Thirty percent of diagnostic angiograms have at least 1 chronic total occlusion (CTO). The 10-year survival of patients with a CTO is improved if they have the CTO successfully recanalized. The success of recanalization with conventional wires is 50% and the impact of new technology on recanalization is unknown. This abstract reports a single center experience with one such new device, the Lumend Frontrunner™ catheter in revascularization of this difficult lesion subset. A consecutive series of 18 patients with CTO’s of native coronary arteries were enrolled in this single center, single operator series. The mean age of the CTO was 5.3 years. The indication for attempt at recanalization was ischemia in the territory of the CTO on SPECT imaging. Success was defined as TIMI flow restoration and < 40% residual stenosis. Primary success (defined as TIMI 3 Flow restoration and < 40% residual stenosis) was achieved in 77% of patients. At 30 days and out to 6 months, clinical TVR was 11% (2/18) in this difficult lesion subset. Conventional predictors of failure to recanalize CTOs do not appear to hold true with the use of the Frontrunner catheter. In this small series, dual cusp injections and use of the Microglide® catheter appears to correlate with favorable outcomes. Fluoroscopy times and contrast use are high when attempting recanalization of CTOs with this technology.

       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 < 40% residual stenosis and TIMI 3 flow. Procedural success was defined as technical success with no in-hospital major adverse cardiac event (MACE). A MACE was defined as occurrence of death, acute MI or urgent revascularization. Urgent revascularization was defined as repeat percutaneous intervention (PCI) of the target vessel during the same hospitalization, or coronary artery bypass graft surgery (CABG), including bypass of the target vessel. Acute MI was defined as CPK elevation that was greater than 3 times the upper limit of normal.
       The angiographic variables examined were the location of the lesion, the length of the occlusion (estimated from the contrast filling of the collaterals), the presence or absence of calcification at the site of occlusion, morphology (tapered or abrupt), the presence or absence of bridging collaterals, as well the presence or absence of a side branch prior to the occlusion site. Grading of the collateral flow was based upon Rentrop’s classification. 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 < 40% residual stenosis, was achieved in 77% (14/18) of patients. No periprocedural complications were noted. No immediate MACE was noted. Two patients required repeat revascularization of their target vessel during the follow up period. No cardiac deaths or acute MI were noted during follow up.
       In the 4 patients whose treatment was unsuccessful, the failure was related to the inability to access the true lumen distally in the vessel. The presence of calcification or lack of vessel taper did not predict failure, neither did side branch proximity or tortuosity of the proximal vessel. There appeared to be a trend towards favorable outcomes with the use of dual cusp injections and a Microglide catheter.

Discussion
       Attempts at revascularizing CTOs in the past with conventional wires have yielded a success rate of approximately 50–60%.^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.

