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96 Cards in this Set
- Front
- Back
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What does ectopic mean?
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impulse arising from anywhere other than SA node
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What is premature depolarization?
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ectopic impulse that follows the preceding P or QRS by and shorter interval than the predominant PP or PR interval
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What is an escape depolarization?
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an ectopic depolarization late after the dominant pacemaker has failed to initiate a systole during the normal RR interval (can save animals that have flatlined)
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What is a conduction block?
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pathologic delay or interruption in conduction
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What is a compensatory pause?
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Pause that follows an extrasystole which does not depolarize the SA node and therefore the next normally conducted QRS falls in line with the previous rhythm. The RR interval of the two normal complexes surrounding the premature complex is exactly twice the normal RR interval
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What is fusion?
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complex formed when a normally conducted impulse and a ventricular ectopic pacemaker simultaneously depolarize the ventricle. It is intermediate in appearance when compared to the extrasystole and normal impulses. It is a signs of AV dissassociation
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What is the J point?
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beginning of the ST segment (after transition point from QRS wave - where is finally flattens back out)
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What is paroxysmal tachycardia?
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Burst of tachycardia, sudden onset and abrupt end
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What is the difference between unifocal and multifocal?
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Unifocal - one source like ventricular premature depolarizations
Multifocal - from different parts of a ventricle = sicker |
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What is fibrillation?
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chaotic, disjointed mosaic myocardial activation, spontaneously depolarizing, not contracting in an organized fashion
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What is extrasystole?
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premature ectopic depolarization dependent on or coupled to the preceding normal beat but originating from an ectopic focus
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What is parasystole?
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independent ectopic rhythm operating alongside the dominant pacemaker but protected from depolarization by the dominant pacemaker. It causes an ectopid depolarization if it discharges during a period when the heart is not refractory. The ectopic depolarization are not coupled to the previous QRS by a fixed interval time.
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What is AV dissociation?
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independent depolarization of atria and ventricles usually associated with abnormal AV conduction of ectopic ventricular rhythms
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What is ventricular capture?
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Normal QRS followed by a period of AV dissociation
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What are the effects of PNS on SA rhythm?
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1. Decreased rate of diastolic depolarization
a. Increase K+ conductance - more hyperpolarized - delay in depolarization b. Decrease cAMP - decreased Ca++ available for depolarization Decreased HR through M2 receptors 2. shifts pacemakers, shortens atrial action potential duration |
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What are the effects of SNS on SA rhythm?
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1. steeper repolarization phase - return RMP to normal
2. Increase cAMP - increase Ca++ available for depolarization Increased HR through B1 receptors |
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What are 3 functions of the AV nodes
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1. conduction bridge btw atria and ventricles
2. induces a delay in A/V depolarizations 3. back up pacemaker for cells in AV node |
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What is AV block?
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AV node may not pass on every pulse from the atria to the ventricles. Can be a protective element so that ventricles do not beat as rapidly
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Who is depolarized/ repolarized first? Which is longer overall?
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Depolarized - endothelial first
Repolarized - endothelial last (epithelial first) Endothelial is longest overall |
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What is the order of ventricular depolarization in category A animals?
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1. Initial- endocardial shell at LV apex - R wave in some
2. free walls - endo to epi - R wave in some 3. Terminal - base of ventricles + septum - S wave |
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What is the order of ventricular activation in category B animals?
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1. Initial - shell
2. mass of ventricles - burst of activation in many directions - no vector 3.General apicobasilar = QRS |
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What animals are in category A and B and how are they different?
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Category A - dogs, cats, man, monkey, rat - subendothelial purkinje
Category B - horse, cow, pig, sheep, goat - purkinje penetration to myocardium to epicardium |
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What are the different parts of an EKG.
P wave PR segment QRS complex T wave QT interval U wave ST segment |
P wave - atrial depolarization
PR segment - AV node conduction time QRS - ventricular depolarization T wave - ventricular repolarization QT interval - ventricular depolarization to repolarization U wave - repolarization of papillary muscles ST segment - plateau of ventricular AP |
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Where is CV6LU (V4)?
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Left 6th intercostal space at costochondral junction
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Where is CV6LL (V2)?
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Left 6th intercostal space at sternum
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Where is CV5RL (RV2)?
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Right 5th intercostal space at sternum
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Where is V10?
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Over spine at T7
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What is lead aVR?
