Atrial abnormality

As discussed previously, the P wave represents the depolarisation of both the left and right atria. The initial half of the P wave represents depolarisation of the right atria as the electrical impulse travels from the Sinoatrial node (SAN) to the right atrium and then the left. The impulse reaches the Atrioventricular node (AV) at the 

---

Changes in the size and shape of the P wave can point towards an atrial abnormality, which may be caused by right or left atrial enlargement (Figs. 5.4 and 5.6 respectively) or more rarely a conduction delay. Additional evidence for the presence of an atrial abnormality, enlargement, dilation or hypertrophy is the coexistence of a ventricular hypertrophy. 

Right atrial abnormality, also known as P. pulmonale (Fig. 5.4). This is seen on the ECG as peaked P waves which are greater than 2.5 mm in amplitude (height). Remember each small square of ECG paper is 1 mm, so it s taller than two and half small squares (Fig. 5.5). 

Left atrial abnormality, also known as P. mitrale, as it is commonly associated with mitral valve disease (Fig. 5.6). Left atrial abnormality is seen on an ECG as broad, notched/bifld M shaped P waves. These P waves are often greater than 2.5 mm in width (see Fig. 5.7). This is best seen in leads II and Vi. Another indicator is seen in lead Vi where there is a negative deflection below the base line of more than 1 mm and a width greater than 1 m (Fig. 5.8). 

Bilateral atrial abnormality refers to an abnormality that affects both atria (Fig. 5.9). This can be detected by the combination of indicators for both right and left atrial abnormality, present on the same ECG. Table 5.1 snmmarises some of the key P wave changes present in right, left and bilateral atrial abnormality. 

Table 5.1 P wave changes in leads 11 and V1, occurring with atrial abnormalities...

S wave in Vi +R wave in Vg >35 mm in height Accompanied left atrial abnormality... 

Right ventricular hypertrophy (Fig. 5.12) is less common than left ventricular hypertrophy. RVH is often accompanied by right atrial abnormality and tall R waves in lead Vi (height of R wave > depth of S wave), and right axis deviation. In more severe cases ST segment depression and T wave inversion, indicating strain pattern can sometimes be seen (Fig. 5.13). 

R wave in Vi + S wave in Ve >10 mm in height Accompanied right atrial abnormality... 

Ql. Left atrial abnormality is also sometimes known as ... 

---