Background. In high-expertise transradial (TR) centers, the radiation exposure to patients during coronary angiography (CAG) is equivalent to transfemoral use. However, there is no definitive information during TR-CAG regarding the use of a single, dedicated catheter to impart less radiation exposure to patients. Objective. We compare the radiation exposure to patients during right TR-CAG with Tiger II catheter (Terumo Interventional Systems) vs Judkins right (JR) 4.0/Judkins left (JL) 3.5 catheters (Cordis Corporation). Methods. This multicenter, randomized, and prospective trial included 180 patients submitted to right TR-CAG, with the primary objective of observing radiation exposure to patients through the measurement of fluoroscopy time, air kerma (AK), and dose-area product (DAP) using Tiger II (group 1) vs JR 4.0 and JL 3.5 Judkins catheters (group 2). Secondary outcomes included contrast volume usage and the need to use additional catheters to complete the procedure (the crossover technique). Results. Group 1 demonstrated reduced fluoroscopy time (2.47 ± 1.05 minutes in group 1 vs 2.68 ± 1.26 minutes in group 2; P=.01) and non-significant reduction of AK (540.9 ± 225.3 mGy in group 1 vs 577.9 ± 240.1 mGy in group 2; P=.34) and DAP (3786.7 ± 1731.7 µGy•m2 in group 1 vs 4058.0 ± 1735.4 µGy•m2 in group 2; P=.12). Contrast volume usage (53.46 ± 10.09 mL in group 1 vs 55.98 ± 10.43 mL in group 2; P=.13) and the need for additional catheters (5.56% in group 1 vs 4.44% in group 2; P>.99) were similar between groups. Conclusion. The Tiger II catheter was able to reduce radiation exposure to patients submitted to TR-CAG through a significant reduction in fluoroscopy time.
J INVASIVE CARDIOL 2021;33(3):E200-E205. Epub 2021 February 18.
Key words: radial access, radiation safety, transfemoral access approach
The increasing advent of dedicated radial devices and the growth of transradial (TR) training programs have established the TR approach as the default strategy for coronary angiography (CAG) in many catheterization laboratories around the world. Besides a well-established benefit in decreasing access-site bleeding, especially in the setting of acute coronary syndromes,1-4 several publications have also demonstrated that in high-expertise TR centers, the amount of radiation exposure to the patient is similar to transfemoral use during CAG and percutaneous coronary intervention (PCI) procedures.5,6 The renewed interest in radiation exposure in the medical environment has gained increasing attention, as the exposure levels have grown dramatically from 0.6 mSv/person/year in the 1990s to 3.2 mSv/person/year after only 2 decades.7 Interventional cardiology and electrophysiology procedures account for nearly 40% of the radiation exposure in medical procedures, when not considering radiotherapy.8 More recently, different trials have investigated the hypothesis that use of a single, dedicated catheter, such as the Tiger II (Terumo Interventional Systems), during TR-CAG could impact radiation exposure in patients when compared with traditional Judkins right (JR) 4.0 and Judkins left (JL) 3.5 catheters (Cordis Corporation).
The differences observed in previous trial designs may hinder the interpretation of our results.9-12 Kim et al performed the first randomized comparison between these catheters in 160 stable patients, demonstrating shorter fluoroscopy time with Tiger II catheter, but without recording differences in direct radiation measurements such as air kerma (AK) or dose-area product (DAP).9 Later, Xantopoulou et al, investigating the use of iodine contrast volume, confirmed as a secondary outcome that Tiger II catheter use resulted in a relative reduction in mean fluoroscopy time of 10.3% compared with multiple Judkins catheters.13 It could be hypothesized that Tiger II use might have a beneficial effect, of particular importance to high-volume centers performing multiple procedures per day, in reducing radiation exposure and even procedural costs.
