Seminars in interventional cardiology : SIIC最新文献

In the presence of an intracoronary thrombus, percutaneous coronary intervention (PCI) will frequently lead to complications. Glycoprotein IIb/IIIa blockade as adjunct to PCI is very effective in patients with non-occlusive clots and biochemical evidence of platelet micro-embolization. Thrombotically-occluded vessels still remain a major clinical problem. This provides a rationale for thrombus debulking prior to PCI. A powerful antiplatelet agent used in combination with a thrombus debulking strategy and stenting of the underlying ruptured plaque offers the potential for further enhancement of PCI. Protection against embolization could potentially be optimized with the use of anti-embolization devices and covered stents.

Intracoronary thrombi are harbingers for increased procedural complications after percutaneous revascularization techniques. Current approaches to treat coronary thrombus prior to plaque intervention are pharmacologic and mechanical. Whereas the use of coronary thrombolysis prior to or during percutaneous coronary intervention have yielded mixed results, the group of the platelet IIb/IIIa inhibitors have uniformly been shown to decrease the procedural complications and the 30 day rate of major cardiovascular events. Mechanical approaches to managing thrombus include: compression with balloon angioplasty or stenting, removal with atherectomy devices, thromboaspiration with the Possis AngioJet and hydrolyser, and vibration disintegration with the ultrasound thrombolysis device. Recent clinical trials have shown that the Possis AngioJet and the ultrasound thrombolysis device are highly effective and safe for removing coronary thrombi prior to coronary intervention.

Percutaneous coronary intervention produces vessel wall injury and activation of platelets that are responsible for producing peri-procedural ischemic complications. The importance of adequate antiplatelet therapy during coronary intervention to reduce platelet mediated ischaemic complications has been recognized for some time. Until recently, adjunctive treatment with aspirin was the only available antiplatelet therapy after coronary intervention that had demonstrated benefit. During the last decade, newer and more potent agents have demonstrated consistent reductions in ischaemic events after intervention and appear to have some enduring effect. Additionally, optimization of antiplatelet therapy with aspirin and the thienopyridines after coronary stenting has been an important advance allowing for the current liberal use of coronary stents.

Detailed knowledge of the pathophysiology as well as the dynamic nature of coronary thrombus formation provides a valuable tool for correct management and proper adjunctive therapy in patients with acute coronary syndromes. Coronary thrombosis is in the majority of cases caused by disruption or fissuring of an atherosclerotic plaque. At the lesion thrombogenic material will be exposed to the flowing blood leading to activation of platelets and the formation of a platelet clot. Simultaneously, the coagulation system is activated resulting in increased thrombin formation. Thrombin is a key mediator in arterial thrombosis, due to its effect on both platelets and fibrin generation. Thrombin contributes to the stabilization of an initially loose platelet clot by generating cross-bound fibrin within the thrombus. During the course of an acute coronary syndrome, the patient presents changing chest pain and dynamic ischaemic ECG findings. This is likely to be related to the dynamic nature of the pathophysiology. The presence of a non-occlusive coronary thrombus may deprive the myocardium its normal blood flow and oxygen supply, leading to ischaemic pain. During lysis or embolization, blood supply may be restored, but the presence of thrombus fragments in the microcirculation holds the potential to sustained interference with myocardial metabolism. The emboli contain activated platelets which release vasoconstrictors that may compromise the microcirculation. Recurrent thrombus formation at the lesion site may result in occlusion of the artery adding to the dynamic nature of the clinical presentation. In conclusion, platelets, the coagulation system, and the endothelium cause a dynamic process of intermittent occlusion, vasospasm and embolization of thrombus material.

Angiographic suggestion of intercoronary thrombus is often seen in patients sustaining acute coronary syndromes (ACS). Even in the era of stenting and glycoprotein IIb/IIIa antagonists, the presence of thrombus-rich lesion during percutaneous coronary interventions portends an increased risk of adverse events. It has been hypothesized that reduction of clot-burden prior to PCI may reduce complications and enhance efficacy. Experimental and clinical data have shown that catheter-based ultrasound thrombolysis is capable of inducing an efficacious and safe thrombus-debulking. This article reviews the collective experience with this promising device solution for the treatment of thrombotic lesions in the setting of ACS.

Data from four surgical trials of laser transmyocardial revascularization (TMR) show pain reductions of at least two classes occurred among 25-76% of patients, significantly greater than with optimal medical therapy. The safety and feasibility of percutaneous TMR (PTMR) was proved in multiple uncontrolled registry studies. With PTMR in two randomized trials enrolling about 550 patients, improvements were found among 45% and 66% of patients as compared with 13% for best medical therapy. Other encouraging observations included significant improvements in exercise time (85 and 100 seconds) as compared with minimal or negative results for medical therapy, consistent overall exercise time improvements for PTMR, and overall patient perceptions of anginal stability and global health. Peri-procedural mortality is low and ranged from 0% to 0.6%. Some skepticism remains about the procedures, arising from failure in most cases to show improvements with SPECT imaging and lack of conclusive insights into the mechanism of action. A randomized 'blinded' study is underway to establish a definitive therapeutic value for catheter-based TMR. Nonetheless, preliminary clinical data seem promising for catheter-based TMR for obtaining symptomatic improvement in patients with chronic refractory ischemic coronary syndromes.

This investigation examines the various laser choices used for transmyocardial laser revascularization (TMLR) with emphasis on the laser-tissue interaction. A series of in vivo (porcine model, n=27) and in vitro experiments were performed to study the effects of CO(2), holmium:YAG, and XeCl excimer lasers on the histological outcome of TMR channels. Computerized histopathological analysis has revealed that the CO(2) and holmium:YAG lasers produce substantial unpredictable thermal damage and differ predominantly in the amount of the mechanical injury or tissue shredding. In comparison, the excimer laser appears to produce the most uniform tissue ablation with the least thermal and shockwave damage.