interpretation of ECG Flashcards
what are 5 things to consider when looking at an ECG recording
- is the ECG of good quality such that you can use it to make a diagnosis (artifact?)
- what is the rate and rhythm
- are the QRS-t complexes normal(ish) or wide and bizarre
- is ther chamber enlargement or hypertrophy
- electircal axis
what type of artefact is this?
electromagentic interference caused by interferences of other electrical devices.
- remove or turn off electrical devices in the environment
what kind of artefact is this
wandering baseline –> loose electrode or pood skin preparation or patient moving
what is rate
how often the le impulses go through the heart
what is rhythm
the pattern of the electrical impulses travel across the heart
what artefacts are present? calculate the heart rat. is the rhytm regular or irregular
artefact: wandering baseline
calculate the rate. is the rhythm regular or irregular
rate: 1500 x13 = 115 bpm
rhythm = regular
what questions should you ask yourself when interpreting rhythm
- is it regular or irregular
- if its irregular is it irregularly irregular or regularly irregular
- is there a P for every QRS
- is there a QRS for every P
- are there Ps and the QRSs consistently and similarly related
- are all the Ps alike
- are all the QRSs alike
- are the QRSs narrow and upright in leads 2/3/avf
- are the QRSs wide and bizarre
describe normal sinus rhythm
- normal impulse originates in the SA node
- The SA node has an inherent pacemaker rate of 70-160 bpm in the dog and 160-240 bpm in the cat
- P waves are usually positive in lead 2
- the PR interval is usually consistent from beat to beat
- the QRS complex is usually “normal”
- the rhythm may be regular or irregular
describe sinus arrythmia
- as normal sinus rhythm except greater variation in P-P or R-R interval
- then rhythm is irregular but regularly so
- if related to the respiratory cycle = respiratory sinus arrhythmia (normal in the dog, abnormal in the cat) mediated by fluctuations in vagal tone, abolished by giving atropine, accentuated by vagal manoeuvres
what is bradydysrhythmia
heart rate lower than normal
what is sinus arrest
- failure of pacemaker to discharge
- pause with no P-QRS-T complex
- heart does not stop!
- next fastest pacemaker takes over
what is persistent atrial standstill
- a type of bradydysrhythmia
- there is a complete absence of P waves
- next fastest pacemaker takes over
- the heart rate is usually slow but regular
- QRST - normal - junctional escape rhythm
what is a first degree AV block
- a type of bradydysrhythmia
- P wave and QRS complex are normal
- the P-R interval is prolonged
what is a second degree AV block
- a type of bradydyrythmia
- P wave not conducted through the AV node = p without QRS
what is a complete (third) AV block
- a type of bradydysrhythmia
- persistent failure of conduction through AV node
- ventricles usually paced (depolarisation originating) from ventricular focus
- wide, bizarre escape complexes at approx 30-40 min (dog)
what is tachydysrhythmia
- heart rate is higher than “normal”
- ectopic activity
- key part of interpretation is to establish origin of abnormal activity
what is seen in supraventricular prematuer complexes
- premature P wave (P’ wave) interrupts normal P wave rhythm
- P’ wave is early I compared with a normal p-p interval)
- P’ wave configuration differs from the normal P waves
- QRST usually normal
describe what happes in a normal ECG wave at each point
what is seen in supraventricular tachycardia
- runs of more than three consecutive supraventricular premature complexes
- heart rate during tachycardia is greater than upper normal limit
- rhythm during tachycardia is usually regular
- site of origin is within atria/junction outside of SA node
- P’ waves differ from the “normal” sinus P wave (if availible)
- maybe sustained (>30s) or non-sustained (paroxysmal, <30s)
- P’-P’ interval is normally regular
- P’-R interval is normally constant IF every P’ wave is conducted
- QRS is usually “normal” - narrow and upright in lead 2
describe what occurs in atrial fibrillation
- heart rate may or may not be within normal limits
- rhythm is irregularly irregular (very obvious on auscultation)
- no isoelectircal baseline
- No P waves
- irregular, variable amplitude fibrillation waves may be evident
- QRS complex is usually “normal” - narrow, upright in lead 2
- usually sustained, maybe non-sustained (paroxysmal)
what happens during ventricular premature complexes
- AKA ventricular ectopics
- site of origin is within ventricles
- rhythm is irregular
- wide and bizarre QRST complex interrupts rhythm
- spread through myocardium, NOT conducting tissue
- usually the underlying NSR is undisturbed
- VPC QRST unrelated to P waves
- VPS QRST complex voltage is usually large
What is bundle branch block wide and bizarre complex
passive spread, conducting system damaged
describe ventricular tachycardia
- a run of 3 or more ventricular premature complexes
- rhythm usually regular during tachycardia
- rate low but > intrinsic rate of the ventricles (>40 bpm in the dog, >60 bpm in the cat)
- may be sustained or not sustained
SA node still firing
describe ventricular fibrillation
- usually terminal
- rhythm associated with cardiopulmonary arrest
- heart rate rapid and irregular
- no isoelectric baseline
- ECG is irregular and chaotic
- no recognisable PQRST complexes
- course or fine depending on the degree of baseline oscillation
