Author + information
- Spencer B. King III, MD, MACC, Editor-in-Chief, JACC: Cardiovascular Interventions∗ ()
- ↵∗Address correspondence to:
Spencer B. King III, MD, MACC, Saint Joseph's Heart and Vascular Institute, 5665 Peachtree Dunwoody Road NE, Atlanta, Georgia 30342
Clinicians are comfortable interacting with patients and performing interventional procedures, and many have become comfortable with interpreting clinical trial results, although not everyone speaks the language of statistical methods. When it comes to pre-clinical investigations or basic science principles, the number of clinical practitioners who are knowledgeable in the concepts becomes much smaller. Scientists and engineers outside of the clinical fraternity also have a hard time relating to some aspects of medicine that are important for patient care. Nonetheless, much is to be gained from struggling to understand what is going on in seemingly unrelated fields. Often the best insights come from questions originating from naivety.
I was reminded of a teaching course that Willis Hurst had organized in 1980, which started in Greece and continued on a ship traveling throughout the Eastern Mediterranean. We were giving talks on the ship to the 50 or so enrollees using suitcases full of old 35-mm slides. I was discussing the hemodynamics of valvular heart disease and had become impressed by the insightful questions coming from an older attendee. One day I asked him where he practiced medicine. “Oh, no. I am not a doctor,” he said. “I am a plumber.” Yet, his questions about fluid dynamics were better than those of the clinicians.
Now that I am reducing my clinical activity, I have enjoyed working with a biomechanical group composed of clinicians and scientists from Emory, headed by: Habib Samady, Chief of Interventional Cardiology; Bill Gogas, who joined us from Rotterdam to concentrate on bioabsorbable technologies; engineers from Georgia Tech; as well as biomathematicians from Emory led by Alessandro Veneziani. The subject of blood flow and the resultant shear forces generated, as they relate to endothelial function, plaque development, and the ultimate rupture of plaque, turns out to be a complex subject that is way outside of my comfort zone, but it is a very interesting one. Don Giddens, formerly head of both aerospace and biomedical engineering and dean of engineering at Georgia Tech, is the senior member of the group of engineers. The concepts of aerospace engineering have many similarities to computational fluid dynamics that are the subject of our studies. However, it is not the metal fatigue of airplane components, but instead, site-specific shear forces inside of coronary arteries that we are focused on. The group and others have published interesting findings on the impact of extremes of wall shear stress on plaque development and composition, much of which is mediated by endothelial function and blood component interactions (1–3). Coronary stents have provided a model for understanding the impact of altered shear on vascular function, but have also created a real need to utilize this understanding in the design of stents. With the advent of bioabsorbable stents, this need has intensified. The acute perturbation of flow by the fixed strut stents may be mitigated by the excellent longitudinal compliance of these devices. Using optical coherence tomography coupled with 3-dimensional special imaging of angiography, highly site-specific shear can be computed.
As I think about what any of this has to do with the clinical problems of patients with coronary artery disease, it occurs to me that we know a lot about the development of coronary plaques, although there is much more to learn, and the size (plaque burden) and the composition of plaque have important associations with clinical events; yet, we still cannot predict with accuracy which plaques will produce the dreaded cardiac event. I asked my engineering colleagues if there is a way to predict structural change in airplane components or bridge struts so that repairs can be accomplished before a disaster occurs. It seems that such pre-emptive repairs may someday be possible to interdict coronary disasters.
My challenge to these incredibly bright minds is to find ways to use our new tools, and those soon to be developed, to understand the solid mechanics that I am told are very important in vascular integrity, as well as the computational fluid dynamics that act on the site of a potential coronary structural failure. Sure, the biology of the vessel wall is important, and the platelets and thrombosis are important, but the mechanical forces that act on the vessel are also critical not only in progression of plaque growth, but also in that ultimate structural failure that precipitates the myocardial infarction.
In this age of bioabsorbable stents, scaffolds, and potentially, plaque sealing, the materials to repair the structural defects (the vulnerable plaques that are about to rupture) will be made available. Predicting where that failure will occur is a daunting challenge, but I am excited that scientists, engineers, and mathematicians, way outside of my comfort zone, have taken this on, and they are equally excited about the clinical implications of this work. Perhaps the systemic solution to atherosclerosis will be found, and we all hope so. But for interventional cardiologists, the curiosity of the plumber on the ship should be a lesson. We should never be uncomfortable leaving our comfort zone to ask the naive question.
- American College of Cardiology Foundation
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