This is a prospective, multicenter, randomized study designed to assess the hypothesis of the superiority of 5 Fr Tiger II catheter in diminishing patient radiation exposure in comparison with 5 Fr Judkins 3.5L and 4R catheters in CAG using the right TR approach. The primary outcome included the measurement of fluoroscopy time, AK, and DAP. Secondary outcomes included the amount of contrast usage and the need to use additional catheters to complete the procedure (the crossover technique). The study was registered at http://plataformabrasil.saude.gov.br (CAAE number, 61928216.4.0000.5259180). A total of 180 consecutive patients undergoing non-urgent CAG were electronically randomized in a 1:1 ratio to the use of 5 Fr Tiger II catheter (group 1) or 5 Fr JL 3.5/JR 4 catheters (group 2). Written informed consent was obtained from all patients, and approval was obtained by the independent ethics committee of each institution participating in the study. Computer-generated random numbers were used for randomization, stratified by center. All operators were highly experienced (>1000 angiograms overall) in TR approach and handling both Judkins and Tiger II catheters. After cannulation of the right radial artery with a 6 Fr Glidesheath (Terumo), all patients received 5000 IU bolus of unfractionated heparin and 200 µg of nitroglycerin intra-arterially. Patients were excluded if they presented with the following: ST-segment elevation myocardial infarction or non-ST segment elevation myocardial infarction with high-risk features demanding urgent CAG <3 hours; hemodynamic instability; negative Allen test or absent radial pulse; Raynaud’s disease; prior coronary artery bypass grafting; and known aortic valve disease or ascending aortic aneurysm. All CAGs were performed with low osmolality iodine contrast (Henetix 350; Guerbet) and the image acquisitions were obtained at 15 frames/second on Artis ZEE (Siemens) and FD20 (Philips) angiography systems. CAG should obtain at least 5 standard views to image the left coronary artery, 3 standard views for the right coronary artery, and 1 view for left ventriculography. After completion of the CAG, hemostasis was obtained with TR Band pulse wrist (Terumo) deflated 2 hours post procedure. Outpatients were oriented to return to medical visit within 48 hours after CAG and those admitted to the hospital received medical visit the next morning to observe any bleeding related to the arterial site. The incidence of radial spasm and the need to crossover to femoral access were registered.
Definitions. All endpoints were measured at the completion of the CAG. In case of CAG progressing to ad hoc PCI, the parameters investigated were all measured upon the end of CAG. The fluoroscopy time was directly obtained in the digital panel, in minutes, but the other direct radiation measures (AK and DAP) had to be multiplied by the correction factor of each x-ray machine to prevent overestimating these values. Obtaining the correction factor consists of adjusting the measuring instrument to the conditions of use by a physicist. The amount of contrast used was calculated at the end of the last injection and the need to use additional catheters was presented in percentage. All results were presented in the intention-to-treat (ITT) principle.
Catheter failure was defined as the need to use different additional catheters to complete the CAG (technique crossover), while access failure was defined as the need to change arterial site due to spasm or vascular anatomical variations (access-site crossover). Radial spasm was noted, but not quantified as light, moderate, or severe due to the difficulty in rating its qualitative nature. Access-site bleeding events were recorded according to the EASY classification system.14
Statistical analyses. The main hypothesis of the study is that there is a difference of up to 20% reduction in fluoroscopy time and radiation dose in the Tiger II group. We assumed a mean TR-CAG reference time of 3.7 minutes of fluoroscopy (interquartile range [IQR], 2.3–6.3 minutes) and 2680 µGy•m2 DAP (IQR, 1550-4520 µGy•m2) of radiation dose in the patients, according to large, previously disclosed analysis for a strategy with traditional Judkins catheters.15 Assuming a 20% chance of decreasing time and dose with Tiger II, a sample calculation of 90 patients in each group was determined.
Continuous variables were tested for normal distribution using the Shapiro-Wilks test. In the descriptive analysis, the numerical variables are expressed as mean ± standard deviation or median (expressed in percentiles). Categorical variables are expressed as percentages (%). Comparisons between continuous variables were performed using the unpaired Student’s t-test and Wilcoxon-Mann-Whitney test. Categorical variables were compared using Fisher’s or Chi-square tests. Multivariable probabilistic sensitivity analysis was performed with the variables with the greatest impact on the model, to test the robustness of the result. The level of significance was set at 5% (P≤.05). All tests were two-tailed. Statistical analysis was performed using SPSS Statistics for Windows, version 25.0 (IBM).
