Statins and Peripheral Arterial Disease: Potential Mechanisms and Clinical Benefits

Barriers to Antiplatelet and Statin Adherence Following Major Vascular Intervention

OBJECTIVES

Antiplatelet and statins therapies are associated with improved cardiovascular outcomes following major vascular intervention. Many vascular surgery institutions are reporting improved prescribing rates for aspirin, P2Y12 antagonists, and statins. Nevertheless, there remains limited publication describing rates and patient-perceived barriers for postoperative adherence. The purpose of this study is to investigate patient non-adherence to antiplatelet and statin therapies following major vascular intervention.

METHODS

A retrospective review of patients who underwent major vascular intervention at a single academic center was performed. The prescribing rates of aspirin, P2Y12 antagonists, and statins were reviewed. Postoperative adherence, defined as consistent intake as prescribed, was evaluated at 1, 3, 6, 9, and 12 months using electronic documentation of both follow-up clinic appointments and phone call assessments then corroborated with pharmacy fulfillment records. Patient-reported barriers for medication adherence were also examined.

RESULTS

A total of 101 subjects underwent major vascular intervention between January 2020 and July 2020, 98% of whom were discharged on at least one antiplatelet or statin agent. Approximately 90% of patients were discharged with aspirin, 32% with a P2Y12 antagonist, and 96% with a statin. All patients who maintained adherence up to 6 months continued to report adherence at 9 and 12 months. Consistent adherence at 12 months was documented in 76% of patients on aspirin, 81% on P2Y12 antagonism therapy, and 73% on statins. New adverse drug reactions represented the most common barrier to achieving adherence (37%[n=20]). Preoperative therapy with aspirin, P2Y12 antagonists, and statins were all independently predictive for postoperative adherence to the same regimen (p<0.001). Female gender was also associated with higher rates of adherence to postoperative P2Y12 antagonism therapy (p<0.05).

CONCLUSIONS

The current prescribing rates for antiplatelet and statin agents are promising, but postoperative non-adherence remains a multifaceted issue.

Toward a Better Understanding of Muscle Microvascular Perfusion During Exercise in Patients With Peripheral Artery Disease: The Effect of Lower-Limb Revascularization

PURPOSE

Leg muscle microvascular blood flow (perfusion) is impaired in response to maximal exercise in patients with peripheral artery disease (PAD); however, during submaximal exercise, microvascular perfusion is maintained due to a greater increase in microvascular blood volume compared with that seen in healthy adults. It is unclear whether this submaximal exercise response reflects a microvascular impairment, or whether it is a compensatory response for the limited conduit artery flow in PAD. Therefore, to clarify the role of conduit artery blood flow, we compared whole-limb blood flow and skeletal muscle microvascular perfusion responses with exercise in patients with PAD (n=9; 60±7 years) prior to, and following, lower-limb endovascular revascularization.

MATERIALS AND METHODS

Microvascular perfusion (microvascular volume × flow velocity) of the medial gastrocnemius muscle was measured before and immediately after a 5 minute bout of submaximal intermittent isometric plantar-flexion exercise using contrast-enhanced ultrasound imaging. Exercise contraction-by-contraction whole-leg blood flow and vascular conductance were measured using strain-gauge plethysmography.

RESULTS

With revascularization there was a significant increase in whole-leg blood flow and conductance during exercise (p<0.05). Exercise-induced muscle microvascular perfusion response did not change with revascularization (pre-revascularization: 3.19±2.32; post-revascularization: 3.89±1.67 aU.s-1; p=0.38). However, the parameters that determine microvascular perfusion changed, with a reduction in the microvascular volume response to exercise (pre-revascularization: 6.76±3.56; post-revascularization: 2.42±0.69 aU; p<0.01) and an increase in microvascular flow velocity (pre-revascularization: 0.25±0.13; post-revascularization: 0.59±0.25 s-1; p=0.02).

CONCLUSION

These findings suggest that patients with PAD compensate for the conduit artery blood flow impairment with an increase in microvascular blood volume to maintain muscle perfusion during submaximal exercise.

CLINICAL IMPACT

The findings from this study support the notion that the impairment in conduit artery blood flow in patients with PAD leads to compensatory changes in microvascular blood volume and flow velocity to maintain muscle microvascular perfusion during submaximal leg exercise. Moreover, this study demonstrates that these microvascular changes are reversed and become normalized with successful lower-limb endovascular revascularization.

