Approach to the ECG Flashcards
Draw and describe the normal ECG
ECG
A recording of the changes in electrical potential difference occuring during depolarisation and repolarisation of the myocardium plotted against time
Describe the cardiac conduction system.
Syno-atrial node - automaticity - cell to cell conduction until it reaches the Atrioventricular node. 0.1m/s
At this point the electrical wave must pass through the annulus fibrosis - narrowing of the conduction system, slows down potentials. 4m/s
Conducts to the bundle of His and then to the left and right bundles(His-purkinje system)
Where on the dogs limbs are ECG electrodes placed?
Olecranon/ stifle area of each limb
Lead i
RF vs LF
Lead II
Right fore vs Left hind
Largest deflection in a normal heart
Lead III
Left fore and left hind
At 50mm/s, each 5cm =
1 second
ie each 1mm = 0.02 seconds
Sinus arrhythmia - can be normal
Indicative of high vagal tone - Brachycephalic dogs
Wandering pacemaker- not altered p wave morphology - varied origin of SAN depolarisation
True or False.
Sinus arrythmia is NOT normal in the cat.
True
Caused by increased vagal tone due to:
pathology in the intracranial, intraocular, respiratory (asthma), GI, or (less common) urogenital systems.
Baseline artifact - struggled breathing
Sinus arrest in one area - accentuated in brachycephalic breeds but may also be normal in sleeping dogs
Sinus arrest and sinus sick syndrome (some complexes have no p waves)
P wave fusion complex
Occurs with PVCs - caused when they occur late in the ECG cycle - they therefore fuse with the p wave of the next wave
Ventricular premature complex - due to depolarisation arising from the ventricular myocardium
Ventricular tachycardia - characteristic wide complexes
Ventricles will be unable to completely fill leading to hypoxia and systemic hypoperfusion
Ventricular fibrillation
