It gives brief idea about arrhythmia. It contains ecg findingsalong with conditions.

1. Speaker:
Rajeev Kumar Mishra
M.V.Sc. L-2015-V-38-M
Division of Veterinary Medicine
GADVASU ,Ludhiana, Punjab

2. Introduction
The four chambered mammalian heart consisting of
the right and left atria and right and left ventricles.
The primary function of heart is to pump blood, which
requires contractile force and this mechanical activity
of heart is depends on electrical activity of heart.
The electric conduction system comprises the sino-
atrial (SA) node, atrio-ventricular (AV) node, bundle of
His, bundle branches and Purkinje fibre network.

4. Evaluating the ECG Tracing:
 An electrocardiogram (ECG) is a test that records the electrical activity of the heart
as a graphic display on graph paper
 The electrical impulses are recorded as waves and one heartbeat is usually
recorded as a grouping of waves known as the P-QRS-T complex.
 The P wave represents atrial depolarization
 The PR interval tracks the impulse from the atria through the A-V node.
 The QRS complex follows the P wave and represents ventricular depolarization.
 The ST segment the beginning of ventricular repolarization.
 The T wave indicates ventricular repolarization.

6. Electrocardio
graphy
Auscultation
History
(clinical sign)

7. ECG
Calculate heart rate
Brady
arrhythmia
Tachy
arrhythmia
Assessment of Regularity of rhythm
R-R
Interval
P
Wave
PR
interval
ST
Wave
QRS
complex

8. R-R Interval not regular(Arrhythmia)
P Wave ??
NO YES
Atrial
standstill
P wave for every
QRS complex?
Sinus arrest may represent
SSS
Amplitude and
width of P Wave
NO
Right atrial
enlargement
amplitude increase
Lt.atrial enlargement
width increase

9. P wave normal
PR Interval ??
Prolonged PR interval
Progressively Prolonged
PR interval
Normal QRS complex
1st Degree AV
Block
Type II 2
degree AV
Block
Shoter PR
Interval
Atria fibrilation
and atrial
flutter
Constant Prolonged
PR interval
Abnormal QRS
complex
Type I
2 degree
AV Block

10. Normal sinus rhythm
 Normal sinus rhythm results from impulse generation in the SA node at a
normal rate
 Normal atrial (P) and ventricular (QRS) rate (approximately 70-160 beats/minute in
dogs,

11. Arrhythmia
 An arrhythmia is any cardiac rhythm which is considered
to be abnormal for an individual animal.
 Abnormalities of cardiac electrical activity result in
arrhythmias.
 Arrhythmias occur due to abnormalities of impulse
generation, abnormalities of impulse conduction, or both.

12. Classification of Cardiac Arrhythmias
 DISTURBANCES OF SINUS IMPULSE FORMATION
• Sinus arrhythmia
• Sinus bradycardia
• Sinus tachycardia
 DISTURBANCES OF SUPRA-VENTRICULAR IMPULSE FORMATION
• Atrial tachycardia
• Atrial flutter
• Atrial fibrillation

13.  DISTURBANCES OF VENTRICULAR IMPULSE FORMATION
• Ventricular tachycardia
• Ventricular flutter
• Ventricular fibrillation
 DISTURBANCES OF IMPULSE CONDUCTION
• Sino-atrial block
• AV block
• Bundle branch blocks

14. Sinus arrhythmia
Sinus arrhythmia results from a variable rate of SA
nodal firing. It occurs with phasic acceleration and
deceleration of diastolic depolarization of the SA
node pacemaker.

15. Causes
Normal predominance of vagal tone in healthy dogs.
 Abnormally increased vagal tone (cats, some dogs):
• Severe respiratory disease (particularly upper respiratory
obstruction)
• Intrathoracic mass lesions
• Severe gastrointestinal disease
• Central nervous system (CNS) disease
• Increased intraocular pressure (e.g. ocular surgery).

