Leonardo Was Right (Part 1): In the Spirit of the Heart Work of Leonardo

Leonardo da Vinci is the universal genius in history with the most unanimous agreement about his giftedness. In this blog article, it will be presented how his intracardiac pressure and hemodynamic discoveries were confirmed to be correct relatively recently. And with medical AI, scientific creativity in this cardiological field can flow anew, as a continuation of his Geist of incorruptible curiosity.

Among the near infinite areas Leonardo showed a profound interest, his unparalleled studies, in fact it was more than just an extreme fixation, about water flow and its dynamics. These led to one of his foremost discoveries about the anatomy of the heard, the intracardiac flows and the precisely and correctly denoted functionality of the heart valves. Some medical historians herald Leonardo’s intracardiac fluid dynamics and valvular mechanisms as his perhaps greatest anatomical discoveries. As recently as nine years ago in 2014 scientists would be able to confirm that Leonardo was right about what causes the tricuspid aortic valve to close.

His intricate observations about rivers and water flow were used to further understand haemodynamics. In one of his notebooks, he observed over seven hundred (700) phenomena in flowing water. Leonardo’s combination of scientific curiosity and artistic virtuosity has bequeathed to us aesthetic drawings of a whole array of anatomical angles, accompanied by notes which are based on practical experiments and intricately scientific observation. He had a long-lasting focus on spirals and curls, visible both in portraits and in his fluid dynamic drawings. The forces creating water eddies in a flowing current or hair curls in a portrait of a woman, or a sketch of his friends’ heads, were parallel in his world. He enjoyed in connecting patterns, and his sharp observations made him observe an unparalleled number of scientific areas hundreds of years before others; and stumblingly close to, e.g., Newton, Galileo and Darwin, to name a few. 1

Leonardo could for instance, study how water falls into a pond, how a water column reacts to various forces, how submerged water bubbles behave, and even build transparent anatomical models to study blood flow and its dynamics. In water he studied how bubbles pop at the surface and sharply observed that the eddies that begin on the surface are filled with air, and those with an origin within the water, are filled with water, and that those are more long lasting, since water within water has no weight. He made hundreds of such observations, then mirrored in haemodynamics, in art and engineering, e.g., in the attempt to divert the Arno. His curiosity went beyond the scientific necessity and went on into the obsession of a genius.

He studied what happens to water blocked by obstacles, subsequent diverted forces, vortices, percussions, impetus, curves and spirals. He understood the nature of waves, and tremors as he called some of them, understood how these propagate in a medium and concluded that sound and light travels in waves.

Leonardo’s superb analogy even transferred waves into emotions, also expressed in the Last Supper, where Jesus causes turbulence by announcing that one of them would betray him – the apostles, symmetrically grouped three by three on either side, all react individually. They form waves of depicted emotions around the epicentre of the harmony disturbing announcement.

One key sign of a great mind is the ability the change and modify the thoughts. Leonardo changed his mind about heart anatomy and fluid dynamics many times – adapting theory after experiment and experience, when they conflicted. Often, he considered several theories, as visible in the Codex Leicester, where we denoted on a large folio twelve parallel theories on river water dynamics. He studied how springs could transport water into rivers, the veins of earth, into the sea, when “logically” water should gravitate and stay at sea level – he eventually understood how the entire water circulation on earth depends on water evaporated from the surface into clouds, and how the same water vapor is also responsible for why the sky is blue. His open-mindedness, willingness to dismiss incorrect theories led him to the correct answers in medicine, geology, physics, and many other areas.2

Leonardo’s anatomical studies are more than just extensive, rather unprecedented. Not only did he draw muscles, nerves, vessels and organ correctly – he also did it aesthetically, artistically and accompanied the drawings with dense and precise commentaries, denoting a deep understanding on function. His anatomical dissections, more than thirty full bodies were autopsied into every minute detail during his career, often taking so long than they started to severely decompose before he was finished. He completed the dissections with parallel studies in a whole array of animals, and also increased his understanding of functional anatomy with his intense studies of live humans. For instance, he could note how all the muscles around the mouth interacted to form various grimaces, and which muscle combinations where not possible – this was then translated into his paintings, which always depict anatomically correct and realistic expressions, and made him fine tune every hint of expression. Leonardo presented the first scientific analysis of the human smile, at the time when he also worked on the Monalisa.

