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1363266976 10 chapter10

  1. 1. 67 Chapter X PERIPHERAL ARTERIAL DISEASE (PAD) OF THE LOWER EXTREMITIES IN DIABETES MELLITUS  EPIDEMIOLOGY AND NATURAL HISTORY  RISK FACTORS AND CLINICAL EVALUATION  INVESTIGATION OF PAD AB INDEX, DUPLEX SCAN, ANGIOGRAM  SURGICAL THERAPY  ENDOVASCULAR SURGERY IN PAD  CRITICAL LIMB ISCHEMIA  MINIMAL VASCULAR EVALUATION AND REFERRAL PAD is one of the commonest manifestations of Diabetes Mellitus. It is one of the many “end organ” failures caused by Diabetes Mellitus and along with neuropathy and infection of the foot it is a leading cause of morbidity and economic loss, probably more than coronary artery disease and cerebro-vascular disease combined!! Though the clinical diagnosis of PAD can be achieved with ease and certainty in most of the patients, unfortunately it is still 'missed' in many patients and places, causing undue delay in diagnosis and therapy, leading to severe morbidity, economic loss and frequently results in mortality. It is a sombre truth that 50% of all extremity amputations occur in diabetic patients. Epidemiology & Natural History: 1. Prevalence of asymptomatic PAD is difficult to determine and reported with wide variation of 0.9 to 22%!! But in persons with diabetes it is 2 to 3 times more prevalent. 2. About 3 to 6 % of the general population suffers from arterial claudication, mostly in men. Prevalence in persons with diabetes is 4 to 5 times higher than this and is nearly equal in both the sexes. 3. Critical Limb Ischemia (CLI) denotes advanced PVD with imminent limb loss (non- healing ulcer, gangrene or rest pain). About 500 per million of the population develop CLI per year, but diabetes doubles this risk! 4. Diabetic PAD is a more aggressive disease and occurs in younger patients. Rapid progression of 'early' critical limb ischemia to gangrene occurs in 40% of the diabetic as opposed to 9% in persons without diabetes. 5. Sudden progression from intermittent claudication to limb threatening ischemia occurs in 35% of persons with diabetes (19% in persons without diabetes) with 21% risk of major amputation (3 % in persons without diabetes).
  2. 2. 68 6. Since vascular disease is a “systemic disease”, about half of the patients have coronary artery / cerebrovascular disease. About a third of the patients with coronary artery disease have PAD. 7. Several consensus statements within last couple years have designated PAD as a risk factor, higher indicator than coronary or cerebrovascular disease for systemic atherosclerosis. The recent TASC II (Trans Atlantic Inter-Society Consensus) statements recommends that any patient with ankle brachial index (ABI) less than 0.90 should be considered at risk for systemic atherosclerosis and ABI might be the easiest screening procedure to identify these patients at risk and submit them to the best medical therapy. Risk Factors for PAD: Apart from Diabetes, several other risk factors could have additive effect on PAD & progression. Smoking is an independent risk factor, which increases the odds of developing PAD by at least 3 times, and has significant additive effect in diabetes. Hyperlipidemia and inflammatory arteriopathies can coexist with diabetes. Hypercoagulable states (congenital or acquired), neglected trauma can cause or worsen the PAD. Hypertension is an important co-morbidity that can aggravate PAD. Clinical Evaluation: About 90% of PAD can be diagnosed with good history and physical examination. Claudication is the earliest and commonest symptom of PAD. Pain or cramps typically appears in a muscle group, mostly in the calf muscles, sometimes in the thigh or hip in aortoiliac occlusion, after walking certain distance. A short rest relieves this and the patient can again walk the same distance i.e, the symptoms are reproducible. It needs to be differentiated from neurogenic claudication, which can occur with first few steps and takes a long time to recover; and the venous claudication, which causes 'bursting' pain mostly towards the end of the day. Since therapy for PAD (surgical or endovascular) is dictated by symptoms, it is important to determine if claudication is 'disabling' for that person or not. It is considered disabling if it interferes with his / her lifestyle. For, a 200-metre claudication is not at all disabling for a 70 year old person with sedentary lifestyle, but would be severely disabling for a young postman or policeman. It should be emphasised that claudication is not an automatic indication for intervention of any form, since critical limb ischemia and limb loss occur in only 5 and 1% respectively. “Rest Pain” occurs as PAD further progresses. It typically occurs in the forefoot and toes, especially at night and relieved by hanging the foot down or walking a short distance. This requires intervention most of the time, as it is disabling and likely to progress to the next stage of tissue loss (ulceration & gangrene). An ulcer in the foot which does not show evidence of healing over 2 to 3 weeks, with good therapy, is considered a 'non-healing' ulcer. Of note is the fact that 85% of persons with diabetes have nonhealing ulcers prior to a major amputation. A gangrene of a part of a foot or toe shows inadequate perfusion, of even resting tissue and would lead to limb loss, more so with heel ulcer, as the pad of fat over calcaneous is vulnerable to ischemia.
