Cardiology Flashcards
How do you approach reading an EKG?
- Rate
- Rhythm
- Axis
- Interval
- Waveform
- Summary
What are the key waveforms on the EKG?
What type of rhythm?
Sinus tachycardia with hidden p waves (camel hump)
What type of rhythm?
Sinus tachycardia, 150 bmp
Common causes of sinus tachycardia? (non-pharm and pharm)
Non-pharmacological
- Exercise
- Pain, anxiety
- Hypoxia, hypercarbia
- Acidaemia
- Sepsis, pyrexia
- Pulmonary embolism
- Hyperthyroidism
Pharmacological
- Beta-agonists: adrenaline, isoprenaline, salbutamol, dobutamine
- Sympathomimetics: amphetamines, cocaine, methylphenidate
- Antimuscarinics: antihistamines, TCAs, carbamazepine, atropine
- Others: caffeine, theophylline, marijuana
What rhythm?
Atrial Flutter with 2:1 Block
There are inverted flutter waves in II, III + aVF at a rate of 300 bpm (one per big square)
There are upright flutter waves in V1 simulating P waves
There is a 2:1 AV block resulting in a ventricular rate of 150 bpm
Note the occasional irregularity, with a 3:1 cycle seen in V1-3
This is the classic appearance of anticlockwise flutter.
What rhythm?
Atrial Flutter with Variable Block
Inverted flutter waves in II, III + aVF with atrial rate ~ 300 bpm
Positive flutter waves in V1 resembling P waves
The degree of AV block varies from 2:1 to 4:1
The diagnosis of flutter with variable block could be inferred here from the R-R intervals alone (e.g. if flutter waves were indistinct) — note how the R-R intervals during periods of 4:1 block are approximately double the R-R intervals during 2:1 block.
What rhythm?
Atrial flutter with 4:1 block
There are inverted flutter waves in II, III + aVF at a rate of 260 bpm.
There are upright flutter waves in V1-2 (= anticlockwise circuit).
There is 4:1 block, resulting in a ventricular rate of 65 bpm.
The relatively slow ventricular response suggests treatment with an AV nodal blocking agent.
What rhythm?
Atrial Flutter with Variable Block
The block varies between 2:1 and 4:1
The presence of positive flutter waves in lead II suggests a clockwise re-entry circuit (= uncommon variant).
What rhythm?
Atrial Flutter with 2:1 Block
There is a narrow complex tachycardia at 150 bpm.
There are no visible P waves.
There is a sawtooth baseline in V1 with flutter waves visible at 300 bpm.
Elsewhere, flutter waves are concealed in the T waves and QRS complexes.
The heart rate of 150 bpm makes this flutter with a 2:1 block.
NB. Flutter waves are often very difficult to see when 2:1 block is present.
Remember
Suspect atrial flutter with 2:1 block whenever there is a regular narrow-complex tachycardia at 150 bpm — particularly when the rate is extremely consistent.
In contrast, the rate in sinus tachycardia typically varies slightly from beat to beat, while in AVNRT/AVRT the rate is usually faster (170-250 bpm).
To tell the difference between these rhythms, try some vagal manoeuvres or give a test dose of adenosine — AVNRT/AVRT will often revert to sinus rhythm, whereas slowing of the ventricular rate will unmask the underlying atrial rhythm in sinus tachycardia or atrial flutter.
What are some characteristics of Atrial Fibrillation?
Atrial Fibrillation (AF) is the most common sustained arrhythmia.
The incidence and prevalence of AF is increasing.
Lifetime risk over the age of 40 years is ~25%.
Complications of AF include haemodynamic instability, cardiomyopathy, cardiac failure, and embolic events such as stroke.
Characterised by disorganised atrial electrical activity and contraction.
Causes of atrial fibrillation?
- Ischaemic heart disease
- Hypertension
- Valvular heart disease (esp. mitral stenosis / regurgitation)
- Acute infections
- Electrolyte disturbance (hypokalaemia, hypomagnesaemia)
- Thyrotoxicosis
- Drugs (e.g. sympathomimetics)
- Pulmonary embolus
- Pericardial disease
- Acid-base disturbance
- Pre-excitation syndromes
- Cardiomyopathies: dilated, hypertrophic.
- Phaeochromocytoma
What rhythm? General characteristics?
Atrial Fibrillation
Irregularly irregular rhythm.
No P waves.
Absence of an isoelectric baseline.
Variable ventricular rate.
QRS complexes usually < 120 ms unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction.
Fibrillatory waves may be present and can be either fine (amplitude < 0.5mm) or coarse (amplitude >0.5mm).
Fibrillatory waves may mimic P waves leading to misdiagnosis.
What rhythm?
Atrial Fibrillation
Irregular ventricular response .
Coarse fibrillatory waves are visible in V1.
“Sagging” ST segment depression is visible in V6, II, III and aVF, suggestive of digoxin effect.
What rhythm?
Atrial fibrillation:
Irregular ventricular response.
Coarse fibrillatory waves are visible in V1.
What rhythm? General characteristics?
Monomorphic Ventricular tachycardia
Ventricular Tachycardia (VT) is a broad complex tachycardia originating in the ventricles.
There are several different varieties of VT — the most being Monomorphic VT.
What rhythm?
Monomorphic VT:
Classic monomorphic VT with uniform QRS complexes.
Indeterminate axis.
Very broad QRS (~200 ms).
Notching near the nadir of the S wave in lead III = Josephson’s sign.
What rhythm?
Monomorphic VT:
Very broad complexes (~ 200 ms in V5-6).
Northwest axis (-120 degrees).
Brugada’s sign – The distance from the onset of the QRS complex to the nadir of the S-wave is > 100ms.
Joesphson’s sign – Notching near the nadir of the S wave is seen in leads II, III, aVF.
Possibly some superimposed P waves in aVF.
What rhythm?
Monomorphic VT alternates withventricularbigeminy. The ventricular complexes have the following features:
Very broad QRS duration (> 160 bpm).
Positive concordance in the precordial leads (dominant R waves in V1-6).
Brugada’s sign – time from onset of QRS to nadir of S wave > 100 ms; best seen in leads aVR and aVL.
The presence of normal sinus beats (capture beats) in the second half of the ECG further supports the diagnosis of VT.
