Efficacy of adjunctive thrombolytic therapy in percutaneous transluminal coronary angioplasty

Percutaneous intervention of old degenerated saphenous vein grafts

The treatment of failing bypass grafts is difficult because repeat surgery carries a higher mortality rate than a first operation. Percutaneous intervention is more difficult because mechanical manipulation of these soft, friable atherosclerotic plaques have been associated with a significant rate of distal embolization, myocardial infarction, late restenosis and death. Balloon angioplasty alone has proven to have serious limitations in the treatment of older degenerated saphenous vein grafts (SVG). Although directional atherectomy yielded a higher angiographic success in a randomized trial, the restenosis rate was similar, and the procedural complications higher. The transluminal extraction catheter (TEC) has also shown significant limitations for the treatment of degenerated or thrombotic vein grafts with a significant procedural complication rate. A randomized trial comparing stenting versus balloon angioplasty in focal SVG lesions showed a higher freedom from major adverse cardiovascular events in the stent group, but there was no significant difference in the angiographic restenosis rates. More recently, rheolytic thrombectomy and mechanical thrombolysis have proven useful in treating thrombotic lesions in SVG. In addition, the recent development of distal protection devices appears very promising and will probably contribute to decreased distal embolization during percutaneous revascularization of these conduits.

Release of endothelin 1 and angiotensin II induced by percutaneous transluminal coronary angioplasty

Endothelial injury plays critical roles in acute and chronic complications after percutaneous transluminal coronary angioplasty (PTCA). We investigated coronary endothelial injury and the release of vasoactive substances induced by PTCA. We examined 44 patients with ischemic heart disease who underwent elective PTCA to isolated stenotic lesions in left coronary arteries. Eleven patients received balloon angioplasty (BA), 14 percutaneous transluminal rotational atherectomy (PTRA), and 19 stent implantation. Blood samples were drawn from the coronary sinus immediately before and after as well as 4 hr and 24 hr after PTCA. Plasma levels of endothelin (ET) 1, angiotensin (ANG) II, von Willebrand factor (vWF), and thrombomodulin (TM) were measured. Seven control subjects who underwent diagnostic coronary angiography (CAG) were used as controls. In all patients, ET-1 levels in the coronary sinus blood significantly increased immediately after PTCA. ANG II levels and vWF activity showed significant increases 4 hr after PTCA. Changes in levels of these markers were similar among the BA, PTRA, and stent groups. TM levels were elevated in all groups of patients, including those simply undergoing diagnostic CAG. Changes in ET-1, ANG II, and vWF levels in the coronary sinus reflect coronary endothelial injury induced by PTCA.

Inhibition of angiotensin converting enzyme cannot prevent increases in angiotensin II production in coronary circulation

OBJECTIVE

To determine whether inhibition of angiotensin converting enzyme (ACE) can prevent angiotensin II production in the coronary circulation induced by percutaneous transluminal coronary angioplasty (PTCA) in patients with myocardial ischaemia.

DESIGN, PATIENTS

41 patients who underwent elective PTCA and six control subjects who received diagnostic coronary angiography were studied. Patients were divided into two groups according to the chronic administration of ACE inhibitors (group A, 15 patients treated with ACE inhibitors; group B, 26 patients without ACE inhibitors). Blood samples were drawn through catheters placed in the aorta and coronary sinus before and 24 hours after PTCA.

RESULTS

Mean levels of ACE activity in the aorta were significantly lower in patients in group A than in group B. However, mean angiotensin II concentrations in the aorta were not significantly different between the two groups. Differences in basal angiotensin II concentrations between the coronary sinus and aorta, which reflected basal angiotensin II production in the coronary circulation, were not significant among group A, group B, and control subjects. The production of angiotensin II in the coronary circulation was significantly increased 24 hours after PTCA in both group A and group B to the same extent. No significant changes were observed in control subjects 24 hours after diagnostic coronary angiography.

CONCLUSIONS

This study revealed that inhibition of ACE activity by ACE inhibitors could not prevent increases in angiotensin II production in the coronary circulation induced by PTCA.

Management strategies for a better outcome in unstable coronary artery disease

Unstable coronary artery disease is a term encompassing both unstable angina and non-Q-wave (non-ST-segment elevation) myocardial infarction. Patients with these conditions are at risk of early progression to acute myocardial infarction and death. Thus, management of these conditions must aim to reduce long-term mortality and morbidity. Risk stratification is crucial for the identification of patients whose risk of early progression is high; they may require coronary angiography and (if suitable) either percutaneous transluminal coronary angioplasty or coronary artery bypass surgery. No single variable can accurately predict risk, but considerable data are emerging to show that biochemical markers of myocardial injury, such as troponin-T and troponin-I, are valuable in combination with electrocardiographic findings and clinical features. Routine early invasive procedures (coronary angiography with or without revascularization) have not yet been shown to have any significant advantage over conservative regimens for the majority of patients. Antiplatelet, anticoagulant, and anti-ischemic agents remain the mainstay of treatment in the acute phase. New agents, such as glycoprotein IIb/IIIa receptor inhibitors and low-molecular-weight heparins, as well as antithrombins and Factor Xa inhibitors add to the treatments currently available. Thrombolytic agents are contraindicated in the absence of ST-segment elevation. After clinical stabilization, ongoing assessment should include exercise testing for all patients who are able; other imaging techniques should be used for patients unable to exercise. A profile indicating a high risk of future events is an indication for elective angiography and consideration for revascularization.