The Heart

On Leonardo’s many pages covering heart anatomy is a section with drawings depicting the papillary muscle, accompanied with a description how it shortens and elongates when the heart beats.

Among Leonardo’s anatomical work his most sustained and successful scientific endeavours is the section encompassing the human heart. He entered the area with already masterful understanding of hydraulic engineering and a in depth fascination of fluid dynamics. This made it possible for him to make discoveries, neither fully understood, nor appreciated for centuries. In the medical science of the early1500s, the understanding of the heart was not more developed than what described in the 2nd century CE by Emperor Marcus Aurelius medical advisor Galen of Pergamum. Galen’s work was revived during the Renaissance and taught that the heart was not just a muscle, but made of a special life force driving substance, and that blood was made in the liver and distributed through the venous system. The heart’s produced vital spirit was distributed through the arteries. Veins and arteries were considered separate systems – no circulation was understood – rather it was believed the blood pulsed back and forth in both systems. Leonardo was among the first to understand the heart was the centre of the blood circulation, Although he was not able to dismiss the Galenian theory of the blood being pumped back and forth – the manifest theory of the time, and a very unusual case where Leonardo may have been blinded by contemporary book learning. Normally he would only base his believes on experiments; the full concept of blood circulation is a rare example of partial failure. A full explanation of the blood circulation would come with William Harvey a century later. But Leonardo was correct in nearly all other observations in this field. All the veins and arteries arise from the heart, in one of his anatomical notebooks.3

He accompanied the statement with minute drawings of how the vessels on both sides become smaller the farther away from the heart they were – he was the first to depict this, with splitting into invisible capillary level. Leonardo debunked Galen’s idea that the heart would be made of a special vital tissue but is rather a muscle. He was able to demonstrate how the heart, like all muscles, has its own blood supply, with own arteries and veins, and nerves. He also showed that Galenic medicine had wrongly believed there where only two ventricles – Leonardo showed there were four cavities: two lower and two upper ventricles. He reasoned that since these ventricles were separated with membranes and valves, they must have different functions.

Driven by his trademark curiosity to figure out how the four ventricles worked, he performed a dissection on a pig, which heart was still beating. He noted that the lower and upper ventricles opened at different times.

The Aortic Valve

Among all Leonardo’s anatomical contributions, his perhaps greatest is understanding of the functions of the aortic valve. His findings were confirmed to be correct in the 1960s. Contributing to his conclusions was his love and fixation for water eddies, swirls, spirals, studies of flowing liquids, cascades, hair curls and wind turbulences.

All this knowledge was used to analyse how blood in the Sinus Valsalva, a portion of the aorta, created fluid turbulent phenomena such as spirals and swirls, closing the valve in a beating heart. His profound analysis of hundreds of words and over twenty detailed and aesthetic drawings fill six full pages in this anatomical notebook. He described the swirls with mathematical equations, among other Fibonacci numbers.

Leonardo had spent years studying fluid dynamics. Around 1510 he studied how water in a pipe behaved when entering a tank. He noted the phenomenon called fluid drag, i.e., the water on the sides flows slower than the water in the middle. The reason for this is rubbing, or friction, against the pipe walls, or the riverbanks. This causes slowing of the flow, a slowing which is continuous so that the central string of water has the highest fluid speed.

When the pipe or river water enters a tank or a pond, the speed differences cause eddies and whirlpools. He noted all types of fluid phenomena associated with vortices, whirlpools and eddies, and also analysed what happens to the fluid when the passed surface is curved or when the width is narrowing or widening. He used these findings to understand cavitation and erosion of coasts, or how blood is pumped out of the heart. His conclusions are also to be found when applied to his artwork, e.g., background landscapes with rivers.

Leonardo eventually paid a lot of attention the triangular opening in the upper portion of the heart, where the blood is pumped out into the radix aortae. He noted that the central stream of the upward directed flow would reach much further, than the blood on the sides. Further he analysed how spiral eddies were formed, when the more rapid central blood flow enters the blood portion which is already in this wide initial portion of the aorta. This section is also called the sinuses of Valsalva, after Antonio Valsalva who described this aortic section in the 18th century, i.e., hundreds of years after Leonardo, who kept most of his discoveries to himself.

