Continuous or intermittent ambulatory electrocardiographic recording with a Holter monitor or an event recorder is helpful in diagnosing suspected arrhythmias, estab- lishing their frequency, relating them to symptoms, and assessing the response to therapy. Although the yield of these tests is relatively low, VT is occasion- A 24-hour continuous Holter recording is appropriate when symptoms occur at least once a day or when quantitation of PVCs/NSVT is desired to assess possible VA-related depressed ventricular function. For sporadic symptoms, event or looping monitors are more appropriate because they can be activated over extended periods of time and increase diagnostic yield.S4.2.2-2,S4.2.2-3 Adhesive patch electrocardiographic monitors can record for weeks and allow for continuous short-term 1-lead monitoring and patient activation for symptoms. Studies have shown satisfactory patient compli- ance, and arrhythmia detection; however, with some monitors, detected arrhythmias are not dis- covered until the patch is returned for analysis.S4.2.2- Serial evaluations with exercise testing and/ or 24-hour ambulatory monitoring are also used to assess rhythm burden and response of VA to therapy. Notably, implantable monitors are covered in Section 4.2.3. Importantly, when the suspicion of VA in a patient is high, outpatient ambulatory monitoring is inappropriate as prompt diagnosis and prevention of VA are warranted. It is important to accurately cor- relate the symptoms with the arrhythmias detected by ambulatory ECG monitoring. 4.2.3. Implanted Cardiac Monitors Recommendation for Implanted Cardiac Monitors Referenced studies that support the recommendation are summarized in Online Data Supplement 5. COR LOE Recommendation IIa B-R In patients with sporadic symptoms (including syncope) suspected to be related to VA, implanted cardiac monitors can be Recommendation-Specific Supportive Text 1. Implanted cardiac monitors provide continu- ous rhythm monitoring and stored recordings of electrograms based on patient activation or pre- set parameters, allowing a prolonged monitor- ing period of a few years. 