Radial Artery Occlusion: Size and More – How Small is Too Small?

Dear Editor:

We would like to congratulate Garg et al¹ for a well structured and essential paper highlighting the Achilles’ heel of transradial intervention (TRI): radial artery occlusions.

However, the results from Garg et al’s study¹ may not be applicable (and acceptable) to all patients taken up for transradial percutaneous coronary interventions.

Patient selection bias may have crept into their non–consecutive cohort, as 80% of patients were male, who commonly have larger radial artery dimensions,^1,2 and the mean radial artery size in their study was 2.8 ± 0.4 mm (versus 1.9 ± 1.1 mm among males in our study on Indian patients).³ Further, it is possible that by the exclusion of patients with failed access (which may have been due to inadequate access artery dimensions) or procedure (failure to achieve radial access, failure to complete transradial angiogram, transfemoral crossover, failed percutaneous coronary artery, or complications: 43/373 [11.5%] as per Figure 11), and by inclusion of only right radial arteries, the cohort was skewed further in favor of bigger arteries, as right radials are usually the largest of the four access arteries.³

Further, their definition of small radial arteries as vessels <2.5 ± 0.4 mm (per ROC analysis), although reasonable for their cohort, may not be universally acceptable for TRIs. Our study, for example, has shown that a diameter >1.7-1.8 mm is usually favorable for TRIs without significant complications, crossovers, or radial artery occlusions, while those <1.7 mm have higher rates of occlusion on follow-up and therefore may also merit definition as “small arteries.”² This size discrepancy is likely in the setting of possible selection biases as described above. 

Garg et al’s study population had a mean preprocedural radial artery size of 2.8 ± 0.4 mm, and despite the use of 6 Fr sheaths (outer diameter, approximately 2.3 mm; hence, >1:1 ratio between artery and sheath),⁴ such high radial artery occlusion rates (11%-15%) are relatively hard to explain. Further clarification regarding occlusions related to various artery sizes, rather than a blanket statement of higher occlusions in arteries <2.5 mm, is needed. Various other factors, such as intra-arterial spasmolytic use, number of catheter exchanges, radial artery spasm, mean (weight-based) heparin dose⁵ used, although missing from the study, are known to play a role in radial artery occlusions and deserve a mention.

As intervention with smaller access arteries is gaining popularity among transradial operators, such as with the use of compression of the other artery technique,⁶ it remains to be seen if the occlusion rates can be kept low in times to come.

References

1. Garg N, Madan BK, Khanna R, et al. Incidence and predictors of radial artery occlusion after transradial coronary angioplasty: Doppler-guided follow-up study. J Invasive Cardiol. 2015:27:106-112.
2. Chugh SK, Chugh Y, Chugh S. Overcoming the challenge of transradial interventions in women: insights from a color Doppler study. J Am Coll Cardiol. 2014;64:B240.
3. Chugh SK, Chugh S, Chugh Y, Rao SV. Feasibility and utility of pre-procedural ultrasound imaging of the arm to facilitate transradial coronary diagnostic and interventional procedures (PRIMAFACIE-TRI). Catheter Cardiovasc Interv. 2013;82:64-73.
4. Saito S, Ikei H, Hosokawa G, et al. Influence of the ratio between radial artery inner diameter and sheath outer diameter on radial artery flow after transradial coronary intervention. Catheter Cardiovasc Interv. 1999;46:173-178.
5. Spaulding C, Lefevre T, Funck F, et al. Left radial approach for coronary angiography: results of a prospective study. Cathet Cardiovasc Diagn. 1996;39:365-370.
6. Chugh K, Chugh S, Chugh Y. Addressing the challenges of access of small radial and ulnar arteries in transradial and transulnar interventions: Insights from a color Doppler study. J Am Coll Cardiol. 2014;63:A442.

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From ¹Sanjay Chugh, Interventional Cardiology Consultant, Gurgaon, Haryana, India; and ²Jacobi Medical Canter/Albert Einstein College of Medicine, Bronx, New York.