Closing Procedure of the Aortic Valve

The swirls per se caused by the blood pumped up into the root of the aorta has the effect that the three leaflets, i.e., the triangular shaped cusps of the tricuspid valve to spread out and cover the opening. It works exactly as when wind swirls fill a triangular sail on a boat and stretches out the corners, Leonardo noted with his typical sense for universal analogy. The revolving blood hits the sides of the valves and closes them so that no blood can descend back into the left chamber. The eddies caused by the next heart then opens the valve. Leonard understood the functions of the cords that open and shut the two sails. He used the word sails in his explanatory texts.

The common view among nearly all cardiologists until the 1960s, was that the aortic valve was closed from above when an exact blood volume had been pumped up into the arcus aortae and then attempted to drop back. This is the commonest modus operandi of nearly all other types of valves – they close upon the swing of the flow. In this way however, the aortic valve would not be closed in a sufficient manner. In the heart it is not the pressure of the blood in the aorta which closes the aortic valve. The amount of blood which tries to regurgitate, under normal conditions, when the heart valves open, is not the blood which closes the valves. Leonardo noted this would be impossible, since it would mean that a high-pressure wave of blood would forcibly beat at the folded and wrinkled heart valves, which would crush the membranes. Leonardo even depicted how the valve would collapse if faced with aortic pressure from above.

Based on analogies from his experience on air and water flow, with its eddies, spirals and vortices, he formed a hypothesis about the aortic valve, and designed an experiment to test it.

He casted glass model of the heart and surrounding vessels, and was able to observe how, as he predicted, the blood would swirl and spiral into the aorta. With a bull’s heart as model, which he filled with wax, he was able to artistically cast a glass model of the heart, vessels and valves. He used the same sculptural techniques he had used for artwork and for the brain model he made of a cow’s brain, where also the cerebral ventricular system was modelled with wax. To make the intracardiac flow more visible he used water with an even distribution of grass seeds.

In the 1960s a team of medical scientists, Bellhouse et al,4 used a glass model, traceable dye and radiographic imaging and could confirm Leonardo’s explanation. The researchers revealed that a perfectly balanced fluid dynamic mechanism moved away the cusps from aortic wall, i.e., the most minute reversed flow closed the valve – they concluded that the swirls and vortices in the radix aortae, which Leonardo had observed 450 years earlier, were the phenomena responsible for the aortic valve closure. The blood swirl produces a push on the aortic valve sinus’ walls and on the valvular cusps – causing a synched and stable closure, exactly as Leonardo had explained.5

In 1991 a Carolina Heart Institute team concluded that Bellhouse’s experiment was nearly a copy of Leonardo setup. As late as 2014 an Oxford team confirmed Leonardo’s theory with an experiment performed in a living human using magnetic resonance imaging (MRI).

As a summary – systolic vortices in the sinus of the aortic valve closes the valve, eventually confirmed in vivo using MRI, AI, computers and the latest technique in medicine of the 21st century.

Leonardo’s Notes on Heart Fluid Dynamics

Leonardo’s anatomical notebooks are full of passion and precision revealing almost more about his personality, than about science. In other words, there is more detail to it than necessary to explain his findings, and the text is more precise and artistically beautiful than “required” for a scientific publication. In essence, there is abundant evidence of a thriving, unhindered and curious universal genius.

On the recto face of image 1 Leonardo depicts a bovine heart, including the major vessels and parts of the respiratory system with the tracheal cartilage and bronchial tree. The drawings are, as always, accompanied by richly explaining texts, here on the interactions and actions of respiration vs. the heart. Most of his depictions were made on an ox. The image depicts the heart and vessels from a posterior view. He clearly depicts the sinus coronarius and ramus circumflex branch of arteria coronaria sinistra, in the posterior left atrioventricular groove, with the middle cardiac vein and posterior interventricular artery descending in the posterior interventricular groove. Leonardo draws how the bronchi are branched, and how their C-shaped cartilaginous tubes decrease down to smaller and smaller bronchi. He shows the correct patterns of surrounding veins and arteries in the respiratory tract, including the bronchial arteries originating from the aortic arch. It can be noted Leonardo used the trachea to any air passage in the respiratory tract.6

For instance, Leonardo’s extensive notes on cardiopulmonary phenomena, he answers to the then conundrum of how we breathe, under the headline, whether air penetrates into the heart or not in this passage:

