It’s a warm evening at Applebee Dome campground. My (Gabriel) group is relaxing after climbing the northeast ridge of Bugaboo Spire when another climber walks over looking for a partner. He tells us that he and his partner just got in from a 2-day drive. His partner is sick, so he’s looking for someone to tie in with. After chatting a bit, my friends and I begin to inquire about his partner. “He started having chest pain on the hike up,” replies the climber. Being a medical professional, I ask about his partner’s age. I learn that he is 53, and on the hike in he began having chest pain and feeling a little more out of breath than he thought he should have been. I ask if I can check on his partner and then grab my medical kit and we go over to his camp. On the brief walk, the differential diagnoses begin running through my head.
The climber is lying in his tent and admits to having some chest pain, but with determination adds, “But I’m fine.” He says this despite being a little pale and looking generally uncomfortable. I express my concern and ask him to humor me by answering a few questions and letting me examine him. I feel his radial pulses and they are strong, regular, and equal at a rate of 88. His breathing is just slightly labored. I pull out a small SpO2 probe from my kit and it shows that his oxygen saturation hovers around 95% (we are at 8,000 ft). Also, as part of my aid kit I have a new “toy,” the KardiaMobile. I turn on my iPhone and ask him to hold the device, allowing me to take a peek at his rhythm. In lead I, I see a normal sinus rhythm but also ST elevation. Then by having the man hold the device to his left calf and then various locations on his chest wall I continue to piece together an ad hoc 12-lead electrocardiogram (ECG) by looking at leads II, III, and Modified Chest Leads (MCL) 1 and 6. I find ST depression in lead III and more ST elevation in MCL 6 indicative of a lateral wall ST segment elevation myocardial infarction (STEMI). I tell the man my suspected diagnosis while sending someone down to the Kain Hut to check in with the custodian about the rescue that needs to happen. Within an hour the climber is on a helicopter, bound for a cath lab.
The above story is fictional, but very loosely based on an encounter I (Gabriel) had a few years ago on a trip. In that situation the climber was ultimately fine and I didn’t have a mini ECG machine. But you might be asking what is this pocket ECG machine and can it actually be used in such a situation?
Pocket-sized medical devices and wearable health gadgets have truly arrived. In this segment of technology column, we are going to highlight one of the more notable devices—the KardiaMobile, a product of Alivecor. The KardiaMobile is a truly ultra-light ECG weighing in at just 18 grams and is smaller than a credit card (8.2 cm x 3.2 cm x 0.35 cm). The Food & Drug Administration (FDA) approved device links to smartphones and tablets providing a one lead rhythm strip, usually lead I. It does this by having the patient place their index fingers on the 2 electrodes and then sending the impulses to a tablet or smartphone via sound. It’s primarily marketed as a tool for patients with atrial fibrillation to record their ECG when symptomatic and send the captured ECG to their physician, or have a cardiologist read their ECG if they are part of the company’s subscription service. At this point, there are multiple “me too” devices on the market allowing similar “rhythm strips” or heart rate trends to be documented, analyzed, and shared. Some Garmin and Fitbit devices, for example, both reveal heart rate trends, heart rate variability, and even training stress scores. Additionally, the Apple Watch offers a single lead ECG allowing some common dysrhythmias to be detected. Indeed, their collaboration with the Stanford School of Medicine assembled the largest ever study population for a rhythm analysis project (>400,000 subjects). In the Apple/Stanford project, the end data point for detection was atrial fibrillation as a risk reduction effort against stroke. While the device and the study remain an impressive effort to apply this technology, it would not necessarily benefit our patient in the scenario above. The KardiaMobile, however, can be uniquely manipulated to show other ECG leads and allow a provider in the austere environment to obtain Leads I, II, III, Modified Chest Leads (MCLs), and even a modified Lewis lead. Such maneuvers were initially demonstrated in a proof of concept through a Penn State Research project (n=5) using rudimentary wires, alligator clips, and ECG pads with comparative reliability in comparison to industry standard ECGs (3). In this article, we have highlighted how these measures could potentially be made with an even more simple technique!
To use the KardiaMobile beyond its standard use one has to go back to the days of single lead cardiac monitors such as the Lifepak 10. Remembering that the left sensor is the positive lead and right the negative, or ground, (Fig 1) simply use your knowledge of Einthoven’s Triangle for the standard limb leads and knowledge of modified chest leads to obtain your precordial leads. Figure 2 shows how to accomplish this with a comparison between the Kardia app and a 12 lead ECG using a Physio-Control Lifepak 15.
In testing this product, I (Gabriel) found it fairly easy to use but with the usual challenges of obtaining a clean tracing. Due to the fact that it uses sound to transfer data to the phone or tablet, it’s not surprising that a noisy environment can cause issues. While the manufacturer states the device only needs to be within 1 foot of your phone or tablet, I found that I needed to have my phone within just a few inches to maintain a good signal. The app filters out some of the artifact during the 30 second recording which is helpful. One thing to note is that the app will “auto-invert” tracings so one has to pay attention and “turn off” that setting when obtaining a tracing.
For the advanced provider in an austere setting the question is whether this device can produce ECGs as reliable as what we can get from our far more expensive, and heavier. machines that we have at our day jobs. There has been some interesting research as well as case studies concerning this product. Relating to the case of our climber with a STEMI, it has been shown to be as reliable as a standard 12 lead in showing STEMI changes. In one case study, a cardiologist with the device happened to witness a man have a syncopal episode and captured the cause of a patient’s syncope, a third-degree atrioventricular block, with the app. By the time the patient arrived at the hospital his rhythm had normalized and he was asymptomatic. Thanks to the ECG that the cardiologist had captured on scene and forwarded to the Emergency Department, the patient received a pacemaker. There has even been more research showing that with computer algorithms the device could be used to evaluate syncope or monitor dialysis patients for hyperkalemia. Along with adaptive computer algorithms, there are some newer devices now present on the market that obviate the maneuvers required to facilitate Einthoven’s triangle but, to date, the KardiaMobile device remains the smallest piece of functional tech that will fit in your climbing pack.
So where does the novelty of a pocket ECG end and the utility begin? We think there is data, albeit small, to support the use of this device to aid the austere provider. With its relative small footprint, as well as relatively small price tag ($99 USD) it’s fairly easy to have an advanced diagnostic tool at your fingertips. Where can we see this tool being used? On a trek where you are the medical provider, either professionally, or with friends. Perhaps a National Park Service Parkmedic; on a hasty search and rescue (SAR) team when it turns out the sprained ankle due to a fall was in fact initiated a syncopal episode of cardiac origins. Or maybe even aiding in the diagnosis of hyperkalemia due to rhabdomyolysis in a hiker during the heat of summer.
At this point, the proof of concept is well established. Indeed, aside from the KardiaMobile device, more applications and studies in pocket sized technologies are already being designed and evaluated. In addition to the Apple Inc./Stanford University atrial fibrillation study, Johns Hopkins University has also entered into the research of wearables in a risk reduction analysis study for sudden death in epilepsy patients using Apple Watch technology. Whether it be alpine cardiology, epilepsy, or diabetes, we are clearly just scratching the surface on the potential applications of pocket technologies in wilderness medicine.
Hopefully, as more end-users engage in these technological opportunities such as revealed here in our discussion of the KardiaMobile, we will identify more potential wilderness medicine applications as well! In conclusion, as technology allows us to take our front country tools into the backcountry it gives the remote medical provider more information but we must be careful to not be blinded by our shiny new toys. As always, we must be attentive to the patient presentation and use of our clinical gestalt. But seriously… how cool is this?!