Phases of the Cardiac Cycle

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🌱 來自: Huppert’s Notes

Phases of the Cardiac Cycle🚧 施工中

Phases of the Cardiac Cycle

•   Diastole:

-   Atrial pressure > ventricular pressure → Tricuspid and mitral valves open → Filling

-   Contraction: Atrial pressure < ventricular pressure → Tricuspid and mitral valves close → S1

•   Mitral valve snaps before the tricuspid valve because the LV contracts first (but normally heard as just one sound)

•   S1 is loudest at the apex (fifth intercostal space, mid-clavicular line)

•   Systole:

-   ↑Ventricular pressure in isovolumetric contraction until ventricular pressure > pulmonary artery/aortic pressure → Pulmonic and aortic valves open → Ejection

-   End of ejection: Ventricular pressure falls → Pulmonic and aortic valves close → S2

•   Aortic sound occurs before the pulmonic sound because the aortic pressure is higher

•   S2 is loudest at the base (upper sternal border)

•   “Split S2”: The close of the aortic valve (A2) and the close of the pulmonary valve (P2) are not synchronized and become wider during inspiration (i.e. widened A2P2) because ↓intrathoracic pressure → ↑Venous return → Longer RV emptying time → Pulmonic valve closes later → P2 comes later