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Diabetes Watch

Can Endovascular Atherectomy Be Beneficial In Diabetic Limb Salvage?

     The non-traumatic lower extremity amputation rate among people with diabetes mellitus has increased 38 percent from 1992 to 2002.1 The number of amputations has increased from 99,552 in 2000 to 110,000 in 2002.2 To appreciate this statistic, this is more than double the number of amputations on U.S. soldiers from the Civil War through Vietnam.3      Peripheral arterial disease (PAD) is largely undiagnosed. Of the estimated 12 million Americans with PAD, 2.5 million are diagnosed and only 4 percent are treated interventionally.4 One to two million people are suffering from critical limb ischemia, which carries a 25 percent one-year mortality rate and 60 percent three-year mortality rate.5 Patients with intermittent claudication show mortality rates from all causes of 30 percent and 50 percent at five and 10 years respectively.6 Due to the high mortality rates, amputation and bypass should be the last resort in the diabetic population as opposed to the first line of defense against peripheral arterial disease. Peripheral arterial disease (PAD) within the diabetic population is an enormous problem. An estimated one in three people with diabetes mellitus over the age of 50 has PAD and, overall, 12 million Americans have PAD.7 If it remains undetected, especially in the diabetic population, PAD can lead to amputation, which increases a person’s risk of heart attack and stroke, and death in approximately one-third of those amputees.8 Traditional treatment for PAD in the diabetic population may include medical management, angioplasty with or without stent, bypass grafting and amputation. Morbidity and mortality can be very high within the diabetic population, particularly with bypass grafting as a last resort. However, a new technique called endovascular atherectomy has emerged in recent years for limb salvage of the dysvascular diabetic limb.

Understanding The Nuances Of Endovascular Atherectomy

     Indeed, plaque excision via the Silverhawk endovascular atherectomy (FoxHollow) has shown promising results with the reduction of mortality and decreased rates of restenosis.      The procedure for utilizing the Silverhawk involves the following steps. Step one. After delivering the catheter to the lesion, one positions it at the selected treatment area and switches the driver to the “on” position. Switching the driver “on” automatically deflects the catheter tip, lifts the cutter and activates the motor. Step two. One proceeds to advance the cutter through the lesion, cutting tissue and collecting it in the nose cone. The operator of the device controls the length of the cut so one can treat any length of lesion. The continual ability to shave the plaque longitudinally facilitates efficient treatment of long lesions. One can fix the cutter height to enhance control and consistency of cut depth. Step three. The surgeon can turn off the driver and either reposition the cutter to treat another lesion area or remove the catheter from the artery. Torque functionality allows selective plaque excision in designated quadrants. After multiple passes, one can remove the diseased tissue from the nosecone. The surgeon can then reinsert the catheter to continue treatment if necessary.

Case Study: A Patient With Severe Claudication And Ulceration

In one case study, a 69-year-old male was referred to a lower extremity limb salvage clinic with severe painful claudication and ulceration.      He had prior amputation of the hallux and second digit of the right foot secondary to gangrene, and a prior endovascular angioplasty of the anterior tibial artery. He was scheduled for a below-knee amputation at another facility. His past medical history included diabetes mellitus for eight years, hypertensive cardiovascular disease and chronic renal failure, which initially required dialysis and eventually led to a right orthotopic kidney transplant. The patient history also included monocular blindness in the right eye.      The patient was a former smoker who quit 30 years ago. His family history was significant for diabetes mellitus maternally and morbid obesity. He did have night cramps and reproducible leg pain with ambulation. His medications included Medrol, Cellcept, Prograf, Avandia, Zocor, Ambien, Atenolol, aspirin and insulin. He denied any known allergies.      In regard to the physical exam, the patient’s vital signs were stable. His blood pressure was 137/84, his pulse was 80, respirations were 14 and his temperature was 98.5ºF. His pain was seven out of 10 on the visual analogue scale (VAS). His random blood sugar (RBS) at three hours postprandial was 131 mg/dL. The vascular exam revealed non-palpable pulses to the right lower extremity. The title= After delivering the catheter to the lesion, one would position it at the selected treatment area and switch the driver on. Switching the driver on automatically deflects the catheter tip, lifts the cutter and activates the motor. Doppler exam revealed a non-Dopplerable posterior tibial artery and a weakly monophasic dorsalis pedis artery. The distal foot was cool to the touch with elevated capillary refill time. An open ulcer was present at the prior amputation site of the first and second digits with gangrenous changes present. His right ankle-brachial index (ABI) was 0.69. Previous vascular intervention results included a balloon angioplasty of the right anterior tibial artery. His prior angiogram revealed a 100 percent occlusion of the posterior tibial artery and 75 percent stenosis of the proximal anterior tibial and fibular arteries.      We referred the patient to a cardiovascular interventionalist for immediate vascular evaluation. The patient underwent a selective abdominal aortogram, which revealed severe infrapopliteal disease bilaterally. The posterior and anterior tibial arteries are 100 percent occluded proximally. The peroneal artery was patent and supplied collateral arterial circulation to the distal anterior and posterior tibial arteries.      The patient underwent endovascular intervention including laser atherectomy, Silverhawk endovascular atherectomy and balloon angioplasty of the anterior tibial artery. The patient required a transmetatarsal amputation (TMA) after the Silverhawk procedure but avoided the need for a significant proximal amputation. There were no complications while healing the TMA. He exhibited no further complications 12 months after the endoscopic atherectomy.

