Dysrhythmias Flashcards
Depolarization
movement of ions across a cell membrane, causing the inside of the cell to become more positive
an electrical event expected to result in contraction
Repolarization
movement of ions across a cell membrane in which the inside of the cell is restored to its negative charge
Ectopic
impulse(s) originating from a source other than the SA node
Permeability
ability of a membrane channel to allow passage of electrolytes once it is open
Absolute Refractory Period
corresponds with the onset of the QRS complex to approximately the peak of the T wave
cardiac cells CANNOT be stimulated to conduct an electrical impulse, no matter how strong the stimulus
Relative Refractory Period
corresponds with the downslope of the T wave
cardiac cells CAN be stimulated to depolarize if the stimulus is strong enough
Location of SA node
top of right atrium
Location of AV node
bottom of right atrium
AV node separates into….
right and left bundles branches
The majority of blood flow from atria to ventricles is:
a) passive
b) active
a) passive
The right ventricle is normally a
a) low pressure system
b) high pressure system
a) low pressure system
pumping blood to lungs which is a short distance
The left ventricle is a
a) low pressure system
b) high pressure system
b) high pressure system
pumping blood to the entire body
requires force to overcome higher resistance in systemic arteries, particularly the aorta
Automaticity
unique ability of the heart
heart can contract by itself, independently of any signals or stimulation from the body
safeguard if SA node isn’t working properly
3 main areas of the heart’s conduction system
1) SA node
2) AV node
3) conduction fibers within the ventricle
specifically:
-bundle of His
-bundle branches
-Purkinje fibers
T or F: The SA node sets its own depolarization
FALSE
Intrinsic pacemaker rate of the SA node (bpm)
60 - 100
Intrinsic pacemaker rate of the AV node (bpm)
40 - 60
Intrinsic pacemaker rate of the Purkinje fibres (bpm)
15 - 40
Cardiac Monitoring
continuous real-time observation of heart’s electrical activity
non-invasive, quick & effective diagnostic tool
typically through a bedside monitor
used for ongoing assessment
Which lead is typically used for cardiac monitoring?
lead 2
upright, positive, easiest to read***
inferior view
can also use lead 3 or 5
Why cardiac monitoring is used (6)
1) To monitor a patient’s HR
2) To evaluate the effects of disease or injury on heart function
3) To evaluate pacemaker function
4) To evaluate the response to medications (e.g., antiarrhythmics).
5) To obtain a baseline recording before, during, and after a medical procedure
6) To evaluate for signs of myocardial ischemia, injury, and infarction.
ECG
measures heart’s electrical activity from different views
do when you suspect that something is wrong
How many leads does a conventional ECG have?
a) 12
b) 16
a) 12
Reasons to use cardiac monitoring (6)
1) To monitor a patient’s HR
2) To evaluate the effects of disease or injury on heart function
3) To evaluate pacemaker function
4) To evaluate the response to medications (e.g., antiarrhythmics)
5) To obtain a baseline recording before, during, and after a medical procedure
6) To evaluate for signs of myocardial ischemia, injury, and infarction
5-Lead ECG placement
RA - white - 2nd intercostal space
LA - black - 2nd intercostal space
V - brown - right of the sternum
RL - green
LL - red
Preload
end-diastolic volume
force exerted by the blood on the walls of the ventricles at the end of diastole
helps to determine how effective contraction with be - e.g. filling a balloon with a lot of air and letting it go
stretch
Afterload
pressure or resistance against which the ventricles must pump to eject blood
what they’re pushing AGAINST
squeeze
Contraction
ability of cardiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus
Venous return
amount of blood flowing into the RIGHT ATRIUM each minute from the systemic circulation
Stroke volume
amount of blood ejected from a ventricle with each heartbeat
Ejection Fraction
% of blood pumped out of a heart chamber with each contraction
A normal ejection fraction is between __ - __ %
50 - 80%
Cardiac Output
amount of blood pumped into the aorta each minute by the heart
SV x HR
Diastole
rest period with filling
phase of the cardiac cycle in which the atria and ventricles relax between contractions and blood enters these chambers
