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Rates >100 represent tachycardia. Whether they are sinus is dependent on
Sinus rhythm with a rate of >100 per minute. RR interval less than 3
big boxes (0.6 secs).
Sinus Tachycardia can be seen in:
and many other conditions.
Sinus rhythm with a rate of < 60 per minute. RR interval more than 5 big
boxes (1 sec)
Sinus Bradycardia can be seen in:
- Raised Intracranial tension
- Obstructive jaundice
- Sinus node dysfunction
- Beta blockers
Premature atrial beats (P')
- Single irritable focus in atria discharging an impulse before the next regular SA
- P' wave is premature
- Contour of the premature P' wave is different
- P'-R is often longer - always different from PR of sinus beats
- QRS following P' is usually normal but may be non-conducted or conducted with
- Pause following P' is not usually fully compensatory
- Encountered in
- Coronary artery disease
Paroxysmal Atrial Tachycardia.
- Single irritable focus in atria taking over pacemaker function of Heart
- Starts with a premature P wave
- Rate is between 140-250 per minute
- P waves are frequently not discernible
- Rhythm is perfectly regular, RR interval constant.
- QRS is usually unchanged
Paroxysmal Atrial Tachycardia. with block.
- P waves are abnormal
- Rate is usually under 200 / minute
- 2:1 or variable block is present
Multifocal atrial tachycardia.
- Frequent premature P waves of varying contour
- Rate is more than a 100/minute
- P'-P' intervals are irregular
- Most commonly seen in severe pulmonary disease
- Irritable focus in atria contracting at a rate that exceeds the rate at which
Ventricles are capable of contracting.
- Ventricles cannot exceed rate of 250/min.
- AV node filters and prevents too many impulses reaching Ventricles.
- Atrial rate is 250-350/minute and regular
- P waves are replaced by "F" waves (saw tooth pattern in II, III, AVF)
- Ventricular rate is lower. Frequently 2-1 or 4-1 A-V conduction is present
- QRS contour is unchanged
- Encountered in
- Post MI
- Rheumatic Heart disease
- Single irritable focus in Ventricles
- Ventricular rate 150-250 bpm
- Wide QRS complexes
- No P wave
- RR intervals approximately equal
- A run of three or more VPB's in a row @ rate greater than 100/min
- AV dissociation may be present
- Atrial capture beats may be present
- Ventricular fusion beats may be present
- Retrograde concealed conduction
- VPB's with the same shape QRS
- Looks like Ventricular tachycardia
- Except the rate is below 100/minute
- Functions as escape rhythm when higher pacemaker fail
- Multiple foci in atria begin initiating impulses.
- No unified atrial contraction, atria primarily quiver.
- AV node permits only few impulses to pass to ventricles at random.
- Atrial rate >400 bpm-- is fibrillating
- Absent P waves
- Ventricular rate variable
- If there is tachycardia then called rapid A-fib
- Irregularly irregular
- Encountered in
- Multiple irritable foci in Ventricles, uncoordinated quivering of Ventricles.
- QRS complexes indistinct chaotic undulations.
- Boundary between the QRS and the ST-T wave of a ventricular tachycardia becomes
- Isoelectric baseline not clear
- Low amplitude chaotic rapid ventricular rate >250 bpm
- P waves not conducted
Premature supraventricular complexes
- P' wave contour different from P wave
- Temporary shortening of PR interval
Premature ventricular complexes (PVC)
- Single irritable focus in Ventricle discharging impulse before the next regular
impulse delivered from sinus node.
- Basic rhythm interrupted by single premature ectopic beat.
- Absent P wave for the beat
- Wide QRS complex
- Runs of PVC