Detection of platelet deposition at the site of peripheral balloon angioplasty using indium-111 platelet scintigraphy

Changes in serum serotonin levels in patients with acute coronary syndrome and stable angina undergoing percutaneous coronary intervention

OBJECTIVE

Activated platelets release serotonin, causing platelet aggregation and vasoconstriction. Serotonin levels were investigated in patients with acute coronary syndrome (ACS) and chronic stable angina (CSA) treated with percutaneous coronary intervention (PCI).

METHODS

Consecutive patients undergoing PCI for either ACS or CSA were enrolled between July 2009 and April 2010. Patients were pre-treated with dual antiplatelet agents (aspirin and clopidogrel) before PCI. Serum serotonin levels, measured at baseline, pre- and post-PCI, and at 90 min, and 6, 12, 24 and 48 h following PCI, were compared between ACS and CSA groups.

RESULTS

Sixty-three patients with ACS and 60 with CSA were included. Overall baseline characteristics were similar between the two groups. Serotonin levels at post-PCI (55.2 ± 120.0 versus 20.1 ± 24.0) and at peak (regardless of timepoint; 94.0 ± 170.9 versus 38.8 ± 72.3) were significantly higher in the ACS versus CSA group. At 90 min and 6, 24 and 48 h post-PCI, serum serotonin was numerically, but not significantly, higher in patients with ACS. Serotonin levels fluctuated in both groups, showing an initial rise and fall, rebound at 24 h and drop at 48 h post-PCI.

CONCLUSIONS

In patients undergoing PCI, serum serotonin was more elevated in patients with ACS than those with CSA, suggesting the need for more potent and sustained platelet inhibition, particularly in patients with ACS.

Sarpogrelate Based Triple Antiplatelet Therapy Improved Left Ventricular Systolic Function in Acute Myocardial Infarction: Retrospective Study

PURPOSE

The purpose of this study was to assess the potential benefit of a 5-hydroxytryptamine receptor antagonist, sarpogrelate-based triple antiplatelet therapy (TAPT) in comparison with dual antiplatelet therapy (DAPT) in patients undergoing primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI).

MATERIALS AND METHODS

119 patients of STEMI were retrospectively assessed. All patients received aspirin and clopidogrel per standard of care. Among them, 53 patients received an additional loading dose of sarpogrelate and a maintenance dose for 6 months post-PCI (TAPT group), while others did not (DAPT group).

RESULTS

The rates of complete ST-segment resolution at 30 minutes post-PCI and post-procedural thrombolysis in myocardial infarction flow were not significantly different between the two groups (52.8% vs. 48.5%, p=0.200; 92.5% vs. 89.4%, p=0.080). In addition, no significant differences were observed between the two groups with regard to 30-day and 12-month clinical outcomes (cardiac death, myocardial infarction, stent thrombosis, target vessel revascularization, and severe bleeding). Meanwhile, improvement in left ventricular (LV) systolic function was observed in the TAPT group [ΔLV ejection fraction (LVEF)=17.1±9.4%, p<0.001; Δglobal longitudinal strain (GLS)=-9.4±4.2% , p<0.001] at 6 months, whereas it was not in the DAPT group (ΔLVEF= 8.8±6.5%, p=0.090; ΔGLS=-4.6±3.4%, p=0.106). In multivariate analyses, TAPT was an independent predictor for LV functional recovery (odds ratio, 2.61; 95% confidence interval, 1.16-5.87; p=0.003).

CONCLUSION

Sarpogrelate-based TAPT improved LV systolic function at 6 months in STEMI patients undergoing primary PCI.

The use of adjunctive GPIIb/IIIa inhibitors in patients with unstable angina/non-Q-wave MI undergoing percutaneous coronary intervention

Glycoprotein IIb/IIIa receptor inhibitors represent a relatively new therapeutic approach in the field of antiplatelet therapy. Following the development of abciximab a number of small molecule GPIIb/IIIa inhibitors have been introduced such as tirofiban and eptifibatide. In this fast-moving field the interventional cardiologist needs a framework to guide decision-making for the individual patient. This review covers the efficacy and safety data from the clinical trials of GPIIb/IIIa inhibitors in the context of patients undergoing percutaneous coronary intervention for unstable angina/non-Q-wave myocardial infarction. There is an increasing body of evidence to support the efficacy of GPIIb/IIIa inhibitors in reducing the risk of adverse ischemic events in high and low risk patients undergoing percutaneous coronary intervention. A number of unresolved efficacy and safety issues remain, including the duration of treatment before and after intervention; whether a reduction in the heparin dose would further decrease the risk of hemorrhage without affecting the periprocedural thrombotic rate in patients undergoing PTCA with adjunctive GPIIb/IIIa inhibitors; and the cost-effectiveness of this therapy. When a thorough analysis of cost-effectiveness has been made, it will be easier to advocate the widespread use of these agents in all patients undergoing coronary intervention.

