With the revelation this past week by the Boston Celtics that their forward, Jeff Green, will be operated on soon for repair of an aortic aneurysm, attention has been focused on this potentially catastrophic condition.
WHAT IS AN AORTIC ANEURYSM?
Simply put, an aneurysm is an area of a blood vessel where the vessel wall has become weakened. This weakening may occur from age-related degeneration of the tissues that make up the vessel wall, or as a result of inherited or congenital conditions at birth. Under the pressure of blood flow, the weakened area may cause abnormal stretching and thinning of the vessel wall, and consequent enlargement of the vessel diameter. This stretching and thinning process may ultimately lead to rupture of the vessel. When the vessel involved is a major artery, such as the aorta, rupture can have catastrophic effects. The difficulty with aortic aneurysms is that they very often cause no symptoms whatsoever (are asymptomatic) until the fateful day when they rupture. In a young man such as Jeff Green, the problem is almost certainly something he has had the potential to develop from birth. One of the more common genetically inherited causes of aortic aneurysm is a condition known as Marfan’s Syndrome. This syndrome is termed a disorder of “connective tissue”. Normal connective tissues are critical to the strength and integrity of many of the structures in the human body, including blood vessels, ligaments, tendons and the connective framework of fibers in muscles, capsules, cartilage, bone, adipose (fatty) tissue, and lymphatic tissue. In Marfan’s Syndrome, the connective tissues are not healthy at the cellular level, and have a tendency to degenerate at an abnormally accelerated rate. One of the characteristics of Marfan’s Syndrome is the tendency for those affected to be unusually tall, so, it is tempting to wonder if Jeff Green may be affected by the condition (his height is reported as 6′ 9″).
THE ANATOMY AND FUNCTION OF THE AORTA
The aorta is the “big Kahuna” of arteries in the human body, responsible for the distribution of freshly oxygenated blood to EVERY organ and living tissue, including the heart itself via the coronary arteries. Take a look at the following 3D medical animation of aortic anatomy and function to get a more graphic idea of how the aorta works.
ANATOMY AND FUNCTION OF THE AORTA
As is apparent from the above animated review, a rupture of the aorta anywhere along it’s length will result in a profound loss of blood flow to tissues and organs distal to (beyond) the rupture. The higher up (or more proximal) the rupture, the greater the adverse effect on blood flow (perfusion). Taking this concept to its logical conclusion, if the aneurysm is located at the root of the aorta at its origin in the heart, a rupture would result in a sudden cut-off of blood flow to the entire body. Following is a 3D medical animation of a rupture involving an abdominal aortic aneurysm.
RUPTURE OF ABDOMINAL AORTIC ANEURYSM
Pretty scary, isn’t it?
RUPTURE OF THE THORACIC AORTA AND CARDIAC TAMPONADE
As if interruption of blood flow to every organ in the body weren’t enough, there is another potentially life-threatening complication of aortic aneurysm rupture. The heart is enclosed by a membranous envelope called the “pericardial sac” or “pericardium”. This membrane serves to isolate the heart and coronary arteries from surrounding structures in the chest cavity (thorax), primarily the lungs. The pericardial attachment to the diaphragm also helps to stabilize and anchor the heart within the chest. Please take a look at the following 3D medical animation demonstrating the relationship of the heart, aota, and pericardium to get a better idea how this all works. Note especially that the first couple of inches of the aorta and its root are also enclosed by the pericardium.
ANATOMY OF THE PERICARDIAL SAC (PERICARDIUM) AND CARDIAC CHAMBERS
While the pericardium is rather elastic in nature, permitting expansion and contraction of the cardiac chambers (ventricles and atria), it clings relatively tightly to all surfaces of the heart, neither permitting fluid to exit, or enter, the sac. It follows, then, that an aortic aneurysm of the aortic root (or close to the root) will also be enclosed by the pericardium, and if the aneurysm were to rupture, the very brisk flow of bleeding (hemorrhage) from the point of rupture will be contained within the pericardial sac (hemopericardium). Although the pericardial sac is capable of considerable expansion over days or weeks if there is a slow accumulation of fluid within its margins, the rapid introduction of blood into the sac, such as occurs with a sudden rupture of an aortic aneurysm, very quickly exhausts the ability of the pericardium to expand. This results in an extremely sudden (paroxysmal) increase in the pressure within the sac, which is exerted on the cardiac chambers. If not relieved on an emergent basis, the increasing pressure on the ventricles and atria causes cessation of the heart’s ability to pump blood, with chamber action coming to a complete standstill (cardiac arrest or asystole). This dangerous phenomenon is known as “acute cardiac tamponade”. Following is a 3D medical animation that demonstrates how rapidly a rupture in the aortic root (such as may result from an untreated aortic aneurysm) leads to asystole. I produced this animation for a criminal case in which a rupture occurred from a knife blow, but the situation is virtually identical to what can happen with sudden rupture of an aortic aneurysm.
