Novel Approaches for the Treatment of Chronic Total Coronary Occlusions

Crossing Total Occlusions: Navigating Towards Recanalization

Chronic total occlusions (CTOs) represent the "last frontier" of percutaneous interventions. The main technical challenges lies in crossing the guidewire into the distal true lumen, which is primarily due to three problems: device buckling during initial puncture, inadequate visualization, and the inability to actively navigate through the CTO. To improve the success rate and to identify future research pathways, this study systematically reviews the state-of-the-art of all existing and invented devices for crossing occlusions. The literature search was executed in the databases of Scopus and Espacenet using medical and instrument-related keyword combinations. The search yielded over 840 patents and 69 articles. After scanning for relevancy, 45 patents and 16 articles were included. The identified crossing devices were subdivided based on the determinant for the crossing path through the occlusion, which is either the device (straight and angled crossing), the environment (least resistance, tissue selective, centerline, and subintimal crossing) or the user (directly steered and sensor enhanced crossing). It was found that each crossing path is characterized by specific advantages and disadvantages. For a future crossing device, a combination of crossing paths is suggested were the interventionist is able to exert high forces on the CTO (as seen in the device approach) and actively steer through the CTO (user: directly steered crossing) aided by intravascular imaging (user: sensor enhanced crossing) or an intrinsically safe device following the centerline or path of least resistance (environment: centerline crossing or least resistance crossing) to reach the distal true lumen.

Hepatoprotective and anti-tumor effects of targeting MMP-9 in hepatocellular carcinoma and its relation to vascular invasion markers

The current study aims to evaluate the hepatoprotective and antitumor efficacy of doxycycline, as an matrix metalloproteases-9 (MMP-9) inhibitor, in an in vivo model of hepatocellular carcinoma (HCC). HCC was induced experimentally by thiocetamide (200 mg/kg) in rats that were treated with doxycycline (5 mg/kg for 16 weeks). Tumor severity was evaluated by measuring α-fetoprotein (AFP) levels, histopathologically by investigating liver sections stained with hematoxylin/eosin and assessing the survival rate. Liver homogenates were used for the measurements of MMP-9, fascin and hepatic heparan sulfate proteoglycan (HSPG) levels. Oxidative stress markers [malonaldehyde (MDA) and glutathione] as well as fibroblast growth factor-2 (FGF-2) gene expression were also among the assessed indicators. HCC in human and animal samples showed significant elevation in the levels of MMP-9 (231.7, 90 %), fascin (33.17, 140 %), as well as FGF-2 gene expression (342 % in animal samples; all respectively), associated with a significant decrease in hepatic HSPG level. Treatment of rats with doxycycline increased the animal survival rate (90 %) and decreased serum AFP level. Moreover, doxycycline ameliorated fibrosis and the induced massive hepatic tissue breakdown. It also restored the integrity of hepatic HSPGs and showed a magnificent inhibitory effect of tumor invasion cascade by significantly reducing the activities of MMP-9 (42 %) and fascin (50 %), as well as reducing the gene expression of FGF-2 (85.7 %). Furthermore, the antioxidant impact of doxycycline was evidenced by the significant elevation in glutathione level and depressing MDA level. To this end, doxycycline, proved promising hepatoprotective and antitumor activity and opens, thereby, a new horizon against vascular migration ability of the tumor cells.

New percutaneous approaches for chronic total occlusion of coronary arteries

Successful recanalization and percutaneous revascularization of coronary arteries with chronic total occlusion (CTO) is one of the 'last frontiers' in coronary interventions. Conquering this obstacle will enable complete percutaneous revascularization in an increasing number of patients. The introduction within the last few years of enhanced guidewires combined with increasing operator experience and creative procedural techniques, such as the retrograde approach and the re-entry subintimal tracking technique (STAR), have significantly reduced the number of CTOs that should now be considered unapproachable. In addition, novel devices have been developed over recent years that may increase the success rate, as well as the safety, of the procedure. The Safe-Cross radiofrequency combines optical coherence reflectometry that warns the operator when the wire tip moves to within 1 mm of the outer vessel wall, combined with radiofrequency energy pulses to facilitate the passage. The CROSSER catheter mechanically vibrates against the face of the CTO at 20 kHz at a stroke depth of approximately 20 microm, creating a channel through the CTO. The most novel approach is the biologic one, in which proteolytic enzymes that digest the CTO cap to facilitate mechanical passage. The success rates for otherwise refractory CTOs will continue to improve with the development and validation of new imaging modalities and active energy source catheters.

Successful use of blunt microdissection catheter in a chronic total occlusion of a celiomesenteric artery

Chronic mesenteric ischemia is often a disabling condition associated with intestinal angina, weight loss, and sitophobia (a morbid aversion of food). Significant stenosis of two of the three main arteries of the gut is usually required to produce symptoms. Surgical therapy has included reimplantation and bypass grafting, usually with synthetic conduits and occasionally endarterectomy. Newer techniques have made endovascular treatment an emerging modality in managing some of the difficult lesions in the mesenteric circulation that cause chronic mesenteric ischemia. We describe the first reported case of blunt microdissection using a Frontrunner XP(R) CTO Catheter (Lumend, Redwood City, CA) to successfully cross, subsequently wire and stent a four-year-old chronic total occlusions in a celiac trunk, which also gave origin to the superior mesenteric artery.

