Therapy

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Therapy for PVD should involve a patient care plan consisting of (1) patient education on pathophysiology of atherosclerosis, risk factors that contribute to disease, and prognosis; (2) encouragement of lifestyle changes that emphasize risk factor modification and routine exercise; (3) pharmacologic therapy to relieve symptoms and treat risk factors; and (4) revascularization procedures to relieve IC and limb salvage in CLI. The goals of therapy are to improve the patient's functional status by relieving symptoms, improving the quality of life, and improving exercise capacity; preserve the limb via revas-cularization and decrease or limit the extent of amputation; prevent the progression of atherosclerosis by aggressive risk factor modification; and reduce cardiovascular and cerebro-vascular mortality and nonfatal events such as MI and stroke.

Risk Factor Management

By far the most important therapy for both primary and secondary prevention of PVD is aggressive management of the risk factors for atherosclerosis. Both the American Heart Association (AHA) and the National Cholesterol Education Program (NCEP) recommend the same level of risk factor modification in patients with PVD as in patients with known CAD (Grundy et al., 2004; Smith et al., 2001). Despite the growing recognition that PVD is associated with a higher mortality rate, the risk factors in patients with PVD have historically been grossly undertreated. This is exemplified by data on a cohort of 1733 patients with known PVD and no overt CAD. Of these patients, only 33.1% were receiving beta-blockade therapy, 28.9% were receiving ACEIs, and 31.3% were treated with a statin. Furthermore, 92% had a recent BP measurement, but 56% had SBP greater than 130 mm Hg, 45.5% had DBP >80 mm Hg, and 13.6% had DBP

>90 mm Hg. In addition, only 62.6% had a screening lipid profile, yet 56% had an LDL-C >100 mg/dL, and 21% had an LDL-C >130 mg/dL. Finally, in patients with diabetes, HbA1c was >7.0% in 54.2% of patients (Rehring et al., 2005). Unfortunately, such data are representative of current practice patterns. The risk factors of atherosclerosis must be aggressively identified and treated to reduce risk for disease progression.

Exercise

Routine aerobic exercise is recommended for all patients with PVD. The benefit of walking programs has been clearly established to increase time-to-claudication and maximal walking distance (Hiatt and Regensteiner, 1990; Hiatt et al., 1994). Regular exercise will have a strong impact on improving functional capacity and quality of life. A minimum of 30 to 60 minutes of exercise is recommended preferably daily, but at least three or four times a week. This should be supplemented by an increase in daily lifestyle activities, such as walking breaks at lunch, gardening, or household chores (Smith et al., 2001).

Weight Management

Obesity is at epidemic levels, which ultimately contributes to the progression of atherosclerosis. Patients should be counseled on weight loss strategies with a target body mass index (BMI) of 18.5 to 24.9 kg/m2 (Smith et al., 2001).

Pharmacologic Therapy

Pharmacologic treatment can be divided into two separate but equally important components: therapy for the control of risk factors and therapy for the relief of symptoms of ischemia or claudication.

Pharmacologic therapy for risk factor modification is the same as for any other forms of atherosclerotic vascular disease, such as coronary or cerebrovascular disease. The most important consideration is that the mortality of patients with PVD is high, and thus they should be treated aggressively. Current national guidelines should be adhered to for the primary and secondary prevention of atherosclerotic vascular disease (ADA, 2005; Grundy et al., 2004; Seventh Report, 2004; Smith et al., 2001). The four primary categories of pharmacologic therapy include antiplatelet therapy, lipid-lowering therapy, antihypertensive therapy, and glycemic-lowering therapy, as discussed earlier. These therapies are complementary and confer additive benefit. From a practical standpoint, patients with several comorbidities may be taking multiple medications daily, so to ensure compliance, they should be repeatedly educated as to the importance of risk factor control.

The only FDA-approved pharmacologic therapy that has a consensus of benefit for the relief of claudication is cilostazol (Pletal). Cilostazol is a phosphodiesterase III inhibitor, which increases the intracellular concentration of cAMP, leading to significant antiplatelet and vasodilatory properties and possibly antiproliferative properties (Tsuchikane et al., 1999). Cilostazol undergoes extensive metabolism by the hepatic cytochrome P4503A4 (CYP3A4) isoform enzyme, and to a lesser extent the 2C19 and 1A2 isoforms. Although cilostazol does not inhibit the CYP450 system, drugs that inhibit CYP3A4, 2C19, and 1A2 can lead to increased levels of cilostazol in serum.

Pentoxifylline (Trental) is another drug FDA approved for claudication. However, no randomized data demonstrate a

Week

Figure 27-27 Mean percentage change from baseline maximum walking distance on a treadmill for patients with intermittent claudication randomly assigned to cilostazol, pentoxifylline, or placebo. *p <0.05 at each 4-week time point for cilostazol versus placebo and pentoxifylline. (Reprinted with permission from Exerpta Medica. Dawson DL, Cutler BS, Hiatt WR, et al: A Comparison of cilostazol and pentoxifylline for treating intermittent claudication. Am J Med 2000;109:523-530, Figure 2.)

