Comparison of Radiation Dose and the Effect of Operator Experience in Femoral and Radial Arterial Access for Coronary Procedures

Comparison of Radiation Dose and the Effect of Operator Experience in Femoral and Radial Arterial Access for Coronary Procedures Johanne Neill, MD*, Hannah Douglas, MBBCh, Geoffrey Richardson, MD, Eng-Wooi Chew, MD, Simon Walsh, MD, Colm Hanratty, MD, and Niall Herity, MD Radial access coronary procedures are associated with fewer access site complications compared to femoral access. There is controversy regarding greater radiation exposure to patient and operator using radial access. We aimed to compare radiation dose during coronary procedures for the 2 access routes and assess the effect of operator experience with radial access on radiation dose. Fluoroscopy time (FT) and dose–area product (DAP) were recorded for all radial access and femoral access procedures during default femoral access, transition phase (femoral access and early radial access), and default radial access. Femoral access cases (n ⴝ 848, 412 diagnostic, 436 percutaneous coronary interventions [PCIs]) and radial access cases (n ⴝ 965, 459 diagnostic, 506 PCIs) were assessed. For diagnostics, median FT for radial access was longer than for femoral access (4.43 minutes, interquartile range [IQR] 2.55 to 8.18, vs 2.34 minutes, IQR 1.49 to 4.18, p <0.001) and associated with larger DAP (radial access 1,837 ␮Gy·m2, IQR 1,172 to 2,783, vs femoral access 1,657 ␮Gy·m2, IQR 1,064 to 2,376, p <0.001). For PCI, FT was longer for radial access (median 12.02 minutes, IQR 7.57 to 17.54, vs femoral access 9.36 minutes, IQR 6.13 to 14.27, p <0.001)—this did not translate into an increased DAP (femoral access median 3,392 ␮Gy·m2, IQR 2,139 to 5,193, vs radial access 3,682 ␮Gy·m2, IQR 2,388 to 5,314, p ⴝ NS). For diagnostic radial access, FT decreased from the transition phase (n ⴝ 134) to the default radial access phase (n ⴝ 323, 5.12 minutes, IQR 3.07 to 9.40, vs 4.21 minutes, IQR 2.49 to 7.52, p ⴝ 0.03). This was not observed for PCI. In conclusion, transition from femoral access to radial access for diagnostics and PCI increased FT. DAP increased for diagnostic radial access but not PCI compared with femoral access. FTs for radial access diagnostic cases decreased with experience. © 2010 Elsevier Inc. All rights reserved. (Am J Cardiol 2010;106:936 –940) Transradial coronary procedures have been shown to have fewer access-site complications1–7 compared to the transfemoral approach and is preferred by patients.7,8 There is controversy with respect to quantity of radiation delivered to patient and operator using the transradial approach.9 –12 There are recent reports of increased radiation exposure when using the radial arterial approach.9,11 Factors such as imaging system used and operator experience and stage on the “learning curve”12,13 may influence radiation dose delivered, but these effects have not been fully elucidated. We have looked at cases across a period when our highvolume practice has transitioned from default transfemoral access through to default transradial access. We compared fluoroscopy time (FT), dose–area product (DAP), and contrast agent delivery between the 2 access routes for diagnostic procedures and for percutaneous coronary intervention (PCI). We also assessed the influence of

Belfast City Hospital, Cardiology Centre, Belfast, Northern Ireland, United Kingdom. Manuscript received February 27, 2010; revised manuscript received and accepted June 2, 2010. *Corresponding author: Tel: 44-0-797-798-5202; fax: 44-0-289-2677706. E-mail address: [email protected] (J. Neill). 0002-9149/10/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.amjcard.2010.06.002

operator experience and the effect of a learning curve on these radiation variables. Methods The study was completed in the Belfast City Hospital (Belfast, Northern Ireland)—a high-volume tertiary cardiology center (1,400 PCIs/year) with 5 cardiologists experienced in femoral access cardiac catheterization (⬎2,000 diagnostic studies) and coronary interventions (⬎1,000 PCIs). All practitioners have been fully trained in the principles of radiation protection in accordance with mandatory regulations. Data were recorded retrospectively from studies in 1 catheterization laboratory only. The imaging system used was Siemens Axiom Artis dFC (Siemens, Erlangen, Germany) installed in 2005 and serviced biannually. Fluoroscopic settings were 7.5 pulses/s and cinematic acquisition imaging frame rates were set at 10 frames/s for coronary images and 15 frames/s for left ventricular angiography. Iontomat (Siemens) automatic exposure control was used. Images were acquired in the standard manner with the assistance of an experienced radiographer and adhering to United Kingdom ionizing radiation medical exposure regulations. Standard operator shielding (lead aprons, lead thyroid collar, lead spectacles, transparent 1.0-cm lead screening between operwww.ajconline.org

