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ecg,veterinary ecg, small animal elecrocardiogram
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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
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.
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.
Indications
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.
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.
Normal Conduction System
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
Positive and Negative Deflection in a lead
A wave of electrical depolarization moves towards the positive pole of the lead – a +ve deflection occurs
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
Types of ECG
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
Position & Restraint
Lateral recumbency - the standard position for canine and feline
electrocardiography No chemical restraint Trained attendant or animal owner Lead placement
Electrodes & Leads
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)
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
STANDARD LEADS
Useful for studying
1. Abnormalities in the P-QRS-T deflection
2. Diagnosing cardiac arrhythmias
3. Determining the mean electrical axis
L I, II, III, aVR, aVL, & aVF - Frontal plane leads. L V1, V2, V3, V4, V5, V6, & V10 – Horizontal
(or transverse) plane leads.
NORMAL ECG
P : Atrial depolarisation
QRS : Ventricular depolarisation
T : Ventricular repolarisation
QRS Complex T wave
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
Amplitudes (mV) in lead II
Canine FelineP amp < 0.4 < 0.2
R < 20 kg: < 2.5 0.9 > 20 kg: < 3.0 <
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
Normal ECG Parameters - Dog & Cat
Rhythm Canine : Normal sinus rhythm Sinus arrhythmia Wandering atrial pacemaker Feline : Normal sinus rhythm Sinus tachycardia
Methodical approaches to ECG
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).
How to measure heart rate ???
See the Rhythm …Regular or irregular???
Rhythm
1. Regular irregular2. Irregular irregular
How to decide MEA???
• 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.
Normal ECG
PQRST Wave System
P wave
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).
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.
Rt Atrial enlargement (P Amp )
QRS wave
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).
Wide QRS Complexes
Etiologies: Aberrant
conduction (Bundle Branch Block)
Myocardial hypoxemia/ischemia
Left ventricular enlargement
Low amplitude QRS complexes
Etiologies: Pleural effusion ,Pericardial effusion, Obesity ,Hypothyroidism, Pneumothorax and Diffuse myocardial disease.
Left Ventricular Enlargement
R wave amplitude in L II increased. QRS duration in L II increased.
Lt Ventricular Enlargement (Increased R Amp)
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)
Rt. Ventricular enlargement
T wave
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.
T wave abnormalities
Should not be greater than 1/4 of the R wave.
Sharply pointed (or) Notched – Electrolyte imbalances
Electolyte abnormality
Peaked T wave
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
Prolongation of Q-T interval Myocardial problems, Toxicity or Hypoxia, Hypokalemia Hyperkalemia Hypocalcemia Antiarrhythmic drugsShortening of QT interval Hypercalcemia
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).
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.
Sinus Arrhythmia
Wandering Atrial Pacemaker in the Dog
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.
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)
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.
Sinus bradycardia
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.
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.
Atrial fibrillation
Irregular rhythm and absence of P waves
Absence of P Wave (Atrial Fibrillation)
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.
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.
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.
Artifacts Muscle tremor artifact. Movement artifact. Electrical interference.
Electrical alternansAlternation in the size of the QRS
amplitude that occurs nearly every other beat.
Artifact
Thank U
Comments, corrections or additions are welcome.