Wearable Devices: A Future Useful Tool for Detection of Silent Ischemia in Patients with Diabetes?

Review Article

J Cardiovasc Disord. 2021; 7(1): 1042.

Wearable Devices: A Future Useful Tool for Detection of Silent Ischemia in Patients with Diabetes?

Vlachakis PK¹*, Tentolouris A², Kanakakis I¹, Eleftheriadou I² and Alexopoulos D³

¹Department of Clinical Therapeutics, School of Medicine, National and Kapodistrian University of Athens, Alexandra General Hospital, Athens, Greece

²First Department of Propaedeutic Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, Athens, Greece

³2nd Department of Cardiology, Attikon University Hospital, National and Kapodistrian University of Athens Medical School, Athens, Greece

*Corresponding author: Vlachakis PK, Department of Clinical Therapeutics, School of Medicine, National and Kapodistrian University of Athens, Alexandra General Hospital, 80 Vasilissis Sofias Avenue, 11528, Athens, Greece

Received: May 26, 2021; Accepted:June 30, 2021; Published: July 07, 2021


As smartphone health care technology continues to evolve, many wearable devices are equipped with Electrocardiographic (ECG) recording. Recently, studies examining the possibility of various wearable devices for continuous ECG recording showed their ability to detect ST-segment alterations. It is known that in almost a quarter of people with diabetes, the presentation of an acute coronary syndrome may be atypical or even asymptomatic (“silent”), and it has been associated with adverse prognosis. The precise mechanisms behind the lack of pain in patients suffering from silent myocardial ischemia remain unknown. The attractive hypothesis that clinicians could use a wearable ECG recording to detect and treat earlier patients suffering from silent myocardial ischemia might change the adverse prognosis of those patients. However, before their clinical application, several obstacles should be overcome in order the physicians to obtain an additional powerful tool in the fight against coronary artery disease in people with diabetes.

Keywords: Silent myocardial ischemia; Diabetes mellitus; Electrocardiogram; Wearable devices; Ambulatory ECG; ST-segment alterations


ACS: Acute Coronary Syndrome; CAN: Cardiac Autonomic Dysfunction; CAD: Coronary Artery Disease; CV: Cardiovascular; DM: Diabetes Mellitus; ECG: Electrocardiogram; LED: Light- Emitting Diode; LBBB: Left Bundle Branch Block; PET: Positron Emission Tomography; SMI: Silent Myocardial Ischemia; STEMI: ST-Segment Elevation Myocardial Infarction


Diabetes Mellitus (DM) is the most common metabolic disorder affecting more than 463 million people worldwide [1]. The presence of DM increases two-fold the risk for Cardiovascular (CV) disease in men as well as three-fold in women [2-4], and CV disease remains the leading cause of morbidity and mortality in people with DM [5]. Atypical presentations of Acute Coronary Syndrome (ACS), such as silent myocardial ischemia (SMI), are more prevalent in subjects with DM and they are associated with worse outcomes [6,7].

It was in 1903, when a bipolar three-channel Electrocardiogram (ECG) was developed and recorded by Einthoven [8]. Since then, the ECG is an essential tool in daily clinical practice for the diagnosis of cardiac diseases. As technology advances in the modern world, portable wearable “smart” devices have already become of utmost importance to everyday life. Nowadays, many of these “smart” devices are used in medicine, and many of them are capable of ECG recording [9]. Several studies have provided evidence regarding the beneficial role of this technology in the detection of arrhythmias, such as atrial fibrillation [10]. Interestingly, some studies have also examined their role in patients suffering from acute Myocardial Infarction (MI) and have provided encouraging data [11,12].

This review aims to consider the tempting hypothesis that wearable devices can detect patients suffering from SMI, including people with DM, through continuous ECG recording. Such an approach may shorten the time of diagnosis and treatment and improve the prognosis of these patients.