A multicenter study of the tolerability of tirofiban versus placebo in patients undergoing planned intracoronary stent placement

BACKGROUND

The use of intravenous glycoprotein IIb/IIIa-receptor antagonists has been shown to improve outcomes in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Tirofiban has shown benefit in a wide range of patients presenting with acute coronary syndromes. Although this agent has been used in patients undergoing percutaneous coronary intervention, a literature search identified no prospective data comparing tirofiban with placebo in patients undergoing planned intracoronary stent placement.

OBJECTIVE

This study examined the tolerability of tirofiban in patients undergoing percutaneous intervention with planned intracoronary stent placement.

METHODS

This was a multinational, multicenter, prospective, randomized, double-blind, placebo-controlled trial in patients scheduled to undergo PTCA with planned intracoronary stent placement. Patients were randomized in a 3:2 ratio to receive tirofiban as an intravenous bolus (10 microg/kg over 3 minutes) and maintenance infusion (0.10 microg/kg per minute for 36 hours) or a bolus and infusion of placebo. All patients received periprocedural aspirin and heparin and an optional postprocedural thienopyridine (ticlopidine or clopidogrel). Laboratory and safety monitoring were performed throughout the 36 hours after the procedure and at hour 40 or hospital discharge. The primary end point was the proportion of patients with bleeding, defined according to Thrombolysis in Myocardial Infarction (TIMI) trial criteria. The number of patients with cardiac events (death, myo- cardial infarction, urgent revascularization) during the first 30 days after stent placement was also assessed.

RESULTS

Eight hundred ninety-four patients (536 tirofiban, 358 placebo) were enrolled, all of whom received aspirin and heparin periprocedurally and optional ticlopidine or clopidogrel after the procedure. No significant between-group differences were observed in the incidence of TIMI major bleeding (0.2% tirofiban, 0.6% placebo) or any TIMI bleeding (3.2% and 1.7%, respectively). The incidence of TIMI minor bleeding was higher with tirofiban than with placebo (2.8% vs 0.6%). The 30-day incidence of the composite end point of any cardiac event was 3.9% in both groups.

CONCLUSIONS

On a background of concomitant aspirin, heparin, and a thienopyridine, tirofiban was generally well tolerated in patients undergoing PTCA with planned intracoronary stent placement. Further investigation is needed to ascertain the optimal dosing of tirofiban and heparin to achieve reductions in ischemic complications of intracoronary stenting with an acceptable incidence of bleeding complications.

Coronary stenting and platelet glycoprotein IIb/IIIa receptor blockade in acute myocardial infarction

BACKGROUND

Myocardial reperfusion in patients with acute myocardial infarction may be successfully achieved with primary angioplasty. However, angioplasty, as a primary reperfusion strategy, has limitations such as early recurrent ischemia and late restenosis and reocclusion. To improve the short- and long-term results of primary angioplasty, the use of adjunct strategies has been proposed.

METHODS

We reviewed published studies on the effectiveness of primary angioplasty, stenting, and platelet glycoprotein IIb/IIIa receptor blockade and identified the advantages and disadvantages of these interventions in patients with acute myocardial infarction.

RESULTS

Recent findings suggest that patients may benefit from stenting of the infarct artery and from the use of more potent antiplatelet agents such as platelet glycoprotein IIb/IIIa receptor inhibitors. In randomized trials that compared primary angioplasty versus primary stenting, stent implantation was associated with a lower rate of death, reinfarction, and especially target vessel revascularization. Platelet glycoprotein IIb/IIIa receptor inhibitors prevented acute ischemic complications after primary angioplasty and primary stenting. In addition to maintaining large vessel patency, these drugs may protect the microvasculature after primary stenting, allowing better functional recovery of the risk area.

CONCLUSIONS

Coronary artery stenting in acute myocardial infarction reduces the rate of restenosis and the incidence of problems related to recurrent ischemia. Platelet glycoprotein IIb/IIIa receptor inhibitors may come to play a key role in association with mechanical reperfusion. However, the cost-effectiveness and long-term clinical outcome of this combined pharmacologic/mechanical intervention require further study before this strategy can be recommended for routine use.

