Left ventricular pressure-time curve
See graph 20050607
Phases
Systolic phases
- Mitral valve closes
- Isovolumetric contraction
- Aortic valve opens
- Isotonic contraction (rapid ejection, then reduced ejection)
- Protodiastole
* Pressure falling just before aortic valve closes
Diastolic phases
- Aortic valve closes
- Isovolumetric relaxation
- Mitral valvle opens
- Rapid filling
- Diastasis (reduced filling)
- Atrial systole
Points to note
- a wave - Due to atrial contraction
- c wave - Bulging of MV into LA due to isovolumetric contraction of LV
- x descent - During rapid ejection, the shortening of LV pulls fibrous atrioventricular ring downwards, lengthening LA and increasing LA size
- v wave - Passive filling of LA against closed MV
- y desecent - Opening of MV and rapid filling of LV
- Incisura (the dicrotic notch) - Due to small retrograde flow at the end of ventricular systole hitting against the AV as it closes (kinetic energy of the reverse flow converted into pressure)
- [BL8:p75] Peak of the flow curve occurs where LV pressure curve intersect the aortic pressure curve
Other notes
LV filling
- 60% in rapid filling phase
- 10% in diastasis
- 30% in atrial systole
Difference in the elderly
- Isovolumetric contraction phase, pressure rise not as sharp
- Higher peak pressure during systole
- Lower heart rate
- Wave forms travel more quickly because of stiffer walls
Venous pulse
Except for the c wave, venous pulse pressure curve closely follows the atrial pressure curve