Minding your P s and Q s Understanding ECG s Samantha Knell, RVT
In Veterinary field for 20 years RVT since 7/2015 Team Leader at Rockville CVCA since 8/2016 Vice President of Maryland Veterinary Technician Association Train dogs in Search and Rescue, Barn Hunt and Nose Works Volunteer with All Shepherd Rescue About me
Quick Overview Heart disease in companion animals ECG basics Lead placement Evaluating the strip Recognizing common abnormalities Arrhythmias in practice Practice
Heart Disease Approximately 10% of dogs affected with some type of heart disease 60% of dogs under 30 pounds over 10 years of age have a heart murmur About 18% of cats have signs of a thickened heart muscle Cavalier King Charles Spaniels- 100 % by the age of 10 have some level of heart disease Doberman Pinchers about 50% Maine Coon Cats- about 1/3 carry HCM gene Ragdoll Cats- about 1/4 carry the HCM gene
Diagnosing Heart Disease Physical Exam and Auscultation Blood pressure Radiographs Cardiac Biomarkers ECG/EKG Echocardiography Angiography
Coughing Weakness/lethargy Respiratory difficulty Decreased appetite Sudden paralysis (saddle thrombus) Sudden death Collapse/syncope Signs and Symptoms Blindness(high blood pressure)
ECG Basics Positioning Right lateral recumbency best Leads not touching Black- left fore White- right fore Red- left rear Green- right rear Grass and snow on the ground Read newspaper with hands- front of body(black and white) Christmas at the end of the year- back of body(red and green)
Paper speed and sensitivity 25mm/sec vs 50 mm/sec- 25 most common and accepted for measurements, 50 used to get a better look at certain parts of the wave forms and in cats ECG Basics 10mm/mv vs 5mm/mv- changes the height of the waveforms- 10mm/mv is standard
Leads Lead 1 - electrical activity between forelimbs Lead 2 - electrical activity between the right forelimb and left hind limb (most commonly used when evaluating a single lead as it most commonly has the highest voltage recordings) Lead 3 - electrical activity between the left forelimb and left hind limb avr, avl, avf - (augmented leads that record from a positive (unipolar) electrode)
Parts of an ECG Tracing P wave Atrial depolarization Should always be positive- above baseline QRS Ventricular depolarization Should be positive in lead 2(except horses) T wave Ventricular repolarization
Heart rate Rhythm P wave P-Q interval P for every QRS QRS for every P QRS shape Evaluating a Tracing
Determining Heart Rate At 25 mm/sec -1 second is 5 big boxes- 15 boxes = 3 sec x20=bpm At 50 mm/sec -1 second is 10 big boxes- 15 boxes =1.5sec x40=bpm Pen method (quick general number) Pen x 10 on 25 mm/sec Pen x 20 on 50 mm/sec Normal Canine- 70-160 bpm Normal Feline- 150-240 bpm
Regular Regularly irregular Irregular Irregularly Irregular Rhythm
Evaluating the Parts of the Tracing Is there a P wave? Is the P wave equal and consistent Is the QRS a normal shape and positive in lead 2 Is there a P for every QRS and a QRS for every P ST segment normal T wave of normal shape and size
Sinus Rhythm Sinus arrhythmia Sinus tachycardia/bradycardia Ventricular premature complex Ventricular tachycardia Accelerated idioventricular rhythm Atrial premature complex Supraventricular Tachycardia Atrial Fibrillation Ventricular Fibrillation Heart block Common Rhythms
Sinus Rhythm Normal speed and complexes Regular Rhythm Normal Finding, no treatment
Sinus Arrhythmia Rate speeds up and slows down based on respirations, increases with inhalation and decreases with exhalation Regularly irregular Normal heart rate and EKG complexes Normal finding in dogs and uncommon in cats High vagal / parasympathetic tone Wandering pacemaker No treatment needed
Sinus Tachycardia and Bradycardia Normal rhythm Normal complexes Abnormal rate Tachycardia- caused by pain, fever, anemia, heart failure, fear, excitement, dehydration Bradycardia- vagal response, hypothermia, hypothyroidism, will respond to atropine Treat underlying condition
Ventricular Premature Complex (VPC) QRS complexes come early, are not preceded by a P-wave, wide and bizarre Wide T-wave opposite in polarity to QRS complex VPCs can go downward or upward in Lead II Downward = LV origin Upward = RV origin Can be seen in heart disease, abdominal neoplasia, GDV, systemic disease Single premature beats not uncommon, require no treatment
Ventricular Tachycardia 3 or more VPC in a row Can compromise cardiac output Treatment includes IV lidocaine, mexiletine, Sotalol Sustained Vtach is life threatening, Considered Vtach with a heart rate over 180 bpm
Accelerated Idioventricular Rhythm Slow Vtach Normal rate Seen in dogs after GDV Seen in pets with severe metabolic issues Often no primary cardiac disease Does not usually affect cardiac output, treat underlying disease
Atrial Premature Complexes Similar to normal complexes but comes early May or may not see P-wave Pause after premature contraction Can be seen in animals with atrial enlargement, or in animals with normal hearts Occasional APC does not require treatment
Supraventricular Tachycardia Elevated heart rate with often a regular rhythm Basically normal QRS complexes P waves may be visible or may be buried in T wave Can be seen prior to atrial flutter or fibrillation Treatment digoxin, diltiazem, beta blockers, sotalol, procainamide
Atrial Fibrillation Elevated rate Irregularly irregular (shoes in a dryer) No P waves, may have atrial fibrillatory waves DCM, severe valve disease(can be the cause) Treatment, lower heart rate, usually do not maintain a cardioversion.
1st Degree AV Block Every P has a QRS P-Q delayed Does not require treatment
Wenckenbach progressive prolongation of the PR interval prior to a blocked p-waveassociated with high vagal tone Mobitz Type 2 occasional P waves do not get conducted, without progressive prolongation of the P-R interval. Progressive to syncope and bradycardiamay need pacemaker 2 nd Degree AV Block
3 rd degree AV Block Complete dissociation of P waves and QRS complex Very slow heart rate Needs a pacemaker May been seen under anesthesia
Practice Makes Perfect Get an overall impression What is the rate? What is the rhythm? P wave P for every QRS, QRS for every P
What is this Rhythm?
Step by Step Rate- 140 bpm Rhythm- irregularly irregular P wave- absent P-QRS relationship- not normal QRS shape- normal Answer- Atrial Fibrillation
What is this Rhythm?
Step By Step Rate-260 bpm Rhythm- regular P wave- not seen( actually there, but hidden at end of T wave) P-QRS relationship- not normal QRS shape- normal Answer- Supraventricular Tachycardia
What is this Rhythm?
Step by Step Rate- Atrial 140 Ventricular 20 Rhythm- irregular P-QRS relationship- not normal- every P does not have a QRS QRS shape- normal Answer- 3 rd degree heart block
Thank You! Any Questions? 9/4/2017 35