The Study To Understand Tilt Tests versus Extended Recordings (STUTTER, POST 10) will test the hypothesis that first performing a diagnostic HUT in older patients with syncope of unknown cause will provide earlier and more diagnoses than inserting an ICM.

A total of 144 patients ≥50 years old with ≥1 syncopal spell in the preceding year who lack a clear etiologic diagnosis for syncope and no clinically apparent structural heart disease will be randomized to first undergo HUT or to first receive an ICM in an open label, parallel group study. The primary outcome measure will be the establishment of a documented etiologic diagnosis of the cause of syncope, defined below. This will be a formal pragmatic study of two diagnostic strategies, designed around the PRECIS2 criteria. The key question addresses which test should be done first, and beyond that care will be left in the hands of the specialist physician with primary responsibility for assessing and managing syncope.

This is a Pragmatic Trial, which is a rigorous randomized trial method that enables the study of interventions in the real world. Pragmatic trials are designed to determine the effects of an intervention under the usual conditions in which it will be applied, in contrast to conventional explanatory biomedical trials that are designed to determine the effects of an intervention under ideal circumstances. The researcher's touchstone is usual syncope specialist management. There are 9 criteria of the PRECIS2 tool for pragmatic trials:1) similarity of eligibility criteria to usual care, 2) no extra recruitment effort, 3) similar setting to usual care, 4) similar health care organization and delivery to usual care, 5) similar flexibility to usual care, 6) similar flexibility in patient monitoring, 7) similar follow-up intensity to usual care, 8) direct relevance of primary outcome to participants, and 9) completeness of data inclusion. Each criterion is scored 1-5; the researchers provide these scores for each criterion. Study design and conduct are designed to resemble real clinical practice with its variable conduct and decision-making. The primary outcome is establishing a diagnosis by one of two recommended methods, and both methods have evidence-based criteria. the researchers will issue a brochure to remind investigators of the guidelines' criteria. Both have objective ECG criteria and tilt tests have BP criteria. Bias is a concern, and the Outcomes Adjudication Committee will adjudicate post hoc all results blindly.

Inclusion Criteria:

• age >50 years old
• ≥1 syncope26 in the prior 12 months
• diagnosis unclear after history, physical exam, and electrocardiogram
• no apparent risk of death due to the cause of syncope

Exclusion Criteria:

• cannot provide informed consent or attend routine follow up
• have known left ventricular ejection fraction < 50%,or have
• pacemaker, ICD, or ICM
• Class I indication for permanent pacing or ICD implantation
• hypertrophic cardiomyopathy
• a history of myocardial infarction within 3 months prior to enrolment
• a major chronic co-morbid medical condition that would preclude 12 months of follow-up
• bifascicular block
• epilepsy proven by electroencephalography
• syncope of known cause