Electrocardiogram Flashcards
what does the action potential propogating through the heart generate?
generates electrical currents that can be detected at surface of the body
what is an EKG/ECG? (3)
- recording of electrical signals
- composite record of AP’s produced by all heart muscle fibers during each heart beat
- an electrocardiograph is used to record the changes
where are elctrodes placed for an EKG?
limb leads are positioned on arms and legs and 6 chest leads are positioned on the chest
what does the electrocardiograph do?
amplifies the heart’s electrical signals to produce 12 different tracings from different combinations of leads
what does the placement of chest and limb leads allow for?
records slightly different electrical activity because at different positions relative to the heat
by comparing EKGs with one another and normal records, what is it possible to determine? (4)
- if conductive pathway is normal
- if heart is enlarged
- if certain regions of heart are damaged
- cause of chest pain
what are the 3 recognizable waves that appear with each heartbeat on an EKG?
- P wave
- QRS complex
- T wave
what does the P wave represent?
atrial depolarization that spreads from the SA node through the contraactile fibers in both atria
what does the QRS complex represent?
rapid ventricular depolarization as the action potential spreads through ventricular contractile fibers
what does the T wave represent?
ventricular repolarization
when does the T wave occur?
just as ventricles are starting to relax
describe the T wave in relation to the QRS complex and why
T wave is smaller and wider than QRS complex because repolarization occurs more slowly than depolarization
describe the EKG tracing during the plateau period of steady depolarization
flat (S-T period)
what can the size of waves on EKG hint at?
can provide clues to abnormalities
what can a larger P wave indicate?
atrial enlargement
what can an enlarged Q wave indiciate?
could indiciate myocardial infarction
what does an enlarged R wave generally indicate?
enlarged ventricles
what does it usually mean when the T wave is flatter than normal?
the heart muscle is receiving insufficient oxygen, as in the case of coronary artery disease
when might the T wave be elevated?
hyperkalemia
what are intervals in EKG analysis?
the time spans between waves
what is the P-Q interval?
the time from the beginning of P wave to beginning of QRS complex
what does the P-Q interval represent, electrically?
the conduction time from beginning of atrial excitation to beginning of ventricular excitation
what does the P-Q interval represent, time wise?
the time required for AP to travel through atria, AV node, and remaining fibers of the conduction system
when might the P-Q interval lengthen?
if the AP has to detour around scar tissue caused by disorders like coronary artery disease
what is the S-T segement?
begins at end of S wave, ends at beginning of T wave
what does the S-T segment represent, time wise?
the time when ventricular contractile fibers are depolarized during the plateau phase of the AP
when would the S-T segment be elevated?
in acute myocardial infarction
when might the S-T segment be depressed?
when heart muscle receives insufficient O2
what is the Q-T interval?
extends from the start of the QRS complex to the end of the T wave
what does the Q-T interval represent?
the time from the beginning of ventricular depolarization to end of ventricular repolarization
what 3 things might lengthen the Q-T interval?
- myocardial damage
- myocardial ischemia
- conduction abnormalities
what is the exercise stress test used for?
to determine heart condition/heart health when muscles are under stress
what is a need/thing that can be found from an exercise stress test?
narrowed coronary arteries may carry adequate oxygenatedblood at rest, but will not be able to meet the heart’s increased need for oxygen during strenuous exercise
describe continuour ambulatory electrocardiographs (3)
- person wears battery-operated monitor that records EKG continuously for 24 hours
- electrodes are attached to chest and are connected to the monitor
- info on the heart’s electrical activity is stored in the monitor and then later retrieved by medical personnel
relate what is happening on an EKG to what is happening in the conduction system in the P wave
- cardiac AP arises in SA node, propogates throughout atrial muscle and down to AV node; then as atrial contractile fibers depolarize, P wave appears
- after P wave begins, atrial systole occurs and conduction of AP slows through AV node; the resulting delay gives atria time to contract, adding to blood vokume in ventricles before ventricular systole begins
relate what is happening on EKG to the conduction system for the QRS complex
- AP propogates rapidly again after passing through AV bundle, bundle branches, purkinjie fibers, and entire ventricular myocardium. depolarization progresses down the septum, upward from the apex, and outward from endocardial surface, producing QRS complex at the same time that atrial repolarization is occurring
- ventricular systole begins shortly after QRS complex appears and continues through S-T segment. as contraction procees from the apex toward base of the heart, blood is squeezed upward towards SL valves
relate what is happening with the EKG and the conduction system during the T wave
- repolarization of ventricular contractile fibers beginsa t apex and spread throughout the ventricular myocardium, producing the T wave in the EKG
- shortly after T wave begins, ventricles start to relax (diastole) and after 0.6 seconds, ventricular repolarization is complete and ventricular fibers are relaxed
what establishes the normal sinus rhythm of the heartbeats
the SA node
what is an arrhythmia?
abnormal sinus rhythm due to a defect in the conduction system
what 3 alterations can happen to the heratbeat as the result of an arrythmia?
heart may beat:
1. irregularly
2. too fast
3. too slow
what are 5 symptoms of arrhythmias?
