cardiac assessment & conduction abnormalities Flashcards
review: what are the 3 layers of the heart
endocardium, myocardium, epicardium
where does contractility occur in the heart
myocardium
4 chambers of the heart
R atrium, R ventricle, L atrium, L ventricle
atrioventricular valves (2)
tricuspid/mitral
semilunar valves (2)
aortic/pulmonic
what are valves connected to
cartilage connected to walls of heart via tendons
coronary arteries
blood supply of heart
- starts at Aorta -> R coronary artery
- L main (widow maker) -> circumflex and Left anterior descending
conduction of heart sequence
SA node -> AV node -> ventricles
Review: depolarization
electrical activation of cell caused by influx of sodium into cell while potassium exits cell
review: repolarization
return of cell to resting state caused by reentry of potassium into cell while sodium exits -> can’t depolarize again
review: what are the 2 refractory periods
effective refractory period
relative refractory period
effective refractory period
phase in which cells are incapable of depolarizing
relative refractory period
phase in which cells require stronger-than-normal stimulus to depolarize
how is a contraction formed
calcium IN -> mycocardial cells -> potassium OUT -> increases positive charge -> depolarizes cell -> allows for contraction
healthy myocardial cells have what 6 properties
automaticity, excitability, conductivity, contractility, rhythmicity (pattern), refractoriness (no stimulus)
___________/_________ maker potential changes based on location
automaticity/pace
SA node
60-100 BPM (innervated by SNS/PNS to increase/decrease rate)
- ex: scared -> catecholamines -> increase HR -> PNS -> signal to slow down -> automaticity -> slower rate
AV node
40-60
Bundle of HIS
25-40
30-40
Purkinje fibers
20-40
what is the cardiac cycle
events that occur in heart from beginning of one heartbeat to next
- number of cycles depends on HR
- 3 major sequential events: diastole, atrial systole, ventricular systole
diastole
start (relaxation)
atrial systole
atria contract first -> blood intro ventricles -> Lub (S1)
ventricular systole
ventricles with volume -> fill with blood -> aorta/pulmonic -> valves close -> Dub (S2)
what is cardiac output
amount of blood pumped out of the L ventricle in L/min
CO equation & normal amount
CO = SV x HR
- normal CO: 4-8L/min
what is stroke volume
amount of blood ejected with each beat
- determined by L ventricle
SV: preload?
degree of stretch of cardiac muscle fibers at end of diastole
SV: afterload
resistance to ejection of blood from ventricle
SV: contractility
ability of cardiac muscle to shorten in response to electrical impulse
- TIP: cardiac myocytes can squeeze/shorten if triggered by: calcium
ejection fraction
percent of END DIASTOLIC VOLUME ejected from the L ventricle with each heart beat
- normal EF: 50-75%
TIP: R ventricle ejects blood -> Lungs. L ventricle stronger than R ventricle
what are the 2 influencing factors of cardiac output
1) control of HR
2) control of SV
how does HR affect CO (2)
1) autonomic nervous system: SNS (increases HR r/t increased catecholamines & excess thyroid hormone) /PNS (travels to vagus nerve to slow HR) -> changes in metabolic demand r/t stress, exercise, and illness = changes in CO
2) baroreceptor reflex (homeostasis): nervous system bundles (increase HR r/t blood pressure) -> accommodates changes in pressure by releasing discharge, transmitting impulses to medulla -> initiates PNS -> (elder) decrease HR and BP
TIP: opposite for hypotension = decrease baroreceptor -> increase BP/HR
How does SV affect CO (preload? after load? contractility?)
augmented by catecholamines, SNS, medications
- preload: determined by volume status
- afterload: determined by vascular resistance
- contractility
what is contractility decreased with? (5)
- hypoxia
- hypoxemia
- acidosis
- some drugs (beta-blockers - decrease contractility, NOT digoxin - increase contractility)
- viable heart muscle available, etc.
assessment of cardiovascular system
(COLDSPA)
health hx (resp, cardiac, everything)
demographic information (environmental exposures)
family/genetic hx
cultural/social factors
risk factors: modifiable/non-modifiable
what are modifiable risk factors for cardiovascular
lack of exercise
diet
obesity
high BP
lipid panels
blood glucose
what are nonmodifiable risk factors for cardiovascular
age
family hx
sex (female/male)
ethnic background
common sx of cardiovascular system (6)
- chest pain/discomfort
- pain/discomfort in other areas of the upper body
- SOB/dyspnea
- peripheral edema, wt. gain, abd distentino
- palpitations (sometimes)
- unusual fatigue, dizziness, syncope, change in LOC = decrease CO = decrease BF = brain
past health, family, and social hx (8) considerations
- medications
- nutrition
- elimination
- activity/exercise
- sleep, rest
- self perception/self concept
- roles and relationships
- coping and stress
physical assessment considerations (7)
- general appearance (pale? ashen? diaphoretic? temperature change?)
- skin and extremities (lack perfusion? bruising?)
- BP, othrostatic changes (15-30 seconds, teach slow movements)
- arterial pulses (radial, femoral, DP/PT, carotid)
- Jugular vein pulsations
- HR, inspection, palpation, auscultation
- assessment of other systems
TIP: good central pulse =/= BP