The da Vincian Cardiovascular System

FRANCE — Did you know that, long before anyone else, Leonardo da Vinci called into question Galen’s description of how the heart works?

This is just one of the many interesting tidbits featured in “Leonardo da Vinci and Anatomy, the Mechanics of Life,” an exhibition that runs until September 17 at the Château du Clos Lucé — a home once owned by da Vinci — in Amboise.

In his book about this exhibition, Jean-Jacques Monsuez, MD, a cardiologist at Paris’ René-Muret Hospital, noted, “For a long time, very few people knew about Leonardo’s observations on the cardiovascular system’s anatomy or his rather physiological analysis of its hemodynamics. Had this not been the case, his work would, very likely, have had a significant influence on the subsequent development of knowledge about the cardiovascular system.”

A Visionary View

In the second century AD, Galen put forth the following novel theory: the liver transforms food into blood. The blood is carried through veins to the various organs and is sent to the right ventricle through ebb and flow and to the left ventricle through intraventricular pores [which, we now know, do not exist].

In the left ventricle, the blood mixes with air — “pneuma” — from the lungs and is transformed into vital spirits. Clear blood, enriched with vital heat, is then carried by the arteries to peripheral tissues.

This erroneous explanation of how blood circulates went unchallenged for hundreds and hundreds of years.

And then along came Leonardo, anatomy pioneer and experimenter extraordinaire. Around 1513, after looking more closely at the heart chambers and the aortic valve, he arrived at the belief that, contrary to Galen’s theory, blood flow starts in the heart, not the liver.

“The heart in itself is not the origin of life, but [simply] a vessel made of dense muscle vivified and nourished by an artery and a vein, as are other muscles.”

He arrived at this insight through his in-depth dissections and studies of pig, ox, and human hearts.

A vast number of folios came about, all dedicated to the functioning of the heart. Taking his lead from Galen and Avicenna, Leonardo started off by drawing two atria and two ventricles along with Galen’s intraventricular pores.

But he quickly moved in a different direction when it came to the question of what enables the heart to produce vital spirits from blood flow.

On a double sheet showing several views of an ox heart, he drew all the components — this time with the aortic valve both open and closed.

“The accuracy of the description of the aortic valve is impressive, considering that, in a normal subject, its surface is on the order of 3 cm²,” Monsuez noted.

But Leonardo went even further, explaining the sequence of the opening and closing of the valve. To complete his demonstration, he even used a model from one of his experiments. He took some water with a suspension of grass seeds and pumped it through a glass tube that had a bulge representing the aortic sinuses. He tracked the resultant flow and eddies that mimic the hemodynamics enabling the valve to open and close.

“Recently, Professor Choudhury’s team at Oxford took Leonardo’s sketch illustrating this ingenious description and superimposed it on the 4D-MRI image of systolic flow vortices. They confirmed that Leonardo was accurate,” Monsuez reported.

But Leonardo’s ideas about the heart didn’t stop there. The polymath also provided a description of cardiac contraction. This was based on observations he had made by watching the movement of spiles that had been driven into the hearts of pigs at a slaughterhouse. He made an ancillary diagram confirming his interpretation. “N, the firm muscle is pulled back, and it’s the first cause of the heart’s movement, for, thus pulled, it lengthens, and lengthening, it shortens.”

Leonardo was the first to explain the role of the atria. “The atria are the antechambers that receive the blood from the heart when it escapes from its ventricle from the beginning until the end of the pressure.”

In addition, he showed, for the first time, the round crown-like appearance of the heart’s vasculature. “The heart has its surface divided into three parts by three veins which descend from its base, of which veins two terminate the extremities of the right ventricle and have two arteries in contact below them […] the surface space of the heart enclosed within its arteries occupies half the surface circle of the thickness of the heart […].”

Finally, Leonardo was the first to give a description and sketch of a bicuspid aortic valve, as can be seen on a 500-year-old plate in the Royal Collection Trust.

Wealth of Knowledge

Because Leonardo’s discoveries about the cardiovascular system remained in the shadows, they did not factor into the thinking of physicians and surgeons during his lifetime or in the years that followed.

That is, until 1773, when Scottish anatomist Dr William Hunter found out that the collection of King Charles II of England contained folios on the human body — folios that were made by Leonardo da Vinci.

The world would have to wait until the 19th century for a complete facsimile edition of the collection kept at Windsor Castle.

This article was translated from the Medscape French Edition.

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