1. Electrocardiography: Application, Normal and Abnormal Heart Rhythms
Reading assignment:
CTVT pp: Stop at equine emergency nursing
VTDRG pp:

2. Applications of the Electrocardiogram
Acute onset of ___________
Shock
Fainting or ______________
Monitoring during and after __________ (monitors depth of anesthesia as well as _______________ monitoring).
All cardiac ________________.
__________________ that is found on thoracic radiographs
______________________ (with hx of heart issues or for all pets ages 7+

3. Applications of ECG continued
________________
Evaluating effect of cardiac drugs
Pericardiocentesis
Systemic diseases
_______________ disturbances
What electrolytes do you
think may be associated with ECG abnormalities?

4. Conduction System of the Heart Review
Electrical impulses are transmitted through the heart via specialized conduction cells in a specific sequence:
_______________________(SA) node
_______________________(AV) node
Bundle of ____________
Left and right ______________ branches
_____________________fibers

6. Remember Depolarization and Repolarization?
________________________- heart muscle contraction in response to electrical stimulus. (_______________)
Occurs when electrolytes ((Na, Ca and K) move across the cell membrane causing a contraction.)
________________________- heart muscle relaxation occurs when the electrolytes move back across the cell membrane rendering the cell ready for the next electrical impulse.

7. Five Physiologic Properties of Cardiac Muscle
Automaticity
Excitability
Refractory Period
Conductivity
Contractility

8. Five Physiologic Properties of Cardiac Muscle
1. Automaticity
_________ node is the primary pacemaker of the heart.
Any cells of conduction system can initiate their own impulses under right circumstances.
The further down in the conduction system, the __________________ the rate of automaticity
2. Excitability
Cardiac muscle is excited when the electrical stimulus reduces the _____________ potential to the ________________ potential
The degree of the resting potential within the cell determines its excitability and obeys the “_____-or-_____” principle.

9. 3. Refractory Period 4. Conductivity
Heart muscle will not respond to external stimuli during its period of contraction (______________ period in between beats)
4. Conductivity
Activation of an individual muscle cell produces _____________ in the neighboring muscle cell.
Conduction velocity varies in the different portions of the specialized conduction system and muscle fibers
Velocity is ______________ in the Purkinje Fibers and _____________ in the mid-portion of the AV node.
Activation sequence is so arranged that the ________________ mechanical efficiency is provided from each corresponding contraction

10. 5. Contractility Occurs in response to ________________ current
The ECG only measures the ______________ for contraction - not the actual contraction itself.
ECG is the tool of choice for measuring _____________________.

11. Major Confusion!!!
Reading an ECG and deciphering what it is telling you can be confusing.
ECGs provide a graphical representation of the ______________ impulses of the heart.
Electrical impulses are what make the heart contract.
This contraction is a result of ________________________and ________________________.

12. Electrocardiogram
Definition: Graphic recording of electrical potentials produced by heart muscle during the different _____________of the cardiac cycle.
The information recorded on the EKG represents the heart’s _________________ activity.
Most of the information on the EKG represents electrical activity of contraction of the ____________________.

13. A Little Vocabulary
___________________ : A wave that arises from sources other than the heart.
Cardiac _________________: Any electrical activity of the heart that differs from that of a healthy, awake patient. Can be inoccuous or life-threatening.
_______________________ : Movement from one side to the other.
____________________: Occurring in an abnormal location/position.
_______________ : An electrical pathway created by the connection of electrodes. Provides a particular view of the electrical activity of the heart.

14. Solid Ground
Having the ECG machine well grounded is an important factor for obtaining an accurate reading.
Placing the patient on a rubber mat and ensuring that the machine is plugged into a grounded outlet as well as checking the ECG machine for loose wires or cracked insulation on wires are steps that can be taken for a good ground.

15. ECG Leads
Are the paths that measure the electrical activity of the heart
Leads are _____________ or ___________. (Settings on ECG machine determine which lead you are recording.)
The most common leads or paths of the heart are I, II, and III.

16. Leads
Selecting specific leads on the ECG machine will cause specific cables to become negative or positive poles.
Lead I: causes right forelimb to become a negative pole and left forelimb to become a positive pole.
***** Lead II: causes right forelimb to become negative and left rear limb to become positive. (Most commonly used)
Lead III: the left hind limb become a positive pole and the left forelimb becomes a negative pole.

18. Electrodes that create the Leads

19. The Electrodes
There are 4 electrodes that are used in veterinary medicine:
____________, ___________, ___________and ___________
The electrodes are placed on the patient in the ______________ locations EVERY time.

20. Placing the Electrodes Correctly
In veterinary medicine, the following is the standard for applying the electrodes to all patients for ECG monitoring:
White electrode: ____________________ limb
Black electrode: ____________________ limb
Green electrode: ____________________ limb
Red electrode: ____________________ limb
“Clouds over grass and smoke over fire.”