The study group comprised a high prevalence of male sex (71.6%) and overweight population (mean body mass index, 27.98 ± 5.2 kg/m2). A balance in clinical presentation was observed between patients with non-ST elevation acute coronary syndrome (52.3%) and those undergoing elective investigation of coronary artery disease (47.7%) (Table 1). No major complications were observed in the CAG procedure, such as major bleeding or perforation of the left ventricle. All ventriculographies were performed by manual contrast injection, given the presence of a single terminal hole in the Judkins catheters, thereby reducing the chance of perforation. Few cases of minor bleeding from the radial puncture site were observed (1.1% in group 1 vs 2.2% in group 2; P >.99), all of which were benign type I hematomas, without any major vascular or ischemic complication related to the access site (Table 2). Regarding the presence of radial spasm, there was a higher incidence in group 2 (2.2% in group 1 vs 6.6% in group 2; P<.27), in accordance with previous analyses,12,15 even though we didn’t observe any need to cross over to femoral access due to spasm.
As for the primary outcome, a significant reduction in fluoroscopy time was observed in favor of group 1 (2.47 ± 1.05 minutes in group 1 vs 2.68 ± 1.26 minutes in group 2; P=.01), with the other parameters also showing decreased radiological exposure but without reaching statistical significance (AK: 540.9 ± 225.3 mGy in group 1 vs 577.9 ± 240.1 mGy in group 2 [P=.34] and DAP: 3786.7 ± 1731.7 µGy•m2 in group 1 vs 4058.0 ± 1735.4 µGy•m2 in group 2; P=.12) (Table 3 and Figure 1). In the studied population, there was no difference in the number of acquisitions recorded between the groups (9.7 ± 0.79 in group 1 vs 9.64 ± 0.78 in group 2; P = .75), as well as regarding the performance of left ventriculography.
As for the secondary outcome related to the volume of contrast, there was a slight tendency to use lower volume of contrast in the single-catheter group (53.46 ± 10.09 mL in group 1 vs 55.98 ± 10.43 mL in group 2; P=.13), even though the sample size was not calculated for this purpose.
In the logistic regression analysis, no variations were found in the results of primary outcomes in any of the analyzed subgroups (clinical, demographic variables, and indication for CAG) including those prone to spasm of the radial artery (small diameter radial artery), such as female sex, diabetics, and low body complexity (BMI <18.5 kg/m2). In other subgroups, such as young population (<65 years old), evident spasm, and anatomical variations, it was not possible to perform the logistic regression analysis due to reduced numerical representation in our trial.
The literature is not conclusive about the gold-standard method to assess radiation exposure in the catheterization laboratory. The greatest radiation load is emitted during acquisition (recording) of images and not during fluoroscopy. During procedures with many image acquisitions, such as CAG evolving to ad hoc PCI, the information from AK and DAP levels is certainly a more relevant parameter than the fluoroscopy time alone, as the radiation dose gets higher. But in procedures such as CAG only, fluoroscopy gains importance as an exposure marker, albeit indirectly, because the number of recordings is generally smaller than in procedures with ad hoc PCI. In order to generate an adequate comparison profile with previous studies, we decided to register all 3 parameters described.