Effectiveness of Intravenous Ilomedin Infusion and Smoking Cessation in the Treatment of Acutely Symptomatic Buerger Disease

We assessed the effectiveness of iloprost treatment in the management of symptomatic Buerger disease (BD) and assessed smoking cessation compliance, based on a single-center experience. Thirteen patients with BD were treated with sessions of intravenous (IV) Ilomedin infusion. At 1-year follow-up, pain status alteration, number of analgesics required, ankle–brachial index (ABI) change, compliance with supervised smoking cessation, and amputation-free rate were recorded. The pain status improved considerably according to a visual analog scale, the number of analgesics required was significantly reduced, and all patients improved their pain-free walking distance, the ABI, and their self-reported quality of life. Only 2 patients required minor amputations. Combination of IV Ilomedin infusion, supervised smoking cessation, and a specific follow-up protocol may lead to improvement in pain-free walking distance, pain status, quality of life, and substantial reduction in amputation risk.

Preoperative Statins and Limb Salvage After Lower Extremity Revascularization in the Medicare Population

Background—

Statins stabilize atherosclerotic plaque, decrease mortality after surgical procedures, and are linked to anti-inflammatory effects. The objective of this study was to evaluate preoperative administration of statins and longitudinal limb salvage after lower extremity endovascular revascularization and lower extremity open surgery.

Methods and Results—

Patients were selected from 2007 to 2008 Medicare claims using the International Classification of Diseases, Ninth Revision, Clinical Modification , diagnosis codes for claudication (N=8128), rest pain (N=3056), and ulceration/gangrene (N=11 770) and Current Procedural Terminology codes for endovascular revascularization (N=14 353) and open surgery (N=8601). Half (N=11 687) were identified as statin users before revascularization using Part D files. Amputations were identified using Current Procedural Terminology codes. Statin users compared with nonusers had lower amputation rates at 30 days (11.5% versus 14.4%; P <0.0001), 90 days (15.5% versus 19.3%; P <0.0001), and 1 year (20.9% versus 25.6%; P <0.0001). Survival analysis demonstrated improved limb salvage during 1 year for statin users compared with nonusers for the diagnosis of claudication ( P =0.003), a similar trend for rest pain ( P =0.061), and no improvement for ulceration/gangrene ( P =0.65).

Conclusions—

Preoperative statins were associated with improved 1-year limb salvage after lower extremity revascularization. The strongest association was found for patients with the diagnosis of claudication. Statins seem to be underused among Medicare patients with peripheral artery disease. Further evaluation of the use of preoperative statins and the potential benefits for peripheral vascular interventions is warranted.

Peripheral arterial disease: implications beyond the peripheral circulation

Peripheral arterial disease (PAD) affects a considerable percentage of the population. The manifestations of this disease are not always clinically overt. As a result, PAD remains underdiagnosed and undertreated. PAD is not just a disease of the peripheral arteries, but also an indication of generalized vascular atherosclerosis. PAD patients also have a high prevalence of other arterial diseases, such as coronary/carotid artery disease and abdominal aortic aneurysms. PAD is also a predictor of increased risk of lung and other cancers. The most often used examination for the establishment of the diagnosis of PAD, the ankle-brachial pressure index (ABPI), is also a predictor of generalized atherosclerosis, future cardiovascular events and cardiovascular mortality. Several markers that have been linked with PAD (e.g. C-reactive protein, serum bilirubin levels) may also have predictive value for other conditions besides PAD (e.g. kidney dysfunction). The management of PAD should therefore not be restricted to the peripheral circulation but should include measurements to manage and decrease the systemic atherosclerotic burden of the patient.

Monocyte chemoattractant protein 1 is correlated with glycemic control and peripheral arterial disease in type 2 diabetic patients with metabolic syndrome

We evaluated the serum levels of monocyte chemoattractant protein 1 (MCP-1) and their association with peripheral arterial disease (PAD) in 199 patients with type 2 diabetes mellitus (T2DM) and metabolic syndrome ([MetS], group A) in comparison with 109 healthy controls (group B). In group A, MCP-1 levels were significantly (P < .001) higher than group B and exhibited a positive correlation with HbA1c (P < .001) and a negative correlation with ankle-brachial index (P < .001). In the same group, patients with PAD had significantly higher MCP-1 levels compared with those without PAD (P < .001). In conclusion, T2DM patients with MetS exhibit higher serum MCP-1 levels. The latter is associated with worse glycemic control and PAD. These results suggest a potential contributory role for MCP-1 in the pathogenesis of PAD in the presence of hyperglycemia and MetS in T2DM.