1. Suero JA, Marso SP. Jones PG, et al. Procedural outcomes and long-term survival among patients undergoing percutaneous coronary intervention of a chronic total occlusion in native coronary arteries: A 20-year experience. J Am Coll Cardiol 2001;38:409–414.
2. Gray DF, Sivananthan UM, Verma SP, et al. Balloon angioplasty of totally and subtotally occluded coronary arteries: Results using the Hydrophillic Terumo Radifocus Guidewire M (glidewire). Cathet Cardiovasc Diagn 1993;30:293–299.
3. Puma JA, Sketch MH Jr, Tcheng JE, et al. Percutaneous revascularization of chronic coronary occlusions: An overview. (Review) J Am Coll Cardiol 1995;26:1–11.
4. Chung CM, Nakamura S, Tanaka K, et al. Effect of recanalization of chronic total occlusions on global and regional left ventricular function in patients with or without previous myocardial infarction. Catheter Cardiovasc Interv 2003;60:368–374.
5. Melchior JP, Meier B, Urban P, et al. Percutaneous transluminal coronary angioplasty for chronic total coronary arterial occlusion. Am J Cardiol 1987;59:535–538.
6. Finci L, Meier B, Favre J, et al. Long-term results of successful and failed angioplasty for chronic total coronary arterial occlusion. Am J Cardiol 1990;66:660–662.
7. Ivanhoe RJ, Weintraub WS, Douglas JS Jr, et al. Percutaneous transluminal coronary angioplasty of chronic total occlusions. Primary success, restenosis, and long-term clinical follow-up. Circulation 1992;85:106–115.
8. Corcos T, Favereau X, Guerin Y, et al. Recanalization of chronic coronary occlusions using a new hydrophilic guidewire. Cathet Cardiovasc Diagn 1998;44:83–90.
9. Corcos T, Favereau X, Guerin Y. Crosswire for recanalization of total occlusive coronary arteries. Catheter Cardiovasc Interv 1999;47:116.
10. Bahl VK, Chandra S. Goswami KC, Manchanda SC. Crosswire for recanalization of total occlusive coronary arteries. Cathet Cardiovasc Diagn 1998;45:323–378.
11. Piscione F, Galasso G, Maione AG, et al. Immediate and long-term outcome of recanalization of chronic total coronary occlusions. J Interv Cardiol 2002;15:173–179.
12. Matsubara T, Murata A, Kanyama H. Ogino A. IVUS-guided wiring technique: Promising approach for the chronic total occlusion. Catheter Cardiovasc Interv 2004;61:381–386.
13. Saito S, Tanaka S. Hiroe Y, Miyashita Yet al. Angioplasty for chronic total occlusion by using tapered-tip guidewires Catheter Cardiovasc Interv 2003;59:305–311.
14. Zidar FJ, Kaplan BM, O'Neill WW, et al. Prospective, randomized trial of prolonged intracoronary urokinase infusion for chronic total occlusions in native coronary arteries. J Am Coll Cardiol 1996;27:1406–1412.
15. Noguchi T, Miyazaki MD S, Morii I, et al. Percutaneous transluminal coronary angioplasty of chronic total occlusions. Determinants of primary success and long-term clinical outcome. Catheter Cardiovasc Interv 2000;49:258–264.
16. Leonzi O, Ettori F, Lettieri C, et al. Coronary angioplasty in chronic total occlusion: angiography results, complications, and predictive factors. Giornale Italiano di Cardiologia 1995;25:807–814.
17. Kereiakes DJ, Selmon MR, McAuley BJ, et al. Angioplasty in total coronary artery occlusion: Experience in 76 consecutive patients. J Am Coll Cardiol 1985;6:526–533.
18. Holmes DR Jr, Vlietstra RE, Reeder GS, et al. Angioplasty in total coronary artery occlusion. J Am Coll Cardiol 1984;3:845–849.
19. Ishizaka N, Issiki T, Saeki F, et al. Angiographic follow-up after successful percutaneous coronary angioplasty for chronic total coronary occlusion: experience in 110 consecutive patients. Am Heart J 1994;127:8–12.
20. Stone GW, Rutherford BD, McConahay DR, et al. Procedural outcome of angioplasty for total coronary artery occlusion: An analysis of 971 lesions in 905 patients. J Am Coll Cardiol 1990;15:849–856.
21. Maiello L, Colombo A, Gianrossi R, et al. Coronary angioplasty of chronic occlusions: Factors predictive of procedural success. Am Heart J 1992;124:581–584.
22. Olivari Z, Rubartelli P, Piscione F, et al. for the TOAST-GISE Investigators. Immediate results and one-year clinical outcome after percutaneous coronary interventions in chronic total occlusions: data from a multicenter, prospective, observational study (TOAST-GISE). J Am Coll Cardiol 2003;41:1672–1678.
23. Rentrop KP, Cohen M, Blanke H, et al. Changes in collateral channel filling immediately after controlled coronary artery occlusion by an angioplasty balloon in human subjects. J Am Coll Cardiol 1985;5:587–592.