Smartphone Application Shows Promise for Assessing Ulnar Artery Patency

The smartphone heart rate monitoring application had higher diagnostic accuracy compared with standard physical examination for determining ulnar artery patency prior to radial access.

In patients who underwent a cardiac catheterization procedure, the use of a smartphone application that monitors heart rate was superior to standard physical examination for determining ulnar artery patency prior to radial access, according to findings from a randomized clinical trial published in the Canadian Medical Association Journal.

Patients from a coronary care unit at an academic center in Canada who were being assessed for catheterization and transradial access were recruited for the Utility of a Smart Phone Application in Assessing Radial Artery Patency (CAPITAL iRADIAL; Identifier: NCT02519491). The investigators randomly assigned participants to receive either the smartphone heartrate monitoring application (HRMA; n=219) or the modified Allen test (MAT; n=219) prior to radial access. The HRMA consisted of the smartphone’s lens being placed on the patient’s index finger, ultimately providing photoplethysmography readings. Conversely, the MAT consisted of manually occluding the ulnar and radial arteries and then releasing the ulnar artery and evaluating palmar blush.

Regardless of treatment allocation, patients then underwent standard plethysmography readings of the index finger and Doppler ultrasonography of the ulnar and radial arteries. The investigators compared the diagnostic accuracy in both groups.

Compared with the MAT, the HRMA was associated with greater diagnostic accuracy (81.7% [95% CI, 76.0%-86.6%] vs 91.8% [95% CI, 87.3%-95.1%], respectively; P =.002), in part due to its significantly high specificity (82.8% [95% CI, 77.1%-87.6%] vs 93.0% [95% CI, 88.7%-96.0%], respectively; P =.001).

In addition, the HRMA demonstrated greater accuracy for evaluating ulnar and radial patency in the contralateral and ipsilateral wrist compared with MAT (94.0% [95% CI, 91.9%-95.6%] vs 84.0% [95% CI, 79.9%-97.4%], respectively; P <.001). There were no differences between the HRMA and MAT groups with regard to diagnostic sensitivity (50.0% [95% CI, 11.8%-88.2%] vs 25.0% [95% CI, 0.6-80.6], respectively; P =.6) or positive predictive values (16.7% [95% CI, 3.6%-41.4%] vs 2.6% [95% CI, 0.7%-13.8%], respectively; P =.09).

Although this study demonstrated the usefulness of the smartphone application for improving diagnostic accuracy in this patient population, the investigators did not evaluate differences between the HRMA and MAT in terms of adverse events. In addition, the application used in this study was run on an iPhone 4s smartphone, so the findings may not be generalizable to other platforms.

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Despite the fact that the application in this study is currently not certified for clinical use, the findings highlight “the potential for smartphone-based diagnostics to aid in clinical decision-making at the patient’s bedside.”


DiSanto P, Harnett DT, Simard T, et al. Photoplethysmography using a smartphone application for assessment of ulnar artery patency: a randomized clinical trial.  CMAJ. 2018;190:E380-388.