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Principles of Electrocardiography Submitted to : Dr. V. K. Gupta, Senior Scientist Division of Veterinary Medicine, IVRI, Izatnagar Submitted by: Suthar Abhinav , Roll no M 5388, Division of veterinary Medicine, IVRI, Izatnagar
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Principles of electrocardiography ppt

May 25, 2015

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Page 1: Principles of electrocardiography ppt

Principles of Electrocardiography 

Submitted to :• Dr. V. K. Gupta,• Senior Scientist• Division of Veterinary

Medicine,• IVRI, Izatnagar

Submitted by:Suthar Abhinav ,Roll no M 5388,Division of veterinary Medicine,IVRI, Izatnagar

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Principles of Electrocardiography 

• What is an ECG?? • Electrocardiogram 

= EKG = ECG • A recording of the 

electrical activity of the heart from electrodes placed on the surface of skin. 

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Electrocardiograph

      Electrocardiograph (ECG machine) is a voltmeter (or galvanometer ) that records the changing electrical activity of the heart between a positive and negative electrode.

      Electrocardiography is the process of recording this electrical changes.

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Indications 

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Indications for an electrocardiogram:

1. Cardiac arrhythmias.2. Acute onset of dyspnoea3. Shock.4. Fainting or seizures.5. Cardiac monitoring during and after surgery.6. Cardiac murmurs.7. Cardiomegaly found on thoracic radiographs.

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8. Cyanosis.

9. Pre operatively in older animals.

10.  Evaluating the effect of cardiac drugs – especially   digitalis, quinidine and propanolol.

11. Electrolyte disturbances, especially potassium abnormalities.

12. Systemic diseases that affect the heart.

13. Serial electrocardiograms as an aid in the prognosis and diagnosis of cardiac disease.

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Normal Conduction System

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The 1st Rule of ECG

• A current of depolarization traveling towards the + electrode is recorded as a positive deflection 

• A current of depolarization traveling away from the + electrode is seen as a negative deflection 

•  A current of repolarization traveling away from the + electrode is seen as a positive deflection 

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Positive and Negative Deflection in a lead

A wave of electrical depolarization moves towards the positive pole of the lead – a +ve deflection occurs

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LIMITATIONS

     ECG must always be evaluated in conjunction with clinical findings    An animal with CHF may have a normal ECG and  normal animal may show non specific electrocardiographic abnormalities

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Types of ECG 

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    Single channel recorderHas one stylus – records one lead at a time

    Multiple channel recorder    Has more than one stylus Provide 

simultaneous  tracings of 3 leads

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Position & Restraint

Lateral recumbency - the standard position for canine and feline

electrocardiography No chemical restraint Trained attendant or animal owner Lead placement

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Electrodes & Leads

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ELECTRODES

Alligator clips or flat contact electrodes

Hair and stern surrounding the electrode should be moistened with conductive gel or alcohol

Standard paper speed : 50 mm/sec.

Left Arm (LA), Right Arm (RA) and Left Leg (LL)

 

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BIPOLAR STANDARD LEADSLead I : Right arm (-) compared with Left (+) armLead II : Right arm (-) compared with Left (+)  legLead III : Left arm (-) compared with  Left (+) leg

AUGMENTED UNIPOLAR LIMB LEADSaVR :Augmented Vector RightaVL : Augmented Vector  LeftaVF : Augmented Vector Front

SPECIAL LEADSLead CV5 RL (V2)Lead CV6 LL (V2)Lead CV6 LU (V4)Lead V10

LEAD SYSTEM

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STANDARD LEADS

Useful for studying

1. Abnormalities in the P-QRS-T deflection

2. Diagnosing cardiac arrhythmias

3. Determining the mean electrical axis

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L I, II, III, aVR, aVL, & aVF - Frontal plane leads. L V1, V2, V3, V4, V5, V6, & V10 – Horizontal

 (or transverse) plane leads. 