Magnetic navigation in percutaneous coronary intervention

Magnetic navigation is the use of adjustable magnetic fields to precisely direct wires and equipment for clinical applications. It is a recently developed option that is now available for interventional cardiology. Procedures are based on the production of a three-dimensional reconstruction of the vessel lumen from standard angiographic images. Knowledge of the positions of the table and image intensifier during angiography allows calculation of the vessel coordinates in real space within the patient's chest. The applied magnetic field can be changed at any time to redirect the wire tip in order to improve navigation through complex and tortuous anatomy. The digital information of the coronary reconstruction can be used in further novel ways. Firstly, the integration of multislice computerized tomography images adds information about the path of the previous lumen of chronic total occlusions. Secondly, the computed center-line of the reconstructed vessel can be superimposed onto the live fluoroscopy images as a three-dimensional guide. The combination of improved navigation together with the other available system features may improve time, contrast, and material usage in a range of coronary lesions. Future potential developments include improvements in equipment and software, and potential therapeutic strategies under consideration include the use of equipment to perform remote control procedures, and the integration of the system to improve bone marrow-derived stem cell delivery.

The 5-Year Projection on the Future of Interventional Cardiology

Interventional cardiology has revolutionized modern cardiovascular care not only with the introduction of new approaches to the treatment of coronary artery disease, but also with the development of new invasive approaches to electrophysiologic procedures and the treatment of noncoronary vascular beds. This revolution continues to gather speed. Creative solutions continue to be proposed, evaluated, and then brought to the patient care arena. Issues remain, but these identify opportunities for continuing improvement.

Novel double catheter technique in complex percutaneous coronary interventions

We present a novel double catheter technique for successful complex intervention of a very old proximal left circumflex chronic total occlusion (>10 years old). Prior attempts of guide wire passage using bare wire alone, over-the wire balloon or microcatheter support techniques were unsuccessful.

Drug-Eluting Stents for Interventional Revascularization of Coronary Multivessel Disease

The treatment of coronary artery disease has changed over the past 35 years since the introduction of coronary artery bypass surgery in 1968. Percutaneous coronary intervention, introduced in 1977 with balloon angioplasty, was accelerated by the establishment of elective stent placement in 1994, together with the development of suitable antiplatelet regimes. In 2002, DES were made commercially available, following the results of clinical trials in single lesions. A meta-analysis of four randomized clinical trials comparing bare stents to bypass surgery for multivessel disease conducted in the 1990s demonstrate no mortality difference at 1 year. Similar 5-year outcomes have been reported by the ARTS trial. These trials, however, showed that repeat revascularization was much higher in the stent arm, due to restenosis. Various single center (RESEARCH, T-SEARCH) and multicenter (ARTS II) registries have consistently showed a low need for repeat intervention in patients with multivessel disease with the use of DES. Three major trials comparing DES against bypass surgery are ongoing or about to start and will determine the optimum revascularization therapy in multivessel disease. The recently commenced SYNTAX randomized trial will enroll only three-vessel or left main disease, while the upcoming FREEDOM and ongoing CARDia trial will specifically enroll diabetic patients only with multivessel disease. Results for these trials are expected in 2006-2007 at the earliest.

A “Grapple Hook” technique using a deflectable tip catheter to facilitate complex proximal circumflex interventions

We present two patients with angulated, proximal left circumflex lesions, one a chronic total occlusion and one an acute subtotal occlusion. In both cases, use of the deflectable tip Venture Catheter (Velocimed, Minneapolis, MN) facilitated guide wire passage and successful percutaneous coronary intervention (PCI) after prior attempts at guide wire passage with standard wires were unsuccessful.

Paclitaxel-eluting stents for the treatment of chronic total coronary occlusions: A strategy of extensive lesion coverage with drug-eluting stents

The recanalization of a chronic total coronary occlusion (CTO) is hampered by a high rate of lesion recurrence. The goal of the present study is to assess the effect of paclitaxel-eluting stents in CTOs in a strategy of extensive stent coverage and the optional use of additional bare metal stents (BMSs). In 82 consecutive patients, a CTO (duration > 2 weeks) was successfully recanalized with implantation of one or more Taxus stents. These patients underwent a repeat angiography after 5.0 +/- 1.5 months and were assessed by quantitative angiography. The patients were compared with 82 clinically and lesion-matched patients from a consecutive series of 148 patients with CTOs treated by BMS in the preceding time period. In 21 of the 82 patients, additional lesions in the target artery not directly related to the original occlusion site were treated with BMSs (hybrid approach). The history of diabetes, extent of coronary artery disease, clinical symptoms, and angiographic features were similar in the Taxus and BMS group. Periprocedural adverse events were 3.3% with Taxus and 3.3% with BMS, but 12 months MACE was significantly lower in the group with exclusive use of Taxus (13.3% vs. 56.7%; P < 0.001), mainly due to a lower target lesion revascularization of 10.0% as compared to 53.4% (P < 0.001). There was only one late reocclusion with Taxus (1.7%) as compared to 21.7% with BMS (P < 0.05). However, in the hybrid group, the MACE rate was considerably higher, with 33.3%. Our data of a 80% reduction of target vessel failure as compared to BMS, with a lower risk of late reocclusions without increased acute adverse events, demonstrate the benefit of paclitaxel-eluting stents in CTOs. However, diffuse atherosclerosis in CTOs should be covered completely by the drug-eluting stents.