A safe and effective regimen without heparin therapy after successful primary coronary stenting in patients with acute myocardial infarction

Short-term heparin therapy has been administered routinely after primary coronary stenting. However. heparin therapy results in a significantly higher incidence of bleeding and vascular complications. A new therapeutic regimen of ticlopidine and aspirin without further heparin after coronary stenting in patients without AMI has been shown to be safe and reduce the incidence of stent thrombosis. The aim of this study was to evaluate whether a new therapeutic regimen of aspirin and ticlopidine without heparin is safe and effective in patients with acute myocardial infarction (AMI) who have undergone primary coronary stenting and have Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow in the infarct-related artery. Between January 1997 and September 1999, one hundred and fifty two consecutive patients with AMI on Killip score 1 or 2 who underwent primary coronary stenting resulting in TIMI grade 3 flow were enrolled and divided into two groups: Group 1 (n = 95 patients) received aspirin, ticlopidine and further intravenous heparin infusion for 48 hours following primary coronary stenting; Group 2 (n = 57 patients) received only aspirin and ticlopidine without further heparin therapy following primary coronary stenting. No in-hospital major cardiac events were observed in either group. However, the combined incidence of bleeding and vascular complications (27.4% vs 12.3%, p = 0.029) and the need for blood transfusions (9.5% vs 0%, p = 0.013) were significantly higher in Group I patients. Furthermore, hospital stay was also longer in Group I patients (5.8+/-2.4 vs 4.7+/-1.7 days, p = 0.0003). At the 30-day follow-up, there were no differences (1.05% vs 0%, p = 0.63) in the combined incidence of vascular complications and the major cardiac events were similar (1.05% vs 1.75%, p = 0.71) between the groups. The results suggest that further heparin therapy following primary coronary stenting increases the combined incidence of bleeding and vascular complications as well as the need for blood transfusions and prolongs the length of hospital stay without further benefit to those patients with coronary flow restored to TIMI 3 grade flow.

Antiplatelet use in interventional cardiology

Thrombosis within the target vessel is one of the most feared complications associated with coronary intervention, as it is often associated with severe adverse clinical sequelae. This thrombosis is mediated via the activation and aggregation of platelets and therefore considerable effort has been directed at ways of inhibiting platelet function. It is now mandatory to consider the use of two and often three different antiplatelet agents, particularly when intracoronary stents are inserted. Using these regimes, many of the adverse clinical outcomes associated with platelet activation can be reduced.

Abciximab in primary coronary angioplasty for acute myocardial infarction improves short- and medium-term outcomes

OBJECTIVES

The purpose of this study was to compare the outcome of primary percutaneous transluminal coronary angioplasty for acute myocardial infarction (MI) when performed with or without the platelet glycoprotein IIb/IIIa antibody, abciximab.

BACKGROUND

Abciximab improves the outcome of angioplasty but the effect of abciximab in primary angioplasty has not been investigated.

METHODS

Data were collected from a computerized database. Follow-up was by telephone or review of outpatient or hospital readmission records.

RESULTS

A total of 182 consecutive patients were included; 103 received abciximab and 79 did not. The procedural success rate was 95% in the two groups. At 30-day follow-up, the composite event rate of unstable angina, reinfarction, target vessel revascularization and death from all causes was 13.5% in the group of patients who did not receive abciximab, 4% (p < 0.05) in the abciximab group and 2.4% (p < 0.05) in the subgroup of patients (n = 87) who completed the 12-h abciximab infusion. At the end of follow-up (mean 7+/-4 months), the composite event rate was 32.4%, 17% (p < 0.05) and 13.1% (p < 0.01) in these three categories respectively. Abciximab bolus followed by a 12-h infusion was an independent predictor of event-free survival, in a Cox proportional hazards model (relative risk 0.49; 95% confidence interval 0.24 to 0.99; p < 0.05).

CONCLUSIONS

Abciximab given at the time of primary angioplasty may improve the short- and medium-term outcome of patients with acute MI, especially when a 12-h infusion is completed.

Randomized, placebo-controlled trial of platelet glycoprotein IIb/IIIa blockade with primary angioplasty for acute myocardial infarction. ReoPro and Primary PTCA Organization and Randomized Trial (RAPPORT) Investigators

BACKGROUND

The benefit of catheter-based reperfusion for acute myocardial infarction (MI) is limited by a 5% to 15% incidence of in-hospital major ischemic events, usually caused by infarct artery reocclusion, and a 20% to 40% need for repeat percutaneous or surgical revascularization. Platelets play a key role in the process of early infarct artery reocclusion, but inhibition of aggregation via the glycoprotein IIb/IIIa receptor has not been prospectively evaluated in the setting of acute MI.