The role of hyperbaric oxygen in the treatment of diabetic foot ulcers

Diabetic foot ulcers are still extremely difficult to heal. Therefore, therapeutic options to improve healing rates are continuously being explored. Hyperbaric oxygen (HBO) has been used in addition to standard treatment of the diabetic foot for more than 20 years. Evidence suggests that HBO reduces amputation rates and increases the likelihood of healing in infected diabetic foot ulcers, in association with improved tissue oxygenation, resulting in better quality of life. Nonetheless, HBO represents an expensive modality, which is only available in few centers. Moreover, adverse events necessitate a closer investigation of its safety. Finally, it is not entirely clear which patients stand to benefit from HBO and how these should be selected. In conclusion, HBO appears promising, but more experience is needed before its broad implementation in the routine care of the diabetic foot.

Optimal statin type and dosage for vascular patients

Statins are an essential component of the management of patients suffering from vascular diseases. As there is neither any consensus nor any guidelines regarding this issue, we aimed to define the optimal statin type and dosage for these patients. MEDLINE was searched for studies comparing different statin types and dosages for vascular patients. In the absence of adverse effects, rosuvastatin or atorvastatin ≥ 20 mg/d is the optimal statin type and dosage for vascular patients. The management of statin-induced adverse events and the options for statin-intolerant patients are also discussed. Routine statin treatment is associated with several beneficial effects in vascular patients whether managed conservatively or undergoing open vascular surgery/endovascular interventions. If possible, statins should not be discontinued before open or endovascular procedures and treatment should be resumed as soon as possible. Future studies should evaluate the effects of an increased statin loading dose prior to vascular procedures.

Dorsal (Posterior) Versus Medial Approach for the Surgical Repair of Popliteal Artery Aneurysms

The surgical approach-of-choice for the management of popliteal artery aneurysms (PAAs) remains controversial. We compared the results of the medial (MA) and dorsal (posterior) surgical approach (DA). Fifty patients (44 males/6 females; median age [range]: 59 [49-84] years) treated for 58 atherosclerotic PAAs were studied (MA: 29 PAAs; DA: 29 PAAs). The 3-year graft patency rates were higher after DA compared with MA (76% vs 52%, respectively), but the difference was not significant (P = .056). There were no differences between the 2 approaches in amputation, restenosis, reoperation, and wound infection rates. Dorsal approach and the MA may be alternative approaches with similar long-term results. Due to the controversial results reported so far, a meta-analysis may be necessary to establish the surgical approach-of-choice. Future studies should take into account additional factors, other than the surgical technique, when assessing outcome (eg, preoperative statin use, age, and emergency vs routine surgery).

Decreasing amputation rates in patients with diabetes-a population-based study

AIMS

To assess the changing rate of amputation in patients with diabetes over a 7-year period.

METHODS

All patients undergoing lower extremity amputation in Tayside, Scotland between 1 January 2000 and 31 December 2006 were identified. Temporal linkage of cases to the diabetes database was used to ascertain which amputations were in patients with diabetes.

RESULTS

The incidence of major amputations fell from 5.1 [95% confidence interval (CI) 3.8-6.4] to 2.9 (95% CI 1.9-3.8) per 1000 patients with diabetes (P < 0.05). There is a clear linear trend in the adjusted incidence of major amputation (P = 0.023 and 0.027 for age- and sex-adjusted, and duration- and sex-adjusted incidences, respectively). The adjusted incidence of total amputations followed decreased linear regression trend over the whole study period when adjusted for age and sex or diabetes duration and sex (P = 0.002).

CONCLUSIONS

There has been a significant reduction in the incidence of major lower extremity amputation in patients with diabetes over the 7-year period.

Statin treatment, carotid atherosclerotic plaque macrophage infiltration and circulating inflammatory markers

BACKGROUND

Statin treatment is considered as first line therapy in patients with atherosclerotic disease. We evaluated the effect of pre-treatment with statins on carotid plaque infiltration by macrophages and on the circulating levels of proinflammatory cytokines in patients who underwent carotid endarterectomy.

