In this chapter, I will attempt to explain why and how my interest in Leonardo’s anatomical studies has influenced me and to some extent my approach to work as a heart surgeon.¹

The interested reader of Leonardo’s notes cannot fail to be impressed with the scope of his work. Perhaps most impressive is the level of detail that he chose to pursue. It is clear that he demanded nothing less than a complete understanding of questions that interested him. As I showed in the preceding chapter, Leonardo was able to derive important and correct conclusions about the function of the heart without any significant prior knowledge, using only observation and reasoning. Two of the most exciting examples are his descriptions of aortic and pulmonary valve closure and the dual circulation to the lungs. The accuracy of this work has only recently been realised, as modern technology has caught up with the vision of Leonardo.

The relevance of these concepts is currently being incorporated into technologies used in modern surgery. Because Leonardo’s work was not published until the nineteenth century and still was ahead of its time, the contemporary medical and scientific fraternity remains largely unaware of this seminal work, which is almost 500 years old. It is immensely rewarding to introduce colleagues in our specialist areas of work to this knowledge. The structures that Leonardo chose to study in depth, such as the aortic root sinuses, are now recognised as having a functional importance that cannot be ignored in the reconstruction of these regions. Vascular replacement grafts are now available that have these sinus recesses built into them.

As explained in the last chapter, Leonardo described the elastic nature of the aortic root, the importance of which recently has been recognised with the development of stentless aortic valve replacement prostheses that are more able to expand in a way similar to the normal aortic root. These prostheses can better absorb the shock of the closure of the valve and dissipate this energy into the surrounding tissues, precisely as Leonardo described. The incorporation of this property into the treatment strategy is likely to lead to a longer life for these valves, although conclusive data have not yet been derived.

The importance of the new knowledge Leonardo revealed in these examples has taken us half a millennium to realise. Exciting as this is, perhaps the most interesting thing that I found was Leonardo’s intellectual methodology, which began to be revealed only with careful and repeated reading of his notes. It is this that really began to influence my own “style” of thinking. Indeed, it reinforced in me the importance of always being ready to see familiar structures with an open mind, thereby encouraging new ideas.² In particular, it has encouraged me to think more expansively about the structural and functional problems encountered in correcting heart valve disease.

Constant critical interrogation of his own ideas is one of the hallmarks of Leonardo’s writing, an approach that has informed me of how much can be achieved through a rigorous philosophical approach. Studying this use of rhetoric has led me to try to pursue a more pure understanding of the functional elements of the heart, particularly the mitral valve. Of course Leonardo’s rhetorical style is not unique to him but reflects the academic culture of the time. This culture of personal internal discussion, challenging one’s own accepted ideas, is something that is rarely taught in the modern medical education system. To find it used to such a powerful effect, revealing scientific truths that are relevant today, has left an indelible impression on me. His reasoning resembles Aristotelian syllogistic logic and other similar deductive processes, and as discussed in an earlier chapter, these logical manoeuvres were reintroduced into the intellectual culture of those times through the translation and dissemination of Arabic versions of ancient Greco-Roman texts.

In our own time, anatomical knowledge acquired during surgical training is necessarily didactic, and the utilisation of this knowledge is usually perfunctory. We use it in the same way that we use a map to reach a destination. However, as with a simple map, the relevance of the geography encountered on the journey is not considered. For example, a London taxi driver studying for “the Knowledge’ (the legendary test that London taxi drivers have to pass before being given their taxi driver’s license) learns the interconnectivity of streets and their locations and how to get from “point a” to “point b”. The driver does not need to know or understand the reason why a particular street has had to deviate from a direct course because of physical impediments such as a river or an excessively steep incline. And so it is in the use of anatomical knowledge in accomplishing a surgical procedure: It is predominantly used as a route map to be navigated successfully. It informs the surgeon what structures will be encountered and their relationship to one another—very important knowledge for safe completion of the procedure—but it does not encourage a continuing review of the impact of functional requirements upon structural appearance. Whilst establishing a safe practice in most cases, this scenario is also mind-numbing and is likely to inhibit new ideas and further attempts to reinterpret established assumptions.

