Immediate- and Short-Term Outcome following Recanalization
of Long Chronic Total Occlusions (> 50 mm) of Native Coronary Arteri

Chronic total occlusion (CTO) is present in approximately 30% of diagnostic angiograms. Data suggest that 10-year survival of patients with CTO is improved if the CTO is successfully recanalized.¹ Percutaneous coronary intervention (PCI) of a CTO now accounts for approximately 10% of patients undergoing PCI.^2–4 However, the success of recanalization with conventional wires is about 50–60%,^5–7 and the impact of the new technology on recanalization is unknown. We are presenting a single-center experience with one device, the Frontrunner™ catheter (LuMend, Inc., Redwood City, California) in revascularization of this difficult lesion subset. Materials and Methods Inclusion criteria. A series of 18 consecutive patients with CTO of native coronary arteries, as noted in previous angiograms, were enrolled in this single-center, single-operator series. The indication for attempt at recanalization was ischemia in the territory of the CTO on single photon emission computed tomography (SPECT) imaging. The mean duration of the CTO was 5.3 years. There were no prespecified selection criteria for inclusion in the study. Thirty-three percent of the patients had prior attempts at recanalization with wire-based technology. All of these attempts were unsuccessful. No dedicated CTO wires were used because they were unavailable for use in the United States. Therefore, these patients represented a consecutive series of patients who on diagnostic angiography were found to have a CTO and whose SPECT imaging demonstrated ischemia in the territory of the occluded vessel. Definitions. A CTO lesion was defined as the absence of antegrade flow distal to the occlusion, thrombolysis in myocardial infarction (TIMI) grade 0 flow, of at least one-month duration. The duration of the occlusion was assessed from the date of a previous Q-wave myocardial infarction (MI) of the area supplied by the occluded vessel, or from an abrupt change in the pattern of angina or from information available from previous angiograms. Technical success was defined as the ability to cross the occluded segment and successfully open the artery with a Grade 0 denotes the lack of collateral vessels. Grade 1 has filling of side branches of the target vessel. Partial filling of the target vessel proper through collaterals is categorized as Grade 2. Complete filling of the target vessel is Grade 3.²³ Interventional technique. Written, informed consent was obtained from all patients prior to the procedure. All interventions were attempted through the femoral artery using 6 Fr or 7 Fr guiding catheters. Patients were pretreated with 325 mg of oral aspirin and 600 mg of clopidogrel. Bivalirudin was the anticoagulant of choice for all the cases. The Frontrunner catheter was used in all patients as frontline therapy. Dual cusp injections were used when retrograde filling of the vessel was the predominant form of collateralization. A Microglide catheter was used when the operator felt that there was need for additional backup support for the Frontrunner catheter. After successful crossing with the Frontrunner catheter, a 0.014-inch guidewire was used to cross the lesion, and angioplasty was performed with appropriate balloon size (1:1). The last step involved stent implantation. The Cypher™ stent (Cordis Corporation, Miami, Florida) was used in all patients in this series. Follow up. All patients were followed up at 1 month, 3 months and 6 months after the procedure in an outpatient setting. The primary endpoint was a cardiac event defined as cardiac death, acute MI (Q- or Non-Q-wave), and the need for repeat PCI or CABG surgery. Follow-up angiography was performed in patients who developed recurrent symptoms within the first 6 months of the procedure, or those in whom SPECT scanning reflected a return of ischemia in the territory of the treated vessel. Results Procedural success, defined as TIMI 3 flow and 5–7 Due to the low success rate when compared with angioplasty in other lesion subsets, newer devices are constantly being tested in this lesion subset. Stiffer wires and hydrophilic wires are now used in attempts to recanalize CTOs. Different groups have reported slightly higher success rates (79–90%) using these stiffer, dedicated CTO wires.^8–11 IVUS-guided wiring techniques have also been reported.¹² More recently, Saito et al. have reported a success rate of about 80% using tapered-tip guidewires.¹³ The use of intracoronary urokinase to facilitate PCI of CTOs was also reported in the 1990s.¹⁴ In these reports, the main reason for failure was the inability to cross the site of occlusion with a guidewire. Previous studies have also shown that lesion calcification, lesion length, lack of a tapered tip and multivessel disease were also associated with higher procedural failure rates.^11,15–17 Noguchi et al. showed a success rate of only 32% in 226 patients when calcification of the lesion was present.¹⁵ In some studies, duration of the occlusion was reported to also be predictive of procedural failure,^15,17–19 but this finding was not supported by the investigators.^11,15 Piscione et al., in their study of 83 patients, suggested that LAD and RCA vessel diseases were also independent predictors of higher procedural success. Length of the occlusion has been reported to be a predictor of procedural failure, with a success rate as low as 40% in lesion lengths > 20 mm.¹⁵ In this small series of patients, the use of the Frontrunner catheter was associated with a higher rate of procedural success when compared to the use of conventional techniques with a guidewire. The presence of calcifications, the absence of a tapered end, the duration of occlusion or the presence of multivessel disease did not predict procedural failure when using the Frontrunner catheter. The presence of bridging collaterals, although reported in some previous studies as a predictor of procedural failure,^17,18,20,21 did not predict failure in our study. Lesion length, which was associated with higher failure rates in other studies, also did not predict procedural failure in this series, where the average length of the CTO was 57 mm. Periprocedural anticoagulation is controversial in CTO recanalizations. There appears to be validity for the use of heparin (ease of reversal with protamine) when wire-based technology is used because stiffer, hydrophilic wires are more likely to cause perforations. The need for reversal of anticoagulation with protamine may be important in those instances. In this case series, since blunt dissection with the Frontrunner catheter was the technology used, there was less of a concern with respect to perforations and tamponade. Anticoagulation with bivalirudin was used in all the cases in this series. In the immediate- or short-term follow up, there were no deaths or myocardial infarctions. Additionally, there were no perforations or tamponade with the use of this device. With the use of drug-eluting stent technology, the TVR was 11% at 6 months. These results are similar to those reported by other groups.^11,15,22 An interesting trend was seen in this case series with respect to the use of the Microglide catheter and dual cusp injection technique. When the contralateral artery provided the distal collaterals, dual cusp injections were very helpful to serve as a roadmap of the distal vessel and facilitated procedural success. Similarly, when backup with the guiding catheter was suboptimal and caused the Frontrunner catheter to back out, use of the Microglide catheter facilitated delivery of the catheter to the proximal cap of the CTO. There was a trend towards a higher rate of procedural success with the use of the Microglide catheter and dual cusp injections. These results, however, were achieved at the cost of long fluoroscopy times and large contrast volumes. Study limitations. This is a single-center, single-operator observational report involved a small number of patients. Mandated coronary angiograms were not performed in follow up unless patients had recurrent symptoms or had abnormal SPECT imaging. Silent angiographic restenosis in a higher number of patients, therefore, cannot be excluded. Absence of long-term data is also another limitation of this observational registry. Nevertheless, this registry provides valuable information about the safety and efficacy of a new device in the arena of treating CTOs. Since the widespread use of dedicated tapered-tip 0.014-inch guidewires in the treatment of CTOs, the Frontrunner device may now be relegated to use only when wire-based technology is unsuccessful. The Frontrunner catheter appears to have a higher procedural success rate when compared to conventional techniques. Predictors of procedural failure with conventional techniques do not appear to influence procedural success with the use of the Frontrunner catheter. Although this device is no longer actively marketed, it is still available and may serve a niche role in the management of CTOs. Long-term outcome data are, however, needed.

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