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NORMAL ECG

P : Atrial depolarisation

QRS : Ventricular depolarisation

T : Ventricular repolarisation

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QRS Complex T wave

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Normal ECG Parameters - Dog & Cat 

Heart Rate (beats per minute) :

Canine :»Adults: 70-160»Toy Breeds: up to 180»Puppies: up to 220 

Feline :»160-240 

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Amplitudes (mV) in lead II

Canine FelineP amp < 0.4             < 0.2

R < 20 kg: < 2.5     0.9 > 20 kg: < 3.0 <

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                                                                            Intervals (seconds)

   Canine FelineP < 0.04                    < 0.04PR         0.06 -0.13         0.05 - 

0.09 QRS      < 20 kg: < 0.05                   < 0.04 

    > 20 kg: < 0.06QT        0.15 to 0.25                  0.12 to 

0.18

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Normal ECG Parameters - Dog & Cat

Rhythm Canine :    Normal sinus rhythm    Sinus arrhythmia    Wandering atrial pacemaker Feline :    Normal sinus rhythm     Sinus tachycardia 

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Methodical approaches to ECG

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ECG interpretation essentially involves four main steps:

Calculation of the heart rate; Determination of the heart rhythm; Measurement of the complex amplitudes and 

intervals;MEASUREMENT OF THE MEAN ELECTRICAL AXIS:

A good understanding of the electrical activity of the heart is key to the accurate interpretations of ECG (Martin, 2002).

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How to measure heart rate ???

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See the Rhythm …Regular or irregular???

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Rhythm 

1. Regular  irregular2. Irregular  irregular

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How to decide MEA???

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• There are three common methods of calculating the MEA in the frontal plane.

• The Vector Method: Using leads I, II or III and the frontal plane diagram, calculate the algebraic sum of the QRS deflections in any two leads.

• The Isoelectric Method.• The Largest Net Deflection Method.

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Normal ECG

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PQRST Wave System

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P wave

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P wave

    Width: maximum, 0.04 sec (2 boxes wide)maximum, 0.05 sec (2 ½ boxes wide) in giant breeds.

    Height: maximum, 0.4 mV (4  boxes tall).

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Left atrial enlargement - P too wide in L II. Dog & Cat : P > 0.04 sec 

Right atrial enlargement - P too high in L II. Dog: P > 0.4 mv ; Cat: P > 0.2 mv 

Biatrial enlargement - P too tall and wide in L II. 

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Rt Atrial enlargement (P Amp )

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QRS wave

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QRS complex

      Width: maximum, 0.05 sec (2 ½ boxes wide) in small breeds.

       maximum, 0.06 sec (3 boxes) in large  breeds.       Height of R wave*: maximum, 3.0 mV (30 

boxes) in large breeds.    maximum, 2.5 mV (25 boxes) in small 

breeds.

P-R interval       Width: 0.06 to 0.13 sec (3 to 6 ½ boxes).

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Wide QRS Complexes 

Etiologies:  Aberrant 

conduction    (Bundle Branch Block)

 Myocardial hypoxemia/ischemia 

 Left ventricular   enlargement 

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Low amplitude QRS complexes 

Etiologies: Pleural effusion ,Pericardial effusion, Obesity ,Hypothyroidism, Pneumothorax  and Diffuse myocardial disease.

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Left Ventricular Enlargement

   R wave amplitude in L II  increased.     QRS duration in L II  increased. 

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Lt Ventricular Enlargement (Increased R Amp)

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Rt. Ventricular enlargement

Presence of an S wave in leads I, II, III.  MEA in the frontal plane shifted to the 

right (pointing to the right ventricle): 100°  to – 75° 

Deep S wave in lead V3; S = 0.7 mv  Deep Q waves in leads I,II and III and 

after  aVF greater than 9.5 mV (5 boxes)

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Rt. Ventricular enlargement

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T wave

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T wave 

     Can be positive, negative or diphasic 

     Not greater than one fourth amplitude of R wave; amplitude range + 0.05 – 1.0 mV  

(1/2 to 10 boxes) in any lead.