When the term diastole is used without reference to a specific chamber of the heart, the term implies ___________ diastole
ventricular
Systole
contraction of the heart during which blood is propelled into the pulmonary artery and aorta
When the term systole is used without reference to a specific chamber of the heart, the term implies _________ systole
ventricular
Blood Pressure
force exerted by the circulating blood volume on the walls of the arteries
Heart Failure
condition in which the heart is unable to pump enough blood to meet the metabolic needs of the body
may result from any condition that impairs:
-preload
-afterload
-cardiac contractility, or
-HR
Shock
inadequate tissue perfusion that results from the failure of the cardiovascular system to deliver sufficient oxygen and nutrients to sustain vital organ function
Cardiac Cycle
refers to 1 complete mechanical cycle of the heartbeat
The cardiac cycle begins with _________ and ends with __________
ventricular contraction
ventricular relaxation
Steps of the cardiac cycle (5)
1) atrial systole
2) isovolumetric contraction
3) ventricular contraction
4) isovolumetric relaxation
5) ventricular diastole
Atrial Systole
atrial kick at end with contraction
rest of blood pushed from atria into ventricles
Isovolumetric Contraction
closed system
AV valves shut - S1 - lub
ALL valves shut
ventricles tensing so pressure beyond aortic and pulmonary
Ventricular Contraction
depolarization is making muscles contract
pumping blood
pressure is greatest in ventricles
semilunar valve open
Isovolumetric Relaxation
closed system
semilunar valves shut - S2 - dub
ventricular pressure decreases
ALL valves shut
Ventricular Diastole
blood flows from atria into ventricles
as atria fill and pressure becomes greater, AV valves open
passive filling of ventricles
T or F: Depolarization is the same as contraction
FALSE
we hope that depolarization results in contraction, but they are not the same
Depolarization is a:
a) electrical event
b) mechanical event
a) electrical event
Contraction is a:
a) electrical event
b) mechanical event
b) mechanical event
Resting State - Extracellular Electrolyte Concentrations for K+, Na+, Ca2+
K+: 4
Na+: 145
Ca2+: 2
Resting State - Intracellular Electrolyte Concentrations for K+, Na+, Ca2+
K+: 135
Na+: 10
Ca2+: 0.1
Phases of an action potential (5)
Phase 0: Upstroke
Phase 1: Overshoot
Phase 2: Plateau
Phase 3: Repolarization
Phase 4: Resting membrane potential
Phase 0: Upstroke
Ionic Movement:
-Na+ into cell
-K+ leaves the cell
-Ca2+ moves slowly into cell
Mechanism:
-Fast Na+ channels open
Phase 1: Overshoot
Ionic Movement:
-Na+ into cell slows
-Cl- into cell
-K+ leaves the cell
Mechanism:
-Fast Na+ channels close partially
Phase 2: Plateau
Ionic Movement:
-Na+ and Ca2+ into cell
-K+ out
Mechanism:
-Multiple channels (Ca2+, Na+, K+) open to maintain membrane voltage
Phase 3: Repolarization
Ionic Movement:
-K+ out of cell
Mechanism:
-Ca2+ and Na+ channels close
-K+ channel remains open
Phase 4: Resting membrane potential
Ionic Movement:
-Na+ out
-K+ in
Mechanism:
-Na+–K+ pump
Rhythm Strip
graphic tracing of electrical impulses
movement of charged ions across membranes of myocardial cells creates certain wave forms on the tracings
Wave forms represent ____________ and _____________ of myocardial cells
depolarization
repolarization
Box width in seconds
0.04
***good to know for midterm
P wave length (seconds)
0.06 to 0.12 seconds
PR interval length (seconds)
0.12 to 0.20 seconds
QRS complex length (seconds)
0.06 to 0.12 seconds
ST segment length (seconds)
deviation from baseline
QT interval length (seconds)
0.34 to 0.43 seconds
EKG Analysis Steps (7)
1) Determine heart rhythm
2) Measure HR
3) P-wave evaluation
4) PR-interval evaluation
5) P-QRS ratio
6) QRS complex evaluation
7) Interpret the rhythm
1) Determining the rhythm
regular or irregular
take paper, measure top of R to R
has to be off by 1 small box to be irregular
2) Measure HR
of QRS complexes in 1 minute
6 second method
R-R intervals in 6 seconds, and multiply by 10
High HR leads to:
a) higher ventricular volume
b) lower ventricular volume
b) lower ventricular volume
less time for passive filling, lower volume in ventricles, less output
3) P-wave evaluation
upright and uniform
What does the P wave represent?
atrial depolarization
time it takes an impulse to travel from the atria to the AV node, bundle of His, and Purkinje fibres
4) PR-interval evaluation
0.12 to 0.20 seconds
5) P-QRS ratio
Is there a P for every QRS?