Economic impact of angioplasty salvage techniques, with an emphasis on coronary stents: a method incorporating costs, revenues, clinical effectiveness and payer mix

OBJECTIVES

We sought to broaden assessment of the economic impact of percutaneous transluminal coronary angioplasty (PTCA) revascularization salvage strategies by taking into account costs, revenues, the off-setting effects of prevented clinical complications and the effects of payer mix.

BACKGROUND

Previous economic analyses of PTCA have focused on the direct costs of treatment but have not accounted either for associated revenues or for the ability of costly salvage techniques such as coronary stenting to reduce even costlier complications.

METHODS

Procedural costs, revenues and contribution margins (i.e., "profit") were measured for 765 consecutive PTCA cases to assess the economic impact of salvage techniques (prolonged heparin administration, thrombolysis, intracoronary stenting or use of perfusion balloon catheters) and clinical complications (myocardial infarction, coronary artery bypass graft surgery [CABG] or acute vessel closure with repeat PTCA). To assess the economic impact of various salvage techniques for failed PTCA, we used actual 1995 financial data as well as models of various mixes of fee-for-service, diagnosis-related group (DRG) and capitated payers.

RESULTS

Under fee-for-service arrangements, most salvage techniques were profitable for the hospital. Stents were profitable at almost any level of clinical effectiveness. Under DRG-based systems, most salvage techniques such as stenting produced a financial loss to the hospital because one complication (CABG) remained profitable. Under capitated arrangements, stenting and other salvage modalities were profitable only if they were clinically effective in preventing complications in > 50% of cases in which they were used.

CONCLUSIONS

The economic impact of PTCA salvage techniques depends on their clinical effectiveness, costs and revenues. In reimbursement systems dominated by DRG payers, salvage techniques are not rewarded, whereas complications are. Under capitated systems, the level of clinical effectiveness needed to achieve cost savings is probably not achievable in current practice. Further studies are needed to define equitable reimbursement schedules that will promote clinically effective practice.

"Back-squeezing" of the clot: an unusual complication of primary coronary angioplasty

Distal coronary embolism of thrombotic material is quite common in the setting of primary coronary angioplasty for evolving acute myocardial infarction. Embolization to another coronary artery is, however, much more uncommon. We report on a case in which a large thrombus migrated from the proximal left anterior descending artery (LAD) to the proximal left circumflex artery (CX) during inflation of the dilatation balloon. The putative mechanism was retrograde expulsion of the thrombus by the deploying balloon.

Site-specific intracoronary thrombolysis with urokinase-coated hydrogel balloons: acute and follow-up studies in 95 patients

Conventional balloon angioplasty in the presence of intracoronary thrombus is associated with an elevated risk for acute myocardial infarction, emergency bypass surgery, and death. The purpose of this study was to assess the safety and efficacy of a new technique to treat thrombus-containing stenoses consisting of the local delivery of urokinase directly to the site of intraluminal clot with hydrogel-coated balloons. Ninety-five patients with angiographically apparent intracoronary thrombus were treated with urokinase-coated hydrogel balloons either prior to (n = 74) or following (n = 21) conventional balloon angioplasty. Clinical diagnoses for the study group included acute myocardial infarction in 50 patients, postinfarction angina in 23 patients, and unstable angina in 22 patients. All hydrogel balloons were initially coated with urokinase by immersing the inflated balloon in a concentrated Abbokinase solution (50,000 units/ml) for 60 s. All patients were subsequently treated with drug-coated balloons using a balloon:artery ratio of 1:1, a mean of 2.2 +/- 1.2 inflations, and a mean total inflation time of 7.5 +/- 4.9 min. Use of urokinase-coated balloons resulted in angiographic disappearance of intracoronary thrombus in 78 patients, improvement in 14, and no change in the remaining 3 patients. Following hydrogel balloon use for the entire 95 patients, TIMI flow increased from 1.4 +/- 1.2 to 2.9 +/- 0.4, minimal lumen diameter increased from 0.4 +/- 0.4 to 2.0 +/- 0.6 mm, and thrombus score decreased from 2.0 +/- 0.9 to 0.2 +/- 0.6 (all P < 0.01). Procedural and early in-hospital complications were noted in 7 of the 95 patients (7.4%) and included abrupt closure in 3 patients, distal embolization in 1 patient, no reflow in 1 patient, sidebranch occlusion in 1 patient, and late closure in 1 patient. Two of the 3 patients with abrupt closure and the single patient with late closure required intracoronary stenting to maintain vessel patency. Two of these 7 patients sustained small myocardial infarctions, although no patient required emergency bypass surgery or experienced a procedural death. Late clinical follow-up (mean = 8.3 +/- 6.6 months; range = 2 wk to 29 mo) demonstrated adverse recurrent events in 29 of the 95 patients (30.5%), including death (n = 5), myocardial infarction (n = 2), and recurrence of angina (n = 22). The results of this study suggest that intracoronary thrombolysis can be safely and rapidly achieved by using limited quantities of urokinase delivered directly to the site of intraluminal clot with hydrogel balloons. Use of this technique may result in improved acute outcomes in comparison with conventional techniques currently being used to treat thrombus-containing stenoses.

