Conditions affecting the left side of the heart
BMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7348.1264 (Published 25 May 2002) Cite this as: BMJ 2002;324:1264
- June Edhouse,
- R K Thakur,
- Jihad M Khalil
Many cardiac and systemic illnesses can affect the left side of the heart. After a careful history and examination, electrocardiography and chest radiography are first line investigations. Electrocardiography can provide supportive evidence for conditions such as aortic stenosis, hypertension, and mitral stenosis. Recognition of the associated electrocardiographic abnormalities is important as misinterpretation may lead to diagnostic error. This article describes the electrocardiographic changes associated with left atrial hypertrophy, left ventricular hypertrophy, valvular disease, and cardiomyopathies.
Conditions affecting left side of heart covered in this article
Left atrial hypertrophy
Left ventricular hypertrophy
Valvular disease
Cardiomyopathies (hypertrophic, dilated, restrictive)
Left ventricular hypertrophy
Voltage criteria
Limb leads
R wave in lead 1 plus S wave in lead III >25 mm
R wave in lead aVL >11 mm
R wave in lead aVF >20 mm
S wave in lead aVR >14 mm
Precordial leads
R wave in leads V4, V5, or V6 >26 mm
R wave in leads V5 or 6 plus S wave in lead V1 >35 mm
Largest R wave plus largest S wave in precordial leads >45 mm
Non-voltage criteria
Delayed ventricular activation time
0.05 s in leads V5 or V6 
0.05 sST segment depression and T wave inversion in the left precordial leads
The specificity of these criteria is age and sex dependent
Left atrial abnormality
The term left atrial abnormality is used to imply the presence of atrial hypertrophy or dilatation, or both. Left atrial depolarisation contributes to the middle and terminal portions of the P wave. The changes of left atrial hypertrophy are therefore seen in the late portion of the P wave. In addition, left atrial depolarisation may be delayed, which may prolong the duration of the P wave.
Biphasic P wave in V1. The large negative deflection indicates left atrial abnormality (enlarged to show detail)
The P wave in lead V1 is often biphasic. Early right atrial forces are directed anteriorly giving rise to an initial positive deflection; these …
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