I found that studious reading of Leonardo’s notes led me to a more challenging mind-set. Of course students of the classics and of philosophical thought would remind us that the intellectual tools of logic allied to a rhetorical dialogue are the engines of human development and are the currency of those disciplines. Sadly, the pressures of a surgical life (as in many other high-pressure careers) all too often stifle their use. The modern education system has moved away from the classical form in which these principles were the rules of academic engagement. I have found that through the charisma of Leonardo it is possible to introduce this more reflective form of thought to those who have never before had the luxury of being exposed to it.

To properly understand Leonardo’s work, a much wider education about his times is needed. This has led me to a very interesting reading list that is quite different from the reading of the average student of medicine. This personal re-education, allied with the comfort and confidence derived from significant surgical experience, began to encourage a more careful and thoughtful approach to my work. An experience of many procedures allows for a mental space in which the wider issues can be considered. It is this state of mind, coincident with a deepening interest in Leonardo’s work, that has led me to find great benefit in these studies.

Clearly Leonardo was well informed about the work of the giants of anatomy from a bygone age, such as Galen, Aristotle, and Hippocrates, but perhaps because he had a limited educational background and was not a physician who had to use his knowledge to intervene in the management of ­disease, Leonardo was able to pursue his anatomical studies with the innocent but inquisitive eyes of a child, for whom everything has an equal importance. His “looking” was informed by an extremely wide knowledge base in many subjects, however, and his attempts to explain the function of the structures that he found involved the use of basic rather than applied science—what today we would call “blue sky” research. His abiding and often-repeated principle that all forms in nature are forged by the forces that act upon them resulted in some accurate descriptions of complex cardiac function. This teleological style of thought is not endlessly rewarding, however, and many would argue that real advances are possible only if the scientific investigator looks beyond this concept. In trying to understand major biological structural forms, however, this form of logic can be very productive in furthering an understanding of complex structures working in a constantly adapting and stressful environment such as the working heart. We will return to this theme shortly.

It is intriguing to wonder why Leonardo undertook this work. In the context of his times, there was no reason for him to investigate the phenomenon of aortic valve closure. His study preceded the accepted date of the discovery of the circulation and complicated the contemporary explanation of the flux and reflux motion of the blood that Galen’s explanation demanded. Thus it is one of the earliest examples of academic research in a form that we instantly recognise today. It is experimental science, and it produced new knowledge for its own sake.

As we have seen, so much of his writing was exercising his understanding of the accepted ideas of the time, particularly the Galenic theory of blood flow. Perhaps his questions about the anatomy of the root of the aorta were fired by its very striking appearance. In the ox heart, this structure is dramatic. The aortic sinuses are particularly large and sit on top of the large muscular outflow tract of the left ventricle. The shape of this structure begs the question of why it is formed like that when the continuation of the aortic tube leading away from the heart is just a simple tube. The cross-sectional shape of this structure clearly brought to Leonardo’s mind his work on previous hydrodynamic settings. He was able to transpose the setting from the heart to the more abstract idea of a column of fluid flowing through a channel of this shape.³ From that point onwards, he would have been in comfortable territory that related to previous work done on rivers and other waterways.⁴ His manuscripts contain clear evidence that this recognition of parallel situations led Leonardo to utilise hydrodynamic principles to reach the correct interpretation of the mechanism of valve closure.

Using his hydrodynamic knowledge, Leonardo developed the hypothesis that these bulges (later known as the sinuses of Valsalva) give rise to vortex formation in the column of blood escaping from the ventricle, and that these vortices are instrumental in beginning the process of valve closure by unfurling the leaflets and pushing them towards each other. This conclusion is made all the more remarkable by the design of an elegant experiment that proved this hypothesis to his satisfaction.

As a consequence of studying Leonardo’s description of these vortices, I set out to try to produce images of them in the intact, functioning human heart. Using new computer software programmes written for advanced magnetic resonance imaging by Dr. Christophe Julie and his colleagues in Switzerland, we were able map the course of the blood flowing through the aortic valve, revealing the vortices as they formed in real time in the functioning human heart. This work has provided tangible evidence that these vortices exist in the intact human heart and not just in an experimental model and that they perform the function predicted by Leonardo about 1513. Furthermore, our studies have revealed that complex vortices form in all chambers of the heart during the normal cardiac cycle (Fig. 5.1).