Address for correspondence: Sanjay Chugh, MD, DM, FACC, FSCAI, Interventional Cardiology Consultant, Gurgaon, Haryana, India-122001. Email: skchughcardiology@yahoo.com

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Author Response:

We would like to thank Dr S. Chugh and Dr Y. Chugh for their keen interest in our study and for congratulating us for this work.¹ We do not agree with their comment that it was a “non-consecutive cohort.” In fact, all consecutive patients who underwent successful transradial angioplasty between January-June 2012 were included in the study. However, we agree that after excluding out patients with failed radial access, transfemoral crossover, and by inclusion of only right radial artery and male predominance in our study, the cohort may have skewed in favor of larger radial artery diameter.  

As far as the definition of small radial artery is concerned, it was defined by ROC curve analysis. This was the most scientific way available to us to do this. We do not agree with him that radial artery less than 1.7-1.8 mm only should be considered as small radial artery. Even going by his logic (previously endorsed by Saito et al²), any radial artery with its internal diameter less than that of the outer diameter of the introducer sheath size used may be considered a small radial artery. We used only 6 Fr sheaths of 7 cm length in all patients (which have an outer diameter of 2.52 mm)³ and the cut-off value for small radial artery came out to be 2.5 mm by ROC curve analysis, which is why we took 2.5 mm as the cut-off for small radial artery. We do not agree with him that the radial artery occlusion rate of 15% in our study is hard to explain. In fact, in the Leipzig registry, the radial artery occlusion rate was 30.5% with the use of 6 Fr sheaths and was very well correlated with the size of transradial sheath (13.7% vs 30.5% in 5 Fr vs 6 Fr sheath).⁴ We agree the radial artery occlusion rate of 15.2% in our study is a little higher than a few other previous studies, but it is still 50% less than the rate reported in the large Leipzig registry.⁴ This could be due to the Doppler-based diagnosis of radial artery occlusion in all of our patients and because of the inclusion of patients with transradial angioplasty only (use of 6 Fr size sheath in all patients). 

We do agree that several factors other than small radial artery are also important and can play a role in radial artery occlusion. They include mean number of intra-arterial spasmolytics,⁵ number of catheter exchanges, and mean heparin dose.⁶ As these factors were not recorded, they were neither analyzed nor mentioned in the manuscript. However, activated clotting time was kept >250 seconds at all times. In addition, as protocol in our catheterization laboratory dictates, we always give a spasmolytic cocktail of nitroglycerin, diltiazem, and lignocaine in all patients just after insertion of the introducer sheath, postprocedurally just before sheath removal, after each catheter exchange, and during radial artery spasm (if encountered). These factors were uniformly taken care of in each patient and therefore are unlikely to have any bearing in the occurrence of radial artery occlusion. However, further large studies exclusively evaluating all these factors will finally settle the issues. 

We are in total agreement with their view that further research is required in the field of transradial intervention. We applaud their sincere efforts in this direction.

Sincerely,

• Naveen Garg, MD, DM, DNB
• B.K. Madan, MD, DM
• Roopali Khanna, MD, DM
• Aditya Kapoor, MD, DM
• Satendra Tewari, MD, DM
• Sudeep Kumar, MD, DM
• Pravin Kumar Goel, MD, DM

Department of Cardiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India

References

1. Garg N, Madan BK, Khanna R, et al. Incidence and predictors of radial artery occlusion after transradial coronary angioplasty: Doppler-guided follow-up study. J Invasive Cardiol. 2015:27:106-112.
2. Saito S, Ikei H, Hosokawa G, et al. Influence of the ratio between radial artery inner diameter and sheath outer diameter on radial artery flow after transradial coronary intervention. Catheter Cardiovasc Interv. 1999;46:173-178. 
3. Kotowycz MA, Dzavík V. Radial artery patency after transradial catheterization. Circ Cardiovasc Interv. 2012;5:127-133. 
4. Uhlemann M, Winkler SM, Mende M, et al. The Leipzig prospective vascular ultrasound registry in radial artery catheterization: impact of sheath size on vascular complications. JACC Cardiovasc Interv. 2012;5:36-43.
5. Dharma S, Kedev S, Patel T, Kiemeneij F, Gilchrist IC. A novel approach to reduce radial artery occlusion after transradial catheterization: postprocedural/prehemostasis intra-arterial nitroglycerin.Catheter Cardiovasc Interv. 2015;85:818-825. Epub 2014 Sep 13.
6. Spaulding C, Lefèvre T, Funck F, et al. Left radial approach for coronary angiography: results of a prospective study. Cathet Cardiovasc Diagn. 1996;39:365-370.