RUPTURE OF THE AORTA WITH ACUTE CARDIAC TAMPONADE
TREATMENT OF AORTIC ANEURYSM – ENDOVASCULAR GRAFT PLACEMENT
From the preceeding, it can be seen that early diagnosis and treatment of aortic aneurysm is essential (prior to rupture!). There are 2 approaches to treatment, both surgical. Aortic aneurysms that are located distal to (away from) the heart, particularly those located in the abdomen, may be treated with a low-invasive procedure known as an “endovascular graft”. In this procedure, the aorta is accessed through small incisions in the femoral arteries, through which a variety of instruments, including a collapsable graft, may be introduced. After positioning across the area of the aortic aneurysm, the graft is expanded to shore up the weakened area. As the old scholar said, “a picture is worth a thousand words”. I have extrapolated this maxim to animation – “an animation is worth a thousand words”. So please take a look at the following 3D medical animation that demonstrates how an endovascular graft works far better than any verbal description.
PLACEMENT OF ENDOVASCULAR GRAFT FOR ABDOMINAL AORTIC ANEURYSM
TREATMENT OF AORTIC ANEURYSM – OPEN SURGERY
Unfortunately, not all aortic aneurysms lend themselves to the relatively low-risk placement of an endovascular graft. Particularly aortic aneurysms that are located in the upper chest, close to the heart, or involving the aortic root, must be treated with an open procedure, where the chest cavity is opened. Moreover, many such cases also require that the heart be stopped during the procedure, and the patient place on a heart-lung machine (cardiopulmonary bypass). When working on, or in close proximity, to the heart, temporary cessation of the heartbeat provides a far easier environment for the operating surgeon. While the heart is stopped, the cardiopulmonary bypass machinery draws oxygen-poor blood from the patient’s venous system, adds oxygen back in, then returns the reoxygenated blood back to to the arterial system. Following is a 3D medical animation showing how cardiopulmonary bypass works.
Typically, patient’s undergoing open surgery will have the area of aortic aneurysm removed either partially or completely, and a synthetic graft sewn into place. As is clear, treatment of aortic aneurysm via the open surgery method is far riskier than endovascular graft placement, but relative to the often fatal prospect of an aortic aneurysm rupture, with death occurring either from hemorrhagic shock or acute cardiac tamponade, open aortic aneurysm surgery is yet another example of modern Medicine’s amazing life-saving and cutting edge capabilities.
JEFF GREEN’S AORTIC ANEURYSM
The news reports of Jeff Green’s particularly situation have been somewhat vague as to the precise nature of his aortic aneurysm. The Celtics are apparently doing a great job so far of protecting his confidentiality (and so they should). All credit goes to the medical personnel who diagnosed the condition. As mentioned earlier, aortic aneurysms are usually silent until they rupture. They are difficult, if not impossible, to detect on routine physical examination, even if thorough. Plain film xrays may or may not show the widened area of the aorta, whereas they are much more readily detected by ultrasound imaging. However Mr. Green’s aortic aneurysm was picked up, his diagnosis is a testament to the thoroughness with which the Celtic’s medical staff care for the players. Despite the lack of specificity of medical reports to the press, the term “open heart surgery” seems to keep cropping up in many of the dispatches. This inclines me to believe that Jeff’s aortic aneurysm likely involves, or is very close, to the root of the aorta where it emerges from his heart. We can only hope (and chances are good) that Jeff’s surgery goes without incident, and that he can return to his role with the Celtics unimpaired, and so ultimately fulfill the athletic promise of his young career. Best of luck with it Jeff…