Week

Figure 27-27 Mean percentage change from baseline maximum walking distance on a treadmill for patients with intermittent claudication randomly assigned to cilostazol, pentoxifylline, or placebo. *p <0.05 at each 4-week time point for cilostazol versus placebo and pentoxifylline. (Reprinted with permission from Exerpta Medica. Dawson DL, Cutler BS, Hiatt WR, et al: A Comparison of cilostazol and pentoxifylline for treating intermittent claudication. Am J Med 2000;109:523-530, Figure 2.)

1980 1985 1990 1995 2000

Figure 27-28 Volume trends for percutaneous revascularization and surgical revascularization for the lower extremities from 1980 through 2000. Data obtained by reviewing ICD-9 codes for all vascular procedures using the National Hospital Discharge Survey of nonfederal U.S. hospitals. (Modified from Anderson PL, Gelijns A, Moskowitz A, et al. Understanding trends in inpatient surgical volume: vascular interventions, 1980-2000. J Vasc Surg 2004;39:1200-1208.)

1980 1985 1990 1995 2000

Figure 27-28 Volume trends for percutaneous revascularization and surgical revascularization for the lower extremities from 1980 through 2000. Data obtained by reviewing ICD-9 codes for all vascular procedures using the National Hospital Discharge Survey of nonfederal U.S. hospitals. (Modified from Anderson PL, Gelijns A, Moskowitz A, et al. Understanding trends in inpatient surgical volume: vascular interventions, 1980-2000. J Vasc Surg 2004;39:1200-1208.)

that it is better than placebo, so there is no recommendation to use this agent for the treatment of claudication. Eight RCTs compared cilostazol to placebo and pentoxifylline (Smith, 2002). In all studies, cilostazol demonstrated a statistically significant improvement in objective and subjective end points compared to placebo. In one study, comparing cilostazol (100 mg twice daily) with pentoxifylline (400 mg three times dally) or placebo, the maximal walking distance on a treadmill increased by 54% from baseline in the cilostazol group, versus 30% increase in the pentoxifylline group (p <0.001), and 34% increase in the placebo group (Fig. 27-27) (Dawson et al., 2000).

Revascularization

Peripheral arterial revascularization is indicated for relief of isch-emic symptoms, including intermittent claudication and resting ischemic pain, and limb preservation in the setting of critical limb ischemia. Historically, revascularization has been performed surgically; however, with advances in endovascular technology, a percutaneous approach is now considered first-line therapy. From 1995 to 2000, the number of percutaneous revascularizations performed in the United States increased by almost 1000%, compared to a 30% to 35% decrease in the number of surgical revascularizations (Fig. 27-28) (Anderson et al., 2004).

An endovascular approach confers a similar acute procedural success rate and similar long-term results, with considerably less periprocedural morbidity, shorter recovery time, shorter hospitalization time, and less pain than a surgical procedure. In addition, failure of the two therapies is completely different. With surgical therapy, graft closure is often sudden without sufficient time to develop collateral flow, leaving the limb in an acutely ischemic situation that frequently results in major amputation. Furthermore, surgical therapy can only be repeated a limited number of times, as dissection planes, surgical targets, and anastomosis sites become obliterated by repetitive surgery and conduit becomes exhausted. On the other hand, restenosis by neointimal hyperplasia of an endo-vascular procedure is a well documented, slow process that occurs over weeks to months, and thus gives the limb ample time to develop collateral flow. Patients returning with failure of an endovascular procedure rarely do so in a limb-threatening situation. Moreover, an endovascular procedure can be repeated as often as necessary to maintain vessel patency.

The appeal of a minimally invasive approach for revascularization is that it significantly lowers the threshold of when to treat patients. Traditional surgical dogma has reserved revascularization until there is a limb-threatening situation. However, this leaves many patients left to face debilitating IC inadequately treated. Endovascular therapy offers a paradigm shift in this philosophy. Because it is safer, effective, and reproducible, patients can be treated earlier in the disease process during the claudication stage, with marked improvement in quality of life (Dippel et al., 2004). Figure 27-29 shows an artery before and after an endovascular revascularization.

From 150,000 to 200,000 nontraumatic amputations are done annually (ADA Fact Sheet, 2005). The alarming statistic is that 40% to 50% of limbs are amputated without a presur-gical angiogram. It is estimated that more than 90% of these limbs could be salvaged, or converted to a lesser amputation, with revascularization. Another advantage of an endovascu-lar approach over a surgical approach is that totally occluded arteries can be revascularized endovascularly with a high acute procedural success rate, even when no distal targets are available to bypass and surgery is not technically feasible. Therefore, it is recommended that patients with CLI or claudication not adequately alleviated with medical therapy be referred for endovascular revascularization. If an endovascular approach is not viable, surgical therapy should be considered as a second-line alternative.

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