Pravastatin and clopidogrel combined inhibit intimal hyperplasia in a rat carotid endarterectomy model.

Intimal hyperplasia, resulting from a complex cascade of events involving platelets, leukocytes, and smooth muscle cells, may be inhibited by the HMG-CoA reductase inhibitor pravastatin, which demonstrates inhibition of platelet activity and leukocyte adhesion and may be associated with inhibition of vascular smooth muscle cell proliferation and migration. Clopidogrel, an adenosine diphosphate (ADP) receptor inhibitor, was shown to decrease platelet activity and aggregation but not intimal hyperplasia (IH). We postulated that the combination of both pravastatin and clopidogrel would significantly decrease IH in a rat carotid endarterectomy model. Male Sprague-Dawley rats (n = 18) divided by treatment regimen underwent treatment for 2 weeks both before and after an open carotid endarterectomy. Serum collected at the time of harvest was measured for C-reactive protein (CRP), platelet activity, and total serum cholesterol; carotid arteries were removed and processed for IH determination. Control rats (n = 7) received oral vehicle daily before and following endarterectomy. Pravastatin-alone rats (n = 6) received oral pravastatin (10 mg/kg/day) before and after endarterectomy. Pravastatin plus clopidogrel rats (n = 5) received oral pravastatin (10 mg/kg/day) plus a preendarterectomy bolus of oral clopidogrel (4.3 mg/kg) before endarterectomy and resumed pravastatin (10 mg/kg/day) plus oral clopidogrel (1 mg/kg/day) postendarterectomy. Pravastatin alone and pravastatin plus clopidogrel significantly decreased CRP compared to controls (120.2 +/-11.2 and 134.1 +/- 9.9 vs 191.1 +/- 9.2 microg/mL, respectively p = 0.003 and p =0.0024). CRP levels were not different between pravastatin alone and pravastatin plus clopidogrel (p = 0.35). Platelet activity was significantly decreased by pravastatin alone and pravastatin plus clopidogrel in comparison to controls (7.3 +/- 2.2 and 6.6 +/- 2.8 vs 19.2 +/- 6.1 platelet reactive units (PRU), respectively p = 0.048 and p = 0.045). No significant difference was noted in platelet activity between pravastatin alone and pravastatin plus clopidogrel (p = 0.89). Pravastatin plus clopidogrel significantly reduced serum cholesterol compared to control and pravastatin alone (84.0 +/- 6.6 vs 110.4 +/- 7.4 and 117.0 +/- 8.8 mg/dL, respectively p = 0.03 and p = 0.01). Pravastatin alone did not decrease serum cholesterol compared to controls (p = 0.54). IH was not reduced by pravastatin alone compared to controls (p = 0.61) but was significantly decreased by pravastatin plus clopidogrel in comparison to control and pravastatin alone (3.0 +/- 1.1 vs 46.3 +/- 13.7 and 37.4 +/- 14.6% luminal stenosis, respectively p = 0.01 and p = 0.05). Pravastatin plus clopidogrel significantly decreased CRP, platelet activity, total serum cholesterol, and IH while pravastatin alone decreased only CRP and platelet activity. Intimal hyperplasia reduction may therefore be dependent on other contributors, possibly growth factors, cytokines, and oxidative stress. The combination of pravastatin plus clopidogrel may have synergistic or even additional inhibitory effects on IH. Pravastatin plus clopidogrel was effective in decreasing IH in a rat carotid endarterectomy model and may prove a useful therapy for IH reduction in the clinical setting.

Percutaneous isolated limb perfusion with thrombolytics for severe limb ischemia.

Patients with severe tibioperoneal disease are poor candidates for a distal bypass. Absence of a distal target, lack of conduit, or multiple medical problems can make these patients a prohibitive risk for revascularization. Acute on chronic ischemia in this group poses a greater challenge. Thrombolytic therapy for acute ischemia can be prolonged and carries a significant risk of bleeding if continued beyond 24 hours. However, if the ischemic limbs can be isolated from the systemic circulation, a higher dose of the lytic agent can be given with lower risk. These are the initial results of a series of 10 patients who underwent percutaneous isolated limb perfusion with a high dose of thrombolytics for severe ischemia. Ten patients (lower extremity 8 and upper extremity 2) presented with severe limb-threatening ischemia. Mean ankle/brachial index (ABI) was 0.15 for the lower extremity, and there were no recordable digital pressures in patients with upper extremity ischemia. No distal target was visible on the initial arteriogram. These patients were then taken to the operating room, and under anesthesia, catheters were placed in an antegrade fashion via femoral approach in the popliteal artery and vein percutaneously. For upper extremity, the catheters were placed in the brachial artery and vein. A proximal tourniquet was then applied. This isolated the limb from the systemic circulation. Heparinized saline was infused through the arterial catheter while the venous catheter was left open. A closed loop or an isolated limb perfusion was confirmed when effluent became clear coming out of the venous port. A high dose of thrombolytic agent (urokinase 500,000 to 1,000,000 U) was infused into the isolated limb via the arterial catheter and drained out of the venous catheter. After 45 minutes, arterial flow was reestablished. In 4 patients, Reopro((R)) was used in addition to thrombolytics. Postprocedure angiograms showed minimal changes, but patients exhibited marked clinical improvement. The ABI changed from 0.15 to 0.5 in the lower extremity and near-normal digital pressures in upper extremity ischemia. Limb salvage and symptomatic relief at 6 months was 90%. All patients except one were kept on anticoagulation postoperatively. No bleeding complications were observed from the procedure. Percutaneous isolated limb perfusion brought symptomatic relief to patients presenting with acute on chronic limb ischemia. This can be an alternate option for patients facing amputation with no revascularization options.

Effect of clopidogrel on platelet aggregation and intimal hyperplasia following carotid endarterectomy in the rat.

Intimal hyperplasia results in significant morbidity and mortality following vascular intervention. Both platelets and elevated homocysteine have been implicated in the development of intimal hyperplasia. We previously demonstrated that a locally applied antiplatelet agent decreases the development of intimal hyperplasia. We were therefore interested in a systemic antiplatelet agent, clopidogrel. We hypothesized that clopidogrel would decrease platelet aggregation and activity and intimal hyperplasia. Male Sprague-Dawley rats underwent carotid endarterectomy (CEA) and treatment with either placebo or varying regimens of clopidogrel, including chronic, pre-CEA bolus, chronic plus pre-CEA bolus, and chronic plus post-CEA bolus; a homocystine diet was used to elevate both plasma homocysteine and the degree of intimal hyperplasia. Platelet aggregation, platelet activity, and intimal hyperplasia were then assessed. Platelet aggregation was not decreased with chronic clopidogrel; however, it was decreased with pre-CEA bolus clopidogrel. Similarly, platelet activity was not inhibited by chronic clopidogrel but was inhibited by pre-CEA and chronic plus pre-CEA bolus clopidogrel. Neither chronic, pre-CEA bolus, chronic plus pre-CEA bolus, nor chronic plus post-CEA bolus clopidogrel resulted in a decrease in intimal hyperplasia. Although pre-CEA bolus clopidogrel resulted in a decrease in both platelet aggregation and activity, it was unable to decrease the development of intimal hyperplasia at any dose. Additional factors must therefore contribute to the pathologic development of intimal hyperplasia.