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+ right arm w/ - left arm and leg
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What is aVL?
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+ left arm w/ - right arm and left leg
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What is aVF?
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+ left leg w/ - right and left arms
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What are 5 changes that occur with myocyte hypertrophy?
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1. myosin ATPase activity
2. Ca++ availability 3. intracellular acidosis 4. subcellular ATP depletion 5. cytokine production |
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What causes concentric hypertrophy? What are 2 beneficial effects?
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Increased afterload
1. total force increased 2. increased ejection fraction |
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What cause eccentric hypertrophy? What are 3 beneficial effects?
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Increased preload
1.increase velocity and myocardial fiber shortening 2. normal or increased ejection fraction 3. more contractile energy goes to shortening than developing tension |
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What are the classic EKG features of right atrial enlargement (P pulmonale)? Which one is the most important?
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On lead II - P wave width < 0.04sec, amplitude >0.4mV dogs, >0.2mV cats
Amplitude is most important |
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What are the classic EKG features of left atrial enlargement (P mitrale)? Which one is most important?
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On lead II - P wave width > 0.04 sec, amplitude < 0.4 mV dogs, < 0.2mV cats
Width is more important |
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What are the classic EKG findings of biatrial enlargement?
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Lead II - width > 0.04 seconds, amplitude > 0.4mV dogs, >0.2mV cats
BOTH width and amplitude are important |
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What are three methods for identifying the mean frontal axis as a method to assess ventricular chamber enlargment?
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1. Find isoelectric lead, find perpendicular lead, determine whether perpendicular lead is +/-
2. Select tallest R wave 3. Plot the sum of QRS complex of leads I and II |
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What are 3 EKG findings you might have with left ventricular enlargement?
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1. increase R wave amplitude in left directed leads
2. Prolonged QRS interval - >0.06sec (>0.07 in giant, >0.04cats) 3. S-T segment depression |
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What are 3 criteria for RVE in cats?
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1. S waves in I, II, III
2. Right axis shift 3. S waves in CV6LL |
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What part of the EKG is affect most in RVE?
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S wave - increased and apparent
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What are some of the 9 specific findings on an EKG that can be found with RVE?
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1. S wave in CV6LL > 0.8mV
2. Mean electrical axis of QRS - 103 3. S wave in CV6LU > 0.7mV 4. S wave in lead I >0.05mV 5. R/S ratio in CV6LU <0.87mV 6. S wave in lead II >0.35mV 7. S waves in leads I, II, III and aVF 8. Positive T wave in V10 - except in chihuhua 9. W shaped QRS in V10 |
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True or False. Biventricular enlargement/hypertrophy is very easy to diagnose accurately from EKG?
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False - difficult to be accurate
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What are 3 common characteristics of biventricular enlargement?
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1. Increased QRS width + amplitude w/ ST segment changes
2. Deep Q waves in leads I, II, III >0.5mV 3. presence of right + left atrial enlargement |
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What are 4 abnormalities seen with left bundle branch block on EKG?
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1. PR interval normal or prolonged (constant)
2. QRS amplitude increased 3. QRS duration >0.08sec (dog), >0.06sec (cat) 4. S-T repolarization changes |
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How can you distinguish between LBBB and LVE on EKG?
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LVE - > 0.06sec (dog) >0.04sec (cat) - slightly longer
LBBB - >0.08sec (dog) >0.06sec (cat) - significantly longer |
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What are 3 EKG features of RBBB?
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1. QRS intervals directed to right - negative
2. Prolonged QRS >0.08 dog, >0.06 cat 3. ST-T repolarization - segment elevation |
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How do you distinguish between RBBB and RVE on EKG?
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RBBB >0.08 dog, >0.06 cat - way above normal
RVE >0.06 dog, >0.04 cat - barely above normal |
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What are 3 changes you see with left anterior fasicular block? What does this sometimes resemble on an EKG?
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1. Frontal plane mean -60 to +30
2. Deep S waves in leads II, III, and aVF 3. Small Q waves and tall R waves in leads I and aVL May look like LVE |
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What animal and disease commonly show LAFB results on EKG?
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cats w/ hypertrophic cardiomyopathy
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One small block on a 25mm/sec EKG is equal to what?
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1mV on Y
0.04 sec on X |
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One small block on a 50mm/sec EKG is equal to what?