P without QRS: means that it didn’t go through SA node to AV node
QRS without P: started in AV node or ventricles, ventricles depolarized but atria did not, safety mechanism
What does the P-QRS ratio represent?
ventricular depolarization
6) QRS complex evaluation
0.06 to 0.12 seconds
1.5 to 3 boxes
T or F: Everyone has a Q wave
FALSE
What does a physiologic Q wave look like?
small, narrow, shallow
What does a pathologic Q wave look like?
wide and deep
usually means they’ve had heart attack in the past
7) Interpret the rhythm
lots of different rhythms :)
Normal Sinus Rhythm
normal everything
Sinus Tachycardia
regular rhythm
HR over 100 bpm
Sinus Bradycardia
regular rhythm
HR under 50-60 bpm
Atrial dysrhythmias definition
reflect abnormal electrical impulse formation and conduction in the atria
rhythms starting elsewhere in the heart, other than the SA node
T or F: Most atrial dysrhythmias are life-threatening
FALSE
most are not
because most of filling into ventricles is passive, only losing about 30% of volume
Type of atrial dysrhythmias (3)
1) Premature Atrial Contraction
2) Atrial Fibrillation
3) Atrial Flutter
Premature Atrial Contraction
Heart rhythm - regular except for premature beats (impulse of origin of the underlying rhythm remains in the SA node)
P waves - regular except 1 or 2 beats are abnormal
Regular P wave – uniform, upright, smooth, rounded
Premature beat – upright, flattened, or notched
QRS MAY be absent following premature P wave
Treatment for Premature Atrial Contraction
usually none, assess patient status and determine if it’s significantly impacting CO
Atrial Fibrillation
1) Heart rhythm - atrial and ventricular rhythms are irregular
2) HR - atrial rate 350 to 700 bpm, ventricular rate varies, usually slower
-Controlled Atrial Fibrillation - less than 100
-Uncontrolled Atrial Fibrillation - greater than 100
3) P waves – no consistently identifiable P wave
4) P to QRS ratio - more fibrillatory waves than QRS, can’t measure
5) PR interval - not measurable
Treatment for Atrial Fibrillation and Atrial Flutter (4)
1) Conversion
2) Rate control (less than 100)
3) Anticoagulation
4) Ablation
Atrial Flutter
1) Heart rhythm - atrial regular, ventricular may be regular or irregular
2) HR - atrial rate 250 to 300 bpm (less than fib), ventricular rate varies, usually slower
3) P waves - flutter waves, “saw tooth” looking, can have multiple waves
4) P to QRS ratio - more flutter waves than QRS
5) PR interval - not measurable
Patients with this dysrhythmia are better candidates for ablation therapy
a) atrial fibrillation
b) atrial flutter
b) atrial flutter
limited to 1 spot
Medications for Atrial Fibrillation and Flutter (5)
1) Calcium channel blockers (Diltiazem)
2) β-adrenergic blockers (metoprolol)
-slowing HR
3) Digoxin
-slowing HR
4) Anti-dysrhythmic agents (amiodarone)
-back into sinus rhythm
5) Anticoagulants
Patients on Digoxin would likely have this chronic condition as well
heart failure
Situations when the ventricles would become the pacemaker (4)
1) SA node fails to discharge
2) impulse from the SA node is generated but blocked as it exits the SA node
3) rate of discharge of the SA node is SLOWER than that of the ventricles
4) irritable site in either ventricle produces an early beat or rapid rhythm
Ventricular Dysrhythmias (3)
1) Premature Ventricular Contraction (PVC)
2) Ventricular Tachycardia
3) Ventricular Fibrillation
Premature Ventricular Contraction (PVC)
1) Heart Rhythm – regular EXCEPT for premature beat if impulse of origin of the underlying rhythm remains in the SA node
3) P waves - regular or premature
4) P to QRS ratio - PVC will not have a P wave
5) PR interval - NONE
6) QRS complex - longer than 0.12 seconds, wide and bizarre
Premature Ventricular Contraction Treatment (3)
none if CO not impacted, frequent PVC’s can decrease CO as they interrupt diastolic filling
1) Oxygen therapy for hypoxia
2) Electrolyte replacement
3) Drugs: β-adrenergic blockers, procainamide, amiodarone, lidocaine
Types of Premature Ventricular Contraction (4)
1) Ventricular Bigeminy
bi=2, every other beat is a PVC
2) Multifocal PVCs
3) Coupled PVCs
2 together
4) Short run of VT
3 or more beats
Ventricular Tachycardia
2) HR - 110 to 250 bpm
3) P waves - usually absent
4) P to QRS ratio - PVC will not have a P wave
5) PR interval – none
6) QRS complex - greater than 0.12 seconds, are all similar, often wide and bizarre
First thing you should do if you see ventricular tachycardia
TAKE PULSE*** (pulse vs pulseless)
CO is compromised, losing a great deal of passive filling
Treatment for pulseless ventricular tachycardia
CPR and defibrillation
Treatment for ventricular tachycardia with pulse
Stabilize patient, treat underlying cause
O2
antiarrhythmic drugs to suppress the rhythm (e.g. procainamide, amiodarone, sotalol)
cardioversion
Cause of ventricular tachycardia
severe underlying myocardial disease
Ventricular Fibrillation
chaotic ventricular rhythm that rapidly results in death
Treatment for Ventricular Fibrillation
CPR
defibrillation
ACLS protocols