In the studied population, decreased radiological exposure was observed for patients in group 1, as evidenced by shorter fluoroscopy time (P=01) and by reduction (although not marked) of AK and DAP (P>.05). Such a reduction in the fluoroscopy time can be justified because there is no exchange of catheters, with a consequent reduction in the time and radiation dose to guide the device to the coronary sinus. Previous analyses with single-catheter techniques (Tiger II and “Jack like” catheter) also observed, almost homogeneously, a marked reduction in the fluoroscopy time when compared with the use of Judkins catheters.9-13,15 The average reduction of 13 seconds observed in the fluoroscopy time in favor of the Tiger II may impact clinical practice in labs with a high volume of CAG procedures, such as those with fellowship training programs in interventional cardiology, due to the longer learning curve of transradial procedures. In the REVERE trial, the major independent predictors of radiation load (AK) were: the number of recordings (image acquisitions); the operator’s experience; and the number of catheters needed to complete the procedure. Such data reinforce the concept of less radiological exposure with fewer catheters.6
In procedures with a higher number of acquisitions recorded (CAG followed by ad hoc PCI), a strong correlation has already been demonstrated between the fluoroscopy time and DAP (r = 0.78; P<.001).17 Our analysis was the first study to demonstrate a positive linear correlation (moderate value) between the variables of DAP and fluoroscopy time (r = 0.49; P<.001) as well as between AK and fluoroscopy time (r = 0.45; P<.001) in CAG-only procedures (Figure 2). Another relevant factor in this context is the potential reduction of the procedural cost, given the need to use only a single catheter compared with the traditional Judkins technique using 2 catheters.18
As for the secondary endpoint of contrast volume, there was no marked difference in the volume used between groups (median reduction of 2.5 mL in group 1). Although the sample size was not calculated with this purpose, a previous trial with a large number of patients has demonstrated significantly less contrast use with Tiger II catheter in TR-CAG.13
A small number of vascular anatomical variations (8.3%) was observed in the studied population, and included tortuosity of the subclavian artery, ascending aorta loop, radial and/or brachial loop, anomalous coronary origin, and high take-off radial artery, with potential to cause access failure resulting in only 2 cases of access crossover to the transfemoral approach, a fact that may be explained by the sample size and the expertise of the operators.
Another outcome analyzed was the low crossover rate for using additional catheters (Amplatz, Judkins, or multipurpose type) in order to complete the CAG in both groups (5.56% in group 1 vs 4.44% in group 2; P>.99), as expected in experienced TR centers.
The higher incidence of radial spasm in group 2 (6.67%, compared with 2.22% in group 1; P=.28), although without statistical significance, can be explained by the greater manipulation of the radial artery when performing the exchange of catheters.19,20 It is important to note the spasm-protective measures taken with the exclusive use of hydrophilic sheaths and a vasodilator cocktail.
Study limitations. The results of the present analysis favoring the use of the Tiger II catheter by reducing the fluoroscopy time should not be extrapolated to other strategies utilizing single dedicated catheters, such as Barbeau (Cordis); MPA (Cordis), and Kimny (Boston Scientific), since these were not tested in the present study.
The non-blinding of the operators for the type of catheter used during CAG may cause potential bias based on the personal preferences of the operators. The study results are consistent with the data published in the literature regarding the fluoroscopy time for Tiger II catheter, as the mean time in previous analyses (2.5 minutes) was similar to ours.9,10,13 It’s notable that we found a higher mean DAP than the large registry used to calculate the sample size, which was most likely due to the high completion of ventriculography in our study (this part of the CAG may be responsible for up to 30% of the radiation exposure), as the French registry concluded the left ventriculography in only 57% of the procedures.15 The limited number of patients makes the results regarding the contrast volume only exploratory.
The use of Tiger II catheter demonstrated reduced radiation exposure to patients during TR-CAG through a significant reduction in fluoroscopy time.
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From the 1University Hospital of the State of Rio de Janeiro, Rio de Janeiro, Brazil; 2Quinta D’Or Hospital, Rio de Janeiro, Brazil; and 3Copa D’Or Hospital, Rio de Janeiro, Brazil.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.
Manuscript accepted July 7, 2020.
Address for correspondence: Felipe Maia, MD, MSc, Rua Almirante Baltazar, 435 (Research Center of Quinta D’Or Hospital), São Cristóvão, Rio de Janeiro 20941-150, Brazil. Email: firstname.lastname@example.org