Coronary Artery Disease/Radial and Femoral Radiation Exposure

937

Table 1 Access site and procedure type during three phases of transition from default femoral to default radial approach (n ⫽ 1,813) Variable Body mass index (kg/m2), mean ⫾ SD Access Femoral Radial Diagnostic angiography Percutaneous coronary intervention

Default Femoral Phase (n ⫽ 340)

Transition Phase (n ⫽ 685)

Default Radial Phase (n ⫽ 788)

p Value

29 ⫾ 5

29 ⫾ 5

30 ⫾ 6

0.04* ⬍0.001†

340 (100%) 0 171 (50%) 169 (50%)

405 (59%) 280 (41%) 330 (48%) 355 (52%)

103 (13%) 685 (87%) 370 (47%) 418 (53%)

0.64†

* Analysis of variance. † Pearson chi-square test.

Figure 1. FTs for diagnostic angiographic (angio) and PCI procedures with femoral (dark gray bars) versus radial (light gray bars) access routes.

ator and patient) was used throughout. Most operators exchanged catheters over the wire for radial access but not for femoral access. No identifying patient data were collected. Three specified periods were studied: January 1 to April 1, 2007, using the default femoral access approach; January 1 to July 1, 2008, with some operators continuing with femoral access and other operators beginning to use radial access (transition phase); and January 1 to July 1, 2009, with all operators deferring to radial access as the first choice (default radial approach). Data recorded for all studies within the defined periods were body mass index (BMI; kilograms per meter squared), access site (femoral or radial artery), procedure complexity (diagnostic angiography or coronary intervention), FT (minutes; has some influence on radiation dose delivered and is an indicator of procedure duration), DAP (micrograys meter squared; reflects radiation dose delivered to patient during fluoroscopy and cinematic image acquisition), and volume of contrast used. The studies consisted of elective and emergency procedures and included complex PCI cases. Because operator experience in femoral access cases was unlikely to be a factor in radiation dose delivery, all femoral access cases were analyzed together regardless of period. Numbers were sufficient for comparison with radial cases using 3 months for the default femoral period.

Figure 2. DAP associated with diagnostic angiographic and PCI procedures with femoral (dark gray bars) versus radial (light gray bars) access routes. Abbreviation as in Figure 1.

All analyses were performed using SPSS 11 for Windows (SPSS, Inc., Chicago, Illinois). Continuous normally distributed variables are reported as mean ⫾ 1 SD; median and interquartile range (IQR) are quoted for data of skewed distribution. Nonparametric correlations were assessed with Spearman rank correlation. Proportions were compared using Pearson chi-square test. Means were compared using Student’s t test or analysis of variance and Mann-Whitney U test or Kruskal-Wallis tests were performed to compare data of non-normal distribution. A p value ⬍0.05 was statistically significant. Results In total 1,813 cases were studied— 848 with femoral access and 965 with radial access. Table 1 presents the distribution of cases across the 3 phases of transition. There was a progressive increase in radial access with time. Similar proportions of diagnostic angiographies and PCIs were performed in each period. Overall mean BMI was 29 ⫾ 5 kg/m2; BMI correlated with DAP (Spearman rank correlation coefficient 0.42, p ⬍0.001). Neither FT nor contrast use correlated with BMI. Analyzing all femoral cases together (412) and all radial cases together (459), for diagnostic angiography (Figures 1

938

The American Journal of Cardiology (www.ajconline.org)

Figure 3. Effect of accumulating operator experience on FT associated with diagnostic angiography (dark gray bars) and PCI (light gray bars) using the radial access approach. (Left) FT associated with femoral cases are shown for comparison. *Only radial cases included.

