Intro to Perfusion & EKGs Flashcards
What is perfusion ?
the flow of blood through arteries and capillaries, delivering nutrients and oxygen to cells and removing cellular waste products
What is cardiac output ?
total amount of blood pumped from the ventricles in 1 min
- HR X SV (stroke volume)
- 4-8 L per min is normal in adults
- a faster HR doesn’t mean better CO
What is stroke volume ?
amount of blood ejected from heart after 1 beat
What is cardiac reserve ?
amount of blood left in the ventricles after each beat
What is preload ?
amount of blood in the ventricles at the end of diastole
- VOLUME
What increases preload ?
- hypervolemia
- regurgitation of valves
- HF (Rt side)
What is afterload ?
resistance the left ventricle must overcome to circulate blood
- BLOOD PRESSURE
- increased afterload leads to increased cardiac workload
What increases afterload ?
- hypertension
- vasoconstriction
What are the 2 main vessels in coronary blood flow ?
- Right Coronary Artery (RCA)
- Left Coronary Artery
- Left anterior descending (LAD)
- Circumflex
What is central perfusion ?
a coordinated effect of electrical and mechanical factors move blood through the heart
- cardiac cells must be oxygenated and perfused just as the peripheral cells do
What is peripheral perfusion ?
volume of blood that flows through target tissues
- different organs require different volumes of blood to function
- central perfusion affects peripheral
- peripheral perfusion can be impaired by itself
What is cardiac conduction in the heart ?
specialized nerve cells which can create and transport electrical impulse
- impulse triggers ventricular contraction
What is the pathway for cardiac conduction ?
- SA node (Rt atrium)
- AV node
- bundle of His
- Purkinje fibers
What are the properties of cardiac cells ?
- automaticity
- excitability
- conductivity
- contractility
What does automaticity mean ?
the ability of a cell to depolarize (contract) itself
What does excitability mean ?
the ease with which cardiac cells undergo a series of events characterized by sequential depolarization (contracting) and repolarization (relaxation)
What does conductivity mean ?
the property of conducting an electric current
What system controls the SA node ?
autonomic nervous system
How does the parasympathetic nervous system affect the heart ?
- decreases rate of SA node
- slows impulse conduction of AV node
- vagal nerve stimulation will decrease the HR
How does the sympathetic nervous system affect the heart ?
- flight or fight will increase the HR
- increases rate of SA node
- increases impulse conduction of AV node
- increases cardiac contractility
How do baroreceptors affect HR ?
react to the volume status
What is cardiac index ?
gives better insight into the hearts ability
- divides BSA (body surface area) with CO
What does intrinsic rate mean ?
the rate at which the heart beats when all cardiac neural and hormonal inputs are removed (no interference from the CNS)
- each node has a different intrinsic rate
What is the intrinsic rate for the SA node, AV node, and His-Purkinje System ?
- SA: 60-100
- AV: 40-60
- His-Purkinje: 20-40
What are some non-modifiable risk factors for heart conditions ?
-age
- gender
- genetic factors
- race and ethnicity
What are some modifiable risk factors for heart conditions ?
- HTN
- smoking
- DM
- physical inactivity
- obesity
- high blood cholesterol
What are some objective assessments of the perfusion ?
- VS
- peripheral pulses
- pitting edema
- capillary refill
- auscultation (S1, S2)
- murmur
- JVD
What is electrocardiogram monitoring ?
graphic tracing of electrical impulses produced by the heart
- waveforms of ECG represent activity of charged ions across membranes of myocardial cells
What does the p-wave indicate ?
time for the passage of electrical impulses through the atrium
- causing atrial contractions
What is the normal interval for a p-wave ?
0.06 - 0.12
What does the PR interval represent ?
time taken for impulse to spread through the atria, AV node, bundle of HIS, bundle branches, and Purkinje fibers to the point proceeding ventricular contraction
What is the normal duration for the PR interval ?
0.12 - 0.20
What does the QRS complex/interval represent ?
ventricular depolarization
What is the normal duration of the QRS complex ?
< 0.12
What does the ST segment represent ?
time between ventricular depolarization and repolarization
- should be isoelectric (flat)
What is the normal duration of the ST segment ?
0.12
What does the T-Wave represent ?
time for ventricular repolarization
What is the normal duration of the T-Wave ?
0.16
What causes the QT interval to increase ?
- electrolyte imbalances
- medication side effects
What is the normal duration of the QT interval ?
0.34 - 0.43
What are some reasons for sinus bradycardia ?
- normal in athletes
- vagal stimulation, carotid massage
- medications can cause this
What is the tx for sinus bradycardia ?
- hold medicine
- Atropine if symptomatic
- transcutaneous pacing may be needed
- permanent pacing if sustained
What are some reasons for sinus tachycardia ?
- stressors like exercise, hypotension, fever, pain, hypovolemia, hypoxia
- effects of medication
- caffeine, cocaine, albuterol
FIND OUT BEFORE TREATING
- caffeine, cocaine, albuterol
What is the treatment for sinus tachycardia ?
- treat the underlying cause
- beta blockers, calcium channel blockers
- vagal maneuvers
- Adenosine: stops the heart and starts it up again in the hopes it normalizes
