The objective of this project is to evaluate the capability of a specific mobile electrocardiogram monitoring of detecting arrhythmic events in children with history of palpitation and or syncope. We will compare this approach with the standard approach of clinical follow-up plus 24-hour Holter ECG monitoring in terms of acceptability and ability to identify significant arrhythmias.

Syncope and palpitation are one of the most common referrals to pediatric cardiology in patients with and without structural heart disease. In children with palpitation supraventricular tachycardia (SVT) is the most common final diagnosis. While some SVTs caused by the presence of an accessory pathway are highly recommend to be treated, other forms of arrhythmia are rarely life threatening and therapy depends on the burden of symptoms. Some SVT can be the first manifestation of an underlying heart disease. Early onset of atrial fibrillation, for example, in childhood usually reveals a genetic pathology and therefore needs further investigation. Besides the need for precise diagnosis to choose adequate management and therapy, unrecognized paroxysmal SVT have shown to lead to misdiagnosis mimicking symptoms of a psychiatric disorder. However, with the current diagnostic tools and protocols in only 10 % to 15 % of children with palpitation an underlying arrhythmia is found.

Syncope commonly is of benign character in children but it can be the first warning sign of a serious condition. Despite considerable testing and expense accurate diagnosis of the underlying cause of syncope is still challenging. The theoretical possibility of an underlying fatal arrhythmia adds remarkable to the mental health challenges of adolescence and the families. Sudden cardiac death (SCD) is a rare but devastating event in children and adolescents.

Syncope and palpitation deserve even higher attention in patients with congenital heart disease (CHD). These patients have an overall higher risk of developing cardiac arrhythmias as consequence of the pre-existing anatomical alterations, as well as the surgical treatment necessary for its correction. In many cases arrhythmia occur earlier in life and sometimes SCD is the first symptom of manifestation.

To study the origin of palpitation and syncope 12 lead electrocardiogram (ECG) and 24-hours Holter monitoring is typically performed. In case of high clinical suspicion, implantable loop-recorder and electrophysiological study can be performed to finally reach a diagnosis. However, it is an invasive test that is thought to be avoided in children if possible and might be poorly tolerated in patients with CHD.

In recent years, technological development has allowed the validation of different tools for detection of arrhythmias by "smart" devices. The "KARDIA" Mobile Cardiac Monitor is a handheld ECG device that enables users to collect and store single-channel ECG recordings using the smart phone, smart watch, or tablet. A recent study has demonstrated the efficacy of this device in the early diagnosis of arrhythmic disorders in adults by performing ECGs twice weekly plus additional ECG if symptomatic. However, its utility for the early detection and diagnosis of arrhythmias in children and patients with a CHD, which have a different normal physiology of the heart rhythm, has not yet been studied.

Inclusion Criteria:

• Age between 5-18 years old with or without the diagnosis of structural heart disease and symptoms suggestive of rhythm disorders as follows: palpitations and/or syncope and/or dizziness.
• 24-hours Holter without diagnosis of arrhythmia.
• Having an smart phone, smart watch, or tablet (the patient itself or a family member who lives together with the patient) compatible with KARDIA mobile ECG monitoring.
• Signed informed consent. In cases under the age of <18 y.o informed consent should be signed by parents or guardians.

Exclusion Criteria:

• Concomitant investigation treatments.
• Being already diagnosed for arrhythmic events.
• Medical, geographical and social factors that make study participation impractical, and inability to give written informed consent.
• Patient's refusal to participate in the study.