Atrial flutter
- Regular rhythm
- Sawtooth pattern
- Narrow QRS
- 2:1, 3:1, 4:1 AV conduction ratio
Atrial fibrillation
- Irregularly irregular rhythm
- Narrow QRS (usually)
- No visible P waves
- Absence of isoelectric baseline
Wandering atrial pacemaker
- R-R intervals vary slightly as the pacemaker site changes
- Rhythm can be slightly irregular
- Morphology of P waves changes
What are the characteristics of Premature atrial contractions
- Premature ectopic beat will interrupt the regularity of the rhythm
- P wave of premature beat will have a different morphology
- Narrow QRS
premature junctional contraction (PJC)
- Premature ectopic beat will interrupt the regularity of the rhythm
- P wave can come before, after or be lost in the QRS (if visible the P wave will be inverted)
- Narrow QRS
Junctional escape rhythm
- R-R intervals are constant
- Regular rhythm
- P waves are inverted and come either before or after the QRS or are lost entirely.
- Narrow QRS
- 40 to 60 bpm
What are the characteristics of SVT
- Rate: 150-200 bpm
- Regular rhythm
- P waves are not present (hidden in the T waves of proceeding beat)
2nd degree heart block type 1 (Wenckebach)
- P-R intervals get progressively longer until one P wave is not followed by a QRS
- Wider, wider, wider, gone
Wolf-Parkinson-White syndrome
WPW is a pre-excitation syndrome cause by additional or accessory AV pathway. Accessory pathways conducts impulses faster.
The ventricles are not conducted via the conduction system = ventricular activation is slow = delta wave and T wave abnormalities
- Short PR interval (less than 0.12 seconds)
- Delta wave present
- T wave abnormalities
- QRS can be narrow or wide
Complications: SVT, AFib, A flutter
1st degree AV block
- Long P-R intervals (greater than 0.20 seconds)
- Regular rhythm
- Narrow QRS
2nd degree heart block type 2
- P waves are consistent, but the QRS are not
- Always more P waves than QRS complexes
What are the characteristics of 3rd degree heart block
- P waves and QRS march to their own beat but they are both regular but not synced with each other.
PVC
- Regular or irregular rhythm
- Wide QRS complex beat thats premature
- No proceeding P wave
Ventricular tachycardia
- Rhythm: regular (can be slightly irregular)
- Atrial rate cannot be determined
- Ventricular rate is 150-200 bpm
- P waves are not present
- QRS are wide and bizarre
- Another type is torsade de Pointes
Ventricular fibrillation (VF)
- No waves or complexes can be analyzed to determines regularity (chaotic)
idioventricular rhythm
- Slow ventricular escape rhythm with wide QRS (wide and slow and the P waves don’t show)
- Ventricular rate 20-40 bpm
- Regular rhythm
- No P waves
- QRS is wide and bizarre
- Accelerated = 40-100 bpm
P wave
Atrial depolarization
<0.12 seconds (3 boxes)
P-R interval
Impulse delay at the AV node
0.12-0.20 seconds (3-5 boxes)
QRS complex
Ventricular depolarization
0.08-0.12 seconds (2-3 boxes)
T wave
Ventricular repolarization
ST-segment
Distance from the end of the S wave to the beginning of the T wave
Depression = Ischemia
Elevation = Infarct
QT-interval
- Time interval between the onset of the depolarization and the termination of repolarization of the ventricles
- Dependent on the heart rate (should be less than half of the R-R interval)
R-R interval
The time between two successive ventricular depolarizations
Brugada Syndrome
Brugada is caused by a mutation in the cardiac sodium channel gene.
High incidence of sudden death. Mean age of 41.
Definitive treatment = ICD
ECG changes can be transient. Brugada syndrome can also be unmasked/triggered by multiple factors;
- Fever/Hyperthermia
- Hypothermia
- Drugs (sodium channel blockers, calcium channel blockers, cholinergic stimulation, cocaine…)
- Hypokalemia, Hyperkalemia
ECG changes:
- Coved ST segment elevation >2mm in one or more leads of V1-V3 followed by a negative T wave (Type 1)
