Left Atrial And Ventricular Pressure Throughout The Stages Of Diastole

The left ventricle’s (LV) variously arranged muscle fibers twist and contract during systole, storing potential energy as blood is ejected (imagine wringing water out of a towel). This stored energy is released in diastole: an energy-dependent myocardial relaxation divided into four phases.

  1. Isovolumetric Relaxation Time (IVRT): interval between aortic valve (AoV) closure and the beginning of LV filling
  2. Rapid Filling: mitral valve (MV) opens, blood suctioned into LV with the creation of flow vortices
  3. Diastasis: LV and left atrial (LA) pressures equalize limiting additional inflow
  4. Atrial Systole (“kick”): atrial contraction ↑ LA – LV pressure gradient promoting additional blood flow into the LV cavity (20-30% of stroke volume in healthy patients, up to 50% in poorly compliant LV).

Pressure gradients are important during diastole. If the LV is poorly compliant due to chronic hypertension, infiltrative disease, etc., there won’t be much of a gradient between the LA and LV. This, in turn, results in poor LV filling and a compromised stroke volume. Arrhythmias can compound the problem by eliminating the all-important atrial kick to drive more volume into the stiff LV. 👨🏽‍⚕️

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