METHODS AND RESULTS

Patients with acute MI of <12 hours' duration were randomized, on a double-blind basis, to placebo or abciximab if they were deemed candidates for primary PTCA. The primary efficacy end point was death, reinfarction, or any (urgent or elective) target vessel revascularization (TVR) at 6 months by intention-to-treat (ITT) analysis. Other key prespecified end points were early (7 and 30 days) death, reinfarction, or urgent TVR. The baseline clinical and angiographic variables of the 483 (242 placebo and 241 abciximab) patients were balanced. There was no difference in the incidence of the primary 6-month end point (ITT analysis) in the 2 groups (28.1% and 28.2%, P=0.97, of the placebo and abciximab patients, respectively). However, abciximab significantly reduced the incidence of death, reinfarction, or urgent TVR at all time points assessed (9.9% versus 3.3%, P=0.003, at 7 days; 11.2% versus 5.8%, P=0.03, at 30 days; and 17.8% versus 11.6%, P=0.05, at 6 months). Analysis by actual treatment with PTCA and study drug demonstrated a considerable effect of abciximab with respect to death or reinfarction: 4.7% versus 1.4%, P=0.047, at 7 days; 5.8% versus 3.2%, P=0.20, at 30 days; and 12.0% versus 6.9%, P=0.07, at 6 months. The need for unplanned, "bail-out" stenting was reduced by 42% in the abciximab group (20.4% versus 11.9%, P=0.008). Major bleeding occurred significantly more frequently in the abciximab group (16.6% versus 9.5%, P=0.02), mostly at the arterial access site. There was no intracranial hemorrhage in either group.

CONCLUSIONS

Aggressive platelet inhibition with abciximab during primary PTCA for acute MI yielded a substantial reduction in the acute (30-day) phase for death, reinfarction, and urgent target vessel revascularization. However, the bleeding rates were excessive, and the 6-month primary end point, which included elective revascularization, was not favorably affected.

Redistribution of von Willebrand factor in porcine carotid arteries after balloon angioplasty

von Willebrand factor (VWF) is a well-characterized multimeric glycoprotein present in platelets and plasma and synthesized by vascular endothelial cells and megakaryocytes. Its role in platelet-vessel wall interactions has been studied extensively, but its involvement in intravascular events after balloon angioplasty has not been clarified. VWF antigen is not present in porcine arterial endothelium (except for the pulmonary artery) but is readily detected in porcine venous endothelial cells. We have examined the localization of VWF in porcine vessel walls during neointima formation after bilateral carotid balloon-angioplasty. Endothelium was denuded by balloon injury but regenerated by 7 days and was fully confluent by 42 days. VWF was detected at the site of injury in localized, adherent platelet aggregates at 10 minutes after angioplasty that were not present at later time points. A well-demarcated homogeneous layer of VWF was observed on the luminal surface from 30 minutes to day 7, but there was a progressive shift of positive staining from the lumen to the outer media from days 1 to 7. VWF was also strongly detected at sites proximal and distal to the balloon injury from 30 minutes to day 7, although endothelial disruption was minimal and the monolayer remained substantially intact at these sites. Regrowing endothelial cells appeared to contain granular VWF from days 12 to 21, but this was not readily evident at later time points. The results suggest that balloon injury is associated with deposition and medial absorption of plasma or platelet VWF in this porcine model over a time period that precedes and overlaps vascular smooth muscle proliferation and endothelial recoverage. The findings provide evidence to support the concept of a wider role for VWF in tissue injury responses.

The significance of increased 111indium platelet accumulation at post-angioplasty sites

We assessed prospectively the significance of 111indium labelled platelet accumulation following angioplasty procedures in 12 patients (9 femoral angioplasties (2 laser, 1 atherectomy) and 3 iliac stents). Autologous 111indium labelled platelets were re-injected immediately after angioplasty. Radioactivity was measured over treated and reference sites, by single probe and gamma camera, and expressed as a radioactivity ratio (RR). All patients had duplex ultrasound assessment and occlusions were confirmed by arteriography. RR was always raised after angioplasty. Three patients who had acute occlusions showed markedly raised average RRs (significant at 99% ANOVA). RR was not raised after laser assisted angioplasty, however, our numbers were small. 111Indium platelet radioactivity did not predict subsequent occlusion after angioplasty but effectively detected existing acute post-angioplasty occlusions.

Effects of platelet glycoprotein IIb/IIIa receptor blockade by a chimeric monoclonal antibody (abciximab) on acute and six-month outcomes after percutaneous transluminal coronary angioplasty for acute myocardial infarction. EPIC investigators

Percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction is an attractive alternative to thrombolysis, but is still limited by recurrent ischemia and restenosis. We determined whether adjunctive platelet glycoprotein IIb/IIIa receptor blockade improved outcomes in patients undergoing direct and rescue PTCA in the Evaluation of c7E3 for Prevention of Ischemic Complications (EPIC) trial. Of the 2,099 patients undergoing percutaneous intervention who randomly received chimeric 7E3 Fab (c7E3) as a bolus, a bolus and 12-hour infusion, or placebo, 42 underwent direct PTCA for acute myocardial infarction and 22 patients had rescue PTCA after failed thrombolysis. The primary composite end point comprised death, reinfarction, repeat intervention, or bypass surgery. Outcomes were assessed at 30 days and 6 months. Baseline characteristics were similar in direct and rescue PTCA patients. Pooling the 2 groups, c7E3 bolus and infusion reduced the primary composite end point by 83% (26.1% placebo vs 4.5% c7E3 bolus and infusion, p = 0.06). No reinfarctions or repeat urgent interventions occurred in c7E3 bolus and infusion patients at 30 days, although there was a trend toward more deaths in c7E3-treated patients. Major bleeding was increased with c7E3 (24% vs 13%, p = 0.28). At 6 months, ischemic events were reduced from 47.8% with placebo to 4.5% with c7E3 bolus and infusion (p = 0.002), particularly reinfarction (p = 0.05) and repeat revascularization (p = 0.002). We conclude that adjunctive c7E3 therapy during direct and rescue PTCA decreased acute ischemic events and clinical restenosis in the EPIC trial. These data provide initial evidence of benefit for glycoprotein IIb/IIIa receptor blockade during PTCA for acute myocardial infarction.

Platelet deposition after angioplasty is abolished by restoration of the endothelial cell monolayer

PURPOSE

Percutaneous transluminal angioplasty of an atheromatous plaque causes endothelial desquamation and intimal dissection with the consequent formation of a thrombogenic flow surface. In this study we investigated the hypothesis that platelet deposition after balloon angioplasty may be decreased by rapid restoration of the endothelial cell monolayer, achieved by transluminally seeding angioplasty sites with endothelial cells.

METHODS

Bilateral external iliac angioplasty was performed in eight New Zealand white rabbits. One angioplasty site was isolated from the circulation and incubated with a supraconfluent endothelial cell suspension with a double balloon catheter; the contralateral angioplasty site was sham seeded with culture medium. The deposition of autologous indium 111-labeled platelets on the angioplasty sites was quantified 30 minutes after restoration of flow and was referenced to an undamaged segment of aorta that acted as a negative control.

RESULTS

Platelet deposition on the nonseeded angioplasty site (13.1 x 10(4) platelets/mm2) was significantly higher than on nondilated segments (3.4 x 10(4) platelets/mm2; p = 0.014). Restorationof endothelial cell coverage by endothelial seeding significantly reduced platelet deposition on dilated arterial segments to levels not significantly higher than in controls (3.6 x 10(4) platelets/mm2; p = 0.014).

CONCLUSIONS

These results illustrate that rapid reendothelialization of angioplasty sites decreases subsequent platelet deposition and may reduce the rate of acute arterial reocclusion complicating endovascular techniques.

Platelet activation during coronary angioplasty in humans

BACKGROUND

Previous studies have indicated that balloon angioplasty is associated with local platelet activation. In addition, different contrast media have different effects on thrombus formation during angioplasty in humans. We hypothesized that coronary angioplasty in humans is associated with activation of platelets to specific platelet agonists and that this activation may be differently modified by different angiographic contrast agents.

METHODS AND RESULTS

We studied 25 patients referred for angioplasty of the left anterior descending or circumflex coronary arteries. All patients were pretreated with aspirin and received heparin. Blood samples for assessment of platelet aggregation to serotonin, ADP, epinephrine, and collagen were obtained from the coronary sinus before any contrast injection, after initial diagnostic contrast injections, and after three balloon inflations. Patients were randomized to receive iopamidol, diatrizoate, or ioxaglate. Contrast alone was not associated with altered platelet aggregation. However, balloon angioplasty was consistently associated with increased platelet aggregation to serotonin but not to ADP, epinephrine, or collagen. These effects were similar with the three contrast agents studied except that the use of iopamidol was associated with increased platelet responsiveness to all concentrations of ADP after balloon dilation.

CONCLUSIONS

Coronary angioplasty in humans was associated with increased platelet aggregation in blood drawn from the coronary sinus. This effect was primarily seen when serotonin was used as an agonist.

Evaluation of ketanserin in the prevention of restenosis after percutaneous transluminal coronary angioplasty. A multicenter randomized double-blind placebo-controlled trial

BACKGROUND

Ketanserin is a serotonin S2-receptor antagonist that inhibits the platelet activation and vasoconstriction induced by serotonin and also inhibits the mitogenic effect of serotonin on vascular smooth muscle cells.

