One hundred fifteen patients(117 lesions) who underwent TRI for CTO(a TIMI 0 or 1 for more than 2 months) were prospectively included in this study. Any bifurcation lesion requiring the kissing balloon technique was excluded from the study. Fifty-four patients were included in the 5F catheter group, and 63 patients were included in the 6F catheter group.

The prerequisites were a sufficient pulsating radial artery and the presence of an ulnar artery with an adequate palmar arch, as evidenced by the absence of digital ischemia according to the Allen test. Transradial angioplasties were performed with the arm and forearm extended, and with the wrist supine and secured next to the hip. The right radial artery was the preferred approach to keep the procedure simple and the radiation exposure as low as possible. The left radial approach was chosen for the patients with a pathological unilateral Allen test on the right or there was a failure of arterial puncture of the right radial artery, and the left radial approach was also employed for the patients who had undergone coronary bypass surgery with using the left mammary artery. After inducing local anesthesia with 2% lidocaine, the radial artery was cannulated with a 5F or 6F arterial sheath(Check-Flo Performer, Cook, Bloomington, IN). To prevent spasm, 600 µg of nitroglycerin was administered through the arterial sheath. During PCI, the activated coagulation time was kept above 300 seconds via intravenous injection of heparin. After the angioplasty had been performed, the sheath was removed immediately and hemostasis was achieved by applying a radial compressive dressing for 5 hours. The radial artery pulse and bleeding were frequently checked by an experienced nurse.

All the angioplasty procedures(balloon angioplasty and stent implantation) were performed with 5F or 6F guiding catheters(Brite Tip, Cordis, FL, USA). The selection of the guiding catheter's diameter was non-randomized and dependent on the operator's discretion, and a 5F guiding catheter was frequently selected for the low risk patient group. Extra-backup or an Amplatz curve was preferentially selected for a guiding catheter to achieve stronger backup support. A deep-seating technique was actively applied when the backup support of the guiding catheter was inadequate, and this typically occurred in calcified tortuous lesions. To improve the crossibility and to facilitate the exchange of a guidewire, we almost always routinely used a supportive infusion catheter with a guidewire. The initially selected guidewires were High Torque Intermediate(Guidant, USA) or hydrophilic coated guidewires, and these were readily changed to taperedtip stiff guidewires if there was resistance to the wire's progression. Once a guidewire had passed through the occlusion site, a 1.5 mm balloon wire was tried first in the tight fibrotic or calcified lesions. Stent implantation was performed only if the vessel diameter was larger than 2.5 mm.

Procedural success was defined as successful cannulation of the guiding catheter in the coronaries, the post-procedural residual stenosis was <50% and there was TIMI-3 antegrade flow with the absence of major complications(including death, Q-wave myocardial infarction, sustained coronary occlusion or the need for emergency coronary artery bypass surgery).

Vascular access site complications were defined as major if they were associated with a hemoglobin loss greater than 2 g/dL, the need for blood transfusions or vascular repair was done. Minor access site complications were defined as local hematoma >3 cm in diameter, or there was a loss of the radial pulse, suggesting radial occlusion or thrombosis. The duration of occlusion was estimated from the date of occurrence of the myocardial infarction in the area supplied by the occluded vessels, or the abrupt worsening of angina pectoris, or from the information obtained from a previous angiogram.

The angiographic morphology of the occlusion entry was classified as tapered if the occluded segment ended in a funnel-shaped form, or it was classified as abrupt when it did not take this form, or as none when it was impossible to locate the entry site.

The demographic, clinical, angiographic and procedural data was prospectively recorded on a prepared case record form. The coronary angiogram was assessed for lesion location, vessel tortuosity, lesion calcification, the occlusion entry morphology, bridging collaterals and the grade of retrograde collaterals, as based on the Retrop classification.7) Quantitative coronary analysis was also performed for the proximal and distal reference diameters of the vessel, the post-procedural residual stenosis, the lesion length and the occlusion length(these were measured after the passage of a balloon catheter in the success group or estimated by considering the contrast filling of the collaterals in the failure group).

The results are expressed as proportions or means±SDs. The differences in the categorical variables were analyzed by Fisher's exact test, whereas the differences in continuous variables were analyzed by Student's t test. P were less than 0.05 were considered statistically significant.

The baseline clinical characteristics of the patients are summarized in Table 1. No major differences were noted between the 2 groups with respect to the distribution of age and gender, the clinical diagnosis of the coronary risk factors, multivessel disease and the left ventricular function. Fifty patients(43%) were treated on a 1-day admission basis; PCI was done on the day of admission and the patients were discharge on the same day(5F: 26(48%), 6F: 24(39%), p=0.34).

The angiographic characteristics of the patients are shown in Table 2. The 5F catheter group was associated with a higher incidence of the tapered type of entry morphology(5F: 74%, 6F: 56%, p=0.04) and shorter occlusion length(5F: 8.8±7.6 mm, 6F: 14.7±12.7 mm, p=0.007). The lesion location, the severity of lesional tortuosity, the lesion calcification and the distribution of the antegrade and collateral flow were similar between the 2 groups. The estimated occlusion duration was also similar between the 2 groups(5F: 17.5‡23.6 months, 6F: 15.3‡18.6 months, p=0.61).

The procedural characteristics for both groups are shown in Table 3. Using a guiding catheter with strong back-up support such as an Amplatz or extra-backup curve was preferred for both the 5F and 6F groups(5F: 61%, 6F: 78%, p=0.82). The deep-seating technique was more frequently applied in the 5F group(5F: 83%, 6F: 51%, p<0.001).

Supportive infusion catheters(Excelsior®, Boston Scientific, MA, USA, or Prowler®, Cordis, FL, USA) were almost routinely used in both groups(5F: 93%, 6F: 97%, p=0.70) Tapered-tipped stiff guidewires(CrossIt 400®, Guidant, USA, or Conquest®, Asahi, Japan) were used in 33% of the 5F group and in 19% of the 6F group (p=0.092).

The crossover to larger guiding catheters or a femoral approach occurred for 2 lesions of the 5F group and for 3 lesions of the 6F group(p=1.0). The duration of the procedure, from starting the guiding catheter cannulation to the end of the procedure, was similar between the 2 groups(5F: 34.3±26.8 min, 6F: 36.7±17.3 min, p=0.58).

The overall procedural success rate was 84%, irrespective of the grade of the antegrade TIMI flow(TIMI 0: 82%, TIMI: 88%, p=0.43). The success rate was similar between the 5F and 6F groups(Table 3). The most frequent cause of procedural failure was the inability to cross the lesion with the guidewire(5F: 10 lesions, 6F: 7 lesions). Among the clinical and angiographic variables, the lesion angulation(>60°), an occlusion duration ≥6 months and a lesion length ≥10 mm were associated with a lower success rate(Table 4).

No major complications such as cardiac tamponade or major hematoma were noted in the study group. No catheter-induced dissections were associated with the deep-seating technique. Coronary artery perforation was noted in 2 patients of the 6F group. These patients were treated with prolonged balloon inflation without further complications. Minor hematoma occurred in 2 patients of the 5F group(Table 5).

Transradial coronary intervention for treating CTO was feasible and safe with a high success rate and a low complication rate. The 5F catheter transradial approach was also feasible and safe in our selected group of patients with chronic total occlusion, and this may contribute to decreased patient morbidity during percutaneous coronary intervention.