Silent Ischemia in People with Diabetes

Angina pectoris is considered the predominant symptom of myocardial ischemia. Nevertheless, angina pectoris might be a poor indicator of myocardial ischemia, particularly in subjects with DM [13]. SMI is defined as the presence of objective findings indicative of myocardial ischemia without angina or anginal equivalent symptoms [14]. In the Framingham Study, approximately one-fourth of the participants with an ACS had SMI or atypical MI [15]. The actual frequency of SMI in that study may have been underestimated since the diagnosis of previous MI was based only on the detection of Q waves on a routine ECG. It is known that asymptomatic MI or asymptomatic myocardial ischemia occurs more frequently in patients with DM [13]. In the Framingham study, the incidence of painless MI was higher in people with DM in comparison with those without DM [16,17].

When the balance between myocardial oxygen supply and demand is disturbed, the resulting mismatch may immediately precipitate a vicious cycle whereby myocardial ischemia is induced. From a pathophysiology perspective, the precise mechanisms of anginal pain and neural pathways are not fully elucidated. Numerous tempting hypotheses have been proposed to shed light on the possible mechanism behind the lack of pain in patients suffering from SMI [14]. Cardiac Autonomic Dysfunction (CAD) is presumed to play a vital role in SMI [18]. CAN is among the most common but least recognized complications of DM [19]. A meta-analysis of 12 studies that included 1460 individuals with DM showed that the prevalence of SMI was higher in DM patients with CAN in comparison with patients without CAN (the pooled prevalence rate risk for SMI was 1.96, 95% CI: 1.53-2.51, p<0.001) [18]. Older studies have speculated that a defective anginal warning system may have a role in the lack of symptoms in SMI patients since it has been reported that cardiac denervation is associated with SMI in patients undergoing cardiac transplantation [20]. In addition, people with CAN may have a higher threshold of pain or even incapability to attain pain threshold during the ischemic episode [14]. The relevant effect of CAN in patients with DM is also suggested by the absence of a peak incidence of myocardial ischemia in the morning hours [21]. In parallel, people with DM with or without signs of autonomic dysfunction have a decreased vagal activity (and therefore a relatively increased sympathetic activity) throughout the night and at the same time of the day during which a higher frequency of CV accidents is observed [22]. Moreover, the ischemic burden might be associated with painless myocardial ischemia. Among 300 patients with established ischemic heart disease and reversible hypoperfusion on exercise sestamibi tomography, those with painless ischemia had less reversible hypoperfusion defects compared to symptomatic patients (mean±SD, 11±7 % vs. 16±10 %, p<0.001, respectively) [23].

B-endorphin, a potent opioid-like peptide, is another factor that is assumed to contribute to this enigmatic pathophysiology. In SMI patients, data from different studies reported that plasma levels of b-endorphin were higher in comparison with symptomatic patients [24]. Predominantly or totally painless myocardial ischemia via generalized defective perception of painful stimuli has also been reported as an alternative underlying mechanism. A possible link between anti-inflammatory cytokines and silent ischemia was evaluated by Mazzone et al. [25]. The investigators noticed that in patients with silent ischemia, the expression of CD11b receptor was lower compared to patients with painful myocardial ischemia. Higher production of anti-inflammatory cytokines was implicated in blocking the pain transmission pathways leading to a higher threshold for nerve activation [25]. Lastly, Rosen et al. tried to examine the possible role of central nervous system in this unresolved equation by using a Positron Emission Tomography (PET) of the brain [26]. In patients with SMI, the activation of the basal frontal anterior and ventral cingulate cortices and the left temporal pole was reduced compared to patients with anginal symptoms [26]. The potential mechanisms that have been described to explain SMI development are summarized in Figure 1.

Citation: Vlachakis PK, Tentolouris A, Kanakakis I, Eleftheriadou I and Alexopoulos D. Wearable Devices: A Future Useful Tool for Detection of Silent Ischemia in Patients with Diabetes?. J Cardiovasc Disord. 2021; 7(1): 1042.