Long-term electrocardiographic monitoring: time to reconsider our standards

Diagnosing arrhythmias is one of the daily challenges of clinical practice. The twelve-lead electrocardiogram is the gold standard for diagnosing most cardiac arrhythmias, but the episodic nature of many arrhythmias and the frequently low correlation between symptoms and electrocardiographic findings make ambulatory recorders indispensable clinical tools. For many years, continuous electrocardiographic monitoring for 24 h to 72 h has been the standard of care for diagnosing suspected paroxysmal rhythm disturbances. Yenikomshian et al. presented the results of a systematic review of one of the newest and most developed long-term ambulatory cardiac monitoring systems, the Zio patch. Based on evidence from 22 studies, the authors demonstrate that the monitoring system results in longer patient wear times and higher arrhythmia detection rates. It is not surprising that devices capable of recording for up to 14days can increase monitoring time and detection rates compared to systems limited to 24hours. However, it is remarkable that it is taking so long to incorporate the newest technology into practice so that patients can benefit from these technological advances. There are a range of health technology products for monitoring heart rhythm but, in many hospitals, physicians must still choose between two extremes – either the relatively cheap and short-term (24h to 72h) Holter monitor or the expensive and long-term (18months to 36months) implantable loop recorders. At the same time, patients are increasingly presenting to clinics with different records from smartphones and other wearable devices, which provide very poor quality data and have not been validated by regulatory agencies. Moreover, the US Food and Drug Administration (FDA) has now approved the Kardia monitor for diagnosing atrial fibrillation, a system created for over-the-counter purchase and use in the general population. In our opinion, every hospital should have non-invasive ambulatory cardiac monitoring systems capable of recording for seven days or more. Most recent research on heart rhythm monitoring is focused on atrial fibrillation, both its diagnosis in populations at risk and its control after ablation. But almost all aspects are subject to some controversy. Who needs to be monitored? For how long? How often should monitoring be repeated? And probably the most important question, what should clinicians do with the findings? No randomized clinical trials have yet found an association between anticoagulation for subclinical atrial fibrillation and improved prognosis. There are ongoing trials evaluating direct oral anticoagulants for preventing stroke, but results are not expected before 2021. Data from patients with pacemakers and implantable cardioverter–defibrillators show an increased incidence of stroke associated with subclinical atrial arrhythmia, but at very different rates depending on the arrhythmia burden, and no chronological relationship between the embolic and the arrhythmic episode. For other arrhythmias, evidence is even scarcer and in many cardiac diseases periodic electrocardiographic monitoring is indicated for reaching a prognosis. In hypertrophic cardiomyopathy, current guidelines recommend monitoring for at least 48 h, and since the detection of non-sustained ventricular tachycardia is a risk factor for sudden cardiac death, it is included in the risk calculator proposed for guiding decisions around the use of an implantable cardioverter–defibrillator. Is a non-sustained ventricular tachycardia detected after 48 h of Holter monitoring the same as one detected after several weeks of periodic monitoring, or after three years of monitoring with an implantable loop recorder? We don’t have evidence to answer these questions, but the plausible answer is no. Thus, both evidence and common sense suggest that the traditional approach to ambulatory detection of cardiac arrhythmias must evolve. Articles published three decades ago already demonstrated that the diagnostic effectiveness of 24 h of monitoring is limited. In the era of almost unlimited diagnostic resources, a careful anamnesis is more important than ever. Clinicians must listen to their patients, finding out how often they experience symptoms and considering the possible diagnoses to decide whether they need ambulatory monitoring and for how long. Current guidelines for syncope, atrial fibrillation and ventricular arrhythmias do not provide specific recommendations to guide the use of prolonged non-invasive recording systems, as they do for 24 h Holter monitoring and implantable loop recorders. This is due to the limited evidence supporting these diagnostic tools, as there are no randomized clinical trials and the prospective registries are relatively small. Hopefully, the evidence emerging from the Yenikomshian et al. systematic review and other forthcoming studies will justify the development of specific indications for these tools in clinical practice guidelines.