- chest pain
- shortness of breath
- lightheadedness
- dizziness
- fainting
what can cause arrhythmias? generally and then give 5 specific
caused by factors that stimulate the heart:
1. stress
2. caffeine
3. alcohol
4. cocaine
5. nicotine
what 5 things other than heart stimulants can cause arrhythmias?
- congenital defects
- coronary artery disease
- myocardial infarction
- hypertension
- defective heart valves
what are the 3 ways to categorize arrhythmias?
- speed
- rhythm
- origination of problem
what is bradycardia?
slow heart rate, below 50 bpm
what is tachycardia?
fast heart rate, above 100 bpm
what is fibrillation?
rapid, uncoordinated beats
describe speed, origination, and episodic manner of supraventricular tachycardia
- rapid but regular rate of 160-200 bpm
- originates in atria
- episodes begin and end suddenly; can last from a few minutes to many hours
how can an episode of supraventricular tachycardia be stopped? generally and then give 3
can sometimes be stopped by maneuvers that stimulate the vagus nerve
1. straining as if having a difficult bowel movement (valsalva maneuver)
2. rubbing area over carotid artery in neck to stimulate carotid sinus
3. plunging face into bucket of ice water to stimulate diver’s reflex
what are 2 treatments for supraventricular tachycardia?
- antiarrhythmic drugs
- radiofrequency ablation
what is a heart block?
an arrhythmia that occurs when the electrical pathway between atria and ventricles are blocked
what is the most common site of heart block?
AV block
how many degrees are there of heart block? describe 1 and 3
3 degrees
1 isn’tt super bad; 3 is super rough
describe 1st degree AV hearet block (2)
- P-Q interval is prolonged
- conduction through AV node is slower than normal
where is atrial fibrillation most common?
in older adults as an acquired disease
describe atrial fibrillation
contraction of atrial fibers in asynchronous and atrial pumping ceases
how fast can the atria beat in atrial fibrillation?
up to 300-600 bpm
what happens to the ventricles in atrial fibrillation?
may also speed up to 160 bpm
what does an EKG look like for atrial fibrillation?
EKG has no clearly defined P waves and irregularly spaces QRS complex
describe the heartbeat in atrial fibrillation and why
heartbeat is irregular in timing and strength because atria and ventricles don’t beat in rhythm
is atrial fibrillation a continuous condition?
no; usually comes in episodes
what does atrial fibrillation do to an otherwise strong heart?
reduces pumping effectiveness of heart by 20-30%
what is the msot dangerous complication of atrial fibrillation and why
stroke since blood mat stagnate in atria, forming blood clots that can travel
give one of the many treatments for atrial fibrillation
treat with beta blockers to reduce epinephrine
where does ventricular tachycardia originate?
in the ventricles duh
what is ventricular tachycardia characterized by?
4 or more premature ventricular contractions (before ventricles filled completely)
what does ventricular tachycardia cause
causes ventricles to beat too fast (120 bpm or more)
what is vtach almost always associated with? and what might is develop into
almost always associated with heart disease or recent myocardial infarction; may develop into ventricular fibrillation
why is sustained vtach dangerous? (3)
- ventricles do not fill properly
- ventricles don’t pump sufficient blood
- may result in low BP and heart failure
what is the most deadly arrhythmia?
ventricular fibrillation (v fib)
what is v fib?
contraction of ventricular fibers completely asynchronous
describe ventricles during v fib as opposed to normal
ventricles quiver in v fib versus the coordinated way of normal contraction
what is the result of ventricular quivering in v fib?
ventricular pumping stops, blood ejection ceases, and circulatory failure results
what is needed when v fib is observed?
immediate medival intervention to stimulate (shock) the ventricles back to normal rhythm
describe the EKG of v fib
no clearly defined P waves, QRS complex, or T waves (just a clusterfuck tbh)
what is the most common cause of v fib?
inadequate blood flow to the heart because of coronary artery disease during a myocardial infarction
what are 4 causes of v fib other than CAD during an MI?
- cardiovascular/cardiogenic shock
- electrical shock
- drowning
- very low K+ levels
why can very low K+ levels lead to v fib?
cause issues with repolarization
in seconds, what does v fib cause?
loss of consciousness
after 5 minutes in v fib, what occurs?
seizures with irreversible brain damage
what is the treatment for v fib?
CPR and defibrillation
what is defibrillation
strong, brief electrial current passed to the heart
what is a defibrillator?
a device that transmits electrical shock by paddle shaped electrodes pressed against the chest
what are AEDs?
protable electronic devices that automatically diagnose the life-threatening cardiac arrhythmias of v fib and vtach and are able to treat them through defibrillation; designed for simple use by laypeople
