ECG: Atrial Bigeminy

1. Prof P. Vijayaraghavan’s Unit
by Dr J. Stalin Roy

2. •Munirathinam 70 yr old male, a known Hypertensive came for
routine check up.
•His pulse was regularly irregular, an ECG was ordered.

5. •Two foci of origin of atrial depolarisation as evidenced by two
different p wave morphologies (the sinus p wave is + followed
by – ie right atrial followed by left atrial; the ectopic p is –
followed by + ie left atrial followed by right atrial)
•The sinus impulse is followed by an Atrial Premature
Depolarisation (APD) which is coupled to the sinus impulse by a
constant interval (0.48sec)
•The APD is followed by a normal ventricular depolarisation as
evidenced by normal QRS
•This rhythm is known as Atrio-Ventricular Bigeminy or simply
Atrial Bigeminy

6. Sinus impulse
•PR 0.12 sec
•QRS 0.10 sec
•QRS axis +30
•ST isoelectric
•T occasionally dented by the
p wave of APD
APD
•PR 0.16 sec
•QRS 0.10 sec
•QRS axis +15
•ST isoelectric
•T normal

8. A P-wave algorithm constructed on the basis of findings from 130
atrial tachycardias correctly localized the focus in 93%

9. Right atrial
•A negative

or biphasic
(positive, then negative) P-
wave in lead V
1 was

associated with a 100%
specificity and PPV for a
tachycardia

arising from the
RA.
Left atrial
•A positive or biphasic
(negative, then

positive) P-
wave in ECG lead V
1 was
associated with a 100%
sensitivity

and NPV for
tachycardia originating in the
LA.

10. •Lead V1 is oriented towards the right atrium, aVL towards the
left atrium, so localization is mainly based on morphologies of p
waves in these leads.
•Lead V1 is always positive when the impulse originates near the
pulmonary veins (left atrial); and negative when the origin is
near the tricuspid annulus (right atrial).
•In general, the polarity

of leads II, III, aVF is deeply negative for
an inferoanterior

location, and low amplitude, positive, or
biphasic for a superior

location.
•Perinodal (near the AV node) and right septal foci are
associated with an isoelectric V1.

11. •Rare rhythm disorder characterized by an APD occurring after
each sinus impulse followed by a non-compensatory pause
(characteristic of APD)
•The APD usually arises from a single irritable focus within the
atria.
•An atrial or junctional focus becomes irritable due to:
•Excess adrenaline due to increased sympathetic stimuli
•Caffeine amphetamines, cocaine and other β1 receptor stimulants
•Excess digitalis, certain toxins, occasionally ethanol
•Hyperthyroidism
•Stretch
•Hypoxia

12. •Usually benign condition
•But it may rarely precipitate supraventricular and ventricular
arrhythmias most commonly Atrial Fibrillation
•Management includes correction of predisposing conditions