1. The Cardiac Cycle & Heart Sounds Jennifer Kwan

2. DISCLAIMER Please note: audio files are not the best in terms of quality, but they are available for you to use with headphones.

3. Key principles Blood flow depends on pressure gradients Pressure gradient = a difference between 2 pressures Pressure gradients in the heart depends on contractile forces Blood pressure maintained by pumping of the heart

4. Pressure gradients: R atrium < R ventricle L atrium < L ventricle

5. Early diastole: atrial filling Ventricular relaxation Arterial pressure > ventricles = SL valves closed Ventricular pressure > atria = AV valves closed  Atrial filling and distension

6. Mid diastole: ventricular filling Atrial pressure > ventricles = AV valves open Blood returning from the veins flows passively from atria to ventricles 80% ventricular filling  SL valves are still closed

7. Late diastole: atrial contraction Contraction of atria Smaller volume within atria means ↑ pressure Forces more blood out of atria into ventricles Remaining 20% ventricular filling – end diastolic volume Ventricles stretched and distended (Starling’s Law)

8. Early systole: ventricular contraction Atria remain relaxed from now on Ventricles begin to contract Ventricular pressure > atria = AV valves closed *1 st heart sound*  Ventricles continue contracting but SL valves closed too Isovolumetric contraction

9. Late systole: ventricular contraction Isovolumetric contraction ↑ ventricular pressure rapidly Ventricular pressure > arteries = SL valves open Rapid ejection phase = pulse Ventricles still contracting so ventricular pressure still rises  AV valves still closed

10. Early diastole again Ventricles begin to relax Arterial pressure > ventricles = SL valves closed *2 nd heart sound* - end systolic volume  Ventricles continue relaxing but AV valves closed too Isovolumetric relaxation Arterial pressure maintained by elasticity

11. Cardiac cycle animated

12. Pressure changes c av

13. Heart sounds 1 st and 2 nd heart sound – “lub” and “dub” 3 rd heart sound common in children 4 th heart sound pathological Auscultation – turbulent blood flow not valve closure! Quality of 1 st heart sound = longer, lower pitch Quality of 2 nd heart sound = shorter, higher pitch “snap”

14. Heart murmurs Blood flow laminar = silent If it strikes obstruction, its flow becomes turbulent This generates abnormal heart sounds = murmurs In the heart, murmurs usually indicate valve problems (In children and elderly, murmurs can be physiological due to thin walls that vibrate with rushing blood)

15. Sites of auscultation

16. Valves Atrioventricular valves Semilunar valves

17. Valve problems Regurgitation – incompetent valves allow backflow of blood after supposedly closing Swishing sound Stenosis – valve less flexible, creating smaller opening that restricts blood flow High pitched click

18. Timing of murmurs PASS and PAID Pulmonary, Aortic Stenosis = Systolic Pulmonary, Aortic Incompetency = Diastolic Reverse for AV valves: (i.e. Mitral, Tricuspid stenosis = Diastole Mitral, Tricuspid Incompetency = Systole)

19. Effect of respiration on murmurs Inspiration – ↑ negative pressure in thorax, so more venous return – Accentuates right- sided murmurs: pulmonary & tricuspid Ask patient to breathe in, hold, then auscultate Expiration –  thoracic volume, so more blood pushed out of lungs – Accentuates left-sided murmurs: aortic & mitral Ask patient to breathe in, out, hold, then auscultate

20. Mitral regurgitation Systolic murmur As ventricle contracts, backflow through mitral valve Auscultate in axilla

21. Mitral stenosis Diastolic murmur As atrial pressure > ventricles, passive blood flow through small opening Auscultate 5 th IC space, mid- clavicular line Patient rolls to left Use bell

22. Aortic regurgitation Diastolic murmur As ventricle relaxes, arterial pressure > ventricles, backflow through aortic valve Auscultate 5 th IC space, left sternal edge Patient leans forward Breathe in, out, and hold

23. Aortic stenosis Systolic murmur As ventricles contract, forces blood through smaller aortic opening Auscultate carotids Use bell Breathe in, out, and hold

24. Thank you! Question time