cardiac cycle

• Phases of cardiac cycle

  • Atrial systole
  • Atrial diastole
  • Ventricular systole
  • Ventricular diastole

  
• Ventricular systole


  1. Isovolumetric contraction

  2. Rapid ejection

  3. Slow ejection

  
• Ventricular diastole


  1. Isovolumetric relaxation

  2. Rapid filling

  3. Slow filling (Diastasis)

  4. Filling due to atrial systole
• Normal volume of blood in ventricles

  • Atrial systole pushes final 20-25 ml blood (20%)
  • After atrial contraction, 110-120 ml in each ventricle (end-diastolic volume)
  • Contraction ejects ~70 ml (stroke volume output)
  • 40-50 ml remain in each ventricle (end-systolic volume)
  • Fraction ejected is ~60% (ejection fraction)
• Stroke volume (SV)


  Volume of blood ejected by each ventricle in a beat
• Ejection fraction (EF)


  Fraction of blood pumped out of the ventricle with each heartbeat
• Arrhythmia


  Abnormal heart rhythm
• Types of arrhythmia


  • Bradycardia (heart rate too slow, less than 60 bpm)
  • Tachycardia (heart rate too fast, more than 100 bpm)
• Effects of tachycardia


  • Reduces stroke volume and cardiac output
  • Decreased ventricular filling time
  • Impaired synchrony and effectiveness of ventricular contraction
• Jugular venous pulse (JVP)

  Pressure change in atrium directly reflected in internal jugular veins
• Jugular venous pulse waves

  • a-wave (atrial systole)
  • C-wave (isometric ventricular contraction)
  • V-wave (late ventricular systole/protodiastole)
  • X-wave (downward displacement of AV valve)
  • Y-wave (opening of AV valve)
• Auscultatory areas


  Areas of the precordium where heart sounds can be heard
• Heart sounds


  Vibrations produced by closure of valves or flow of blood

  
• Heart sounds


  • First heart sound (S1)
  • Second heart sound (S2)
  • Third heart sound (S3)
  • Fourth heart sound (S4)
• First heart sound (S1)

  Due to closure of both atrioventricular (AV) valves, low pitched, soft sound "LUBB", duration 0.15s, frequency 25-45Hz, auscultatory areas - Apical (Mitral) & Tricuspid area, coincides with isometric contraction phase, peak of R wave in ECG
• First heart sound (S1)

  • Mitral valves normally no splitting, Splitting - Right Bundle Branch Block, Left BBB - reverse splitting
• Second heart sound (S2)

  Due to sudden closure of both semilunar valves, higher pitched, sharp sound "DUBB", duration 0.12s, frequency 50Hz, auscultation area - Aortic and Pulmonary area, coincides with onset of ventricular diastole, preceded/coincides or follows T wave in ECG
• Third heart sound (S3)

  Caused by vibrations in the ventricles during early rapid ventricular filling phase, soft, low pitched sound, duration 0.1s, frequency 20Hz, not regularly heard in normal adults except in children, important sign of cardiac failure
• Fourth heart sound (S4)

  Also called atrial sound, produced during atrial contraction, very low-pitched, not heard normally, heard when ventricles are stiff or non-compliant, preceded by P wave in ECG, mostly pathological
• Heart murmur


  Abnormal or unusual sound produced in the heart, caused by audible vibrations due to increased turbulence from accelerated blood flow, normal blood flow through narrowed/irregular orifice, or backward flow through incompetent valve, septal defects or shunts
• Types of murmurs


  • Systolic murmur
  • Diastolic murmur
  • Continuous murmur
• Systolic murmur


  Occurs between S1 and S2, associated with ventricular systole and ejection, can be divided into 4 subtypes based on timing
• Systolic murmur of aortic stenosis

  Blood ejected from left ventricle through small fibrous opening of aortic valve, causes nozzle effect and turbulence, resulting in loud murmur during systole
• Systolic murmur of mitral regurgitation

  Blood flows backward through mitral valve into left atrium during systole, causes high-frequency "blowing," swishing sound

  
• Diastolic murmur


  Occurs after S2 and before S1, associated with ventricular relaxation and filling, can be divided into 2 subtypes based on timing
• Diastolic murmur of aortic regurgitation

  Blood flows backward from high-pressure aorta into low-pressure diastolic left ventricle, causes "blowing" murmur of relatively high pitch with swishing quality
• Continuous murmur


  Murmur that begins in systole and continues without interruption through S2 into all part of diastole without change in character