Criteria for Left Atrial Enlargement

 

Situations where left atrial enlargement may occur:

(1) mitral stenosis

(2) cardiomyopathies

(3) arterial hypertension

(4) ischemic heart disease

 

Criteria from the electrocardiogram for left atrial enlargement (Table I, page 830, Munuswamy et al, 1984):

(1) P terminal force in lead V1 more negative than ( < ) -0.04 mm•s.

(2) duration of the negative of phase of the P wave in lead V1 > 40 ms (0.040 seconds)

(3) depth of the negative phase of the P wave in lead V1 >= 1 mm (0.10 mV)

(4) total P wave duration > 110 ms (0.110 seconds)

(5) notched (indented) P wave in any standard lead (such as II or III) with an interpeak duration > 40 ms (0.040 seconds)

(6) ratio of (total P wave duration in seconds) / (P-R interval in seconds) > 1.6

 

where:

• P terminal force = (depth of the terminal phase of P wave in mm) * (duration in seconds); the depth of the terminal phase is taken as a negative number. This also termed the Morris index.

• P-R interval is the time from the beginning of the P wave to the beginning of the R wave

• The notching in the P wave is due to separation of left and right atrial peak potentials.

 

Performance of the criteria when compared to M-mode echocardiography:

Criteria	Sensitivity	Specificity
1	69%	93%
2	83%	80%
3	60%	93%
4	33%	88%
5	15%	100%
6	31%	64%

Table III, page 831, Munuswamy et al (1984). Hazen et al (1991) showed similar findings for criteria 1, 4 and 5 (Table II, page 825) except for better sensitivity for criterion 4 (62%).

 

Limitations:

• The diagnosis of left atrial enlargement by electrocardiography is neither sensitive nor specific. Combining 2 or more of the criteria above did not improve performance.

• Many of the electrocardiographic changes associated with left atrial enlargement are related to a prolonged interatrial conduction time (Josephson et al, 1977). A patient with an interatrial conduction defect may give a false positive for left atrial enlargement by ECG, while a patient with left atrial enlargement but without a conduction defect could appear as a false negative.

• Echocardiography and other imaging modalities can be used now if the diagnosis is in question.