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T wave abnormalities

    Should not be greater than 1/4 of  the R wave.

    Sharply pointed (or) Notched – Electrolyte imbalances

  Electolyte abnormality

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Peaked T wave

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Q-T interval duration

Dog : 0.15 to 0.25 sec (7 ½ to 12 ½ boxes) 

  Cat: 0.12 to 0.18 sec   Faster the heart rate, shorter the Q-T 

interval    Q-T interval should be less than half 

the preceding R-R interval

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Prolongation of Q-T interval Myocardial problems,  Toxicity or Hypoxia, Hypokalemia Hyperkalemia    Hypocalcemia Antiarrhythmic drugsShortening of QT interval Hypercalcemia 

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ST segment abnormalities

ST segment depression - 0.2 mV ;seen in    Myocardial ischemia    Myocardial infarction    Hyper and Hypokalemia     Trauma to the heart.ST segment elevation - 0.15 mV in Lead I ; seen in     Pericarditis,    Severe ischaemia/infarction (e.g. full wall 

thickness).

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Sinus Arrhythmia and Wandering Atrial Pacemaker in the Dog

Sinus arrhythmia - Irregular ventricular rhythm which is of sino-atrial origin. On the EKG, the QRS to QRS interval varies and there is a P wave for every QRS complex.

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Sinus Arrhythmia

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Wandering Atrial Pacemaker in the Dog

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Sinus rhythm:

A sequence of beats originating from the sino atrial node forms a rhythm, known as the sinus rhythm. there are four common sinus rhythms.

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Sinus Bradycardia in the Dog

1. Hypothyroidism ,  2. Hypothermia,     3.    Hyperkalemia,          4.  Hypoglycemia 

5. Enhanced parasympathetic tone as with: Increased inspiratory effort, Gastric irritation, 

  Increased CSF pressure. Atropine will abolish the bradycardia (atropine - 0.04 mg/kg IV) 

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Sinus bradycardia 

In Sinus bradycardia, the SA Node generates an impulse and depolarization occurs more slowly than normal. This can be a normal feature in some giant breed dogs and in athletically fit animals. The ECG shows a normal sinus rhythm but at a slower rate than normal.

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Sinus bradycardia 

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Sinus tachycardia 

In Sinus tachycardia, the SA Node generates an impulse and depolarization occurs faster than normal. The ECG shows a normal sinus rhythm but at a faster rate than normal.

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Sinus Tachycardia 

• It is a sinus rhythm with an increased ventricular rate.  Dog (<20 kg) with heart rate 180 bpm  Dog (20 kg) with heart rate 160 bpm  Puppies with heart rate 220 bpm  Cat with heart rate 240 bpm 

• Etiology: Pain,Fever, Anemia, Reduced cardiac output, Hyperthyroidism & Excitement.

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Atrial fibrillation

Irregular rhythm and absence of P waves

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Absence of P Wave (Atrial Fibrillation)

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Ventricular premature contractions (VPC)

Premature beats. QRS complexes are wide & bizarre. Common finding in dogs and cats and arise from an ectopic focus or foci within the ventricular myocardium.

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Ventricular Tachycardia (VT)

Refers to runs of greater than 3 PVC's in sequence. Markedly reduce cardiac output (dysynergy of contraction).Etiology is as for PVC.

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Other abnormalities

Right bundle branch block   Wide S waves    QRS complex greater than 0.08 sec.

Left bundle branch block   QRS complex greater than 0.08 sec duration   QRS complex wide and +ve.

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Artifacts    Muscle tremor artifact.     Movement artifact.     Electrical interference.

Electrical alternansAlternation in the size of the QRS 

amplitude that occurs nearly every other beat.

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Artifact

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Thank U 

Comments, corrections or additions are welcome.