METHODS AND RESULTS

We conducted a randomized, double blind, placebo-controlled trial to assess the effect of ketanserin in restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA). Patients received either ketanserin (loading dose, 40 mg 1 hour before PTCA; maintenance dose, 40 mg bid for 6 months) or matched placebo. In addition, all patients received aspirin for 6 months. Coronary angiograms before PTCA, after PTCA, and at 6 months were quantitatively analyzed. Six hundred fifty-eight patients were entered into the intention-to-treat analysis. The primary clinical end point of the study was the occurrence between PTCA and 6 months of any one of the following: cardiac death, myocardial infarction, the need for repeat angioplasty, or bypass surgery. It also included the need for revascularization actuated by findings at 6-month follow-up angiography. The primary clinical end point was reached by 92 (28%) patients in the ketanserin group and 104 (32%) in the placebo group (RR, 0.89; 95% CI, 0.70, 1.13; P = .38). Quantitative angiography after PTCA and at follow-up was available in 592 patients (ketanserin, 287; control, 305). The mean difference in minimal lumen diameter between post-PTCA and follow-up angiogram (primary angiographic end point) was 0.27 +/- 0.49 mm in the ketanserin group and 0.24 +/- 0.52 mm in the control group (difference, 0.03 mm; 95% CI, -0.05, 0.11; P = .50).

CONCLUSIONS

Ketanserin at the dose administered in this trial failed to reduce the loss in minimal lumen diameter during follow-up after PTCA and did not significantly improve the clinical outcome.

Endothelial cell seeding of damaged native vascular surfaces: prostacyclin production

Endothelial cell seeding has been successful in reducing the thrombogenicity of prosthetic vascular grafts in animal and clinical studies. The reduction in thrombogenicity may be attributed to the intrinsic properties of endothelial cells themselves, and their ability to produce anti-thrombogenic mediators such as prostacyclin, and endothelium-derived relaxing factor. Endothelial seeding of damaged vascular surfaces produced during percutaneous transluminal angioplasty and endarterectomy is an attractive possibility due to the excellent attachment characteristics of the sub-endothelial tissue exposed during these procedures. The ability of endothelial seeded damaged vascular surfaces to produce prostacyclin was measured in an in vitro model of vascular injury. Endothelial-seeded damaged surfaces produced significantly higher prostacyclin release than did vessels damaged by balloon dilatation (265.5 pg cm-2 min-1 and 87.5 pg cm-2 min-1 respectively). This study provides evidence that endothelial seeding of damaged native vascular surfaces is technically feasible and that seeding may reduce the thrombogenicity of vascular surfaces following balloon dilatation.

Pulsed laser and thermal ablation of atherosclerotic plaque: morphometrically defined surface thrombogenicity in studies using an annular perfusion chamber

Although clinical trials using laser and thermal angioplasty devices have been underway, the effects of pulsed laser and thermal ablation of atherosclerotic plaque on surface thrombogenicity are poorly understood. This study examined the changes in platelet adherence and thrombus formation on freshly harvested atherosclerotic aorta segments from Watanabe-heritable hyperlipidemic rabbits after ablation by two pulsed laser sources (308-nm xenon chloride excimer and 2,940-nm erbium:yttrium-aluminum-garnet [YAG] lasers) and a prototype catalytic hot-tip catheter. Specimens were placed in a modified Baumgartner annular chamber and perfused with citrated whole human blood, followed by quantitative morphometric analysis to determine the percent surface coverage by adherent platelets and thrombi in the treated and contiguous control areas. Pulsed excimer laser ablation of plaque did not change platelet adherence or thrombus formation in the treated versus control zones. However, photothermal plaque ablation with a pulsed erbium:YAG laser resulted in a 67% reduction in platelet adherence, compared with levels in control areas (from 16.7 +/- 2.2% to 5.5 +/- 1.8%; p less than 0.005). Similarly, after plaque ablation using a catalytic thermal angioplasty device, there was a 74% reduction in platelet adherence (from 29.2 +/- 5.1% to 7.7 +/- 1.6%; p less than 0.005) and a virtual absence of platelet thrombi (from 8.6 +/- 2.3% to 0.03 +/- 0.03%; p less than 0.005). This reduced surface thrombogenicity after plaque ablation with either an erbium:YAG laser or a catalytic hot-tip catheter suggests that thermal modifications in the arterial surface ultrastructure or thermal denaturation of surface proteins, or both, may be responsible for reduced platelet adherence. These in vitro findings indicate that controlled thermal plaque ablation by catheter-based techniques may elicit endovascular responses that can reduce early thrombus formation during angioplasty procedures.

Platelet accumulation after laser angioplasty--a scintigraphic assessment

Indium 111-labeled platelet scintigraphy was performed to evaluate platelet deposition in response to different levels of Nd:YAG laser/thermal energy. A dose-related increase in platelet deposition was observed. In clinical studies after laser-assisted balloon angioplasty, intense platelet deposition was observed in 2 patients who subsequently developed clinical arterial thrombosis. The pathogenesis of reocclusion appears, however, to be more complicated and ill understood. The authors suggest further extensive studies incorporating several parameters in the evaluation of the pathogenic factors involved in reocclusion after laser angioplasty. Such studies should also consider the role of arterial injury produced by the balloon catheter after laser-assisted balloon angioplasty.