used were similar (radial access 100 ml, IQR 90 to 130, femoral access 100 ml, IQR 90 to 130, p ⫽ 0.30). Analyzing all femoral cases together (436) and all radial cases together (506) for PCI (Figures 1 and 2), BMI was similar between groups (radial 29 ⫾ 5 vs femoral 29 ⫾ 5 kg/m2, p ⫽ 0.85). FT was longer in the radial access group (12.02 minutes, IQR 7.57 to 17.54) compared to the femoral access group (9.36 minutes, IQR 6.13 to 14.27, p ⬍0.001). This did not translate into significantly greater DAP (radial access DAP 3,682 ␮Gy·m2, IQR 2,388 to 5,314, vs femoral access DAP 3,392 ␮Gy·m2, IQR 2,139 to 5,193, p ⫽ 0.08). Contrast volumes used were similar (radial access 193 ml, IQR 150 to 240, femoral access 190 ml, IQR 150 to 240, p ⫽ 0.53). To test the effect of increased operator experience and to assess the duration of any learning curve, radiation variables from radial access cases during the transition phase were compared to radial cases from the subsequent default radial phase (Figures 3 and 4). For diagnostic procedures FT during the transition phase was 5.12 minutes (IQR 3.07 to 9.40) and decreased during the default radial phase to 4.21 minutes (IQR 2.49 to 7.52, p ⫽ 0.03). This was not associated with a decrease in DAP. BMI and contrast volume used did not change (transition phase BMI 29 ⫾ 5 vs default radial phase BMI 30 ⫾ 7 kg/m2, p ⫽ 0.14; transition phase contrast use 100 ml, IQR 90 to 130, vs default radial phase 100 ml, IQR 90 to 130, p ⫽ 0.95). For interventional procedures FT increased from the transition phase to the default radial phase (10.51 minutes, IQR 7.2 to 15.82, to 12.14 minutes, IQR 8.25 to 17.45, p ⫽ 0.02). This was not associated with an increase in DAP (Figure 4). BMI and contrast volume used did not change (transition phase BMI 29 ⫾ 5 vs default radial phase BMI 29 ⫾ 5 kg/m2, p ⫽ 0.69; transition phase contrast used 180 ml, IQR 140 to 230, vs default radial phase 195 ml, IQR 150 to 246, p ⫽ 0.07). Discussion

Figure 4. Effect of accumulating operator experience on DAP associated with diagnostic angiography (dark gray bars) and PCI (light gray bars) using the radial access approach. (Left) DAP associated with femoral cases are shown for comparison. *Only radial cases included.

and 2), BMI was greater in the radial access group (30 ⫾ 6 kg/m2) compared to the femoral access group (29 ⫾ 5 kg/m2, p ⫽ 0.03). Radial access was associated with a longer FT (4.43 minutes, IQR 2.55 to 8.18) and larger DAP (1,837 ␮Gy·m2, IQR 1,172 to 2,783) compared to femoral access (FT 2.34 minutes, IQR 1.49 to 4.18, DAP 1,657 ␮Gy·m2, IQR 1,064 to 2,376, p ⬍0.001). Before correction for BMI, radial access was associated with a 70% (95% confidence interval [CI] 54 to 89) increase in FT and a 20% (95% CI 10 to 31) increase in DAP compared to femoral access. After correction for BMI by analysis of covariance the increase in FT (70%, 95% CI 53 to 88) and DAP (14%, 95% CI 6 to 23) remained significant. Contrast volumes

Results from this study indicated that transition from a default transfemoral access approach to a default transradial approach was associated with significantly increased FT. This translated to an increased DAP for diagnostic procedures but not for interventional procedures. For diagnostic cases there was evidence of a learning curve with shortening of FT with accumulating experience. This was not seen for PCI cases. There is conflict in the literature about differences in radiation dose in radial and femoral access coronary procedures.6,8 –12,14,15 Most studies are small (several hundred patients) and count diagnostic and PCI procedures as 1 category. Also, the effect of operator experience with transradial access on radiation delivered has not been established. We found radial access diagnostic angiography to be associated with longer FT and larger DAP compared to femoral access studies. FT and, hence, procedure duration were almost 2 times as long in the radial access group (median 4.43 vs 2.34 minutes in the femoral group). In the initial stages of radial experience, longer FTs are required to navigate the guidewire to the aortic root, overcoming ana-