To me it seems impossible that any air can penetrate into the heart through the trachea [ie. bronchi], because if one inflates [the lung], no part of the air escapes from any part of it. And this occurs because of the dense membrane with which the entire ramification of the trachea is clothed. This ramification of the trachea as it goes on divides into the most minute branches together with the most minute ramification of the veins which accompany them in continuous contact right to the ends. It is not here that the enclosed air is breathed out through the fine branches of the trachea and penetrates through the pores of the smallest branches of these veins. But concerning this I shall not wholly affirm my first statement until I have seen the dissection which I have in hand.7

Leonardo changed his mind several times, all depending of experimental outcome. At first, he did not support the traditional belief of air passing from the lungs into the heart, which he though illustrates on the ventral side of image 1 – here air mixes directly with blood anywhere in the cardiopulmonary system. His skepticism was based on his form belief in experiments, and he often held a provisional hypothesis, as a genuine scientist should do. Four lines from the bottom of the image, Leonardo could have given us a correct rendering of the gaseous exchange in the alveolar membrane. But still, he kept the word not in his text.

Image 1: Leonardo da Vinci (Vinci 1452-Amboise 1519). The heart, bronchi and bronchial vessels (recto); A sketch of the heart and great vessels (verso) c.1511-13.8

In image 2 Leonardo depicted the heart valves and the internal blood flow. He also describes how he used wax to form a mold, with which he cast a transparent glass model of the heart, including the aortic valve. He even presents a diagram in the upper right corner with a mould of gypsum for blowing up inside with thin glass… But first pour wax into the gate of an ox’s heart so that you may see the true shape of the gate. With this simple and ingenious experiment, he noted the widening just superior to the aortic valve, i.e., the aortic sinus. On the versal side he wrote that he could see in the glass what the blood does in the heart when it closes the little doors of the heart.

Image 2: Drawing by Leonardo of the aortic valve, circa 1512-13.9


In 2019, five years after Oxford team’s ultimate in-vivo confirmation of Leonardo’s explanation of the fluid dynamics and intracardiac pressure circumstances, and 500 years after his heart drawings and texts, emerged the AI-empowered concept of wireless, non-invasive, intracardiac pressure monitors (ICPM).

After half a millennium medical science, empowered with artificial intelligence, is ready to move on with intracardiac pressure and fluid dynamics, where Leonardo left us.

With non-invasive intracardiac pressure monitors we will be able to optimise heart failure treatment, amplify resources and widen our understanding and satisfy our creative curiosity – all in the spirit of Leonardo.

1. Walter Isaacson, Leonardo da Vinci, Simon & Schuster, 2017


2. Leonardo da Vinci; Edard MacCurdy (translator), Ladislao Reti (translato); Charles Nicholl (intro), The Notebooks of Leonardo da Vinci in 3 volumes, Folio Society, London, 2009


3. Leonardo da Vinci; Edard MacCurdy (translator), Ladislao Reti (translato); Charles Nicholl (intro), The Notebooks of Leonardo da Vinci in 3 volumes, Folio Society, London, 2009


4. Bellhouse, B., Bellhouse, F. Mechanism of Closure of the Aortic Valve. Nature 217, 86–87 (1968).


5. Boon B. Leonardo da Vinci on atherosclerosis and the function of the sinuses of Valsalva. Neth Heart J. 2009 Dec;17(12):496-9.


6. Frank Zöllner, Johannes Nathan, Leonardo Da Vinci. Obra Gráfica, Bibliotheca Universalis, 2014


7. M. Clayton and R. Philo, Leonardo da Vinci: Anatomist, London 2012


8. Image 1: Recto: Pen and ink on blue paper. Verso: Black chalk on blue paper | 28.8 x 20.3 cm (sheet of paper) | RCIN 919071. Provenance: Bequeathed to Francesco Melzi; from whose heirs purchased by Pompeo Leoni, c.1582-90; Thomas Howard, 14th Earl of Arundel, by 1630; probably acquired by Charles II; Royal Collection by 1690.


9. Image 2: Pen and ink on blue paper | 28.3 x 20.4 cm (sheet of paper) | RCIN 919082. Provenance: Bequeathed to Francesco Melzi; from whose heirs purchased by Pompeo Leoni, c.1582-90; Thomas Howard, 14th Earl of Arundel, by 1630; probably acquired by Charles II; Royal Collection by 1690.


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