==Left ventricular hypertrophy==
[[Image:E_lvh.jpg|thumb|LVH. R in V5 is 26mm, S in V1 in 15mm. The sum is 41 mm which is more than 35 mm and therefore LVH is present according to the Sokolow-Lyon criteria.]][[Image:LVH.png|thumb]]
As the left ventricular becomes thicker, the QRS complexes become larger. This is especially true for leads V1-V6. The S wave in V1 is deep, the R wave in V4 is high. Often some ST depression can be seen in leads V5-V6, which is in this setting is called a 'strain pattern'.
Left ventricular hypertrophy has prognostic consequences as has been found in several studies.<cite>Levy</cite><cite>Sundstrom</cite>
Image:LVH.jpg|ECG of patient with left ventricular hypertrophy according to the Sokolow-Lyon criteria
==Right ventricular hypertrophy==
[[Image:RVH.png|thumb]][[Image:E_rvh.jpg|thumb|Right ventricular hypertrohpy, the R wave is greater than the S wave in V1]]
Right ventricular hypertrophy occurs mainly in lung disease or in congenital heart disease.
The ECG shows a negative QRS complex in I (and thus a right [[heart axis]]) and a positive QRS complex in V1.
==Left atrial enlargement==
;Criteria for left atrial voor left atrial enlargement. Either
:P wave with a broad (>0,04 sec or 1 small square) and deeply negative (>1 mm) terminal part in V1
:P wave duration >0,12 sec in laeds I and / or II
[[Image:left_atrial_enlargement.jpg|thumb| Left atrial enlargement]]
[[Image:LAE.png|thumb| Left atrial enlargement with ECG.]]
[[Image:LAE-v1.png|thumb| Left atrial enlargement as seen in lead V1.]]
[[Image:LAE_12lead.jpg|thumb| Left atrial enlargement as seen on a 12 lead ECG]]
Left atrial enlargement is often seen in mitral valve insufficiency, resulting in backflow of blood from the left ventricle to the left atrium and subsequent incresed local pressure.
==Right atrial enlargement==
;Right atrial enlargement is defined as either:
:P >2,5 mm in II / III and / or aVF
:P >1,5 mm in V1.
[[Image:right_atrial_enlargement.jpg|thumb| Right atrial enlargement]]
[[Image:RAE.png|thumb| Right atrial enlargement]]
Right atrial enlargement can result from increased pressure in the pulmonary artery, e.g. after pulmonary embolisation. A positive part of the biphasic p-wave in lead V1 larger than the negative part indicates right atrial enlargement. The width of the p wave does not change.
In biatrial enlargement is the ECG whos signs of both left and right atrial enlargement. In V1 the p wave has large peaks first in positive and later in negative direction.