The cardiac cycle consists of rhythmic changes that occur with each heartbeat. It has several phases including isovolumic contraction, ejection, isovolumic relaxation, and atrial systole. Heart sounds are produced by the closing of valves and include S1, S2, S3, S4, and murmurs. An electrocardiogram (ECG) records the electrical activity of the heart through electrodes on the skin and analyzes waves, intervals, and other characteristics to evaluate heart rate and identify conditions like coronary artery disease.

1. Cardiac Cycle, Heart Sounds and
Electrocardiography
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2. Cardiac Cycle

3. What is the Cardiac Cycle?
72 beats per minute
60 mins per hour
24 hours per day
365 days per year
72 x 60 x 24 x 365 x 70 = more than 2.5 x 109
An average person's heart beats more than 2 billion
times in a lifetime of 70 yrs
Rhythmic changes that happen with each beat are
called the cardiac cycle

4. Cardiac Anatomy in brief
Two atria and two ventricles
Ventricles – main pumping
chamber
Atria – reservoir / booster
pump
Atrioventricular valves –
allow flow from atrium to
ventricle only
Semilunar valves – allows
flow from ventricle to great
artery only

5. Rhythm generation and
conduction
Sinoatrial node –
pacemaker of the heart
Atrioventricular node –
conducts impulse from
atrium to ventricle
Delay at AV node allows
time for filling of
ventricles

6. Cardiac Cycle - Components

7. Isovolumic contraction
First phase of ventricular
systole
Ventricular pressure ++
Ventricular volume =
Begins with first heart
sound

8. Ejection
Ventricular pressure +
Ventricular volume --

9. Protodiastole
Sometimes named as a separate phase
Continuing ejection before closure of the
semilunar valves

10. Isovolumic relaxation
Ventricular pressure --
Ventricular volume =

11. Rapid filling
Ventricular pressure =
Ventricular volume ++

12. Slow filling (diastasis)
Ventricular pressure =
Ventricular volume +

13. Atrial systole
Ventricular pressure =
Ventricular volume +

14. Wigger's diagram

15. Heart Sounds

16. Heart sounds
Sounds produced by the beating heart
Turbulent blood flow when valves close
Usually listened with a stethoscope
Very useful for physician to identify
cardiac abnormalities

17. Heart Sounds
First heart sound (S1)
Second heart sound (S2)
Third heart sound (S3)
Fourth heart sound (S4)
Murmurs

18. First heart sound
Produced by closure of atrioventricular
valves at beginning of systole
Mitral (M1) and tricuspid (T1) valve
closures very close together – so usually
not appreciated separately

19. First heart sound
Soft
Rheumatic fever
Heart failure
Loud
Mitral stenosis
Anemia
Pregnancy
Variable intensity
Complete heart block
Atrial fibrillation

20. Second heart sound
Produced by closure of the semilunar
valves at the end of systole
Closure of the aortic valve (A2) occurs
before closure of the pulmonary valve
(P2)
A2-P2 can be heard as a split and this is
wider during inspiration

21. Second heart sound
Wide split
Pulmonary stenosis
Pulmonary hypertension
Right bundle branch block
Wide and fixed split
Atrial septal defect
Reversed split (paradoxical split)
Severe aortic stenosis
Hypertrophic cardiomyopathy
Loud P2
Pumonary hypertension

22. Third heart sound
Low frequency sound in early diastole
Due to rapid filling of the ventricles
S3
May be normal (physiologic)
Ventricular dysfunction
Pregnancy, anemia
Left to right shunts

23. Fourth heart sound
Low frequency sound in late diastole
Due to filling during atrial systole
S4
May be normal in older individuals
LV S4 – aortic stenosis, systemic hypertension, coronary
artery disease
RV S4 – pulmonary stenosis, pulmonary hypertension

24. Murmurs
A series of vibrations arising from the
turbulent flow of blood across valves or other
openings
Systolic – after S1 and before S2
Diastolic – after S2 and before S1

25. Murmurs
Systolic murmurs
Normal (innocent murmur)
Ejection across semilunar valves - pulmonary stenosis,
aortic stenosis
Regurgitation (leak) across atrioventricular valves –
mitral regurgitation, tricuspid regurgitation
Ventricular septal defect
Diastolic murmurs
Always abnormal
Aortic or pulmonary regurgitation
Mitral or aortic stenosis

26. Murmurs due to valve disease
Systolic Diastolic

27. Basics of ECG

28. ECG
Electrical field generated by heart that is
recorded on body surface
Three bipolar limb leads (I, II, III)
Three unipolar limb leads (aVR, aVL and aVF)
Six unipolar precordial leads (V1 – V6)

29. ECG – waves and intervals

30. Heart rate
Can be calculated by measuring interval
between two beats (small square = 0.04
seconds, large square = 0.2 seconds)
Shortcut – 300 divided by number of large
squares between two beats
Normal adult rate between 60 and 100 bpm

31. P wave
Atrial depolarization
Tall P wave – Right atrial enlargement
Broad P wave – Left atrial enlargement

32. QRS complex
Ventricular depolarization
Broad QRS
Bundle branch blocks
Ectopic rhythms (Ventricular tachycardia,
ventricular pacing)

33. T wave
Ventricular repolarization
Tall T waves – Hyperkalemia
T inversion – Coronary artery disease

34. PR interval
AV conduction
Prolonged PR interval – First degree AV
block
Short PR interval - Preexcitation

35. QT interval
Ventricular repolarization
Prolonged QT interval
Congenital long QT syndrome
Acquired long QT - drugs

36. ECG in coronary artery
disease
Most important clinical use of ECG
ST segment shifts identify ischemia and
infarction
Q waves indicate old infarction

37. ECG in coronary artery
disease