PHYSIOLOGY - ARRYTHMIAS Flashcards
What are the different causes of Arrhythmias?
1) Abnormal rhythmicity of the pacemaker
2) Shift of pacemaker activity
3) Conduction Blocks
4) Abnormal pathways of impulse transmission
5) Spontaneous generation of abnormal impulses
7 Questions that must be asked to determine whether or not arrythmias are present
1) What is the heart rate? 2) What is the rhythm? 3) Are P waves present? 4) Is there a P wave for every QRS complex? 5) Is there a QRS for every P? 6) Are the P’s and QRS’s consistantly related? 7) Do all the P’s and QRS’s look alike?
3 Different Types of Normal Cardiac Rhythms
1) Normal Sinus Rhythm 2) Sinus Arrhythmia 3) Wandering Atrial Pacemaker Look at Lead 2 (60 Degrees)
What Arrhythmias produce different speeds of heart rate?
Sinus Brachycardia
Sinus Tachycardia
Sinus arrhythmia
Impulses originate at the SA node at a varying rate = fires FASTER and then SLOWER
All complexes are normal but RHYTHMICALLY IRREGULAR
Longest PP or RR interval exceeds shortest by 0.16 sec or more
CAUSED BY HEAVY RESPIRATION
Wandering atrial pacemaker
Impulses originate from varying points in atria between SA and AV nodes
P Wave changes configuration as signal begins at different areas
QRS is NORMAL
Sinus Brachycardia
Impulses originate at SA Node at a SLOW rate
Normal sinus rhythm w/ HR
Parasympathetic Causes - increased vagal tone, beta-blockers, propanolol, digitalis
Sinus Tachycardia
Impulses originate at the SA Node at a RAPID rate
Normal sinus rhythm w/ HR > 160 bpm
Sympathetic Causes = exercise, fever, hyperthyroidism, shock, etc.
Sinus arrest
Abnormal Arrhythmia
SA node stops firing (beats with a pause = NORMAL PACING WITH A BASELINE PAUSE
Escape Beat = first large upward deflection after pause
A dog faints due to loss of blood to the brain. What would be the compensatory effect to help blood get to brain since blood is not fighting gravity?
Sinus Arrest
Abnormal Rythms that result from Impulse Conduction Blocks
1) 1st Degree Atrioventricular Block
2) 2nd Degree AV Block
3) 3rd Degree AV Block
Causes of AV Blocks include: ischemia of AV node, compression or inflammation of AV node/Bundle, and increased stimulation of heart by vagus nerve
First degree AV block
Abnormal rhythm that results from Impulse Conduction Blocks (potential wide P Wave)
Fixed but PROLONGED PR INTERVAL
Partial block above OR below AV Node
Potential Causes = Mitral insufficiency, Digoxin toxicity
Not dangerous but will progress
Second degree AV block
Abnormal rhythm that results from Impulse Conduction Blocks
2 Different Types:
1) Mobitz Type I - PROGRESSIVE LENGTHENING of PR interval before dropped beat
Coduction starts off normal but gets progressively work with accompanied lengthening B4 dropped QRS = AV node recovers and PR Interval is normal again
Wenckbach Phenomenom
Potential Causes = Digoxin Toxicity
2) Mobitz Type II - SUDDEN QRS dropped W/OUT prior PR Interval lengthening
AV Block at level of Bundle of His OR at bilateral bundle branches OR at trifascicular
Atrial rate is greater than the ventricular rate (MORE P waves due to QRS drop)
Non-Wenkebach
Can have MULTIPLE P waves without a QRS Complex
Third degree AV block
Abnormal rhythm that results from Impulse Conduction Blocks
COMPLETE AV BLOCK
NO RELATIONSHIP BETWEEN P WAVES AND QRS COMPLEXES
2 different scenarios - SA Node conducts impulse in atria (P waves) BUT:
1) Block ABOVE AV Node = AV Node conducts impulses to ventricles
2) Block BELOW AV Node = Purkinje Fibers conduct impulse to ventricles
Atria and Ventricles fire a DFFERENT rates
QRS rate is SLOWER than the P rate bc AV node and Purkinje fibers fire at slower rates than the SA Node
Pacemake placed in ventricles to allow P wave and QRS complexe rates to match up
Supraventricular (ABOVE) and Ventricular Abnormalities
Different Types:
1) Premature Contraction:
2) Tachycardia
3) Fibrillations
Premature Contraction (Supraventricular and Ventricular Abnormalities)
Produces PULSE DEFECIT = ventricle DO NOT fill with blood properly = stroke volume is DECREASED or ABSENT
BIGEMINAL PULSE = Every other beat may be premature
Most caused by ectopic foci (pacemakers) from ischemia, calcified plaques, toxic irritation of different areas of the heart due to drugs
Tachycardia (Supraventricular and Ventricular Abnormalities)
Atleast 3 or more PREMATURE CONTRACTIONS
