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Widened Horizon. The artery disorders for which DeBakey and his colleagues have devised ever more daring surgical procedures fall into two main classes: blockages and aneurysms. Blockages may be almost anywhere—in the greatest vessel of all, the aorta, in the coronary arteries embedded in the heart wall itself, in arteries leading to the legs, and in the carotid and vertebral vessels carrying blood to the brain (see diagram, opposite page). The brain itself, however, is the province of the neurosurgeons.
Blockages in coronary arteries may go undetected for years, or cause moderately disabling disease, then suddenly become total or near-total shutdowns and cause the type of heart attacks called coronary occlusions. The reaming out of such an artery ("endarterectomy") is impossible in most cases and immensely hazardous at best.
Partial shutdowns of the aorta are sometimes caused by narrowing ("coarctation"), which may be present from birth, but more often by the later development of obstructive deposits containing calcium and cholesterol. What is responsible for these deposits is one of the basic questions not yet answered. In this area, DeBakey's work first dealt with shutdowns in the abdominal section of the aorta, because there the big blood vessel could be clamped shut well beyond the point where arteries branch off to supply the brain. The lower part of the body could be deprived of its blood supply long enough to let the surgeons cut out the diseased section and replace it with knit Dacron tubing. When the heart-lung machine became a practical adjunct in surgery, the horizon was suddenly widened. It became possible to operate anywhere along the aorta, while the machine supplied blood continuously to the brain.
Clots & Strokes. Obstructions involving the iliac, femoral and popliteal arteries supplying the legs and feet are common, and may actually begin in the aorta just before it splits to form the two main iliac arteries. A familiar feature of insufficient blood supply to the legs, which causes pain in the calf muscles so acute that the victim can hardly walk, is its on-again, off-again nature. Ten days after DeBakey has bypassed the blocked artery with a length of tubing, the patient who previously could walk no farther than a city block without disabling pain can usually go a leisurely mile.
The most daring, and still somewhat controversial, of Dr. DeBakey's innovations is an operation on arteries leading to the brain; it is done to ease the effects of a stroke and to reduce the likelihood that the patient will have more strokes. Though some strokes are the result of hemorrhaging from burst arteries, the great majority are caused by clot shutdowns where the arteries are inside the skull and inaccessible. But Dr. DeBakey thinks that as many as 20% of the clots occur in the carotid and vertebral arteries, below the floor of the skull, where the surgeon can get at them through an incision in the neck.
Clotting in the carotids, as in the coronaries, results from narrowing of the vessels by atherosclerosis, the deposition of porridge-like material containing cholesterol and other complex chemicals. Again, though theories abound, no one knows the underlying cause of the process or how the sites of deposits are determined.