Catheter-based local thrombolysis with urokinase: comparative efficacy of intraluminal clot lysis with conventional urokinase infusion techniques in an in vivo porcine thrombus model

Local delivery of urokinase directly to the site of intraluminal clot using catheter-based technology has recently been introduced as a new technique to treat intracoronary thrombus and thrombus-containing stenoses. The purpose of this study was to compare the efficacy of urokinase therapy administered by local drug-delivery catheters with conventional urokinase-infusion techniques in dissolving intraluminal clot and intramurally depositing drug at the site of arterial injury in an in vivo porcine model. Five techniques of urokinase administration were studied in 65 pigs, including intravenous systemic bolus (1,000,000 units), guiding catheter infusion (500,000 units), local intraluminal infusion with a Roubin catheter (150,000 units), local infusion by the Dispatch catheter (150,000 units), and local delivery by the hydrogel-coated balloon (700 units). All five techniques were initially compared with respect to the quantity of intraluminal lysis of 123I-fibrinogen-labeled thrombus in an in vivo thrombus model. Conventional balloon angioplasty was also assessed in this model as a nonpharmacologic, mechanical control. In addition, all five techniques were compared with respect to the quantity and efficiency of intramural urokinase deposition at coronary angioplasty sites. In the in vivo thrombolysis experiments, the quantity of artificial clot lysis measured 6.8% for systemic therapy, 20.8% for guiding catheter infusion, 25.2% for Roubin catheter infusion, 62.8% for Dispatch catheter infusion, 98.8% for hydrogel balloon delivery, and 53.6% for conventional balloon angioplasty. Both the Dispatch catheter and the hydrogel balloon resulted in more clot lysis than the systemic, guiding catheter, or Roubin catheter approaches (P < 0.05). In comparison with conventional balloon angioplasty, only the hydrogel balloon resulted in higher levels of thrombus dissolution (P < 0.05). In the intramural deposition studies, the efficiency of urokinase delivery was 0.0004% for systemic therapy, 0.004% for guiding catheter infusion, 0.004% for Roubin catheter infusion, 0.08% for Dispatch catheter infusion, and 1.8% for hydrogel balloon delivery. The Dispatch catheter resulted in higher intramural drug levels than did all other techniques (P < 0.05), whereas the efficiency of urokinase deposition was higher with the hydrogel balloon than with all other approaches (P < 0.05). In the porcine model, it is subsequently concluded that local delivery of urokinase by catheter-based techniques can result in more complete lysis of intraluminal thrombus by using similar or lower doses of drug than by using conventional urokinase infusion techniques. Mechanical deformation of thrombus, possibly to increase the surface area available for thrombolysis and to physically disrupt clot, may be an important component of the mechanism of site-specific thrombolysis, particularly with the hydrogel balloon. Local delivery techniques also deposit significant quantities of urokinase at balloon angioplasty sites, creating an intramural reservoir of drug that may result in prolonged local thrombolysis.

State-of-the-Art Review : Management of Patients Who Require Invasive Procedures Immediately Following Thrombolytic Therapy

In recent years the use of thrombolytic ther apy has been demonstrated to be valuable in the treat ment of patients with acute myocardial infarction. Often, because of the frequency of reocclusion of the infarct- related artery, identification of a treatable vascular le sion, or, rarely, failure of thrombolytic therapy, patients will require more invasive procedures to prevent further ischemic injury to the myocardium. These procedures in clude anything from cardiac catheterization to emergency coronary bypass surgery. The perioperative evaluation and management of patients who have recently received thrombolytic therapy requires an understanding of the changes in coagulation proteins that occur with the use of these therapeutic agents. The appropriate understanding and use of antifibrinolytic agents and blood products will allow for these procedures to be performed safely with a minimum of bleeding complications.