Sleuthing and Syncope: The Case for Implantable Loop Recorders in Elderly Adults

An 84-year-old, independently living woman with a history of hypertension was assessed in the outpatient clinic for a 6-year history of intermittent syncope. She had experienced four episodes of syncope: three while standing and one while sitting at the hairdresser's having her hair washed. She experienced prodromal symptoms of presyncope before losing consciousness. She also described other occasional episodes of lightheadedness. Her medications included metoprolol, hydrochlorothiazide, and losartan. On examination her supine blood pressure was 151/73 mmHg, and heart rate was 64 beats per minute (bpm). After 60 seconds, her blood pressure decreased to 123/69, and her heart rate increased to 80 bpm. After 120 seconds, her blood pressure remained low at 126/69 mmHg, and her heart rate was 76 bpm. Her presyncopal symptoms were reproduced on standing, and she felt she would lose consciousness if she continued standing. Her 12-lead electrocardiogram (ECG) is shown in Figure 1A. She was diagnosed with symptomatic orthostatic hypotension. Hydrochlorothiazide was discontinued, and 40-mmHg compression stockings were prescribed. She was seen in follow-up 3 months later. She had not experienced any further syncopal episodes, and her postural lightheadedness had improved. Postural vital signs no longer demonstrated a reduction in blood pressure. Nine months later, she returned after another syncopal episode while sitting. The episode occurred suddenly, with no warning. On examination at this time, she had orthostatic hypotension, although she was asymptomatic during standing. Her 12-lead ECG was unchanged. An implantable loop recorder (ILR) was inserted for symptom-rhythm monitoring. She returned 2 months later, having experienced another syncopal episode. The ILR was interrogated, and the rhythm strips are shown in Figure 1B. Intermittent high-grade atrioventricular block associated with syncope was diagnosed. A permanent pacemaker was inserted, and the ILR was removed. Syncope is a common and often debilitating symptom, particularly in elderly adults. It occurs frequently, with an incident rate of 11 per 1,000 person-years after age 70, and is associated with 30% higher mortality.1 The most common causes of syncope in elderly adults are reflex syncope, orthostatic hypotension, and cardiac arrhythmia, including atrioventricular block.2 Syncope in elderly adults is often multifactorial, and thus it is important to consider multiple diagnoses in older adults presenting with syncope. One series found that 25% of patients evaluated in a syncope clinic met criteria for more than one cause for syncope.3 Initial evaluation of elderly adults with syncope includes a careful history, physical examination with orthostatic blood pressure measurement, and ECG. Additional considerations include carotid sinus massage to evaluate for carotid sinus hypersensitivity and tilt-table testing to further evaluate for reflex syncope.2 ILRs have become increasingly recognized as a useful diagnostic tool in individuals with syncope. Early reports of ILRs showed a diagnostic rate of 100% and symptom-rhythm correlation in 60% in individuals with recurrent, unexplained syncope after routine initial investigations.4 The Randomized Assessment of Syncope Trial compared ILRs with conventional external monitoring and showed that a syncope diagnosis was established 55% of the time with ILRs, compared with 20% in the conventional arm. Furthermore, monitoring with ILRs was found to be cost-effective.5 There is less information on ILRs in individuals aged 80 and older, in whom carotid sinus hypersensitivity and arrhythmia are more common.6 The history of the woman described herein was suggestive of orthostatic hypotension, but despite treatment for this, syncope recurred without warning. Reassessment prompted further investigation. In summary, this case demonstrates two disease processes contributing to recurrent syncope in an elderly woman and the potential utility for ILRs in this population. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: Both authors contributed to the literature review, case summary, and discussion portion of the manuscript. Sponsor's Role: None.