What The Research Reveals About The Endovascular Atherectomy

Many study models have investigated the longer-term results of the Silverhawk procedure. The TALON study is a national registry which tracks outcomes after treatment with the Silverhawk system, and has over 506 patients and 1,099 lesions enrolled to date.9 Thirty-two percent of the patients had critical limb ischemia with ABIs below 0.6. Minimal lumen diameter improved from 1.6 mm pre-procedure to 4.5 mm post-procedure and the diameter stenosis improved from 87.1 percent to 9.9 percent. The mean pre-surgical ABI was 0.61 + 0.12 and improved to a post-op ABI of 0.79 + 0.11. The overall patency rate at six months was 90.4 percent.9      The Arizona Heart Hospital 12-month outcomes data involved 181 patients and 202 limbs.10 The mean ABI increase was 0.27. Ninety-two patients (45.5 percent) of patients completed the six-month follow up, resulting in a primary patency rate of 96 percent.10 More recently, researchers reported an 86 patency rate at 12 months for 104 patients with peripheral vascular disease treated with Silverhawk. These findings are encouraging evidence that the Silverhawk system also provides good long-term benefit.      The Cardiovascular Institute of the South conducted a six-month follow-up study investigating the rate of restenosis following the Silverhawk procedure.11 From Sept. 2, 2003 to June 1, 2004, researchers treated 133 superficial femoral artery lesions (64 patients) with the Silverhawk system. At six months, they examined all 64 patients with Duplex ultrasound and examined 42 (65 percent) of the patients via CT angiogram (CTA). Using the Duplex ultrasound, investigators observed a 9.4 percent (6 of 64) restenosis rate, which was very close to the 9.6 percent (5 of 42) restenosis rate observed with CTA.

In Conclusion

     The cases submitted to the TALON registry, as well as more recent 12-month reports from the Arizona Heart Hospital, indicate a high level of safety and efficacy associated with using the Silverhawk device for lower extremity lesions. This evidence has been confirmed in numerous single-center studies in high volume facilities across the country. Physicians at these facilities have observed high rates of procedural success in above-the-knee and below-the-knee lesions with very low complication rates. The remarkable observation in many centers was the increasing number of patients who were at one time scheduled for a significant lower extremity amputation but had successful limb salvage procedures with the Silverhawk system. Peripheral arterial disease in high-risk patient groups, such as those with diabetes mellitus, now may have a reliable, lower risk alternative for treatment and limb salvage. However, specific cohort studies investigating the long-term benefit of the Silverhawk procedure, particularly in the diabetic population, are still needed.      Dr. Wilusz is a Clinical and Surgical Instructor at the Foot and Ankle Clinic at the Southeastern Michigan Surgical Hospital in Warren, Mich. He is a Diplomate of the American College of Foot and Ankle Surgeons, and is certified in forefoot and rearfoot reconstructive foot and ankle surgery. He is in private practice in Dearborn, Mich.      Dr. Pupp is a Fellow of the American College of Foot and Ankle Surgeons. He is the Clinical Director of the Foot and Ankle Clinic at the Southeast Michigan Surgical Hospital in Warren, Mich.      Dr. Steinberg is an Associate Professor in the Department of Plastic Surgery at the Georgetown University School of Medicine in Washington, D.C.


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Diabetes Watch
By Peter Wilusz, DPM, and Guy Pupp, DPM
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