ECG BASICS & PHYSIOLOGY OF HEART

1. ECG BASICS&PHYSIOLOGYOFHEART

2. Heart is a pumping organ

4. How heart keeps pumping? 1.special structure of cardiac muscle • syncytial nature • both resting membrane potential & action potential are different form skeletal muscle 2.auto rhythmicity of heart

5. Action potential of heart muscle

6. Factors affecting action potential • 1 K+ concentration • 2 Ca++ concentration • 3Na+ concentration • 4 temperature

7. Excitation contraction coupling

8. Excitation contraction coupling

9. Duration of contraction • Atria 0.2sec • Ventricle 0.3 sec • Normally contraction time is 40% of cardiac cycle. When heart rate increases 3 times it is 65% of cardiac cycle. • Relaxation decreases • Ventricular filling decreases

10. Cardiac cycle

11. Atrial systole

12. IMC

13. ejection phase

14. IMR

15. Heart sounds

17. Regulation of pumping • 1Frank Starling mechanism • 2 autonomic innervation • Within physiological limit heart pumps all the blood that comes to it without allowing excessive pooling of blood in the veins

18. Parasympathetic innervation

19. Effects of autonomic stimulation • Chronotropic effect • Dromotropic effect • Bathmotropic effect • Inotropic effect

20. Effects of autonomic stimulation • Sympathetic stimulation: HR can go upto 250 bpm in young individual. • Parasympathetic stimulation: HR can go down to zero. Although vagal escape follows. • Both Sympathetic and parasympathetic system maintain a low level firing at resting condition.

21. Energy considerations • Source: oxidative respiration • FA- biggest source • glucose/ lactate also used • Energy efficiency max 20-25%, rest is converted to heat (HF: 5-10% ) • Expenditure increases when ventricles are dialated BP is elevated Energy expenditure is measured by oxygen comsumption

22. Special conductive system

23. Rate of discharge • SA node 70-80 bpm • AVnode 40-60 bpm • AV bundle 15-40 bpm

24. Autorhythmicity of SA node

25. Autorhythmicity of SA node

26. Autorhythmicity of SA node

27. Autorhythmicity of SA node

28. Autorhythmicity of SA node

29. Special conductive system • Nodal delay • .09sec AV node • .04 sec penetrating portion • Additional .03 sec internodal pathway

30. Ectopic pacemaker • Heart block • Stokes Adams syndrome

31. ECG

38. Heart muscle wraps around heart like a double spiral with a fibrous septa between the spiral layers.

39. Flow of current

40. leads

42. Other leads • Chest leads 6 in no. • + pole connected to chest, -ve to all 3 limbs • Infrequently 7th & 8th chest leads & esophageal leads used. • aVR- Rt +ve • aVF- Lt leg +ve • aVL- Lt arm +ve • Recording of V1 V2 upside down as it is more closer to base rather than apex

43. Axis of leads

44. Vector • Instantaneous mean vector: At any given instance the total amount of current flowing in the heart is represented in magnitude and direction by the vector. Current flows from DEPOLARISED to POLARISED area i.e. NEGATIVE to POSITIVE

45. Vector analysis • Closer the angle higher is the component • +ve vector: reading above the baseline • - ve vector: reading below the baseline