This document discusses the normal waves of an electrocardiogram (ECG). It describes the P wave, which represents atrial depolarization originating from the sinoatrial node. The QRS complex represents ventricular depolarization, which occurs through the interventricular septum and ventricular walls. The T wave represents ventricular repolarization. The U wave is sometimes present following the T wave but is usually small. Lead placement affects whether the QRS complex appears as qR or rS, depending on whether the lead is oriented towards the left or right ventricle, respectively.

1. WAVES OF ECG
DR.PRAVEEN

2. NORMAL WAVES OF ECG
 P wave
 QRS complex
 T wave
 U wave

3. P WAVE
 It represents atrial depolarization.
 P wave is initiated from the SA
node(RA and SVC junction just
below the epicardium).

5. P WAVE
 Best seen and studied in standard lead II.
 Frontal plane P wave axis is usually directed to the positive pole of the lead II.
 Pyramidal in shape with a somewhat rounded apex.
 Duration of P wave is usually in the range of 0.08sec to 0.10sec but is no
greater than 0.11 sec. ( < 21/2 boxes).
 The maximum normal amplitude is 2.5mm.

6. P WAVE IN LEAD V1
 Initial and terminal components of P wave are clearly identified and easily
separated in this lead.
 Diphasic ( initial positivity and terminal negativity)
 Duration of the P wave is usually about 0.05sec.
 Does not exceed 0.08sec.
 The terminal negative deflexion should not exceed 1 mm in depth and 0.03
sec in duration.

8. QRS COMPLEX
 It denotes depolarization of the ventricles.
 IVS
 free wall of the ventricles
 Initially in the Lower one third of IVS from left to right.
 With small opposing force from right to left
 Its called as septal force or vector.

9.  Free wall of both ventricles
 Endocardial to epicardial
 LV is larger than RV in muscle mass (so large vector of LV, small vector of
RV )
 Large right to left force of LV free wall counteracts smaller left to right force
of the free RV wall.

12. THE EFFECT ON A LEFT ORIENTED LEAD
 A lead oriented to the left ventricle (V6,AVL,I) first senses the relatively small
resultant septal vector, which is directed away from the positive pole of such a
lead and will consequently reflect a small initial downward deflexion – a small
q wave.
 Large resultant vector of the free left wall – tall R wave.
 A qR complex

13. THE EFFECT ON A RIGHT ORIENTED LEAD
 A Lead oriented to the right ventricle (V1,V2) will first sense the small resultant
septal vector, which is directed towards it.
 Small initial upward deflexion – a small r wave.
 Large resultant vector of the free left wall – away from the positive pole of the
lead – large S wave.
 rS complex

16. QRS COMPLEX

17. R WAVE PROGRESSION

18. T WAVE

20. U WAVE
 The end of the T wave completes the normal cardiac cycle.
 The U wave is not always present.
 The size of the normal U wave is small, measuring approximately one-tenth of
the size of the T wave.
 Best recorded in the leads V2 and V3 ( closest to the ventricular myocardium).
 Usually visible when the heart rate is low (<65 bpm) and rarely visible with
faster heart rates (>95 bpm).

22. J POINT
 The J point, also called the J junction, marks the end of the QRS complex and
beginning of the ST segment.

23. THANK YOU