Late hemodynamic failure following percutaneous transluminal angioplasty for long and multifocal femoropopliteal stenoses

The outcome of percutaneous transluminal angioplasty (PTA) was evaluated for treatment of 87 limbs with femoropopliteal stenoses, including 55 short stenoses (2.4 +/- 1.6 cm, mean +/- SD), seven single long stenoses (10.4 +/- 2.0 cm), and 25 multifocal stenoses (2.1 +/- 1.6 cm), where two to four separate segments were dilated. Following 98% initial technical success, 3-year patency was 68% for single short stenoses, as opposed to 20% for long and multifocal stenoses (p = 0.05, logrank test). Antiplatelet therapy with acetylsalicyclic acid was not found to influence occurrence of restenosis. The study documents the poor PTA results for long and multifocal stenoses and suggests precautions to be taken during PTA in order to minimize the area of artery wall damage.

Influence of contrast media on thrombus formation during coronary angioplasty

The influence of contrast media on thrombus formation during percutaneous transluminal coronary angioplasty was assessed in 124 consecutive patients undergoing coronary angioplasty and receiving either ionic (n = 57) (Group I) or nonionic (n = 67) (Group II) contrast medium. The presence of thrombus was assessed by qualitative analysis of angiograms in identical pre- and postangioplasty projections by four observers who had no knowledge of other data. Quantitation of stenosis severity before and after angioplasty and qualitative analysis of lesion eccentricity and complexity and of the presence of dissection were also performed. Although the baseline clinical characteristics of the two groups (including presenting syndromes and procedural and angiographic variables) did not differ, more patients in Group II than Group I developed new thrombus during coronary angioplasty (18% vs. 4%, p less than 0.02). In particular, patients with a presenting syndrome of recent myocardial infarction or rest angina, or both, and patients with an eccentric coronary plaque were more likely to develop new thrombus if they received nonionic than if they received ionic contrast medium (p less than 0.05). Patients with new thrombus formation and patients with thrombus present both before and after angioplasty had a high incidence of acute procedural complications (36% and 23%, respectively). Patients in Groups I and II had a similar incidence of ischemic events during follow-up.

Detection of arterial thrombosis after laser angioplasty by platelet scintigraphy

Indium-111-labelled platelet scintigraphy was performed in two patients after laser-assisted balloon angioplasty. Both patients demonstrated a significant 'hot spot' at the angioplasty site 24 h after successful recanalisation with laser and balloon. Clinically apparent thrombosis of the recanalised arteries occurred 5 and 6 days after angioplasty in both patients. Laser-assisted balloon angioplasty leads to significant platelet deposition over recanalised segments of the artery, which may result in arterial thrombosis, as evident from the reports presented. Indium-111-labelled platelet scintigraphy emphasises the extent of trauma caused by laser and balloon angioplasty to the arterial wall.

Restenosis following coronary angioplasty

The last decade has witnessed an enormous increase in the use and success of percutaneous transluminal coronary angioplasty. During this time, our knowledge of the mechanisms of angioplasty and of how it relates to the pathophysiology of restenosis has also grown. Despite our better understanding of the mechanisms responsible for it, restenosis remains a significant problem in coronary angioplasty, affecting approximately one third of patients. A variety of factors can affect the measured rate of restenosis, such as the symptomatic status of the patient and the timing of restenosis studies. Certain clinical, anatomic, and procedural factors are associated with increased rates of restenosis. Pharmacologic interventions are ineffective in preventing restenosis. A variety of new mechanical devices are being developed, but their efficacy at this time does not appear to be superior to angioplasty alone. While attempts at preventing restenosis have thus far been unsuccessful, the information gained through the various studies has added tremendously to our knowledge base of angioplasty. Through this better understanding of the mechanisms of angioplasty and restenosis, it is likely that the problem of restenosis will be improved, either through existing technology or by methods yet to be discovered.

Nuclear medicine and atherosclerosis

Although the pathomechanisms of atherosclerosis are well known, their radioisotopic monitoring is still in its early childhood. The current radioisotope techniques are of only limited value for contributing to the clinical diagnosis of atherosclerosis. The limited reaction time of cellular blood constituents (platelets, monocytes) with the vascular surface at the injury site makes it very difficult to catch the point of injury. Lipoproteins excellently allow receptor imaging, while vascular monitoring is only of scientific interest at present. Labelling and subsequent imaging of components of the coagulation cascade have not succeeded so far, nor have attempts using unspecific labels such as porphyrin, polyclonal IgG and Fc fragments, for example. Preliminary evidence indicates that radioisotopic techniques may be of great benefit in the future in elucidating functional aspects of the disease, while they do not contribute to examining the stage and extent of atherosclerosis.

