A Comparison of Smartphone-Based ECGs for Horses

Veterinarians use electrocardiogram recordings (ECGs) to diagnose arrythmias, or irregular heart rhythms, in horses. Because ECG equipment isn’t always available (or requires a laptop and Wi-Fi connection) when practitioners are examining horses on the farm, manufacturers have begun developing portable ECG devices vets can use and interpret simply using a smartphone app.

“If these devices could deliver good-quality ECGs, or at least sufficient-quality ECGs, they might aid the practitioner in the field to record ECGs and better diagnose arrythmias,” said Lisse Vera, DVM, during the 2019 British Equine Veterinary Association Congress, held Sept. 11-14, in Birmingham, U.K.

Vera, a PhD candidate and predoctoral fellow with the Equine Cardioteam in Ghent University’s Department of Large Animal Internal Medicine, Faculty of Veterinary Medicine, in Merelbeke, Belgium, and her colleagues recently performed a study evaluating the quality and ease of use of different ECG device and app combinations. Their goal was to determine which pairing produced the best recordings.

The study included 24 healthy horses with normal heart rhythms. Vera’s team recorded each horse’s resting ECG using a traditional ECG device simultaneously with a smartphone-based device. They repeated this with three different smartphone-based devices:

  • AC-002 designed for veterinary use.
  • AC-009 designed for human use.
  • An adapted AC-009 that had been modified by Vera’s team.

They tested each device in combination with two apps:

  • The AliveCor app designed for veterinary use.
  • The Kardia app designed for human use.
A Comparison of Smartphone-Based ECGs for Horses

Smartphone-based ECG devices are essentially phone cases with electrodes that veterinarians can place against the horse’s skin at the left atrium (behind the elbow at the girth). They work by emitting ultrasound waves that the smartphone’s microphone picks up and uses to produce an ECG recording. Vera designed the adapted AC-009 device in an attempt to improve its quality and ease of use. She attached wires to the device’s electrodes and connected them to self-adhesive electrodes placed on the horse’s left wither and left apex beat area for wider spacing of the electrodes and better contact.

To compare the devices’ ease of use, Vera’s team assessed the time it took each one to record a 60-second ECG. They found that:

  • The adapted AC-009 had the shortest recording times, with a median of 67 seconds with the veterinary app and 60 seconds with the human app.
  • The AC-002 had a slightly longer recording time, with a median of 100 seconds with the veterinary app and 70 seconds with the human app.
  • The AC-009 had the longest recording time, with a median of 110 seconds with the veterinary app and 70 seconds with the human app.

“There was a large range in recording times (60-480 seconds), so these results were not significantly different,” said Vera. “But you can tell that it took longer for the veterinary app than the human app.”

When comparing other ease-of-use features between the two apps, she noted that the veterinary one:

  • Can only be used on Apple iOS devices;
  • Can produce a continuous recording;
  • Can easily send ECGs via PDF for consultation; and
  • Allows the user to adapt the ECG’s paper speed (at which the graph paper moves during the recording) and amplitude (wave height).

The human app, on the other hand:

  • Can be used on both Apple and Android devices;
  • Has a limited maximum recording time of five minutes;
  • Can easily send ECGs via PDF for consultation; and
  • Doesn’t allow the user to adapt the paper speed or amplitude.

Then Vera’s team compared recording quality based on baseline wander (a baseline that undulates), presence of artifacts (abnormalities not related to heart activity), P wave (the first part of the heartbeat) visibility, and overall quality. Each ECG was blinded and scored on a scale of 0 to 5, with 0 being poor quality and 5 being excellent.

Vera said only the adapted AC-009 (combined with either app) scored similarly to the standard ECG device for all quality criteria. The AC-002 combined with the veterinary app had similar baseline wander, artifact presence, and overall quality scores as the standard device, but significantly reduced P wave visibility.

“We can say that the AC-002 device in combination with the veterinary app (the pairing most veterinarians have access to) can be used to record good-quality ECGs in horses, but the P wave visibility is significantly less compared to what we are used to with our standard device,” she summarized. “The adapted AC-009 device further improves P wave visibility and gives good quality both in combination with the vet app and human app. And you have the benefit that it can be used on both apple and android devices.”

Vera reminded veterinarians that the recordings in her study were all made in healthy horses. “So we know the devices can be used to collect good-quality ECGs, but we now need to confirm this in horses with arrhythmias,” she said.

Practitioners can use the information from this study to make ECG device purchasing decisions and better interpret their findings, said Vera.