21. Color-Coded Cables Placement Black and white on front limbs
Placed at the ___________________ region
Green and red on back limbs
__________________, electrode gel, or ECG pads can be used as conduction agents for more accurate readings. If your patient has long hair, it should be shaved at the site of cable placement in order to achieve adequate conduction.

22. White
Right
Front
Leg/arm
Green
Right
Back
Leg
Black
Left
Front
Leg/arm
Red/Orange
Left
Back
Leg

23. Leads Continued…
__________________ deflection on the ECG-produced when electrical impulses travel towards a _________________electrode.
__________________ deflection on the ECG-produced when impulses travel toward a _____________________electrode.
_________________: produced when there is no electrical spread through the heart.
***We only need to use lead II to assess arrhythmias in animals.

24. Electrocardiograph used in SX

25. ECG Technique Position: __________lateral recumbency;
but the patient may be placed in a natural position (sitting, standing, or resting) in critical cases or for routine monitoring.
I want you to
place your animals
in right lateral
recumbency.

26. Former Students in Action

27. Wave Forms
Connection of the amplifier to selected body parts (usually the limbs) with wires (known as electrodes) and to a recorder (electrocardiograph), provides a characteristic wave form.
The wave form is a recording of the electrical activity of the heart. This wave form recording is the electrocardiogram (ECG).
Each event has a distinctive waveform.

28. What are these so called waves and what do they mean?

29. The P wave The first ___________ pulse of the ECG
The P wave is formed when the _______ contract to pump blood into the _____________.
This is known as Atrial ______________________.
Stimulated by the SA Node.

30. P-R interval Reflects the activation of the AV node.
Measured from the beginning of the P wave to the beginning of the QRS complex.
Flat portion is due to delay of depolarization at the AV node (allowing time for the ventricles to fill)

31. QRS waves (QRS complex)
Formed when the ventricles (the two lower chambers of the heart)
are contracting to pump out blood.
Q wave is the 1st negative deflection
R wave is the 1st positive deflection
S wave is the negative deflection that follows the R wave

32. QRS Wave Complex
The ______________ contract (ventricular ________________) and the atrium expands (atrial ____________________).

33. S-T Segment
Measures the end of the contraction of the _________________ to the beginning of the rest period before the ventricles begin to contract for the next beat.
Think of it as a __________ before the T wave.

34. The T wave
The next slight _________ section, the T wave, measures the resting (relaxation or ventricular _________________) period of the ventricles.
T waves can be ___________, ___________ or biphasic (having 2 distinct phases).

35. T Wave
The T Wave is the last wave for each heart beat; it represents ventricular _______________ (relaxation).
The interval between waves is measured in milliseconds.

36. QT Interval
The summation of ventricular depolarization and repolarization
Represents electrical ________________
Q-T interval is measured from the onset of the Q-wave to the end of the T-wave

37. R-R Interval to Measure HR

38. Calculating Heart Rate
Use a ruler to determine set length of tracing.
Determine how many seconds are represented in that tracing.
Count R-R intervals in that set amount of tracing and multiply by the time.
This will give you the heart rate.

40. Classification of Arrhythmias
Normal sinus impulse formation
Normal sinus rhythm
Sinus arrhythmia
Disturbances from sinus
Sinus bradycardia
Sinus tachycardia
Disturbances of atrial impulse formation
Atrial premature complexes
Atrial tachycardia
Atrial flutter
Atrial fibrillation
Disturbances of ventricular impulse formation
Ventricular premature complexes
Ventricular tachycardia
Ventricular asystole- no contraction
Ventricular fibrillation
Disturbances of impulse conduction
Sinus arrest
Atrial standstill
First-degree AV block
Second degree AV block
Third degree AV block

41. Normal Sinus Rhythm
Normal ECG tracing depicting a normal rhythm of electrical conductivity through the heart
Top illustrates a POSITIVE QRS complex AND a NEGATIVE QRS complex. Both are NORMAL, determined by lead selection.

42. (Respiratory) Sinus Arrhythmia
Increased number of cardiac cycles during _____________________; decreased number during _______________________ in dogs.
Is ________________ normal in cats.

