Hemodynamic changes and atrial function
Normal hemodynamics begins with a pressure gradient. When the pressure in the atria naturally increases, blood rushes into the ventricles, filling their cavities. This process is crucial for preparing the heart for the subsequent powerful ejection.
By the end of atrial systole, baseline pressure values are established in the chambers. In the right ventricle, it reaches up to 5 mm Hg, whereas in the left ventricle this indicator is slightly higher — up to 10 mm Hg. At the same time, the blood volume in the ventricles increases to its maximum value. This indicator is called the end-diastolic volume (EDV) and is normally 125 ml.
Blood pressure in the left ventricle
On the cardiac cycle graph, left ventricular pressure is usually displayed as a dotted line (Curve III). This curve demonstrates the most significant and sharp pressure drops in the entire cardiovascular system.
Depending on the specific phase of the cycle (systole or diastole), pressure values in the left ventricular cavity can range from minimum values close to 0 mm Hg to a maximum of 120 mm Hg. It is this colossal differential that provides sufficient force to eject blood into the systemic circulation.
Aortic pressure dynamics
Aortic blood pressure (Curve I) reflects changes in blood pressure directly at the outlet of the left ventricle. Several key elements are distinguished on the graph, each corresponding to a specific mechanical event:
- Anacrotic wave — the initial phase of a steep pressure rise. It is formed during the active ejection of the stroke volume of blood from the ventricle.
- Catacrotic wave — the subsequent phase of pressure drop, when ejection is completed and blood is distributed through the vascular bed.
- Incisura — a characteristic sharp notch on the descending part of the curve. It strictly corresponds to the moment the aortic valve cusps close.
- Dicrotic wave — the so-called dicrotic rise of the wave. This small secondary pressure peak is caused by the elastic recoil of the blood mass from the freshly closed aortic valve.
Left atrial pressure
Unlike the ventricles and aorta, blood pressure in the left atrium (Curve II, often indicated by a dashed line) has no sharp spikes. The graph reflects only low-amplitude pressure oscillations. This is because the atria primarily function as blood reservoirs and conduits without generating powerful resistance and high pressure.
Briefly: answers to topical questions
What is the maximum systolic pressure in the right ventricle?
The maximum systolic pressure in the right ventricle normally reaches 15–30 mm Hg (while the ejection pressure into the pulmonary trunk is 25–30 mm Hg).
What phases and periods does ventricular systole include?
Ventricular systole includes two main periods, each divided into phases:
- Period of tension — consists of the phase of asynchronous contraction and the phase of isometric contraction.
- Period of blood ejection — consists of the rapid ejection phase and the reduced ejection phase.
What is the end-systolic volume (ESV) of the ventricles and what is its normal value?
End-systolic volume (ESV) is the residual volume of blood remaining in the ventricle after the completion of its contraction (systole). The normal value of end-systolic volume is 60 ml (according to graphs, it may be indicated at around 50 ml).
To memorize the elements of the aortic curve, use the mnemonic AKID: Anacrotism (upward), Catacrotism (downward), Incisura (notch), Dicrotism (rebound).
Class and exam questions
What is the end-diastolic volume of the ventricles?
Normally, the end-diastolic volume (EDV) is 125 ml. This is the maximum volume of blood before ventricular contraction begins.
What pressure is recorded in the ventricles at the end of atrial systole?
In the right ventricle, it reaches a maximum of 5 mm Hg, and in the left ventricle — up to 10 mm Hg.
What are the incisura and dicrotism on the aortic pressure graph?
The incisura is a notch indicating the moment the aortic valve closes. The dicrotism is the subsequent small pressure rise caused by the recoil of blood against the closed valve cusps.
What else to study on this topic
- Mechanisms of low-amplitude oscillations in the left atrium
- The relationship of anacrotism and catacrotism with the elasticity of the aortic wall
- Synchronization of pressure curves I, II, and III within a single cardiac cycle
- Physiological significance of the pressure gradient in the left ventricle from 0 to 120 mm Hg
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