Friday, August 05, 2005

Clarissa - 8/5/2005 - Carotid Endarterectomy, SilverHawk, and Brief Timeline

So, this past week was fairly busy, with my time divided between watching surgeries in the OR, seeing patients with Dr. Bush in the surgical associates clinic, and working on a timeline for the evolution of aneurysm treatments.

Carotid Endarterectomy

In the OR, most of the surgeries this past week consisted of endarterectomies (femoral and carotid), which are surgical procedures that remove plaque material from the lining of the occluded artery.

A carotid endarterectomy is shown here:

In some cases, an endarterectomy can be performed without opening up the artery in question. This would require the minimally invasive approach of using a special catheter which would travel up the artery and "shave" off the plaque on the artery wall. Such atherectomy devices remove plaque from the artery wall by cutting, pulverizing or shaving.

SilverHawk Plaque Excision Catheter

On the technology forefront is the FoxHollow SilverHawk plaque excision catheter (FoxHollow Technologies, Redwood City, CA) has been approved as of June 2003 for treating peripheral vascular disease. Previous atherectomy devices used a balloon to engage the cutting blade into the plaque, using a combination of balloon angioplasty and atherectomy that often resulted in barotrauma (or vessel overstretch). The main advantage of the SilverHawk device is the elimination of barotrauma. The SilverHawk Plaque Excision System is a two-part system that uses a low-profile catheter and a palm sized drive unit that controlls the device functionality. When activated, a tiny blade on the catheter tip rotates and shaves off thin slices of plaque from the arterial wall. After each pass, the plaque is collected into a storage chamber. When the chamber reaches its full capacity, the device can be removed, cleaned, and re-inserted to treat additional areas. The unique mechanical design of the SilverHawk catheter allows significant amounts of plaque to be removed without injuring or overstretching the vessel walls. The device is also easily positioned using fluoroscopy.

The SilverHawk is shown here:

And here is the procedure step-by-step:

The SilverHawk catheter is inserted through a small puncture site and travels through the artery to the site of blockage.

Once at the site, a tiny blade is activated by the drive unit. The rotating blade advances through the blockage, shaving off tiny slices of plaque from the arterial wall.

The plaque collects in a storage chamber at the tip of the catheter, which can be removed and cleaned.

Timeline of the Evolution of Aneurysm Treatments

Here is just a short selection of some interesting historical facts...[sorry for the empty space below, blogger doesn't seem to like tables]

c. 2000 B.C.The Ebers Papyrus, one of the earliest known texts, contains a clear description of the diagnostic features and management of what, presumably, were traumatic aneurysms of the peripheral arteries. The Egyptians treated aneurysms with magico-religious therapies, and studies of Egyptian mummies have revealed that atherosclerosis and arterial calcification were probably relatively common.
c. 170Galen described an aneurysm as a localized pulsatile swelling which disappeared on pressure. He is considered the first to define and describe the disease, recognizing the false variety and those arising spontaneously by dilation. Considering the frequent use of venesection, and the fact that he is said to have been a physician to the gladiators, Galen probably saw traumatic aneurysms rather frequently.
c. 200Antyllus practiced an operational procedure that involved application of proximal and distal ligatures to isolate the aneurysm followed by an incision into the sac and evacuation of its contents. Antyllus believed that some of the aneurysms occurred due to simple dilation.
1510-90Ambrose Paré, the great medieval surgeon, was severely critical of any procedure that involved opening the aneurismal sac, and strongly advocated the application of a proximal ligature alone.
1550Syphilis is considered to be a cause of aneurismal dilation, and Paré also claims that aneurysms could also be caused by “anastomosis, diapedesis, rupture, erosion, and wound” and also realized that not all aneurysms are pulsatile, attributing the absence of pulsation to the large amount of thrombus in the sac.
1555Andreas Vesalius provided one of the first descriptions of an abdominal aortic aneurysm, and was first to diagnose such.
1728Lancisi in his book De Aneurysmatibus, published posthumously, discusses the etymology of the term aneurysm, and was possibly the first to infer that a congenital defect may be the cause of aneurismal dilation in some cases.
1779-93John Hunter observed that there was a communication of the arteries above the aneurysm with those below by means of anastomosing branches. He operated on a patient with a large popliteal aneurysm by exposing the femoral arterial in the subsartorial canal and by means of an eyed probe passed two double ligatures around it; the four ligatures thus created were then gently tied. This was the longest and best documented successful vascular operation yet recorded. In another experiment, Hunter exposed the carotid of a dog, dissected off much of the wall, till it was extremely thin, and blood could be seen through it. Then, three weeks later, he re-exposed the part and found no dilatation, but only a repaired vessel wall, thus concluding that pre-existing arterial disease was required to produce an aneurysm.
1864Moore introduced the technique of induction of aneurysm thrombosis by filling the sac with long lengths of coiled wire.
1900'sAtherosclerosis (Atheroma) overtook syphilis as the leading cause of aneurysms
1923Barney Brooks of Nashville was producing excellent arteriograms using intra-arterial injections of sodium iodide. Moniz further developed this technique to visualize the intracranial circulation in an attempt to improve the localization of cerebral tumours
1950Jacques Oudot performed the first successful operation for an occlusion of the aortic bifurcation using a preserved homograft and it was therefore inevitable that an attempt to perform a similar procedure on an aortic aneurysm would shortly transpire.
1951Dubost and his team in Paris performed the first entirely successful resection of an infrarenal aortic aneurysm via a thoraco-abdominal extraperitoneal approach using a frozen cadaver homograft.
1952Voorhees experimented with a polyester material known as Vinyon-N, a material easily obtained from the post-war surplus of parachute fabric. The prosthetic fabric graft provided a durable replacement for the dilated segment
1953Cooley and DeBakey used the Dubost technique to treat a ruptured abdominal aortic aneurysm, a condition that was universally lethal before graft repair
1955Albert Einstein died of rupture of an infrarenal aneurysm that had been wrapped with cellophane 6 years earlier
1966Feri accomplished superselective catheterization with minimal vessel damage with the creation of the paraoperational device catheter. To ease the difficulty of directing the paraoperational device catheter through the tortuosities of the intracranial vasculature, Frei and colleagues designed a catheter tip with an attached micromagnet. Therefore, and external magnetic field could be used to control the intravascular catheter.
1974Serbinenko published an article on balloon catheterization and occlusion which detailed an influential advancement that became a conventional treatment for intracranial aneurysms
1976-90John Parodi noted that the very patients who were at highest risk for the development of aortic aneurysms were also at greatest risk for morbidity from a major surgical intervention such as the open surgical repair of the aneurysm. Parodi and Palmaz used a device composed of Dacron tubes sutured to a Palmaz stent, compacted into a sheath, and introduced through the femoral artery, treated two patients.

More to come...


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