16. Sinus bradycardia
 Sinus bradycardia result from decreased firing of the SA node or
decreased conduction of the SA node impulse to the atrial myocardium.
 ECG characteristics:
Slow atrial (P) and ventricular (QRS) rate (approximately <70
beats/minute in dogs, <140 beats/minute in cats).

18. Cause
• Normal (physiological) elevation in vagal tone:
• Abnormally increased vagal tone
• Autonomic nervous system disorders
• Metabolic abnormalities
• Intrinsic SA node disease:
• Drugs (usually in high or toxic doses):

19. Clinical sign
• Lethargy
• Seizures
• Exercise intolerance
• Loss of consciousness
• Episodic muscle incoordination (ataxia)
• Excessively slow breathing (hypoventilation), especially
under anesthesia

20. Sinus Arrest
Sinus arrest is a disorder of impulse generation,
occurring with temporary cessation of SA nodal firing.
It most commonly occurs with increased vagal tone or
intrinsic SA node disease. It may also occur following
tachycardia, which temporarily depresses the
pacemaker function of the SA node (overdrive
suppression).

22. ECG characteristics:
Pause in sinus rhythm.

23. Sinus Tachycardia
 Sinus Tachycardia can be recognized by the gradual acceleration
of heart rate. It is a normal response to stress, pain, excitement,
shock, anemia, hypoxia, exercise and anxiety.
 Sinus tachycardia results from increased SA nodal firing.
 Heart rates approaching 300 beats/ minute can be seen in athletic
dogs with sinus tachycardia during peak performance.

25. Atrial tachyarrhythmias
 Atrial tachyarrhythmias result from either abnormal firing
or re-entry, and are localized to the atrial myocardium
only.

26. Causes
 Atrial dilatation (secondary to cardiac disease) (most common) Structural
disease of the atria (myocardial disease, infiltration, neoplasia. inflammation,
fibrosis)
 Trauma to the atria (e.g. trauma during pericardiocentesis, cardiac
catheterization)
 Autonomic imbalance
 Electrolyte imbalances (hypokalaemia)
 Drugs (digitalis glycosides, quinidine, sympathomimetic agents,
phosphodiesterase inhibitors, anaesthetic agents).

27. Atrial tachycardia
 Atrial tachycardia is defined as multiple consecutive APCs, is results
of rapidly firing ectopic foci within the atria. Atrial tachycardia can be
classified as focal or multifocal.
 Focal atrial tachycardia occurs when the arrhythmia originates from
a single ectopic site. This is the most common form of atrial
tachycardia.
 Multifocal atrial tachycardia is diagnosed when the tachycardia is
caused by ~3 coexisting ectopic foci. This is less common, but can
be present with pulmonary disease or CHF.

29. Atrial flutter
 Atrial Flutter is rare in small animals. It is due to the firing of an ectopic
focus in the atria, which sets up reentry pathways that rapidly stimulate the
AV node. Only some of these impulses conduct to the ventricles.
 Typical atrial flutter results in flutter waves with a 'saw-tooth' pattern on the
surface ECG.

31. Atrial fibrillation
 Atrial fibrillation is the most common persistent arrhythmia
seen in small animals. It is characterized by chaotically
irregular depolarizations throughout the atria.

33.  Atrial Fibrillation is described as an "irregularly irregular"
rhythm because it is unpredictable and chaotic with no
underlying rhythm.
 There are no organized P-waves produced on ecg. Rather, F-
waves (fibrillation waves) are seen and are caused by
multiple coexisting reentrant wavelets that circulate within
the atria.
 QRS complexes normal.

35. Sinoatrial block
SA block is a disorder of impulse conduction. Unlike sinus
arrest, the SA node continues to fire, but the impulse is
not conducted to the atrial myocardium.
It is therefore also referred to as SA exit block. SA block
can be differentiated from sinus arrest based on pause
duration.

36.  ECG characteristics:
• Pause in sinus rhythm of multiples of PP intervals (2 or
more).
• Progressive shortening of the PP interval may occur
prior to pause.