Kinetics of pulmonary platelet deposition and clearance during thrombin-induced microembolism in rabbits

Using 111In-labeled autologous platelets, we studied the kinetics of pulmonary platelet deposition and clearance in relation to hemodynamic and structural events during thrombin-induced pulmonary microembolism in rabbits. Autologous platelets were radiolabeled and returned to animals prior to infusion of thrombin (100 units/kg over 15 min) (n = 20) or saline (n = 6). All animals were pretreated with tranexamic acid, an inhibitor of fibrinolysis. Thrombin-treated animals manifested progressive increases in mean pulmonary platelet activity, reaching a maximum of 38% above baseline (p less than .0001), whereas no change was observed in saline-treated controls. Animals that died during, or immediately following, thrombin infusion manifested significantly greater increases in pulmonary platelet uptake (mean 1.55 +/- 0.47 times baseline), compared to surviving animals (1.14 +/- 0.16; p less than .05 survivors vs. nonsurvivors). In surviving animals, following cessation of thrombin, pulmonary platelet activity cleared gradually, with a half-time of approximately 12 min. Thrombin reduced circulating platelet counts (p less than .001), increased mean pulmonary artery pressure (13 +/- 3 mm Hg to 18 +/- 6 mm Hg; p less than .0001), and reduced mean systemic arterial pressure (55 +/- 10 mm Hg to 44 +/- 7 mm Hg; p less than .001). The time courses of these events approximated that of thrombin-induced pulmonary platelet uptake. Furthermore, the increase in pulmonary artery pressure occurred predominantly in the group of animals in which the increase in pulmonary radiolabeled platelet activity exceeded the median value of 20%. Postmortem histology showed extensive pulmonary thrombus extending from small arterial to capillary levels in animals that died during, or immediately following, thrombin infusion, but not in surviving animals. Our findings suggest that platelet aggregation plays an important role in the pathogenesis of hemodynamic change following thrombin-induced pulmonary embolization.

Aspirin and dipyridamole in the prevention of acute coronary thrombosis complicating coronary angioplasty

To test the hypothesis that pretreatment with adequate antiplatelet therapy reduces the likelihood of acute coronary thrombosis during routine percutaneous transluminal coronary angioplasty (PTCA), we reviewed, blinded to treatment group, the films and records of 300 consecutive initially successful PTCAs. Films before PTCA, immediately after, and at least 30 min after the last balloon inflation were assessed for the presence of any thrombus at the PTCA site. We excluded 37 patients who received streptokinase before PTCA or who had 100% occlusion or thrombus on pre-PTCA films. New thrombi were classified as clinically significant (defined as causing 100% occlusion or requiring emergency surgery or streptokinase therapy) or as not significant (not causing an acute problem or requiring intervention). Patients were classified into three groups, based on the type and extent of antiplatelet therapy received. Group 1 (no aspirin, n = 121) consisted of patients who did not receive aspirin either before admission or in hospital before PTCA (with or without dipyridamole). Group 2 (standard treatment, n = 110) received aspirin with or without dipyridamole but did not receive both drugs before admission and in hospital before PTCA. Group 3 (maximal treatment, n = 32) received both aspirin and dipyridamole before admission and in hospital before PTCA. New thrombi were detected at 39 (14.8%) PTCA sites, of which 15 (5.7% of all PTCA sites) were considered clinically significant. Group 1 had the highest incidence of both thrombus (21.5%) and clinically significant thrombus (10.7%). A reduction was seen in group 2 in thrombus (11.8%; p = .07) and in clinically significant thrombus (1.8%; p = .005). Group 3 had no thrombus (p = .001) and no clinically significant thrombus (p = .04). In addition to inadequate pretreatment with antiplatelet therapy, univariate analyses demonstrated several other risk factors for thrombus: higher percent diameter stenosis before PTCA (p less than .008), higher platelet count (p = .013), and current smoking (p = .03). Only higher platelet count (p less than .001) and inadequate pretreatment (p = .001) were associated with clinically significant thrombus. Stepwise logistic regression analysis demonstrated that for thrombus, the lack of effective antiplatelet therapy was the most discriminatory variable, followed by current smoking, higher percent diameter stenosis, and dissection. For clinically significant thrombus, once the lack of pretreatment with effective antiplatelet therapy was considered, no other factors added significant discriminatory information.(ABSTRACT TRUNCATED AT 400 WORDS)