  3. 3. 69 Clinical examination in chronic arterial occlusive disease would reveal loss of hair over toes, brittle nails, thin shiny skin, cooler skin temperature, discoloration progressing to gangrene. Dependent rubor erythematous hue that appears on hanging the foot down is a sign of advanced PAD, but difficult to make out in our patients. A diligent palpation of the pulses will reveal absent or diminished pulsation of posterior tibial &/or dorsalis pedis artery. The popliteal and femoral pulses, as are the pulses in the abdomen, upper extremities, neck should be examined and auscultated for a bruit. Though subjective, pulses should be graded in a standard manner: - 0 -- Absent, 1 -- Feeble, 2 -- Normal, 3 -- Prominent, 4 -- Aneurismal. Investigation: Routine laboratory investigations should include complete blood count, platelet count, fasting blood glucose or HbA1c, S. creatinine, lipid profile and ECG. Additional testing, dictated by patient's symptoms and findings, include further cardiac workup, hypercoagulability screen, screening for other vascular diseases like carotid stenosis, aneurismal disease and these should not be done routinely in all the patients. Ankle Brachial Index (ABI): This simple and extremely useful measurement can be performed with a handheld Doppler with appropriate blood pressure cuffs for arm and thighs. ABI is the ratio between ankle and brachial pressure and is around 1. The ratio of over 0.9 is considered normal. A claudicator has a ratio of usually over 0.7 and those with critical limb ischemia less than 0.5 and this is a good predictor of deterioration of PAD, with 2 ½ times increased chance of amputation. Some diabetics have non - compressible arteries because of calcification and ABI can be falsely higher than 1.0. A toe cuff would be useful in these patients and the toe pressure is about 10 mm of Hg, less than the ankle pressure. An ankle pressure of 70 mm of Hg indicates a very low risk of amputation. (Fig 39) Duplex Scan: This combines B Mode ultrasound with colour Doppler imaging and is an extremely useful noninvasive diagnostic tool for initial imaging and in fact in many diabetic patients who cannot undergo angiography therapy can be based on duplex scan findings. Most, if not all, patients with PAD should undergo this test as an initial diagnostic test. Apart from direct imaging, duplex scan also records flow velocities and graphic waveforms can also be recorded. Angiogram: This remains the “Gold Standard” for imaging in PAD. But, it should not be used as a screening test and should be used only in those patients in whom intervention is contemplated, which again is dictated by symptoms and findings of other modalities of testing. Digital subtraction angiogram has virtually replaced “standard” angiogram, since imaging of the leg and foot arteries is much superior with usage of lesser amount of dye. The procedure is well tolerated, with complication rate of less
  4. 4. 70 than 2%, but caution should be exercised in patients with compromised renal function and / or in the diabetic patient who is poorly hydrated, since dye induced nephropathy can add significantly to morbidity of these patients. A good lower limb angiogram should provide imaging of arteries from abdominal aorta to plantar arch. Other imaging modalities like MR angiogram and CT angiogram are excellent modalities for vascular imaging and with advancing technology, some of these may replace the angiogram in future. CT angiogram does require a large amount of dye and hence cannot be used in patients with renal failure. MRA is safe in patients with CRF and might replace conventional angiogram in future. Carbon dioxide angiogram: CO2 is a radio-opaque gas, which can be used for imaging the arterial system. Large volumes can be injected into the arterial system without any adverse effects and is completely excreted during the first pass through the lungs. It is not nephrotoxic and hence can be used in patients with compromised renal function. But the opacification is not as good as iodinated contrast agents and the gas “breaks up” as it passes down the arterial tree. Hence it is an acceptable contrast agent for imaging the infra renal aorta, iliac and femoral arteries. The “medical grade CO2” used for laparoscopic insufflations is used and care should be taken to avoid mixing of air, as this would lead to serious effects of air embolism. Distribution of PAD in persons with diabetes is different from nondiabetic atherosclerosis. They are more prone to have infra-inguinal and infra-popliteal disease than aorto-iliac occlusive disease. It is important to note that the microangiopathy does not adversely affect the outcome of vascular reconstruction in diabetic patients. Therapy for Intermittent Claudication: Therapy involves a four-pronged approach as recommended by National Cholesterol Education Program (NCEP-Panel III) 1. Life style modification. 2. Risk factor reduction. 3. Supervised exercise program and medical therapy. 4. Revascularization in severe cases. Life style and risk factor modification involves cessation of smoking and tobacco use with counseling and assistance as needed. Good glycemic control, control of hypertension, treatment of dyslipidemias. Supervised exercise program and structured training on a treadmill have been shown to be superior to just counseling about exercise program. Pharmacotherapy involves use of circulation enhancing drugs and at present cilastazole (to be used with caution in patients with LVF) and L-Carnitine are the drugs available for treatment of claudication. Pentoxyfilline has not proven to be better than placebo for the treatment of claudication. Anti-platelet agents Aspirin and clopidogrel should be used in all patients with PAD. As the prices come down
