In 2028 it is 400 years since Harvey published his groundbreaking work De motu cordis et sanguinis in animali.
He was the first to realise that blood was not produced in the liver and absorbed in target organs but instead that the blood circulates from arteries to the organs and through capillaries and veins back to the heart.
His work is considered a major breakthrough in physiology and is the foundation of our understanding of cardiac function and the role of blood circulation to the present day.
Over 400 years many eminent researchers, physiologists, physicians and physicists have built upon his work expanding our knowledge of blood circulation in human health and disease. Almost all the positions put forward in Harvey’s work remain unchallenged and valid in the present day.
However, Harvey may have been incorrect in his conviction that arteries only passively underwent the pressure wave from the heart and that all energy bringing the blood into motion was derived from the heart. Modern physiology shows that early during each heartbeat a short-lived contraction occurs in the smooth muscle layers of the arterial tree. This short-lived contraction amplifies and distributes the pressure from the heart contraction over the many branches of the arterial tree ensuring that blood is brought into motion throughout the body.
Nec crassities tunicarum arteriæ nobis imponat, facultatem pulsificam provenire à corde per ipsas tunicas.
Have you ever had difficulty explaining to your students what is the difference between the propagation of a pressure wave and the actual movement of blood? In Neuromon's CardioVascularSimulationApp 1.14 we have incorporated the animation of a single stroke volume being pushed forward along the arterial tree. The model demonstrates that the stroke volume moves considerably slower than the blood pressure wave. The effect of arterial acceleration can easily be demonstrated by turning it off or on.
One of the main changes with aging is loss of elasticity. Arteries contain fibrinogen as well as elastin. With aging elastin degrades and arteries become wider (dilatation) and longer (elongation). Dilatation causes a decrease of intra-arterial blood flow velocity and elongation causes kinking and coiling so typical during angiography or duplex investigations of the elderly.
For the interpretation of blood flow velocities within the middle cerebral artery it is crucial to take age into account. In Trancranial Doppler (TCD) machines sold by Compumedics DWL this has been achieved by introducing Z-scores. Z-scores express how many standard deviations a given measurement lies above or below the value expected for that age. Z-scores can be calculated for the different components of the flow velocity waveform: Sys1, Sys2 and D560. Together with heart rate they can be combined into a single radar plot.
The normal values underlying the calculation of Z-scores are published in the Journal of Vascular Ultrasound 2024.
Detailed waveform analysis of arterial blood pressure and blood flow to the brain reveals that the relation between these two may vary within the scope of a single heart beat. Increased intracranial pressure may severely impair diastolic flow whereas it may leave the first systolic peak or S1 largely unaffected. This peak S1 is hypothetically due to arterial acceleration (a brief peristaltic contraction in the body's conducting arteries). The differences in relation between pressure and flow translate to variation in the so called apparent resistance.
The working of the S1-PaR is demonstrated in Neuromon's cardiovascular simulation: S1-PaR explanation.
Read more in our publication published in Neuro Critical Care: an international collaboration between investigators in Brasil and the Netherlands.
During the first half of 2023 Neuromon has released new updates for its CardioVascularSimulation model: version 1.2 in January, followed by versions 1.3 in March, 1.4 in April 2023, 1.5 in May, 1.6 in July and 1.7 released January 2024. The latest model available on the AppStore for MacOS is version 1.14 published January 2026.
Apart from the well known model of hemodynamics, the model features a Patient Condition window and a Patient Monitor window. Also, the tilt table test is introduced, demonstrating the effect of hydrostatic pressure on blood distribution within the body. After assuming an upright posture and without cardiovascular reflexes active the blood supply to the brain rapidly becomes inadequate and the patient may lose consciousness. Repeating the manoeuvre with cardiovascular reflexes active prevents this unwanted effect. For educational purposes the effect of cardiac arrest is added to the more than 16 other scenario's, such as carotid occlusion, intracranial pressure elevation, respiratory failure etc. Also, in its latest release the model simulates how the stroke volume travels over the arterial tree and, thereby, demonstrates how the distribution of blood differs from the distribution of the pressure wave.
For an extensive documentation about the way the model works, what assumptions were made and which theories implemented, please consult: CardioVascularSimulation Documentation.