Utility of a Smart Phone Application in Assessing Radial Artery Patency - the CAPITAL iRADIAL Study

Overview

Accessing the arteries of the heart through the blood vessels of the wrist is becoming increasingly popular. By obtaining access via the artery in the arm as opposed to the groin, there is less risk of complications and improved patient satisfaction. However, using the wrist can cause blockage of the artery after the procedure. If there is too little blood flow from a second artery that supplies the hand, this could result in significant injury. Therefore, it is important to test these blood vessels in the wrist prior to having this procedure. The best way to evaluate these arteries involves the use of ultrasounds but this takes a long time and is expensive. Therefore, the artery is usually evaluated with a clinical test known as the modified Allen's test, which relies on the doctor watching the flushing of the hand during compression of the artery. Currently smart phones with cameras are able to assess blood flow by passing light through the skin and watching differences in brightness. This may be a better way to assess the arteries in the hand as it is less subjective than simply watching the flushing of the hand. This study aims to assess the ability of an iPhone application in determining whether there is sufficient blood flow through the arteries of the wrist and comparing it to the clinical test commonly used.

Over the past decade, the transradial approach to cardiac catheterization has emerged as the preferred method of angiography and intervention. There have been several observational and randomized controlled trials which have shown an association between transradial access and reduced risk of bleeding and other vascular complications, increased cost-effectiveness, improved patient satisfaction, and a mortality benefit in high-risk patient populations. However, this technique does carry risks of complications including radial artery occlusion, non-occlusive radial artery injury, radial artery spasm, hand ischemia, pseudoaneurysm, radial artery perforation, nerve damage, arteriovenous fistulisation, and bleeding. Radial artery occlusion is the most commonly noted complication and the clinical impact is unclear. In individuals with intact collateral palmar circulation from the ulnar artery, the individual is usually asymptomatic and do not require further intervention. However, if an individual lacks adequate collateral circulation, that individual is at risk of hand ischemia and loss of tissue or function necessitating surgical intervention or, ultimately, amputation. Thus, it is common practice to assess competency of the collateral palmar circulation prior to transradial cardiac catheterization to mitigate the risks associated with this approach. The gold standard for assessment of radial artery patency is colour Doppler ultrasound imaging of the artery. This gold standard allows for direct, objective assessment of arterial patency and competency through direct visualization of blood flow. The use of pre-procedural ultrasound remains both labour and resource intensive and hence is not feasible for practical use, therefore a physician must rely on clinical assessment of collateral circulation. This has been traditionally evaluated through use of the modified Allen's test (MAT), a technique performed at the bedside as part of the pre-procedural physical examination. More recently, the introduction of plethysmography and pulse oximetry have been utilized to theoretically provide a more objective measure of assessing collateral circulation, though these too are limited by the available resources. Given the ever increasing prevalence of smart phones, this study aims to address the utility and feasibility of an iPhone application in determining adequacy of collateral palmar circulation. Should this iPhone application provide superior diagnostic accuracy, it could quickly become an alternative method of providing an objective measure of collateral palmar circulation rather than relying on the subjective MAT.