The specialty is called Cardiology. The physician is called a Cardiologist. The Board Certification, however, is Cardiovascular Disease. So what happened to the “vascular “ part in common parlance? Does anybody care?
It is absolutely fitting that the “cardio” part should be at the heart of any discussion of the circulatory system, the complex network of tissues and organs that carry blood around the body. The heart is the pump, the core, the major force that drives blood circulation. But without the vessels that actually transport the blood, there would be no circulation. Think of the fluid delivery system that transports water from a central reservoir to the faucet in your sink. No matter how much the reservoir holds and is able to release, without the pipes that carry the water to its ultimate destination, your tap is dry. Those pipes are like the blood vessels in your body, the conduits in the circulatory system.
The circulatory system is both a two-way street and a continuous loop. It’s a two-way street because blood flows both out from the heart around the body and back to the heart. It’s a continuous loop because the blood is essentially recycled around and around the body. There is no faucet at the end of the outward flow; the fluid returns to the reservoir, so to speak, and is recirculated continuously.
The system of blood vessels carrying blood away from the heart is called the arterial system. The vessels transporting blood back to the heart constitute the venous system. Arteries: outward flow; veins: inward flow.
Simple? Not so much.
The arterial and venous systems both have large and small blood vessel components. Like a tree with a thick bore trunk that sends out large branches that then taper to smaller and smaller branches the farther they are from the central trunk, the circulatory system has large central vessels and smaller and smaller branches the further they are from the heart.
The largest artery in the body, the aorta, arises right at the exit from the left ventricle, the main pumping chamber of the heart. The aorta receives all the blood pumped out with each heartbeat. The aorta immediately begins to send out branches to different organs and tissues. The first branches are the coronary arteries which arise almost at the origin of the aorta and supply blood to the heart muscle itself. Next are a complex set of branches that ultimately supply blood to the upper part of the body, including the brain and the arms. Then the aorta literally reverses direction in a sweeping curve and turns toward the lower part of the body. As it courses downward it sends branches to the intestinal blood vessels, the kidney blood vessels, the pelvic blood vessels, and finally to the blood vessels of the legs. At each stage, the relatively large aortic branches give rise to smaller and smaller branch vessels that ultimately reach the individual cells of the body tissues.
At the very end of the arterial system branches, very thin and fragile vessels called capillaries form a weblike network that connects with the smallest branches of the venous system. This represents the beginning of the pathway of blood returning to the heart. In a reversal of the arterial system, where the smallest vessels are at the end of the blood flow path, the smallest venous vessels are at the beginning of the blood return system. As more blood is collected from different organs, the veins grow larger as they approach the heart. The two largest are known as the vena cava: The so-called superior vena cava carries blood from the upper part of the body, while the inferior vena cava drains blood from the lower portion of the body. The vena cava empty into the right side of the heart, from where blood is pumped to the lungs to receive new oxygen and eliminate carbon dioxide.
When people, including physicians, talk about peripheral vascular disease (PVD), they usually refer to arterial vascular disease of the legs, meaning insufficient blood supply to the legs. This is, indeed, probably the commonest form of peripheral vascular disease. It’s estimated millions of people in the U.S. and worldwide have it, and most estimates are based on only those people with symptoms. The prevalence of disease of these blood vessels without the presence of symptoms is probably much higher.
But besides PVD of the legs, every artery in the body can, under certain circumstances, develop disease, usually of the arteriosclerotic variety, meaning cholesterol and other lipid-laden plaques blocking the flow the blood. Many strokes, for example, are the result of disease of the blood vessels supplying blood to the brain; this is obviously a form of PVD. Less often, diseases of the renal arteries, those supplying blood to the kidneys, may occur with serious consequences including hard-to-control hypertension (high blood pressure) and kidney failure. Even less frequently, a condition known as mesenteric ischemia, meaning impaired blood flow to the intestines, can be present with a variety of digestive and abdominal symptoms.
Of course, the arteries aren’t the only blood vessels subject to disease. The venous system is also prime territory for vascular disease. From varicose veins, which may be mild and inconsequential or more severe and serious, to so-called deep vein thrombosis with the ensuing danger of pulmonary embolism (blood clots traveling to the lungs), veins can be the site of vascular disease. Incidentally, the diagnosis of pulmonary embolism is often missed by medical professionals and is the cause of death in many hospitalized or otherwise immobile or bedridden patients.
All of this does not detract from the central importance of the heart as the core of the circulatory system. But it means we should remember that the accurate specialty designation is cardiovascular disease. Your blood vessels are critical parts of your circulatory system. And you, and your physicians, should pay attention to what they may be telling or showing you.
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