Coronary Artery Disease/Radial and Femoral Radiation Exposure

tomic variations and loops. Catheter engagement to the coronary ostia may also require more manipulation compared to the femoral approach. The fact that contrast volume used in the femoral and radial cases was similar supports the theory that longer FTs in radial cases were mainly due to difficulties in catheter placement. Although DAP was statistically significantly greater in the radial group, the absolute difference was small (180 ␮Gy·m2). Cinematic image acquisition contributes more to the DAP than fluoroscopy; cinematic imaging time was likely similar in the 2 groups, explaining this lesser magnitude of difference. The difference between radial access and femoral access for diagnostic studies is equivalent to 0.4 mSv or 20 chest x-rays.16 The difference in magnitude of increase in risk over natural lifetime risk of inducing cancer from a radial diagnostic study compared to a femoral diagnostic study is 0.002%. In PCI cases FT was longer in the radial group, likely reflecting similar technical obstacles as for diagnostic cases. The difference between radial and femoral access cases was less marked than in the diagnostic cases. Once the coronary ostium is engaged by a guide catheter, radial and femoral access procedures are essentially identical. Hence, guide catheter manipulation is likely to explain the difference in FT, and the absence of a difference in DAP is likely to indicate the relatively small contribution of guide catheter fluoroscopy to the overall radiation burden of PCI cases; however, the p value did approach a significant level (0.08). Our results are consistent with previously reported data. Most studies have reported an increase in radiation dose delivered to patient and operator when the transradial route is used,6,9 –11 but the differences vary substantially. The increases in FT and DAP in these studies also appeared more marked in diagnostic cases. Geijer and Persliden8 reported a 13% decrease in DAP after multiple regression when the transradial approach for PCI was employed; however, this study was small (n ⫽ 114 for femoral cases, n ⫽ 55 for radial cases). We did not measure operator exposure directly; however, Lange et al9 found a 100% increase in diagnostic cases and a 50% increase in intervention cases for operator dose when the radial route was compared to femoral access. Similarly, Brasselet et al11 report an 82.7% increase in dose to the operator in diagnostic cases and a 38.1% increase in PCI cases. All operators in this study had many years of experience of femoral access diagnostic angiography and PCI in a high-volume tertiary center. We showed that given a baseline level of considerable experience the learning curve effect on these radiation variables was short. For diagnostic cases FT was shorter during the course of 1 year by almost 1 minute. This was not translated in the DAP, which was similar in the 2 periods. In contrast, for PCI cases the FT increased in the second period. The invisible nature of radiation can lead to complacency in operators and efforts to decrease radiation exposure should be optimized regardless of approach. Several studies have shown that operators differ significantly in radiation delivery10,11 and that operator awareness and desire to decrease radiation dose are more important factors rather than experience per se. In our institution radiation delivery is a joint responsibility between an operator (FT, cinematic image acquisition time, and view selection) and a radiographer

