This case of smart watch detected cold drink-induced paroxysmal AF illustrates several practical lessons for clinicians who care for patients with palpitations. The first lesson is the valuable role direct-to-consumer smart watches can play in helping identify arrhythmic causes of palpitations. The arrhythmia most reliably detected by wearable smart devices—and the one most studied—is AF [3, 19, 20]. A recent prospective study of 5 commercially available smart devices tested their ability to detect and correctly identify AF in a real-world cohort of 201 cardiology patients [21]. 30% of patients were in AF at the time of testing. Devices commonly deemed the tracings inconclusive, the prevalence of which varied by device, ranging from 17 to 26%. Though the smart devices were unable to interpret inconclusive tracings, cardiologists were able to interpret nearly all of them. This demonstrates the need for physician confirmation or overread of smart device tracings, both those the device could and could not interpret. Nearly all tracings taken in the study were clinically useful in the AF diagnostic evaluation. Apart from inconclusive cases, these 5 smart devices performed equally well, with high sensitivity and specificity for AF [21]. Other studies have also required clinician arrhythmia confirmation, as in our case [22, 23].

The critical contribution to palpitation diagnostics made by smart watches is accentuated when the limitations of post-discharge monitoring are highlighted. Our patient had 2 palpitation episodes over 5 years and was unlikely to benefit from a short run of home monitoring. Outside the cardiology suite, generalists are advised to “…restrict a 24-hour Holter monitor to patients who have at least daily symptoms, a 48-hour Holter monitor to those with symptoms on most days, and a seven-day monitor to those with weekly symptoms, even if the 12-lead [ECG] is normal. Inappropriate use of short periods of ambulatory monitoring for infrequent symptoms is cumbersome for patients, delays the diagnosis, and is costly.” [24].

Lacking a tracing of the cold-induced rhythm 5 years prior limits us from assigning it a diagnosis of AF with certainty, as other etiologies are possible [19, 20]. AF, however, is the most probable etiology for that prior episode given his recent AF diagnosis.

The second lesson we can learn is that some cases of paroxysmal AF have modifiable ingestion triggers, in this case, cold drink, a condition sometimes called Cold Drink Heart [7, 8, 10, 16,17,18, 25]. Some patients are more susceptible to AF when cold trigger exposure occurs following exercise or strenuous exertion [16, 17]. Patients with cold drink or food-triggered AF have variable degrees of cold sensitivity. In some patients, AF is always or nearly always triggered with rapid ingestion of cold drink, which is not true for most Cold Drink Heart patients.

Helping patients make the causal connection between trigger and AF—or simply validating a connection patients have already drawn—allows clinicians to collaborate with their patients in devising a strategy for trigger reduction. Many clinicians, however, are unaware that cold drink and food can trigger AF and have been known to dismiss patient claims that cold drink precipitates their paroxysmal AF [7]. To address this, one large U.S. medical group included a cold drink prompt for physicians in their clinical decision support tool for the comprehensive management of AF in the ED [26]. The support tool reminded physicians to ask patients with intermittent AF if they had noticed that ingesting cold drink/food precipitated AF within seconds or minutes of ingestion. Along with the cold drink prompt, the support tool reminded physicians to inquire about alcohol ingestion, another modifiable AF trigger [9, 27,28,29].

Cold drink avoidance has been reported by Cold Drink Heart patients to reduce AF recurrence [7, 10, 18]. A study of patients with trigger-induced paroxysmal AF found trigger reduction decreased AF events [29]. The number of patients in this trial with triggers of cold drink or food was quite small (n = 5), preventing a meaningful analysis of this particular subcohort. The relative safety and low cost of a trigger reduction strategy lends itself to an informal n = 1 trial. If successful, trigger reduction may be a simple means of reducing the number of AF episodes, which may reduce AF-related symptoms, need for urgent medical care, and missed days of work.

In sum, we report a case of cold drink-triggered AF whose diagnosis was aided by an informative 1-lead ECG tracing captured by a smart watch. Clinicians caring for patients with transitory palpitations should inquire about cold drink triggers and use available smart watch tracings as diagnostic adjuncts.