Atrial hypertrophies Flashcards
What is the activation process of the atrium?
Signal starts in the SAN, Bachmann’s bundle to LA
What does hypertrophy mean?
Enlargement/thickening of the muscle in response to an increase in workload.
So if there is any alteration in the atria, what part of the ECG is affected?
Normal P wave measurements
Best seen in Lead II
Pyramidal in shape
Smooth apex
Amplitude not exceeding 2.5mm/0.25 mV
Duration not exceeding 0.10secs
Components of the Normal P wave
Both RA and LA components are directed towards lead II giving positive waveforms
RA component is first half of P wave and LA component is second half
P wave morphology in lead II and V1 and reasoning
The RA is situated anteriorly and to the right of the ventricles.
The LA is situated more posteriorly, behind the ventricles.
The RA activity is directed towards lead V1 hence the 1st, RA component is upright in V1.
The LA activity is directed slightly away from V1, hence the 2nd, LA component is slightly negative
RA enlargement ECG explained
The RA component of the P wave is increased in voltage and duration.
Since the RA component of the P wave is normally seen as a positive deflection in both leads II and V1 the P wave height is increased in both these leads.
RA depolarisation is normally complete well before LA depolarisation. The prolonged conduction time of RA enlargement is not sufficient to affect the overall duration of the P wave.
Only amplitude of the P wave is affected NOT duration
ECG criteria for RA enlargement
P wave amplitude > 2.5mm in leads II,III or aVF.
Positive component of V1 > 1.5mm.
Usually RVH
Clinical significance?
Usually due to pulmonary disease leading to RVH and then RA enlargement, hence the term “P-pulmonale”.
Any other disease leading to RVH eg. Pulmonary stenosis.
Rarely RA infarction/ischaemia.
P pulmonale ======> peaked P waves
Left atrial enlargement
The LA component of the P wave is increased in duration and voltage.
Since the terminal part of the P wave is produced by LA depolarisation, the total duration of the P wave is increased.
The LA component increases in amplitude and the P wave in lead II becomes bifid. In lead V1, the negative component becomes dominant.
ECG criteria for LA enlargement
“M”-shaped P wave > 0.10 secs in leads II,III and Avf.
P wave in V1 shows a dominant negative component.
Frequently LVH.
With mitral stenosis only, LA enlargement can be found with RVH.
Clinical significance:
Any condition that gives rise to LVH.
AS, AI, HOCM, hypertension
Mitral stenosis
LA infarction/ischaemia
P mitrale ===> M-shaped P waves
Biatrial enlargement
Easier to diagnose than biventricular hypertrophy.
Each atrium affects a different part of the P wave - hypertrophy of each ventricle affects the same part of the QRS.
ECG criteria for Biatrial enlargement
Diagnosis can be made when the criteria for both RA and LA hypertrophy are met.
Limb leads
P wave > 2.5mm in height
P wave > 0.10secs in duration
V1
Positive component > 2mm in height
Negative component > 1mm deep
