Anatomy

CLASSICS IN THORACIC SURGERY

Leonardo da Vinci and the Sinuses of Valsalva Francis Robicsek, MD The Carolinas Heart Institute, the Heineman Medical Research Laboratory, and the Carolinas Medical Center, Charlotte, North Carolina

Recent studies indicate that eddy currents generated by the sinuses of Valsalva play an important role in the physiologic closure of the aortic valve. This process is briefly discussed and evidence is presented that this fact was well known and elaborated upon by the renaissance artist Leonardo da Vinci. This fact is illustrated with his words and drawings.

(Ann Thoruc Surg 1991;52:328-35)

God geornetricizes Leonardo da Vinci

he semilunar valves, in contrast to atrioventricular T valves, have no direct attachment to the myocar- dium; therefore, their function is generally thought to be entirely passive responding to fluctuation of the pressure between the left ventricle and the aorta. Whenever the pressure generated by ventricular systole exceeds that reigning in the thoracic aorta, the aortic valve opens; whenever the left ventricular pressure decreases to less than the pressure in the aorta, the valve shuts. Recent research, however, indicates that this process, which occurs about 115,000 times a day, is far more complex. As has been demonstrated by Clark [1] and others [ 2 4 ] , although the leaflets are the most dynamic parts of the aortic valve, the motion of other associated structures such as the vascular wall and the expansion of the entire valve complex itself [ P 6 ] also play an important role. Even more important in aortic valve function than these factors are some particular features of the blood flow induced by the presence of ellipsoidal sacculations of the aortic wall, named after the great Italian anatomist, An- tonio Valsalva .

If one may ask a cardiac surgeon what the aortic valve consists of, the answer will likely be: “Three leaflets and three commissures.” The same inquiry directed to a physiologist would probably evoke a different response: “Three leaflets, three commissures, and three sinuses.” This emphasis on the functional significance of the si- nuses of Valsalva is becoming more and more clear to those who study circulatory dynamics, but is still not appreciated by those who perform reconstructive opera- tion at the aortic root.

The first scientific study in modern times on the role of these sinuses in the closure of the aortic valve was made by Henderson and Johnson [7], who demonstrated in hydrodynamic model studies that the closure of the aortic valve under pulsatile flow is not an abrupt event triggered by sudden drop in ventricular pressure alone but rather a

Address reprint requests to Dr Robicsek, Heineman Medical Research Center, PO Box 35457, Charlotte, NC 28235.

gradual process in the course of which during decelera- tion of flow the valve leaflets move gradually toward closure. These observations have received additional sup- port by van Steenhoven [&-lo], Peskin [ll, 121, Bellhouse [1>15], and their associates. In elegant experiments Bell- house constructed a rigid model of the aortic root with a flexible valve and perfused it with a pulsatile flow of water. The flow pattern was outlined by dye injection and recorded by serial cinematography. The principal obser- vations made in these studies were that after a rapid and full opening of the leaflets, some of the blood ejected from the left ventricle coils back at the sinus edge, then decel- erates, reverses its direction along the sinus wall, and forms vortices in the sinuses of Valsalva before it rejoins the mainstream of forward flow. He further stipulated that due to these eddy currents and deceleration, the pressure exerted at the lateral aspects of the leaflets exceeds that on their central surfaces and causes the leaflets to approximate even before the systole is com- pleted [14]. Because of this process only minimal reversed flow is required for final valve closure, and regurgitation does not occur (Figs 1, 2).

Nearly identical experiments were performed and sim- ilar conclusions were drawn by Leonardo da Vinci in 1513 (Fig 3).

Leonardo was not only a superb painter and sculptor, he also was a Renaissance man in the true sense of the word: an exceptional architect, a talented mechanical and hydraulic engineer, as well as the founder of functional anatomy. His heritage includes about 200 richly annotated anatomical sketches, all but a few now housed in the private collection of Her Majesty the Queen of England [161.

The lion’s share of Leonardo’s work on anatomy falls into two distinct periods. His earlier drawings were made about 1487 to 1493, mostly in Florence and in Milan. They show his preoccupation with the structure of the skull and the eye, which he called the ”window of the soul.” His later work began around 1506 and continued until his death in 1519 in France [17]. This period encompasses studies on other organs and is permeated with the recog- nition as to how mechanics relate to human physiology. His views as an architect-engineer opened a heretofore unseen functional perspective into the study of the hu- man body, which he regarded as a God-created structure ”which feels and moves” but also as an “edifice governed by the laws of mechanics” [18]. After comprehending function, Leonardo proceeded with attempts to enhance the same; he designed life belts and webbed gloves to enable man to swim better, and fabricated wings and parachutes to make him float in the air.

0 1991 by The Society of Thoracic Surgeons 0003-4975/91/$3.50

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Rene Laennec, 1781 - 1826 Inventor of the Stethoscope 80

In 1816, I was consulted by a young woman laboring under general symptoms of diseased heart, and in whose case percussion and the application of the hand were of little avail on account of the great degree of fatness. The other method just mentioned [direct auscultation] being rendered inadmissible by the age and sex of the patient, I happened to recollect a simple and well-known fact in acoustics, . . . the great distinctness with which we hear the scratch of a pin at one end of a piece of wood on applying our ear to the other. Immediately, on this suggestion, I rolled a quire of paper into a kind of cylinder and applied one end of it to the region of the heart and the other to my ear, and was not a little surprised and pleased to find that I could thereby perceive the action of the heart in a manner much more clear and distinct than I had ever been able to do by the immediate application of my ear.

Rene Laennec, August 1819 In the preface to, De l'Auscultation Médiate

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First stethoscope in the United Kingdom Brought from Paris in 1822 by Thomas Hodgkin Hodgkin’s Disease Displayed at Gordon Museum of Pathology, King’s College London

Normal Resting Values 6000 ml/min or 6.0 l/min = 75/beats/min X 80 ml/beat

Moderate Exercise Values 13.44 l/min = 120/beats/min X 112 ml/beat

Heavy exercise CO can be 18-30 l/min

Elite athletes CO can increase ≈ 700% to 40 l/min!!!!

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