PAROXYSMAL - last for seconds, minutes, hours, or longer and stop as quickly as they start
Fibrillations (Supraventricular and Ventricular Abnormalities)
Many separate and small waves spreading at the same time in DIFFERENT DIRECTIONS over the cardiac muscle
Supraventricular premature contraction
Premature beats
P occurs before T wave of preceding complex = P-Q-R-S-P-T
Morphology of beats look SIMILAR to sinus beats
Duration of QRS complexes are NORMAL
Produces ATRIAL PREMATURE COMPLEXES
Can produce PULSE DEFECIT and BIGEMINAL PULSE
Atrial Paroxysmal Tachycardia
Occurs as PAROXYSMS (bursts)
Inc in heart rate
Inverted P wave the is superimposed on T wave before every QRS Complex
ABNORMAL SHAPE OF P WAVE
Atrial flutter
Supreventricular Paroxysmal Tachycardia
Impulses travel CIRCULAR COURSE in atria = regular, rapid FLUTTER WAVES (F) w/ NO isoelectric baseline
Produces VARIABLE BLOCK (3rd Degree Heart Block
Atria contracting quickly
QRS can be regular, irregular, or slower depending on block
Possible Cause = Digoxin
LOTS OF LITTLE ROUNDED WAVES BETWEEN Q AND Q
Atrial Fibrillation
Supreventricular Paroxysmal Tachycardia
Disorganized electrical impuses from atria = irregular ventricular rhythm
It produces NO DISTINCT P waves (due to NO ATRIAL CONTACTION) = BASELINE UNDULATIONS instead
QRS looks normal BUT are IRREGULARLY SPACED
SA Node fire but no contraction due to chaotic signal
Similar to atrial flutter when looking at ECG
2 types = Course (larger deflections) and Fine (smaller deflections)
LOTS OF LITTLE WAVES BETWEEN Q AND Q
Ventricular premature contraction
Due to ectopic focus (PACEMAKER) in Ventricular myocardium
Causes WIDE AND BIZARRE QRS complexes (usually NO P wave present)
One ventricle contract before the other
T wave = opposite deflection of QRS complex
MULTIPLE ectopic foci/pacemakers = VARYING MORPHOLOGY of QRS complexes MULTI-FORM VPC:
1) Ventricular Bigeminy
2) Ventricular Paroxysmal Tachycardia
Ventricular bigeminy
Ventricular Premature Contraction that occurs every other beat
normal—->premature—->normal—->premature
Due to ectopic focus (pacemaker)
Ventricular Paroxysmal Tachycardia
runs of 3 or more VENTRICULAR PREMATURE CONTRACTIONS in SEQUENCE
Due to ectopic focus (pacemaker)
Serious condition bc typically due to ischemic damage of ventricles AND can initiate VENTRICULAR FIBRILLATION
Ventricular fibrillation
Chaotic ventricular depolarization
Due to ectopic foci (pacemakers) with in Twave or in vulnerable period (ventricular depolarization)
MOST SERIOUS OF ALL CARDIAC ARRHYTHMIAS
Produces = no QRS waves, no cardiac output = Death in a few min
2 Types = Course (larger deflections) and Fine (smaller deflections)
LOTS OF DEFLECTIONS IN A ROW = CRAZY TRACING
Causes = electrical shock, ischemia
VULNERABLE PERIOD = during ventricular repolarization bc somareas are in refractory period and others aren’t = single electric shock = fibrillation
Intraventricular conduction defects
impulses aren’t as fast, QRS duration will be longer
Left bundle branch block
wide and positive deflections in I, II, III, aVF, and inverted aVR and aVL, large R waves
Right bundle branch block
right axis deviation usually present, large S waves in I, II, III, aVF
Supraventricular paroxysmal tachycardia
clusters of premature contractions
Sinatrial Block
Block at SA Node
No P waves
AV Node produces impulse in ventricles = QRS waves
Supraventricular Paroxysmal Tachycardia
1) Atrial Paroxysmal Tachycardia
2) AV Node Paroxysmal Tachycardia
AV Node Paroxysmal Tachycardia
Aberrant rhythm in AV node = abnormal QRS Waves and NO P Waves
Phenomenon of Re-entry
Causing abnormal contraction that disturbs normal pace setting
Can occur due to 3 different reasons:
1) heart is dilated lengthening the pathway the impulse has to take to cause conduction throughout the heart = so when it returns the muscles are no longer in their normal refractory period
2) Blockage of Purkinje system, ischemia of the heart, high blood potassium levels, etc. cause decreased of velocity of the impulse causing the same consequence
3) Various drugs cause shortened refractory period of cardiac muscles = same consequence
Electrical Shock Defibrillation of the Ventricles
Strong electrical current passed through the heart for a short interval throws ALL muscle into refractoriness simultaneously
BC all impulses STOP = pacemaker and regain control of the heart
