G3iii: Draw and label LA pressure curve. Label physiological factors which affect LAP and explain their effects

  • LA is in series w pulmonary circulation & LV
  • Blood flows in from pulmonary circulation → through MV → into LV
  • Factors affecting all these:
    • LA filling
    • LA compliance
    • LA emptying
    • Ventricle emptying

C = ∆V/P

∴Compliance & blood volume will also contribute to LAP

  • Normal LAP = 0 – 8mmHg (RAP = 0 – 5mmHg)
Pressure
ACV

LA Filling

  • Posture = upright = ↓VR = ↓LAP
  • Intrathoracic P = +ve (IPPV / expiration) = ↓VR = ↓LAP
  • Venous tone = high = ↑VR = ↑LAP
  • Blood volume = high = ↑VR = ↑LAP

LA Compliance

C = ∆ V / P

  • ↓Compliance for same volume = ↑LAP
  • Infarction = scar tissue = ↓C
C

LA Emptying

LV Compliance

    • ↓ compliance = ↓ pressure gradient =
      1. Pressure filling (↑LAP)
      2. ↑work of atrial contraction (↓LAP)

MV Size

  • Mitral stenosis = ↓valve SA = ↓R to flow
  • ∴↑work (=↑LAP)

MV Compliance

    • Regurg = ↑LA blood volume =
      1. ↑LAP
      2. Dilates LA

Atrial Contraction (1/5)

  • Absence (AF) = ↑LA vol = ↑LAP (1/5 of LA filling)

Ventricular Emptying

  • ↓ventricular emptying = ↑back pressure = ↑LAP → because they’re all in series
  • AoV competence: aortic regurg = ↓LV emptying = ↑LV ESV = ↑LAP
  • AoV size: stenosis = ↑LV work + pressure = ↑LV ESV

                                 = ↑diastolic filling P = ↑LAP

  • LV contractility = ↓contractility = ↑LV ESV
    • = ↑diastolic filling P
    • = LAP
  • Effect of afterL by IPPV → ↑intrathoracic P = transmural P = ↓wall tension = ↓afterL = ↓LV ESV = ↓LAP