Cardiac Function

  1. Sequence of events in the cardiac cycle
    Atrial systole, Isovolumetric Contraction, Rapid ejection, Reduced ejection, Isovolumetric relaxation, Rapid filling, reduced filling
  2. Pressures and Valive sequences in the RV
    • Lower pressures S/D = 18/4 (18/0)
    • Pulmonary artery S/D = 18/12 mean=15mmhg
    • R artrium a/v = 5/4 mean=3
    • RV pumps only through the pulmonary circulation
    • RV valves open sooner and close later due to differences in electrical activation and pressures
    • Pulmonary artery valve closure becomes longer during breathing-get splitting of the second heart sounds
  3. Cardiac Output
    • CO=HR*SV
    • =HR*(EDV-ESV)
    • Preload/EDV depends on HR (time for filling), muscle movment (increased venous return), blood volume and blood pressure (eg position could be a factor)

    Afterload/ESV modulated by length of cardiac myocytes and inotropic state of the heart (Can be effected by HR due to changes in Ca2+ balance)
  4. HR effects on CO
    Acts directly and indirectly via determinants of SV-particularly preload and inotropic state
  5. Ventricular-Pressure-Volume Loop
Card Set
Cardiac Function
Cardiac function