37. Atrioventricular block
 AV block is a disorder of impulse conduction; typically a delay or
failure of conduction of a sinus or atrial impulse through the AV
node or His bundle (AV junction).
 Different types of AV block can occur, termed first degree, second-
degree and third-degree
 AV block is rare in healthy dogs, but older dogs are at higher risk.
 American cocker Spaniels, pugs, and dachshund breeds are
known to be predisposed to second degree AV block.

39. Cause
Elevated vagal tone (physiological or abnormal)
Intrinsic AV node or His- Purkinje disease
Drugs (usually high or toxic doses)
Hyperkalaemia
Autonomic nervous system disorders

40. First-degree atrioventricular block
First-degree AV block is characterized by a delay of
conduction through the AV junction, resulting in a
prolonged PR interval.
ECG characteristics: Prolonged PR interval

41. Second-degree atrioventricular block
 Second-degree AV block is characterized by intermittent
failure of AV conduction, resulting in non-conducted P
waves.
 AV block can be classified according to the PR interval
and width of the conducted QRS complexes.

42. Mobitz type I has QRS complexes of normal width and is
considered to be caused by block above the bifurcation of
the His bundle.
 Mobitz type I has wide QRS complexes and is considered
to be caused by block below the bifurcation of the His
bundle.

43.  ECG characteristics - Mobitz type I block:
P-R interval progressively prolongs before “dropping”
Conducted ORS complex morphology normal.

44.  ECG characteristics - Mobitz type ll block:
• Single or multiple, non-conducted P waves.PR interval
constant prior to block.
• Conducted ORS complex morphology normal or wide.

45. Third-degree atrioventricular block
 Third-degree AV block (complete AV block) is characterized by
persistent failure of conduction through the AV junction
 Third-degree AV block is almost invariably caused by
myocardial damage.
 Dilatation of all four heart chambers is a common
echocardiographic finding.

46. Atrial standstill
 Atrial standstill occurs when the SA node fires but the impulse is
not conducted to the atrial myocardium.
 It results in a complete absence of P waves on the surface ECG
 Atrial standstill can be the result of primary myocardial disease
(persistent), or secondary to severe hyperkalaemia or digitalis
toxicity (temporary). Persistent atrial standstill may be the result of
an atrial myopathy or atrial myocarditis. Terminal atrial standstill
may occur with cardiac arrest.

47. complete absence of P waves

48. Bundle branch block
 BBB refers to failure or delay of impulse conduction through
one or more branches of the His bundle
 Block in a bundle branch results in delay in depolarization of the
region of ventricular myocardium supplied by it, resulting in a
QRS complex of abnormal (wide and bizarre) morphology.
 Causes: Structural heart disease, Hyperkalaemia,
Hypocalcaemia.

50. Right bundle branch
 The right bundle branch connects the AV junction to the
right ventricle (RV). It is a discrete structure that runs
most of its course just beneath the endocardial surface. It
is therefore susceptible to damage from disease affecting
the RV, such as pulmonic stenosis and pulmonary
hypertension causing right bundle branch block (RBBB).

51. 2.Left bundle branch block
 The left bundle branch is larger than the right, with division
into anterior and posterior fascicles. Left bundle branch block
(LBBB) can occur at the proximal main branch or at both
fascicles (bifascicular block).
 Because of the large size and extensive nature of the left
bundle branch, lesions that result in block are also usually
extensive, such as myocardial disease.

52. Ventricular arrhythmias
 Ventricular arrhythmias originate from an ectopic focus
or foci located entirely within the ventricular myocardium,
distal to the bifurcation of the His bundle.

53. Causes
 Structural heart disease
 Systemic disease:
 Drugs
 Specific causes in canine breeds:
• Boxer arrhythmogenic right ventricular cardiomyopathy
• Dilated cardiomyopathy in Dobermanns
• Inherited ventricular arrhythmias in young <18 months old) German
Shepherd Dogs.

