The incidence of unwilling passage of guidewire was as high as 9.5% in transradial CAG, and its related perforation was rare but serious. There’s hardly any unwilling passage of guidewire in the Knuckle group, which improved the safety. Shorter fluoroscopy duration decreased radiation exposure and increased efficiency.
High incidence of unwilling passage of guidewire has not been reported for various reasons, but it is an inevitable problem in daily practice. Based on a similar parallel course of pericardiacophrenic artery  and radial recurrent artery  to the normal arteries, the guidewire must have inadvertently entered at some point during repeated manipulation without early recognition. Sometimes hydrophilic guidewire may slip into the same branch recurrently and hard to be corrected. Meticulous advancement and unrecognized abnormalities could result in dissection and perforation. Early recognition and prompt action may prevent fatal outcomes. Asymptomatic dissection was hard to see without routine angiography and self-healing over time . Immediate recognition of perforation and prompt action including neutralization of heparin, crossing with a wire, and deployment of either a diagnostic or guide catheter across and external compression by sphygmomanometer cuff may help seal the perforation. Furthermore, invasive solutions including prolonged balloon inflation, embolization, and covered stents should be entertained according to the patient’s hemostatic response after abovementioned noninvasive therapy has clearly failed [7, 9, 17, 18]. Though the incidence of perforation is low [9, 22], its consequence may be serious for the patient [7, 13]. And we all know that prevention is always more effective than cure.
We have designed a novel approach to prevent guidewire associated unwilling passage and complications. Knuckle guidewire exhibits some superiorities, consisted mainly of preference for main artery not small branches and friendly to vessel wall with smooth tip [23, 24]. Predefined knuckle could avoid slipping into the small branches and the knuckle may enlarge and unfasten in a large luminal caliber. Recurrent radial artery branch always originated from the radioulnar alpha and runs parallel to the radial artery, which was easy to be strayed into and hard to see with empirical advancement of guidewire under fluoroscopy. Maneuvering catheter passage may cause pain, vessel spasm, even perforation [6, 9, 17]. The most loops were easily crossed and straightened using knuckle guidewire, while the traditional method was sometimes hard to cross through the loop due to multiple branching patterns along the loop . IMA is far smaller than and nearly perpendicular to the subclavian artery, which prompts knuckle guidewire to keep away from IMA. More often male, hyperlipidemia, mellitus diabetes and smoking indicated more atherosclerosis in the Knuckle group, which could cause difficult passage of J-tip guidewire . However, knuckle guidewire exhibited equal passage with original angle hydrophilic guidewire. Smooth tip could be friendlier to the vessel wall than original angle tip, especially when encountering tortuosity and loop. The angle tip contacting with vessel wall increases risk of dissection and perforation [9, 10, 17]. According to its preference for main artery and smooth tip, advancement of guidewire becomes more efficient. Fluoroscopy dose is linear correlation with fluoroscopy time so that shorter duration of guidewire advancement will protect both the doctor and patient due to decreased radiation exposure.
Some interventional doctors prefer J-tip guidewire, whose tip is partly similar to the knuckle guidewire with decreased branch enter. However, it was designed for transfemoral approach of large lumen, and indicated some limitations in transradial access. First, the safe J tip formed when it entered in a large vessel or encountered a branch. Before that, the tip kept straight in the small radial artery so that potential risk remained . Furthermore, J tip is smaller than our knuckle tip, which entered into branches and lead to perforations [6, 12, 17, 25]. Finally, J-tip guidewire was difficult to pass tortuosity and severe angle of subclavian-innominate-aorta axis at times, which was dealt with hydrophilic angle guidewire [7, 15]. Knuckle guidewire could enlarge and unfasten its knuckle in large lumen, possessing the ability of direction change to accomplish angiography in patients (Online video 6).