WAVES OF ECG.pptx

PPT IS ABOUT THE WAVES OF ECG AND THE PHYSIOLOGY BEHIND THEM

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).

4. 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.

5. 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.

6. 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.

7. 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.

8. 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

9. 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

10. QRS complex

11. R wave progression

12. T wave

13. 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).

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

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