  5. 5. 71 clopidogrel could be preferred as it has less GI side effects Though they do not have direct effect on PAD or its symptoms, they are documented to reduce cardiovascular morbidity and mortality in these patients. Use of statins has been shown to be beneficial even in normolipemic patients. Control of risk factors and lifestyle modifications are an important and integral part of the treatment of PAD. Cessation of smoking, control of hyperlipidemia and control diabetes with good glycemic control should be achieved. But, unfortunately, glycemic control does not necessarily mean arrest of progression of PAD. Since neuroischaemic ulcers in the foot are more common than PAD alone, a multi disciplinary approach to Foot problems cannot be stressed enough. Simple preventive measures will reduce the amputation rate in diabetics by about 50%. Pharmacotherapy in PAD has limited role to play. Pentoxyfilline, a haemorrheologic agent, was thought to have a role in claudicators, but studies have shown it not better than placebo. Cilastazole does improve claudication distance in significant number of patients and should be used as initial therapy in claudicators. None of these drugs (eg. I.V. pentoxyfilline) are of any use in critical or acute limb ischemia. Vasodilators are mentioned here, only to be condemned, as they have no role to play, except in certain select circumstances. Antiplatelet drugs are used in arterial thromboembolism, but should be used in all PAD patients lifelong to decrease the cardiac and cerebrovascular mortality and morbidity. Anticoagulation has limited role to play and prostanoids are used in non reconstructible critical limb ischemia. Surgical Therapy remains the mainstay to achieve revascularisation of PAD of lower limbs, especially in diabetics. Most of these patients have long segment; infrapopliteal occlusions and majority are amenable to vascular bypass procedures. The selection of patients shall be stringent and non disabling claudicator should not be subjected to these procedures. Surgical and interventional procedures (angioplasty, stenting) should be offered to those who fail to improve on good medical therapy, but should be considered in all patients with rest pain and tissue loss. The “bypass” procedures can be performed to any level in the lower extremities from aorto iliac reconstruction to bypass to foot arteries. Most of the “bypass” procedures done in diabetic PAD is to the paramalleolar arteries posterior tibial, anterior tibial or peroneal artery near the ankle. The selective beta blockers like metoprolol or bisoprolol are not detrimental to PAD but are definitely cardioprotective as well as beneficial in preventing cerebrovascular events in the perioperative period. They could be continued for about three months in the post operative periods for these benefits. ARBs and ACEI are also protective in this period. The goal of therapy is functional limb salvage, not necessarily long term graft patency. Proximal reconstructive procedures (aorto iliac femoral bypass procedures) have a 5 and 10 year patency rate up to 80%. Infrainguinal / infrapopliteal bypass procedures have much lower patency rates (about 50-60% at 3 years) but the limb salvage remains high, about 80-90%. Once the initial wound heals
  6. 6. 72 with risk factor control, appropriate lifestyle medication and foot care, further ischemic limb loss can be prevented. Artificial grafts (Dacron, PTFE) are ideally suited for aorto iliac femoral reconstruction. Femoral popliteal bypasses with artificial graft do nearly as well as saphenous vein. Infra- popliteal bypass should be performed with vein graft wherever possible, since artificial grafts do poorly in these locations. Endovascular Surgery / Intervention: These are minimally invasive procedures ideally suited for certain lesions. These catheter based techniques are gradually replacing some surgical procedures and many more will be added to this list in future. Balloon angioplasty with or without stenting is ideally suited for short segments, stenotic lesions of iliac artery and selected lesions in femoral and distal vessels. A variety of lesions are now being treated with these methods, but these are expensive procedures and their usage is limited because of it. The advantages are short hospitalization and rapid return to work. The lesions are divided into four categories Grades A and B are usually short segment stenosis and occlusions and these can be treated with endovascular interventions. Grade C and D lesions usually require surgical intervention. Primary stenting is indicated in iliac lesions, but has not changed the outcome in femoral and distal vessels and their outcome is no better than balloon angioplasty alone. With inexorable progress of technology, more such procedures will be performed at a lower cost in future. Amputation is the “finale” of either failure to treat or failed treatment of severe limb ischemia. Every attempt should be made to obtain functional limb salvage, especially in persons with diabetes, since many have multi-system involvement and loss of a limb adds markedly to their disability. It is felt by some in India that amputation is better than vascular reconstruction as it is a 'quicker and cheaper' option. This is far from the truth and the following facts should be borne in mind. Facts about amputation for Critical Limb Ischemia: 1. In the US, about 150,000 per year require amputation for the legs. In India, this figure is likely to be much higher. 2. Perioperative mortality for below knee amputation is about 8 to 10% and that of above knee amputation is 15 to 20%. The mortality for vascular reconstruction remains lower at 2 to 5 % as is the morbidity. 3. 40% die within 2 years of their first major amputation. 4. A second amputation is required in 30% of the patients. 5. Only 50% of the patients with below knee amputation and 25% of those with above knee amputation will ever achieve full mobility. The figures are probably worse in India since “modern” prosthesis may not be available or affordable to all. 6. The mid and long term cost of amputation is higher than vascular reconstruction.
