Photoplethysmography using a smartphone application for assessment of ulnar artery patency: a randomized clinical trial

Abstract

Background: Radial artery access is commonly performed for coronary angiography and invasive hemodynamic monitoring. Despite limitations in diagnostic accuracy, the modified Allen test (manual occlusion of radial and ulnar arteries followed by release of the latter and assessment of palmar blush) is used routinely to evaluate the collateral circulation to the hand and, therefore, to determine patient eligibility for radial artery access. We sought to evaluate whether a smartphone application may provide a superior alternative to the modified Allen test.

Methods: We compared the modified Allen test with a smartphone heart rate-monitoring application (photoplethysmography readings detected using a smartphone camera lens placed on the patient's index finger) in patients undergoing a planned cardiac catheterization. Test order was randomly assigned in a 1:1 fashion. All patients then underwent conventional plethysmography of the index finger, followed by Doppler ultrasonography of the radial and ulnar arteries (the diagnostic standard). The primary outcome was diagnostic accuracy of the heart rate-monitoring application.

Results: Among 438 patients who were included in the study, we found that the heart rate-monitoring application had a superior diagnostic accuracy compared with the modified Allen test (91.8% v. 81.7%, p = 0.002), attributable to its greater specificity (93.0% v. 82.8%, p = 0.001). We also found that this application had greater diagnostic accuracy for assessment of radial or ulnar artery patency in the ipsilateral and contralateral wrist (94.0% v. 84.0%, p < 0.001).

Interpretation: A smartphone application used at the bedside was diagnostically superior to traditional physical examination for confirming ulnar patency before radial artery access. This study highlights the potential for smartphone-based diagnostics to aid in clinical decision-making at the patient's bedside. Trial registration: Clinicaltrials.gov, no. NCT02519491.

Conflict of interest statement

Competing interests: Roxana Mehran has received research grants paid to her institution from Astra Zeneca, The Medicines Company, Bristol-Myers Squibb/Sanofi, Eli Lilly and Company and Daiichi Sankyo outside the submitted work. She has received consultant fees from AstraZeneca, Bayer, CSL Behring, Janssen Pharmaceuticals, Merck & Co., The Medicines Company and WaterMark Consulting. She has received renumeration as a member of the advisory boards of Abbott Laboratories, AstraZeneca, Boston Scientifc, Covidien, Janssen Pharmaceuticals, Merck & Co., The Medicines Company and Sanofi-Aventis. She holds less than 1% equity in Claret Medical and Elixir Medical Corporation. No other competing interests were declared.

© 2018 Joule Inc. or its licensors.

Figures

Figure 1:

Participant recruitment and allocation. HRMA = heart rate–monitoring application, MAT = modified Allen test.

Figure 2:

Demonstration of the modified Allen test and the smartphone-based heart rate–monitoring application. (A) Bilateral occlusion of the radial and ulnar arteries followed by clenching and opening of the hand 3 times. (B) Release of compression of the ulnar artery with blanching of the hand. (C) Restoration of palmar blush within 5 seconds, suggesting patency of the ulnar artery. (D) Placement of the smartphone camera on the index finger. (E) Screenshot capture of the instant heart rate interface showing a normal photoplethysmographic tracing below the participant’s heart rate with isolated radial artery compression. (F) Dampening of the pulse tracing with isolated radial artery compression. (G) Loss of the pulse tracing with radial artery compression. Note: bpm = beats per minute.