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1mV on Y
0.02 sec on X |
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What are the 3 main functions that can be compromised with tachyarrhythmias?
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1. Decreased ventricular filling time
2. Reduced coronary perfusion 3. Increased myocardial oxygen demand |
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What percentage can atrial and ventricular contractions decrease cerebral circulation?
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25-50%
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How does coronary blood flow change during atrial fibrillation or ventricular tachycardia?
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Atrial fibrillation - decrease to 60% of normal
Ventricular tachycardia - decrease to 40% of normal |
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How much can renal blood flow be decreased during atrial fibrillation or ventricular tachycardia?
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Atrial fibrillation - 20% decrease
Ventricular tachycardia - 60% |
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How do you calculate HR from an EKG?
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Count 3 seconds then multiply the number of QRS intervals by 20
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What is sinus arrhythmia? In what species can it be normal?
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Irregular sinus rhythm - HR speed during inspiration
Dogs and horse |
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What does sinus arrhythmia look like on EKG?
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1. Slow to normal rate - occasional escapes occur if very slow. Respiratory SA - HR speeds during inspiration
2. cyclic irregularity of rhythm 3. Normal P-QRS-T relationships 4. wandering pacemaker - P wave regularly and gradually changes as rate speed during inspiration and slows during expiration |
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What HR qualifies as bradycardia for the dog, cat, cow, horse?
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Dog <60bpm
Cat <160bpm Cow <46bpm Horse <24bpm |
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What HR qualifies as tachycardia for dogs and horses?
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Dogs >160bpm
Horses >60bpm |
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Besides high HR what other abnormality would you on a sinus tachycardia EKG?
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P and T waves may be superimposed
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What are 4 common EKG findings for supraventricular premature depolarizations?
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1. Irregular RR intervals
2. premature QRS 3. PR interval altered 4. not full compensatory pause |
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How would you determine the origin of supraventricular premature depolarizations? Give 3 examples.
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P wave examination
1. Upright, before QRS - Rt atrial impulse 2. Negative, before QRS - Lt atrial impulse 3. No P wave, or negative AFTER QRS - junctional |
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What are some causes of supraventricular premature depolarization?
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chronic valvular and myocardial heart disease, toxemia, digitalis intoxication, atrial stretch, pulmonary disease, pulmonary hypertension
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What are 3 other names for supraventricular tachycardia?
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1. Paroxysmal supraventricular tachycardia
2. Paraxysmal atrial tachycardia 3. Paraoxysmal junctional tachycardia |
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What causes paroxysmal atrial tachycardia?
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Atrial dilation or disease, atrial or AV conduction disease or accessory conduction pathways
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What are 4 characteristics of supraventricular tachycardia on EKG?
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1. rapid HR - often paraxysmal
2. regular RR, may have variable RR 3. Ectopic P wave - anterograde or retrograde relationship to QRS 4. Normal QRS |
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What is the mechanism involved in paraxysmal atrial tachycardia?
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ectopic atrial pacemaker that spontaneously discharges - tachycardia ends w/ P block
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What is atrial flutter? How does it progress?
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rapid, regular atrial activation w/ slower ventricular response
Rhythm is unstable and converts back to sinus rhythm or evolves to atrial fibrillatin |
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What are 4 ECG signs of atrial flutter?
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1. rapid or normal rate - depends on degree of AV block
2. irregular RR intervals 3. F waves - saw toothed flutter waves replace P wave 4. Absent isoelectric shelf in some leads |
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What are causes of atrial fibrillation?
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cardiomyopathies of giant breeds, chronic mitral valve disease, congenital heart disease
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What are 4 signs of atrial fibrillation on ECG?
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1. Rapid rate - irregular RR intervals
2. No P waves 3. F waves = baseline undulations 4. QRS appears normal |
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What are 3 other names for Ventricular premature depolarizations?
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1. ventricular premature contractions
2. ventricular premature complexes 3. ventricular extrasystoles |
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What are 4 classes of associations that cause ventricular premature depolarizations?
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1. Primary myocardial - hypoxia, ischemia
2. Extracardiac - sepsis, GDV, uremia 3. Electrolyte imbalances 4. Drug induced |
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What are 6 important ECG findings that indicate VPC?
