes? = U wave
Sinus (SA) Node Arrhythmias
- Sinus bradycardia (100) Normal with exertion/fever Ischemia, hypoemia Increases myocardial workload, decreases coronary artery perfusion
Sinus arrest & Sick sinus syndrome
Sinus Arrest: Failure of SA node, usually intermittent
Sick Sinus Syndrome: d/t SA node injury,
unknown cause
Premature atrial complexes (PAC)
Early depolarization originating in the atria (not SA node)
Common
(premature atrial contraction)
Paroxysmal supraventricular tachycardia (PSVT)
- 140-240/min, sudden onset and cessation
- d/t ischemia, reentry
- wolff parkinson white syndrome
Atrial flutter
- Ectopic atrial tachycardia 240-450/min
- d/t reentry
Atrial fibrillation
- Chaotic depolarization with only occasional contraction
- Paroxysmal/chronic
- d/t MI, HF
What is happening in the heart? - Quivering muscle
- Poor emptying of atria
- Poor filling of ventricle = decreased CO
How will your patient present? - Heart rate will be irregular
- Pulses will be irregular with varying strength
- BP will be low
- All other systems will exhibit the S&S of decreased CO
AV Conduction Arrhythmias (1st degree block)
Blocks (1st, 2nd, 3rd degree)
AV node/Bundle of His/bundle branch issue
1st degree Atrioventricular Block
Consistent long PR interval, followed by a QRS
2nd degree block
Mobitz Type 1/Wenckebach - Increasing PR until QRS dropped Mobitz type 2 - Occasional dropped QRS - PR stable
3rd degree block
- No electrical communication between atria and ventricles
Ventricular Arrhythmias (PVC)
- Premature ventricular complexes (PVC)
- d/t irritability (ischemia/necrosis)
- common
- isolated (single)
- couplet (two-three in a row…not good)
- bigeminy (every 2nd beat)
Ventricular fibrillation & Asystole
Ventricular fibrillation: ventricle is vibrating, no blood can be pumped.
Asystole: when the heart is not doing anything
Cardiac Conduction Diagnostics
- Electrocardiography (ECG)
12 lead
16 lead - Holter Monitor
Exercise Stress Test
Electrophysiologic Studies
Treatments for Conduction Disorders
Cardioversion - the person is still conscious
- Pharmacological (digoxin)
- Physiologic (precardial thump, cough)
- Electrical (paddles)
Defibrillation - defibrilating the person
- Electrical
Pacemaker
Surgical
- Ablation/pacemaker/defibrillator