54. Ventricular tachycardia
 Ventricular tachycardia is defined as seven or more
consecutive VPCs, and results from rapidly firing ectopic
foci within the ventricles. The complexes can be
monomorphic, pleomorphic or polymorphic depending
on the number of foci and variability of conduction

56. Ventricular flutter
 Ventricular flutter is the name given to a ventricular
tachycardia that is so rapid that each ORS complex
merges with the preceding T wave, resulting in a 'sine
wave' appearance. No isoelectric baseline is visible
between complexes.

57. Cardiac arrest rhythms
 Cardiac arrest rhythms are arrhythmias that are associated with absent
cardiac output. Immediate recognition and treatment are essential to
prevent irreversible hypoxic damage to the brain.
 require cardiopulmonary-cerebral resuscitation (CPCR). They may occur in
animals with severe systemic and/or cardiac disease.
 Arrest rhythms are:
• Ventricular standstill (asystole).
• Pulseless electrical activity.
• Ventricular fibrillation.

58. Ventricular standstill
 Ventricular standstill (asystole) refers to a complete absence of
ventricular electrical activity.
 ECG characteristics
• Complete absence of ORS complexes.
• Normal P waves may be seen with concurrent third-degree AV block.

59.  Transient ventricular standstill may occur in dogs and
cats with third-degree AV block and unstable escape
rhythms. This can be a cause of syncope in these
patients.
 Patients with prolonged ventricular standstill require
immediate CPCR

60. Pulseless electrical activity
 Pulseless electrical activity (PEA) refers to any
coordinated cardiac electrical activity that does not result
in discernible cardiac output.
 The ECG rhythms are usually pulseless

61. Ventricular fibrillation
 Ventricular fibrillation is characterized by chaotically irregular
ventricular depolarizations. It can be caused by multiple foci of
re-entry or abnormal firing. There is an absence of coordinated
ventricular activity
 ECG characteristics
• Distinct P waves and ORS- T complexes absent.
• Baseline oscillations of varying contour and amplitude
(fibrillatory waves).

63.  Ventricular fibrillation causes cardiac arrest and is often a
terminal event. Cardiac output is essentially zero due to
weak, uncoordinated ventricular contractions. The ECG
shows completely irregular chaotic deflections of varying
amplitude, width, and shape.

66. Drug Dose Arrhythmia
Aminophylline–theophylline PO: 10 mg/kg q12h (extended
release) (D, dog;) IV: 10 mg/kg
(D)
Sick sinus syndrome, second-
and third-
IV: 10 mg/kg (D) degree AV
block
Atenolol PO: 0.2–2 mg/kg q12–24h Supraventricular tachycardia or
VT (rate
control or conversion), atrial
fibrillation
(rate control
Atropine SC, IM, IV: 0.02–0.04 mg/kg Sinus bradycardia, sick sinus
syndrome,
first- and second-degree AV
block
Digoxin PO: 0.005 mg/kg q12h Atrial fibrillation (rate control)

67. Diltiazem IV bolus: 0.1–0.4 mg/kg over 5
min
PO: 1–2 mg/kg q8h
Supraventricular tachycardia
(rate control or conversion),
atrial fibrillation (rate
control)
Esmolol IV bolus: 0.2–0.5 mg/kg over 1
min,
repeat q5min
Supraventricular tachycardia or
conversion
Glycopyrrolate SC, IM, IV: 0.005–0.01 mg/kg Sinus bradycardia, sick sinus
syndrome,
first- and second-degree AV
block
Isoproterenol CRI IV: 0.04–0.09 μg/kg/min, Second- and third-degree AV
block

68. Lidocaine IV bolus (maximum of three): 2
mg/kg over 30 sec
Supraventricular tachycardia
conversion,
vagally mediated atrial fibrillation
conversion, VT conversion
Mexiletine PO: 4–8 mg/kg PO q8h Sinus rhythm maintenance
Procainamide IV bolus: 5–15 mg/kg over 1 min Supraventricular tachycardia
conversion
Sotalol PO: 1–3 mg/kg q12h Supraventricular tachycardia or
VT
conversion; sinus rhythm
maintenance
Terbutaline PO: 0.2 mg/kg q8–12h Sinus bradycardia, sick sinus
syndrome