43. Sinus Bradycardia
Regular _____________ rhythm but heart rate is ______________ normal
Dogs under 45 lb: HR less than ________ BPM
Dogs >45 lb: HR less than ________ BPM
Cats: _______ BPM or less
CS: weakness, hypotension, __________________

44. Sinus Tachycardia
Regular sinus rhythm with _______________ventricular rate
Dogs less than 45 lb; HR >_________ BPM
Dogs more than 45 lb; HR >_________ BPM
Cats: HR greater than _________ BPM
Causes include: __________, fever, __________________, hyperthyroidism

45. Atrial Premature Complexes
Premature atrial impulses originating from atrial site other than ____ node
Seen in dogs and cats with ____________enlargement, electrolyte disturbances, drug reactions, congenital heart disease, and ____________
Premature P wave causes a heartbeat sooner than it should be
QRS complexes are _______________ unless the P wave is so immature that it overlaps to varying degrees

46. Atrial Premature Complexes
Notice the negative P wave before the APC

47. Atrial Flutter
Appears as a regular, “_______________” formation between the mostly normal QRS complexes
Occurs when the _______________rate differs from the ____________ rate
Single area in atrium other than SA node starts impulse
AV node “gatekeeper” only allows some impulses through to ventricles (lots of P waves, regular QRS)
Atrial flutter is the precursor to atrial ________________

48. Atrial Fibrillation
Fibrillation is the rapid, ____________, and _______________________ contraction of muscle fibers
Caused by numerous disorganized _________ impulses frequently bombarding the AV node
Ventricular ___________________ rate is irregular and rapid
NO ____ waves are evident; replaced by numerous f (fibrillation) waves

49. Ventricular Premature Complexes (VPCs)
“______________beats” - cardiac impulses initiated within the __________________ instead of the sinus node
Ventricle discharges before the arrival of the next anticipated impulse from the ______ node. (Takes a shortcut)
Can occur at any rate but pose a greater danger with __________________.
Associated with _______________ defects, cardiomyopathy, GDV, drug reactions, cardiac neoplasia, ____________, acidosis, hyperthyroidism, hypokalemia
Also referred to as Premature Ventricular Complexes or PVCs.

50. VPCs (cont’d) The P wave is often not seen on the ECG tracing
A wide, distorted/bizarre _______ complex is evident
The beat preceding the VPC and the beat following are usually equal to two normal beats
May treat with IV lidocaine

51. Ventricular Tachycardia “V-Tach”
One strong ventricle impulse that hijacks the conduction system of the heart. Patient may be “stable” with a pulse or unstable with “no pulse”
_____ node is on its own and _____ node is not working
A series of __________ or more PVCs in a row
_________________________!
Treatment is reset heart via __________________________

52. Ventricular Fibrillation
The mechanical pumping of the heart is not ____________ on the ECG
Many __________ impulses other than AV node present in ventricles
The ECG has ____________ baseline with prominent undulations due to weak and uncoordinated ventricular contractions
Low to __________ cardiac output
Associated with shock, trauma,
electrolyte imbalances, drug reactions,
electric shock, hypothermia, cardiac sx
Rapidly _______________

53. V Fib cont. There are no recognizable ____ waves or ______ complexes
Irregular, ___________, deformed reflections of varying ____________, amplitude, and ___________
Unless controlled immediately, ventricular fibrillation will result in ___________________ _____________.

54. Conduction Issues ______________ Standstill Heart ____________
First degree
Second degree
Third degree
_________________

55. Atrial Standstill SA node sends impulse but _________ do not contract
No ____ waves seen
___________________ is most common cause  increased potassium
English Springer Spaniel – fibrous tissue take over myocardium and impairs its ___________________.
If not due to increased potassium, _________________ is warranted.

56. Heart Block
Electrical impulse is not transmitted through the heart

57. First Degree AV Block
Delay in conduction of an impulse through the AV junction and Bundle of His
The _________ interval is longer than normal
This type of heart block is a result of a minor conduction defect
Seen in __________ patients secondary to ________________ changes in the conduction system

58. Second Degree AV Block
Some atrial pulses are not conducted through the AV node and therefore do not cause depolarization of the ventricles
There are two types:
Mobitz Type I: ________________ lengthening of the PR interval until no complex is conducted
P waves occurring without QRS complexes “__________________ beats”

59. Second Degree AV Block (cont’d)
Mobitz Type II: A intermittent block at the AV node, that conducts some impulses but _____________others
Is considered more _____________ than Mobitz Type I.
A constant PR interval that is usually of normal duration with ______________ dropped beats
In the case of type 2 block, atrial contractions are not regularly followed by ventricular contraction
2 or more dropped QRS in a row

60. Third degree AV block (Complete Heart Block)
The cardiac impulse is completely blocked in the region of the AV junction and/or all bundle branches
The most ________________ heart block
No relationship between P waves and QRS complexes; atria and ventricles each beat ___________________ and do not ________________________at all.

61. Heart Blocks

62. Asystole (Flat line)
___________________arrest: no cardiac _____________ activity, no cardiac ____________= no blood flow
At this point the heart will probably not respond to defibrillation
Causes: hypoxia, hypothermia, hypoglycemia, or an electrode has fallen off (hopefully)
Epinephrine or atropine have probably already been given…

64. DONE with ECG/Arrhythmias!