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1. ectopic complex - may or may not be coupled to normal P-QRS-T
2. compensatory pause after VPC 3. Widened QRS - RV=upright, LV=negative, morphology may vary - indicated multifocal extrasystoles 4. T wave is widened and in opposite direction from QRS wave 5. flattened ST isoelectric shelf 6. No P waves - fusion beat |
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What is accelerated ventricular rhythm? What are the causes?
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"slow" ventricular tachycardia >60bpm <160bmp in dog
Basically is race between sinus and ventricular focus who will depolarize the ventricles Same as VPC - GDV, iatrogenic, autonomic imbalance |
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What do you see on an ECG of accelerated ventricular rhythm?
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"slow" ventricular tachycardia >60bpm <160bmp in dog
Fusion beats are frequently noted |
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What are the ECG signs of ventricular tachycardia?
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1. >3 linked ventricular ectopic impulses
2. P wave buried in QRS 3. normal rhythm may follow after spontaneous conversion |
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How would you recognize ventricular fibrillation on ECG?
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irregular, disorganized ventricular activity w/ no recognizable QRS-T complexes
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Which is more dangerous a premature impulse that occurs on the T wave or after T wave? Why?
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On the T wave because it is occurs during ventricular repolarization and can lead to fibrillation
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Which is more dangerous a late or early diastolic premature impulse?
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Early because late allows more time for ventricular filling
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At what bpm are ventricular tachycardias considered dangerous in dogs?
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160-180bpm
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What are 4 signs of SA arrest on ECG?
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1. slow or normal rate
2. pause equal to (SA block) or greater than (SA arrest) two PP intervals w/out atrial activity (no P waves) 3. P-QRS-T predominate - ventricular escapes common 4. Sick sinus = sinus bradycardia alternates w/ sinus or supraventricular tachycardia |
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What causes atrial standstill? What diseases cause this?
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Hyperkalemia - addison's, urinary obstruction, renal failure, acidosis
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Name 3 characteristic ECG features of hyperkalemia and why.
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1. sinus tachycardia (reduced MP) then bradycardia (K+ drift across membraned)
2. flattening and loss of P waves - atria lose ability to become excited 3. Tented T waves (shorted repolarization), Wide QRS (prolonged depolarization + fasicular blocks) then QRS T fusion = sine-wave |
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What is persistent atrial standstill? What breed is affected?
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Persistent absence of P waves - atrial muscular dystrophy and loss of atrial myocytes
Springer Spaniels predisposed |
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What are common ECG findings of junctional escape complexes?
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1. slow HR
2. irregular RR interval 3. junctional QRS follow long pause - rescuing the ventricle 4. abnormal P-QRS 5. P wave is present usually negative in lead II - before, after or buried in QRS - depends on ectopic focus |
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What are common ECG findings of junctional escape rhythms?
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1. slow HR
2. regular RR interval 3. retrograde P wave - neg in lead II and aVF, AFTER QRS 4. normally oriented QRS |
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What do ventricular escapes look like on ECG?
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1. depolarization late after pacemaker should have discharged - rescue
2. P wave may or may not be present - if present has no QRS related 3. QRS - wide and bizarre (originates in ventricle) 4. T wave wide and opposite QRS direcion 5. idioventricular rhythm (28-40bpm) |
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What are 3 features of first degree AV block?
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1. variable rate
2. P wave for every QRS-T 3. PR interval prolonged and varied |
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What is the main difference between a mobitz type I and type II second degree AV block on an ECG?
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Type I - PR interval prolongs w/ each beat until a ventricular beat is dropped (P wave w/o QRS-T)
Type II - PR interval is constant but some P waves are not followed by QRS |
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What is the difference between first and second degree AV blocks?
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1st - P wave for every QRS-T
2nd - at some point there will be a P wave w/o a QRS-T |
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What can cause Mobitz type I or type II blocks?
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Type 1 - normal in horses
Type 2 - occurs in AV junction or His bundle, indicates disease in conduction system or electrolyte abnormality |
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What is preventricular excitation?
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When conduction from atria to ventricles is accelerated due to accessory AV pathways
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What is the difference between WPW and LGL preventricular excitation?
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WPW - part of ventricle will become depolarized before normal impulse is through AV junction
LGL - complete pre-excitation of ventricles via AV nodal bypass tract |
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What are some causes of altered ST-T segments?
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1. LVE
2. Endocardial or peicardial injury 3. Pericaridal disease 4. Electrolyte abnormalities 5. Hypoxia 6. digitalis 7. exercise |