PATIENTS AND METHODS

One hundred fourteen patients were enrolled; 89 men and 25 women (mean age 67+/-8 years; range 42-83 years). Fifty three patients (46%) were on statin treatment at least 3 months before endarterectomy and 61 (54%) had never received statin treatment. The serum levels of high sensitivity C reactive protein (hsCRP), serum amyloid A (SAA), tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta and IL-6 were evaluated preoperatively. The intensity of macrophage infiltration was evaluated by immunochemistry, using the monoclonal antibody CD 68. The area of the plaque covered by macrophages was measured as a proportion of the whole plaque area, using a custom designed image tool analysis.

RESULTS

Patients on statins had lower serum total cholesterol levels (172+/-50 vs 194+/-35 mg/dl, p= 0.014), lower low density cholesterol levels (103+/-44 vs 123+/-31 mg/dl, p= 0.010) and lower serum hsCRP levels (1.8 [1.1-3.4] vs 3.4 [1.3-4.9] mg/l, p= 0.03), while SAA, TNFalpha, IL-6 and IL-1beta levels did not differ between the 2 groups. The infiltration of atherosclerotic plaque by macrophages was similar in statin treated patients and in controls (0.55+/-0.15% vs 0.49+/-0.19%, p= 0.21).

CONCLUSION

Patients on statins have similar macrophage accumulation in their carotid atherosclerotic plaques compared with patients not on statins. Inflammatory markers were also similar in both groups except for hsCRP which was significantly lower in those taking statins.

Do Different Vascular Risk Factors Affect All Arteries Equally?

Established vascular risk factors (ie, smoking, hypertension, diabetes mellitus, and dyslipidemia) play an important role in the development of vascular disease. Emerging evidence suggests that some of these risk factors may have a more intense effect on specific arterial beds, a finding that holds implications for a prognostic role for certain types of vascular disease.

Assessment of Lower Extremity Peripheral Arterial Disease Using a Novel Automated Optical Device

The resting ankle-brachial pressure index (rABPI) is used in the diagnosis of lower extremity peripheral arterial disease (PAD) in symptomatic and asymptomatic patients. This article compares the rABPI with a new optical device based on photoplethysmograph (PPG) technology with new algorithms for the assessment of PAD. Functional PPG (fPPG) is a promising noninvasive automated device using a novel cuffless functional test for assessing mild or significant PAD without the operator dependency issues associated with rABPI. This system utilizes both changes in pulsatile arterial blood volume and skin color redness in lower limbs. All subjects underwent rABPI, fPPG, and duplex angiography (DA). Significant correlation was found between fPPG and DA scores, rABPI and DA, and fPPG and rABPI. In the hands of operators with little experience, fPPG may prove to be superior to rABPI and may be useful as a simple screening tool for early detection of PAD in primary care.

The role of fibrinogen and fibrinolysis in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with high rates of cerebrovascular and cardiovascular events; PAD is a marker of systemic atherosclerosis. As a result, standard therapy for all PAD patients should be directed at both peripheral and systemic atherosclerosis. Modification of established risk factors in the form of smoking cessation, correcting hypertension, optimizing diabetic control and normalizing lipids is essential. Furthermore, novel risk factors have emerged including fibrinogen and other hemostatic factors. Fibrinogen is a coagulation factor and a marker of the acute phase response (inflammation), a platelet activator, a major determinant of plasma viscosity and a component of the atherosclerotic plaque. Fibrinogen appears not only to predict the severity of PAD, but also serves as a marker for future development of PAD. Whether reducing the levels of fibrinogen and other coagulation factors will decrease the incidence and progression of PAD remains to be resolved. This review summarizes the role of fibrinogen in the pathogenesis of PAD and its association with other hemostatic factors. The role of fibrinolysis in patients with PAD is also considered.

The role of established and emerging risk factors in peripheral vascular graft occlusion

Several studies have evaluated the association between established as well as emerging vascular risk factors with peripheral graft occlusion. There is evidence for a link between the risk for graft occlusion and total serum cholesterol, low-density lipoprotein cholesterol and triglyceride levels. The overall effect of smoking shows a 2.35-fold increase in risk of graft failure. Studies involving diabetic patients undergoing peripheral bypass may have failed to detect higher occlusion rates, possibly due to increased morbidity and mortality as well as higher amputation rates even if the graft is patent. Both antiplatelet agents and anticoagulation seem to be effective in the prevention of graft occlusion. Unconvincing data have been published with regards to the effect of hypertension on graft patency. Emerging factors such as fibrinogen, lipoprotein (a), C-reactive protein and homocysteine levels should also be considered when assessing the risk of graft occlusion. More research is needed to prevent graft occlusion due to the obvious clinical relevance, quality of life and cost issues.