939

(collimation, beam angling, and general optimization parameters). This optimizes the images acquired and minimizes doses delivered. Shielding equipment should be optimized for transradial access. Equipment designed for use in transfemoral cases is often inadequate because gaps may be present between the imaging field and the operator, allowing greater scatter exposure to staff. Because the small increase in radiation dose in radial access seems to be largely contributed by the diagnostic study, operators should consider “ad hoc” PCI (decision taken to treat a lesion immediately after the diagnostic pictures as 1 procedure), if required. This is generally the case in our institution. Catheters specially designed for radial access have decreased manipulation times and, hence, FTs. Likewise, improvements in modern imaging systems will maintain or improve image clarity and minimize radiation dose delivered. This study was a retrospective comparison of all radial and femoral cases carried out in the periods specified. The case mix consisted of diagnostic studies and all PCIs whether straightforward or complex, emergency or elective. No attempt was made to separate these PCI cases into categories because doing so would have limited numbers in each category and thus limit interpretation of results. The case mix did not vary significantly over the periods and the study had sufficient case numbers to reflect real-life experience in a high-volume center. Five different principal operators’ work was analyzed; operators clearly differ in case mix attempted, views acquired, equipment used, and PCI approach. We made no attempt to separate cases by operator because the same operators worked across all periods and the only difference was the gradual change to radial access. The facility is a teaching unit and some procedures were carried out by registrars under consultant supervision. The radiation variables chosen for analysis represent the dose delivered from the imaging system—not the dose received by the patient or operator; we did not measure these indices in this large patient group. There may have been disproportionate increases in dose received by patient or operator that the variables analyzed do not measure. 1. Mann T, Cubeddu G, Bowen J, Schneider JE, Arrowood M, Newman WN, Zellinger MJ, Rose GC. Stenting in acute coronary syndromes: a comparison of radial versus femoral access sites. J Am Coll Cardiol 1998;32:572–576. 2. Kiemeneij F, Laarman GH, Odekerken D, Slagboom T, van der Wieken R. A randomised comparison of percutaneous transluminal coronary angioplasty by the radial, brachial and femoral approaches: the Access Study. J Am Coll Cardiol 1997;29:1269 –1276. 3. Agostoni P, Biondi-Zoccai GGL, De Benedictis ML, Riggatieri S, Turri M, Anselmi M, Vassanelli C, Zardini P, Louvard Y, Hamon M. Radial versus femoral approach for percutaneous coronary diagnostic and interventional procedures: a systematic overview and meta-analysis of randomized trials. J Am Coll Cardiol 2004;44:349 –356. 4. Rao SV, Ou FS, Wang TY, Roe MT, Brindis R, Rumsfeld JS, Peterson ED. Trends in the prevalence and outcomes of radial and femoral approaches to percutaneous coronary intervention: A report from the National Cardiovascular Data Registry. JACC Cardiovasc Interv 2008; 1:379 –386. 5. Jolly SS, Amlani S, Hamon M, Yusuf S, Mehta SR. Radial versus femoral access for coronary angiography or intervention and the impact on major bleeding and ischaemic events: a systematic review and meta-analysis of randomized trials. Am Heart J 2009;157:132– 140.

940

The American Journal of Cardiology (www.ajconline.org)

6. Brueck M, Bandorski D, Kramer W, Wieczorek M, Holtgen R, Tillmanns H. A randomized comparison of transradial versus transfemoral approach for coronary angiography and angioplasty. JACC Cardiovasc Interv 2009;2:1047–1054. 7. Cooper CJ, El-Sheikh RA, Cohen DJ, Blaesing L, Burket MW, Basu A, Moore JA. Effect of transradial access on quality of life and cost of cardiac catheterization: A randomized comparison. Am Heart J 1999; 138:430 – 436. 8. Geijer H, Persliden J. Radiation exposure and patient experience during percutaneous coronary intervention using radial and femoral artery access. Eur Radiol 2004;14:1674 –1680. 9. Lange HW, von Boetticher H. Randomized comparison of operator radiation exposure during coronary angiography and intervention by radial or femoral approach. Catheter Cardiovasc Interv 2006;67: 12–16. 10. Larrazet F, Dibie A, Philippe F, Palau R, Klausz R, Laborde F. Factors influencing fluoroscopy time and dose-area product values during ad hoc one-vessel percutaneous coronary angioplasty. Br J Radiol 2003; 76:473– 477. 11. Brasselet C, Blanpain T, Tassin-Mangina S, Deschilde A, Duval S, Vitry F, Gaillot-Petit N, Clement JP, Metz D. Comparison of operator

12.

13.

14.

15.

16.

radiation exposure with optimized radiation protection devices during coronary angiograms and ad hoc percutaneous coronary interventions by radial and femoral routes. Eur Heart J 2008;29:63–70. Bhatia GS, Ratib K, Lo TS, Hammon M, Nolan J. Transradial cardiac procedures and increased radiation exposure: is it a real phenomenon? Heart 2009;95:1879 –1880. Mesbahi A, Aslanabadi N, Mehnati P. A Study on the impact of operator experience on the patient radiation exposure in coronary angiography examinations. Radiat Prot Dosim 2008;132:319 –323. Bertrand OF, Arsenault J, Mongrain R. Operator versus patient radiation exposure in transradial and transfemoral coronary interventions. Eur Heart J 2008;29:2577–2578. Agostoni P, Testa L, Biondi-Zoccai GGL. Comment on “Comparison of operator radiation exposure with optimized radiation protection devices during coronary angiograms and ad hoc percutaneous coronary interventions by radial and femoral routes.” Eur Heart J 2008;29: 2820 –2821. Einstein AJ, Moser KW, Thompson RC, Cerqueira MD, Henzlova MJ. Radiation dose to patients from cardiac diagnostic imaging. Circulation 2007;116:1290 –1305.