What are the three parts of an action potential?
- Resting when the membrane is polarized (+ on the outside and - on the inside)
- Depolarization (+ on the inside and - on the outside)
What are the major charge carriers in cardiac muscle cells?
Sodium, Potassium, Calcium
What are the 5 phases of an action potential? What is happening in each?
0: rapid depolarization, Na+ in
1: early repolarization, K+, Cl- out
2: the plateau, Ca+ in, K+ out
3: rapid repolarization, K+ out
4: the resting membrane, K+
What is automaticity?
- Spontaneously initiate an action potential
- back up system for the health to start up an action potential
Explain SA node, AC node, and Purkinjes.
SA node: 60-100/ where rhythmic impulse is generated
AV node: 40-60/ impulse from atria is delayed
Purkinjes: 20-40/ conducts impulse to all parts of the ventricles
What is excitability?
Responding to an impulse and then generating its own action potential
What is conductivity?
To conduct impulses
What is remissibility?
Having a beat that is regular
Explain the pathway in the electrical system of the heart.
Sa node/ Bachmann’s bundle > internodal tracts > AV node > bundle of his > left & right bundle branch > perkinjes
Explain the Depolarization and repolarization of an ECG.
- SA node-> AV node = atrial depolarization
- atrial depolarization= P wave (induces atrial systole)
- AP spread through bundle of his, bundle branches, punkinjes =ventricular depolarization
- ventricular depolarization= QRS (induces ventricular systole)
- ventricular diastole is induced when AP passes out of ventricles
- ventricular repolarization = T wave
- purkinje repolarization= U wave
What does fibrillation mean?
Disorganized current flow
What is sinus bradycardia? Manifestations?
- Normal/ ischemia (restriction of blood supple, decreased oxygenation
- S&S of decreased perfusion
What is sinus tachycardia? Manifestations?
- > or equal to 100
- normal with exertion/ fever
- ischemia, hypoxemia
- increased myocardial workload, decreases coronary artery perfusion
What is sinus arrest? Manifestions?
- Heart stops and starts up again
- not common and not forever (short pause)
What is sick sinus arrest?
- sinus arrest occurs frequently
- may need a pacemaker
What is premature atrial complexes (PAC)?
- Early depolarization occurring in the atria (not SA node)
- May happen when drinking coffee- little jolt, extra beat
What is supra ventricular tachycardia (PSVT)?
P happens once in a while, S is above the ventricle
- really fast for various reasons
- 140-240/min, sudden onset and cessation
- Due to ischemia, reentry (Wolff-Parkinson-White Syndrome)
What is atrial flutter?
- Ectopic atrial tachycardia 240-450/min d/t reentry
- Atrium contact 4 times before the ventricle contacts (but people survive as long as the ventricle continues to contract)
What is atrial fibrillation?
- Chaotic depolarization with only occasional contraction
- Paroxysmal/ chronic d/t MI, HF
- Atria is vibrating, so it is not contracting so blood is not going to the ventricles (blood is being pushed through but not by contraction.. it is trickling down)
- Cardiac output is down by 30%
What is AV conduction Arrhythmias?
Blocks: AV node, bundle of His, bundle branch issue
1st degree atrioventricular block is consistent
Explain 2nd degree AV blocks.
Mobitz type 1/ Wenckebach
- increasing PR until QRS drops
- people can live with tired AV node (has a regular rhythm with a pause)
Mobitz type 2
- occasional dropped QRS
- PR stable
- There is something wrong with the AV node
Explain 3rd degree AV block.
- Atria and ventricles are working but there is no electrical connection between the two (AV node stopped working)
- Shows P and QRS wave but no connection
- Firing at 40-60
What is ventricular arrhythmias (Premature ventricular complexes, PVC)?
- When you drink coffee (normal)
- Had a heart attack (bad thing leading to ischemia)
- d/t irritability (ischemia/necrosis)
What is ventricular tachycardia?
-No cardiac output, arrest situation, lethal rhythm and leads to death
What is ventricular fibrillation?
It is lethal and leads to death
What is asystole?
-Lethal rhythm (flat line)
What is happening in the heart during atrial fibrillation?
- quivering muscle
- poor emptying
- poor filling of the ventricle= decreased CO
How will your patient present during atrial fibrillation?
- Tired (brain is not getting enough O2)
- Irregularly irregular HR
- pulse will be irregular and different strengths
- Low BP
- All other systems will show signs of decreased CO
How many leads can be on an ECG (electrocardiogram)?
12 or 16
What is a holter monitor? and what is other cardiac conduction diagnostics?
- A monitor that is attached to a person while they’re performing their daily activities.
- Exercise stress test and electophysiologic studies
What are different treatments for conduction disorders?
- cardioversion (pharmacological, physiologic, electrical)
- ablation, pacemaker, defibrillator