  7. 7. 73 7. There is no effective drug therapy in critical limb ischemia and usage of vasodilators and others only delay proper therapy and entail unnecessary cost. 8. The quality of life of amputees is poor and several psychological testings have shown this to be similar to patients with cancer in critical and even terminal phases. 9. Even the elderly and those with multiple medical problems tolerate vascular bypass as well, if not better, than amputation. Our experience at Jain Institute of Vascular Sciences, Bangalore has shown that limb salvage in these diabetic patients is about 90%, though our mortality and morbidity is higher than quoted in literature. It is because of late presentation and referral to us and most of the patients have significant co-morbidities. 10. About 70% of over 600 lower limb vascular “bypass” procedures performed by us in last five years are on persons with diabetes and over half of these were to infra popliteal arteries. Nearly all the diabetic patients had at least one other comorbidity. The out comes were: Graft failure 7%, Post bypass amputation 6%, Mortality 7%. There is however a significant overlap in these figures (eg. Patient who had failed bypass and also underwent amputation, has also a high chance of mortality) and hence the over all mortality and morbidity is about 9%, which means over 90% 0f these patients leave the hospital with intact functional limbs. Conclusions: There is a high prevalence of PAD in persons with diabetes, resulting in limb loss, which can have devastating effects on these patients. With appropriate therapy, functional limb salvage can be obtained in a majority of the patients and this can be sustained by risk factor modification and foot care. Even high-risk patients do well with vascular reconstructive procedures rather than amputation and hence every attempt should be made to avoid major amputation in these patients. Minimum Vascular Evaluation and Care For Patients with Diabetic Foot Problem Recommendation 1: Since all persons with diabetes, irrespective of gender, are at a high risk of Peripheral Arterial Disease, clinical examination of the Vascular System, especially of the lower limbs should be carried out every 3 months, in asymptomatic patient. This should include notation of any ischemic changes in the feet and palpation of femoral, popliteal, Dorsalis pedis and posterior tibial pulses. Appropriate record should be maintained of the clinical findings. Recommendation 2: When a patient develops claudication, non- healing ulcer or other form of tissue loss, rest pain, he / she should be referred to the vascular surgeon or to a surgeon with special interest in vascular diseases, as soon as possible. Recommendation 3:
  8. 8. 74 If vascular occlusion is suspected on clinical exam, it is recommended that non invasive testing (duplex scan) be performed and any further testing especially invasive testing like arteriogram be performed only after evaluation by a vascular surgeon. Recommendation 4: When a diabetic patient with symptoms suggesting acute limb ischemia presents himself, urgent referral to a vascular surgeon is needed to prevent amputation. Administration of analgesics and heparin before referral is acceptable, but no other medication is of any proven value in this situation. Recommendation 5: Haemorrheologic agents like pentoxyfilline can be used only in claudicators, but the drug of choice at present is cilastazole. These two have no documented value in diabetic foot ulcers and acute ischemia. Use of other drugs like vasodilators is not recommended as they have no proven value. Antiplatelet agents have definitive role to play in arterial diseases but have no effect in diabetic foot or acute ischemia. Recommendation 6: Even minor surgical procedures in diabetic foot should be preceded by adequate vascular assessment. Recommendation 7: In any diabetic foot, which has vascular insufficiency, arterial reconstruction should be attempted, if functional limb salvage can be obtained.